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Machining Question
I'm close to milling my AR lower receiver, this "95%" machined receiver needs a pocket for the fire control group and 3 holes cross drilled for 2 pins and a selector/safety. I found some instructions for machining the pocket using a DRO, they recommend drilling the selector switch hole, machining the pocket then drilling the trigger & hammer pin holes. Why not drill all 3 cross holes in that 1 setup and then machining the pocket? I would think the drill bits might be more likely to walk as they start through the 2nd side. I don't see a benefit to set up for drilling, turn turn the part for milling, then turn back to the first setup to drill 2 more holes, any idea why they would do, or recommend this? https://colfaxtactical.com/docs/Fire...%20a%20DRO.pdf RogerN |
Machining Question
RogerN wrote: I'm close to milling my AR lower receiver, this "95%" machined receiver needs a pocket for the fire control group and 3 holes cross drilled for 2 pins and a selector/safety. I found some instructions for machining the pocket using a DRO, they recommend drilling the selector switch hole, machining the pocket then drilling the trigger & hammer pin holes. Why not drill all 3 cross holes in that 1 setup and then machining the pocket? I would think the drill bits might be more likely to walk as they start through the 2nd side. I don't see a benefit to set up for drilling, turn turn the part for milling, then turn back to the first setup to drill 2 more holes, any idea why they would do, or recommend this? https://colfaxtactical.com/docs/Fire...%20a%20DRO.pdf RogerN I drill all the holes in one setup long before milling the FCG cavity. I suppose one theory for drilling after the FCG cavity would be to reduce the chances of the drill getting off course, but that doesn't seem to be an issue in my experience. The Ray-Vin guide is the best reference IMO. |
Machining Question
"Pete C." wrote in message ...
RogerN wrote: I'm close to milling my AR lower receiver, this "95%" machined receiver needs a pocket for the fire control group and 3 holes cross drilled for 2 pins and a selector/safety. I found some instructions for machining the pocket using a DRO, they recommend drilling the selector switch hole, machining the pocket then drilling the trigger & hammer pin holes. Why not drill all 3 cross holes in that 1 setup and then machining the pocket? I would think the drill bits might be more likely to walk as they start through the 2nd side. I don't see a benefit to set up for drilling, turn turn the part for milling, then turn back to the first setup to drill 2 more holes, any idea why they would do, or recommend this? https://colfaxtactical.com/docs/Fire...%20a%20DRO.pdf RogerN I drill all the holes in one setup long before milling the FCG cavity. I suppose one theory for drilling after the FCG cavity would be to reduce the chances of the drill getting off course, but that doesn't seem to be an issue in my experience. The Ray-Vin guide is the best reference IMO. That's more what I was thinking, drill the cross holes first in one setup and then mill the fire control group. I have the Ray-Vin guide and a blank lower also, the "95%" machined lower should get me shooting right away and the 0% won't be rushed. Do you know how long it takes to completely machine a lower using the Ray-Vin guide? RogerN |
Machining Question
RogerN wrote: "Pete C." wrote in message ... RogerN wrote: I'm close to milling my AR lower receiver, this "95%" machined receiver needs a pocket for the fire control group and 3 holes cross drilled for 2 pins and a selector/safety. I found some instructions for machining the pocket using a DRO, they recommend drilling the selector switch hole, machining the pocket then drilling the trigger & hammer pin holes. Why not drill all 3 cross holes in that 1 setup and then machining the pocket? I would think the drill bits might be more likely to walk as they start through the 2nd side. I don't see a benefit to set up for drilling, turn turn the part for milling, then turn back to the first setup to drill 2 more holes, any idea why they would do, or recommend this? https://colfaxtactical.com/docs/Fire...%20a%20DRO.pdf RogerN I drill all the holes in one setup long before milling the FCG cavity. I suppose one theory for drilling after the FCG cavity would be to reduce the chances of the drill getting off course, but that doesn't seem to be an issue in my experience. The Ray-Vin guide is the best reference IMO. That's more what I was thinking, drill the cross holes first in one setup and then mill the fire control group. I have the Ray-Vin guide and a blank lower also, the "95%" machined lower should get me shooting right away and the 0% won't be rushed. Do you know how long it takes to completely machine a lower using the Ray-Vin guide? Nope, but close. I use the 30% lowers from TM, so that saves the magwell and decking steps. The 30s take most of a day to machine on a manual mill working at a careful pace with lunch and dinner breaks. A good chunk of the time is the 8 or so setups and getting each one indicated and edge located. |
Machining Question
"Pete C." wrote in message ...
RogerN wrote: snip Do you know how long it takes to completely machine a lower using the Ray-Vin guide? Nope, but close. I use the 30% lowers from TM, so that saves the magwell and decking steps. The 30s take most of a day to machine on a manual mill working at a careful pace with lunch and dinner breaks. A good chunk of the time is the 8 or so setups and getting each one indicated and edge located. I have one lower raw forging now and 4 more that have been on order since early February. I'm hoping the other 4 come in and I can machine them as a batch of 5. I would like to machine them all to the 80% stage so I could legally sell some if I wanted to. I could complete however many I think I wanted to keep. I now have one rifle and one carbine less lowers, would like to also get a 300 blackout, I hear barrel and ammo is the only difference from the .223/5.56. An area gun shop had a Bushmaster 450 upper, I'm not sure what cartridge they shoot. RogerN |
Machining Question
On Sun, 7 Apr 2013 19:12:24 -0500, "RogerN" wrote:
I'm close to milling my AR lower receiver, this "95%" machined receiver needs a pocket for the fire control group and 3 holes cross drilled for 2 pins and a selector/safety. I found some instructions for machining the pocket using a DRO, they recommend drilling the selector switch hole, machining the pocket then drilling the trigger & hammer pin holes. Why not drill all 3 cross holes in that 1 setup and then machining the pocket? I would think the drill bits might be more likely to walk as they start through the 2nd side. I don't see a benefit to set up for drilling, turn turn the part for milling, then turn back to the first setup to drill 2 more holes, any idea why they would do, or recommend this? https://colfaxtactical.com/docs/Fire...%20a%20DRO.pdf RogerN Know where a complete drawing is? Would 6016-t6 bar be a suitable peice to start with? Remove 333 to reply. Randy |
Machining Question
Randy333 wrote: On Sun, 7 Apr 2013 19:12:24 -0500, "RogerN" wrote: I'm close to milling my AR lower receiver, this "95%" machined receiver needs a pocket for the fire control group and 3 holes cross drilled for 2 pins and a selector/safety. I found some instructions for machining the pocket using a DRO, they recommend drilling the selector switch hole, machining the pocket then drilling the trigger & hammer pin holes. Why not drill all 3 cross holes in that 1 setup and then machining the pocket? I would think the drill bits might be more likely to walk as they start through the 2nd side. I don't see a benefit to set up for drilling, turn turn the part for milling, then turn back to the first setup to drill 2 more holes, any idea why they would do, or recommend this? https://colfaxtactical.com/docs/Fire...%20a%20DRO.pdf RogerN Know where a complete drawing is? Would 6016-t6 bar be a suitable peice to start with? There are a bunch of AR prints on the 'net, just search around a bit. 7075-T6 is what you want. |
Machining Question
RogerN wrote:
I'm close to milling my AR lower receiver, this "95%" machined receiver needs a pocket for the fire control group and 3 holes cross drilled for 2 pins and a selector/safety. I found some instructions for machining the pocket using a DRO, they recommend drilling the selector switch hole, machining the pocket then drilling the trigger & hammer pin holes. Why not drill all 3 cross holes in that 1 setup and then machining the pocket? I would think the drill bits might be more likely to walk as they start through the 2nd side. I don't see a benefit to set up for drilling, turn turn the part for milling, then turn back to the first setup to drill 2 more holes, any idea why they would do, or recommend this? https://colfaxtactical.com/docs/Fire...%20a%20DRO.pdf RogerN does anybody make plastic unfinished lowers, just for machining practice? It would seem like a shame, and expensive to be using trashed lowers for the next aluminum casting project. |
Machining Question
On Mon, 8 Apr 2013 17:14:22 +0000 (UTC), Cydrome Leader
wrote: RogerN wrote: I'm close to milling my AR lower receiver, this "95%" machined receiver needs a pocket for the fire control group and 3 holes cross drilled for 2 pins and a selector/safety. I found some instructions for machining the pocket using a DRO, they recommend drilling the selector switch hole, machining the pocket then drilling the trigger & hammer pin holes. Why not drill all 3 cross holes in that 1 setup and then machining the pocket? I would think the drill bits might be more likely to walk as they start through the 2nd side. I don't see a benefit to set up for drilling, turn turn the part for milling, then turn back to the first setup to drill 2 more holes, any idea why they would do, or recommend this? https://colfaxtactical.com/docs/Fire...%20a%20DRO.pdf RogerN does anybody make plastic unfinished lowers, just for machining practice? It would seem like a shame, and expensive to be using trashed lowers for the next aluminum casting project. Real AR-15s and M-16s have 7075-grade uppers and lowers. You can't cast that with home hobby equipment. I've read that some of the aftermarket is using 6061 for lowers. But the people making those comments probably don't really know. Yield strength of 6061 is roughly half that of 7075. 6061 is a wrought grade, but it can be cast without doing anything special. -- Ed Huntress |
Machining Question
Ed Huntress wrote:
On Mon, 8 Apr 2013 17:14:22 +0000 (UTC), Cydrome Leader wrote: RogerN wrote: I'm close to milling my AR lower receiver, this "95%" machined receiver needs a pocket for the fire control group and 3 holes cross drilled for 2 pins and a selector/safety. I found some instructions for machining the pocket using a DRO, they recommend drilling the selector switch hole, machining the pocket then drilling the trigger & hammer pin holes. Why not drill all 3 cross holes in that 1 setup and then machining the pocket? I would think the drill bits might be more likely to walk as they start through the 2nd side. I don't see a benefit to set up for drilling, turn turn the part for milling, then turn back to the first setup to drill 2 more holes, any idea why they would do, or recommend this? https://colfaxtactical.com/docs/Fire...%20a%20DRO.pdf RogerN does anybody make plastic unfinished lowers, just for machining practice? It would seem like a shame, and expensive to be using trashed lowers for the next aluminum casting project. Real AR-15s and M-16s have 7075-grade uppers and lowers. You can't cast that with home hobby equipment. I've read that some of the aftermarket is using 6061 for lowers. But the people making those comments probably don't really know. Yield strength of 6061 is roughly half that of 7075. 6061 is a wrought grade, but it can be cast without doing anything special. I meant once you bungle a partially made lower, you're finished, and it's just expensive scrap metal, of a useless shape probably only good for tossing into the aluminum scrap pile for some backyard casting. It seems like a shame. |
Machining Question
On Mon, 8 Apr 2013 19:24:51 +0000 (UTC), Cydrome Leader
wrote: Ed Huntress wrote: On Mon, 8 Apr 2013 17:14:22 +0000 (UTC), Cydrome Leader wrote: RogerN wrote: I'm close to milling my AR lower receiver, this "95%" machined receiver needs a pocket for the fire control group and 3 holes cross drilled for 2 pins and a selector/safety. I found some instructions for machining the pocket using a DRO, they recommend drilling the selector switch hole, machining the pocket then drilling the trigger & hammer pin holes. Why not drill all 3 cross holes in that 1 setup and then machining the pocket? I would think the drill bits might be more likely to walk as they start through the 2nd side. I don't see a benefit to set up for drilling, turn turn the part for milling, then turn back to the first setup to drill 2 more holes, any idea why they would do, or recommend this? https://colfaxtactical.com/docs/Fire...%20a%20DRO.pdf RogerN does anybody make plastic unfinished lowers, just for machining practice? It would seem like a shame, and expensive to be using trashed lowers for the next aluminum casting project. Real AR-15s and M-16s have 7075-grade uppers and lowers. You can't cast that with home hobby equipment. I've read that some of the aftermarket is using 6061 for lowers. But the people making those comments probably don't really know. Yield strength of 6061 is roughly half that of 7075. 6061 is a wrought grade, but it can be cast without doing anything special. I meant once you bungle a partially made lower, you're finished, and it's just expensive scrap metal, of a useless shape probably only good for tossing into the aluminum scrap pile for some backyard casting. It seems like a shame. Well, it is a shame, but I wouldn't toss a high-zinc alloy, which also has around 1.5% copper, into a pile I was going to use for backyard aluminum casting. Zinc and copper will hake it hard to make a casting without internal shrinkage voids. -- Ed Huntress |
Machining Question
Cydrome Leader wrote:
RogerN wrote: I'm close to milling my AR lower receiver, this "95%" machined receiver needs a pocket for the fire control group and 3 holes cross drilled for 2 pins and a selector/safety. I found some instructions for machining the pocket using a DRO, they recommend drilling the selector switch hole, machining the pocket then drilling the trigger & hammer pin holes. Why not drill all 3 cross holes in that 1 setup and then machining the pocket? I would think the drill bits might be more likely to walk as they start through the 2nd side. I don't see a benefit to set up for drilling, turn turn the part for milling, then turn back to the first setup to drill 2 more holes, any idea why they would do, or recommend this? https://colfaxtactical.com/docs/Fire...%20a%20DRO.pdf RogerN does anybody make plastic unfinished lowers, just for machining practice? It would seem like a shame, and expensive to be using trashed lowers for the next aluminum casting project. As long as you follow the directions and have some ability they are not real hard to machine. The biggest thing involved is to KNOW the machine you will be using. If you know that your machine has .020 backlash on the X axis repeatably then you can correct for it. If you think it does but in reality it isn't repeatable then OOPS you get a scrap upper. -- Steve W. |
Machining Question
On Apr 8, 11:26*am, Ed Huntress wrote:
On Mon, 8 Apr 2013 17:14:22 +0000 (UTC), Cydrome Leader wrote: RogerN wrote: I'm close to milling my AR lower receiver, this "95%" machined receiver needs a pocket for the fire control group and 3 holes cross drilled for 2 pins and a selector/safety. I found some instructions for machining the pocket using a DRO, they recommend drilling the selector switch hole, machining the pocket *then drilling the trigger & hammer pin holes. *Why not drill all 3 cross holes in that 1 setup and then machining the pocket? *I would think the drill bits might be more likely to walk as they start through the 2nd side. *I don't see a benefit to set up for drilling, turn turn the part for milling, then turn back to the first setup to drill 2 more holes, any idea why they would do, or recommend this? https://colfaxtactical.com/docs/Fire...%20with%20a%20.... RogerN does anybody make plastic unfinished lowers, just for machining practice? It would seem like a shame, and expensive to be using trashed lowers for the next aluminum casting project. Real AR-15s and M-16s have 7075-grade uppers and lowers. You can't cast that with home hobby equipment. I've read that some of the aftermarket is using 6061 for lowers. But the people making those comments probably don't really know. Yield strength of 6061 is roughly half that of 7075. 6061 is a wrought grade, but it can be cast without doing anything special. -- Ed Huntress- Hide quoted text - - Show quoted text - The original ARs back in the Vietnam timeframe had 6061 forgings. They had some trouble with corrosion from guys' sweat, so 7075 was the next step. Some of the early clone lowers were castings, some so bad that they broke when the rifle fell over onto the floor. Stoner's genius was you could probably make a lower out of recycled bubblegum and have it work as long as it stood up to the fire control springs' pressure. So 6061 or 7075, doesn't make much difference except when anodizing. .223 recoil is about nil, the forgings/castings don't directly take chamber pressure so yield strength is irrelevant for most civilian uses. If you intend on beating up bunnies or whacking coyotes with the buttstock, it might make a difference. Stan |
Machining Question
Ed Huntress wrote:
On Mon, 8 Apr 2013 19:24:51 +0000 (UTC), Cydrome Leader wrote: Ed Huntress wrote: On Mon, 8 Apr 2013 17:14:22 +0000 (UTC), Cydrome Leader wrote: RogerN wrote: I'm close to milling my AR lower receiver, this "95%" machined receiver needs a pocket for the fire control group and 3 holes cross drilled for 2 pins and a selector/safety. I found some instructions for machining the pocket using a DRO, they recommend drilling the selector switch hole, machining the pocket then drilling the trigger & hammer pin holes. Why not drill all 3 cross holes in that 1 setup and then machining the pocket? I would think the drill bits might be more likely to walk as they start through the 2nd side. I don't see a benefit to set up for drilling, turn turn the part for milling, then turn back to the first setup to drill 2 more holes, any idea why they would do, or recommend this? https://colfaxtactical.com/docs/Fire...%20a%20DRO.pdf RogerN does anybody make plastic unfinished lowers, just for machining practice? It would seem like a shame, and expensive to be using trashed lowers for the next aluminum casting project. Real AR-15s and M-16s have 7075-grade uppers and lowers. You can't cast that with home hobby equipment. I've read that some of the aftermarket is using 6061 for lowers. But the people making those comments probably don't really know. Yield strength of 6061 is roughly half that of 7075. 6061 is a wrought grade, but it can be cast without doing anything special. I meant once you bungle a partially made lower, you're finished, and it's just expensive scrap metal, of a useless shape probably only good for tossing into the aluminum scrap pile for some backyard casting. It seems like a shame. Well, it is a shame, but I wouldn't toss a high-zinc alloy, which also has around 1.5% copper, into a pile I was going to use for backyard aluminum casting. Zinc and copper will hake it hard to make a casting without internal shrinkage voids. So it's a total loss then. How much might it cost to make some really crappy molds (we're talking 1970s Hong Kong grade stuff) to make these out of plastic? |
Machining Question
On Mon, 8 Apr 2013 13:43:26 -0700 (PDT), Stanley Schaefer
wrote: On Apr 8, 11:26*am, Ed Huntress wrote: On Mon, 8 Apr 2013 17:14:22 +0000 (UTC), Cydrome Leader wrote: RogerN wrote: I'm close to milling my AR lower receiver, this "95%" machined receiver needs a pocket for the fire control group and 3 holes cross drilled for 2 pins and a selector/safety. I found some instructions for machining the pocket using a DRO, they recommend drilling the selector switch hole, machining the pocket *then drilling the trigger & hammer pin holes. *Why not drill all 3 cross holes in that 1 setup and then machining the pocket? *I would think the drill bits might be more likely to walk as they start through the 2nd side. *I don't see a benefit to set up for drilling, turn turn the part for milling, then turn back to the first setup to drill 2 more holes, any idea why they would do, or recommend this? https://colfaxtactical.com/docs/Fire...%20with%20a%20... RogerN does anybody make plastic unfinished lowers, just for machining practice? It would seem like a shame, and expensive to be using trashed lowers for the next aluminum casting project. Real AR-15s and M-16s have 7075-grade uppers and lowers. You can't cast that with home hobby equipment. I've read that some of the aftermarket is using 6061 for lowers. But the people making those comments probably don't really know. Yield strength of 6061 is roughly half that of 7075. 6061 is a wrought grade, but it can be cast without doing anything special. -- Ed Huntress- Hide quoted text - - Show quoted text - The original ARs back in the Vietnam timeframe had 6061 forgings. They had some trouble with corrosion from guys' sweat, so 7075 was the next step. Something is strange there. I'd have to dig out my ASM book to check, but 7075 has low corrosion resistance overall and is not recommended at all for marine environments (or salty sweat, one would assume). 6061 is somewhere in the middle. Some of the early clone lowers were castings, some so bad that they broke when the rifle fell over onto the floor. Stoner's genius was you could probably make a lower out of recycled bubblegum and have it work as long as it stood up to the fire control springs' pressure. So 6061 or 7075, doesn't make much difference except when anodizing. .223 recoil is about nil, the forgings/castings don't directly take chamber pressure so yield strength is irrelevant for most civilian uses. If you intend on beating up bunnies or whacking coyotes with the buttstock, it might make a difference. Stan |
Machining Question
On Mon, 8 Apr 2013 20:54:33 +0000 (UTC), Cydrome Leader
wrote: Ed Huntress wrote: On Mon, 8 Apr 2013 19:24:51 +0000 (UTC), Cydrome Leader wrote: Ed Huntress wrote: On Mon, 8 Apr 2013 17:14:22 +0000 (UTC), Cydrome Leader wrote: RogerN wrote: I'm close to milling my AR lower receiver, this "95%" machined receiver needs a pocket for the fire control group and 3 holes cross drilled for 2 pins and a selector/safety. I found some instructions for machining the pocket using a DRO, they recommend drilling the selector switch hole, machining the pocket then drilling the trigger & hammer pin holes. Why not drill all 3 cross holes in that 1 setup and then machining the pocket? I would think the drill bits might be more likely to walk as they start through the 2nd side. I don't see a benefit to set up for drilling, turn turn the part for milling, then turn back to the first setup to drill 2 more holes, any idea why they would do, or recommend this? https://colfaxtactical.com/docs/Fire...%20a%20DRO.pdf RogerN does anybody make plastic unfinished lowers, just for machining practice? It would seem like a shame, and expensive to be using trashed lowers for the next aluminum casting project. Real AR-15s and M-16s have 7075-grade uppers and lowers. You can't cast that with home hobby equipment. I've read that some of the aftermarket is using 6061 for lowers. But the people making those comments probably don't really know. Yield strength of 6061 is roughly half that of 7075. 6061 is a wrought grade, but it can be cast without doing anything special. I meant once you bungle a partially made lower, you're finished, and it's just expensive scrap metal, of a useless shape probably only good for tossing into the aluminum scrap pile for some backyard casting. It seems like a shame. Well, it is a shame, but I wouldn't toss a high-zinc alloy, which also has around 1.5% copper, into a pile I was going to use for backyard aluminum casting. Zinc and copper will hake it hard to make a casting without internal shrinkage voids. So it's a total loss then. Well, if you have enough aluminum to sell your scrap from time to time, you could toss it in there. How much might it cost to make some really crappy molds (we're talking 1970s Hong Kong grade stuff) to make these out of plastic? First off I'd look at the redesign of the plastic lower that those 3D printing guys have designed. Just duplicating the aluminum one in plastic led to a very short life, so they've redesigned it. As for the molds, it depends on what plastic and how many. It also will depend somewhat on the configuration and drafts. For machined molds, aluminum (2024 or 6061) is used for injection-mold prototyping and very short runs but some plastics require a chrome plating. After that, it's mold steel, and big bucks unless you're machining it yourself. If you're using a pourable resin, like epoxy or rigid polyurethane, you can make molds out of plaster of Paris. They'd be stronger than most injection-moldable plastics but they're much more expensive, too. -- Ed Huntress |
Machining Question
Steve W. wrote:
Cydrome Leader wrote: RogerN wrote: I'm close to milling my AR lower receiver, this "95%" machined receiver needs a pocket for the fire control group and 3 holes cross drilled for 2 pins and a selector/safety. I found some instructions for machining the pocket using a DRO, they recommend drilling the selector switch hole, machining the pocket then drilling the trigger & hammer pin holes. Why not drill all 3 cross holes in that 1 setup and then machining the pocket? I would think the drill bits might be more likely to walk as they start through the 2nd side. I don't see a benefit to set up for drilling, turn turn the part for milling, then turn back to the first setup to drill 2 more holes, any idea why they would do, or recommend this? https://colfaxtactical.com/docs/Fire...%20a%20DRO.pdf RogerN does anybody make plastic unfinished lowers, just for machining practice? It would seem like a shame, and expensive to be using trashed lowers for the next aluminum casting project. As long as you follow the directions and have some ability they are not real hard to machine. The biggest thing involved is to KNOW the machine you will be using. If you know that your machine has .020 backlash on the X axis repeatably then you can correct for it. If you think it does but in reality it isn't repeatable then OOPS you get a scrap upper. It's a chicken and egg sort of deal to anybody (like me) that's new to machining, but familiar with what the finished product should be. Do I right now have the ability to finish a lower receiver? No, I do not. Could I learn? sure, but it will take lots of practice, which at this point would be futile and expensive if I bought a box of forgings and jumped right in. I'm sure I'd learn quite a bit trying though, while making a huge pile of scraps, but again, it costs to much to try. |
Machining Question
On Apr 8, 2:48*pm, Cydrome Leader wrote:
Steve W. wrote: Cydrome Leader wrote: RogerN wrote: I'm close to milling my AR lower receiver, this "95%" machined receiver needs a pocket for the fire control group and 3 holes cross drilled for 2 pins and a selector/safety. I found some instructions for machining the pocket using a DRO, they recommend drilling the selector switch hole, machining the pocket *then drilling the trigger & hammer pin holes. *Why not drill all 3 cross holes in that 1 setup and then machining the pocket? *I would think the drill bits might be more likely to walk as they start through the 2nd side. *I don't see a benefit to set up for drilling, turn turn the part for milling, then turn back to the first setup to drill 2 more holes, any idea why they would do, or recommend this? https://colfaxtactical.com/docs/Fire...%20with%20a%20.... RogerN does anybody make plastic unfinished lowers, just for machining practice? It would seem like a shame, and expensive to be using trashed lowers for the next aluminum casting project. As long as you follow the directions and have some ability they are not real hard to machine. The biggest thing involved is to KNOW the machine you will be using. If you know that your machine has .020 backlash on the X axis repeatably then you can correct for it. If you think it does but in reality it isn't repeatable then OOPS you get a scrap upper. It's a chicken and egg sort of deal to anybody (like me) that's new to machining, but familiar with what the finished product should be. Do I right now have the ability to finish *a lower receiver? No, I do not. Could I learn? sure, but it will take lots of practice, which at this point would be futile and expensive if I bought a box of forgings and jumped right in. I'm sure I'd learn quite a bit trying though, while making a huge pile of scraps, but again, it costs to much to try. You are not as far off as you think if you invest the time and you continue to think and ask questions about why you are having problems You have tremendous resources in this group: Lloyd Sponenburgh, Precision Machinist, Bottlebob, and lots of others. Use them. The more parts you make out of different materials, the better you will get. |
Machining Question
Cydrome Leader wrote: Ed Huntress wrote: On Mon, 8 Apr 2013 17:14:22 +0000 (UTC), Cydrome Leader wrote: RogerN wrote: I'm close to milling my AR lower receiver, this "95%" machined receiver needs a pocket for the fire control group and 3 holes cross drilled for 2 pins and a selector/safety. I found some instructions for machining the pocket using a DRO, they recommend drilling the selector switch hole, machining the pocket then drilling the trigger & hammer pin holes. Why not drill all 3 cross holes in that 1 setup and then machining the pocket? I would think the drill bits might be more likely to walk as they start through the 2nd side. I don't see a benefit to set up for drilling, turn turn the part for milling, then turn back to the first setup to drill 2 more holes, any idea why they would do, or recommend this? https://colfaxtactical.com/docs/Fire...%20a%20DRO.pdf RogerN does anybody make plastic unfinished lowers, just for machining practice? It would seem like a shame, and expensive to be using trashed lowers for the next aluminum casting project. Real AR-15s and M-16s have 7075-grade uppers and lowers. You can't cast that with home hobby equipment. I've read that some of the aftermarket is using 6061 for lowers. But the people making those comments probably don't really know. Yield strength of 6061 is roughly half that of 7075. 6061 is a wrought grade, but it can be cast without doing anything special. I meant once you bungle a partially made lower, you're finished, and it's just expensive scrap metal, of a useless shape probably only good for tossing into the aluminum scrap pile for some backyard casting. It seems like a shame. It depends on exactly what you bungle, but most mistakes in the machining can be remedied/worked around to make a perfectly serviceable lower. On the 7075 vs. 6061 thing, operationally it won't make much difference since the AR receiver basically guides parts and have very very little stress placed on it due to the fact that the bolt locks into the barrel extension and no into any portion of the receiver. I believe the first M16s were 6061 and they only changed to 7075 due to corrosion issues in the 'Nam jungles. With the lower forgings running in the $25-$80 range depending on completion state, the financial risk isn't really much more than the financial risk of breaking an end mill or reamer in the machining. |
Machining Question
On 4/8/2013 4:06 PM, Ed Huntress wrote:
Snipped - just to show it's technically possible... Something is strange there. I'd have to dig out my ASM book to check, but 7075 has low corrosion resistance overall and is not recommended at all for marine environments (or salty sweat, one would assume). 6061 is somewhere in the middle. I wondered about that too. What's the story here? |
Machining Question
Pete C. wrote:
Cydrome Leader wrote: Ed Huntress wrote: On Mon, 8 Apr 2013 17:14:22 +0000 (UTC), Cydrome Leader wrote: RogerN wrote: I'm close to milling my AR lower receiver, this "95%" machined receiver needs a pocket for the fire control group and 3 holes cross drilled for 2 pins and a selector/safety. I found some instructions for machining the pocket using a DRO, they recommend drilling the selector switch hole, machining the pocket then drilling the trigger & hammer pin holes. Why not drill all 3 cross holes in that 1 setup and then machining the pocket? I would think the drill bits might be more likely to walk as they start through the 2nd side. I don't see a benefit to set up for drilling, turn turn the part for milling, then turn back to the first setup to drill 2 more holes, any idea why they would do, or recommend this? https://colfaxtactical.com/docs/Fire...%20a%20DRO.pdf RogerN does anybody make plastic unfinished lowers, just for machining practice? It would seem like a shame, and expensive to be using trashed lowers for the next aluminum casting project. Real AR-15s and M-16s have 7075-grade uppers and lowers. You can't cast that with home hobby equipment. I've read that some of the aftermarket is using 6061 for lowers. But the people making those comments probably don't really know. Yield strength of 6061 is roughly half that of 7075. 6061 is a wrought grade, but it can be cast without doing anything special. I meant once you bungle a partially made lower, you're finished, and it's just expensive scrap metal, of a useless shape probably only good for tossing into the aluminum scrap pile for some backyard casting. It seems like a shame. It depends on exactly what you bungle, but most mistakes in the machining can be remedied/worked around to make a perfectly serviceable lower. On the 7075 vs. 6061 thing, operationally it won't make much difference since the AR receiver basically guides parts and have very very little stress placed on it due to the fact that the bolt locks into the barrel extension and no into any portion of the receiver. I believe the first M16s were 6061 and they only changed to 7075 due to corrosion issues in the 'Nam jungles. With the lower forgings running in the $25-$80 range depending on completion state, the financial risk isn't really much more than the financial risk of breaking an end mill or reamer in the machining. hmm, I've not stumbled across the $25 ones, but that would be worth it just for the practice. |
Machining Question
On Mon, 08 Apr 2013 18:29:54 -0500, Richard
wrote: On 4/8/2013 4:06 PM, Ed Huntress wrote: Snipped - just to show it's technically possible... Something is strange there. I'd have to dig out my ASM book to check, but 7075 has low corrosion resistance overall and is not recommended at all for marine environments (or salty sweat, one would assume). 6061 is somewhere in the middle. I wondered about that too. What's the story here? Ok, from ASM's "Metals Handbook," 9th Edition: 7075 is more corrosion-resistant thant 2024 but worse than any other wrought alloy. The zinc is no help, but it's the copper that's the big problem, as it is with 2024. However, the copper improves resistance to stress-corrosion cracking. So in terms of general corrosion, 7075 kind of stinks. 6061 is good even in marine environments -- although some 5xxxx and 1100 are better. -- Ed Huntress |
Machining Question
Richard wrote:
On 4/8/2013 4:06 PM, Ed Huntress wrote: Snipped - just to show it's technically possible... Something is strange there. I'd have to dig out my ASM book to check, but 7075 has low corrosion resistance overall and is not recommended at all for marine environments (or salty sweat, one would assume). 6061 is somewhere in the middle. I wondered about that too. What's the story here? Current Mil spec is 7075 - T6 The original design called for either a 6 or 7 series alloy. The 6 was cheaper and easier to work with so that was what ended up being used. The problem is that between corrosion and thread deformation the spec was re-written to 7075 - T6 being the "correct" alloy to use. I have shot both and other than knowing the alloy due to the makers you couldn't tell any real difference. 6061 is still used by a few companies and with the design of the AR the strength in Civilian use isn't an issue. However if you plan on needing to depend on the rifle in real combat where you may be using it as a club, hammer or whatever, the 7075 has the edge with regard to wear and tear. I have used both forgings and solid billet as a starting point. With forgings you are limited as to what you can add/subtract. With billet you can have fun. I machined in a solid trigger guard, milled my logo in 3D on the side, and a few other tricks. -- Steve W. |
Machining Question
On Mon, 08 Apr 2013 20:00:59 -0400, Ed Huntress wrote:
On Mon, 08 Apr 2013 18:29:54 -0500, Richard cavelamb wrote: On 4/8/2013 4:06 PM, Ed Huntress wrote: Snipped - just to show it's technically possible... Something is strange there. I'd have to dig out my ASM book to check, but 7075 has low corrosion resistance overall and is not recommended at all for marine environments (or salty sweat, one would assume). 6061 is somewhere in the middle. I wondered about that too. What's the story here? Ok, from ASM's "Metals Handbook," 9th Edition: 7075 is more corrosion-resistant thant 2024 but worse than any other wrought alloy. The zinc is no help, but it's the copper that's the big problem, as it is with 2024. However, the copper improves resistance to stress-corrosion cracking. So in terms of general corrosion, 7075 kind of stinks. 6061 is good even in marine environments -- although some 5xxxx and 1100 are better. Which of 7075 and 6061 has better corrosion resistance when they are anodized? -- jiw |
Machining Question
"Ed Huntress" wrote
Real AR-15s and M-16s have 7075-grade uppers and lowers. You can't cast that with home hobby equipment. -- Ed Huntress You're wrong Ed , I've melted and cast 7075 in my home foundry . Now what I can't do is heat-treat and forge it at home . I'm not sure what's involved with forging , though I'm pretty sure Al is worked cold . Might have to carry a billet up the road and see what my neighbor can do with his trip hammer ... Heat-treat requires some expensive precision equipment though . -- Snag |
Machining Question
"Ed Huntress" wrote in message
... On Mon, 8 Apr 2013 19:24:51 +0000 (UTC), Cydrome Leader wrote: Ed Huntress wrote: On Mon, 8 Apr 2013 17:14:22 +0000 (UTC), Cydrome Leader wrote: RogerN wrote: I'm close to milling my AR lower receiver, this "95%" machined receiver needs a pocket for the fire control group and 3 holes cross drilled for 2 pins and a selector/safety. I found some instructions for machining the pocket using a DRO, they recommend drilling the selector switch hole, machining the pocket then drilling the trigger & hammer pin holes. Why not drill all 3 cross holes in that 1 setup and then machining the pocket? I would think the drill bits might be more likely to walk as they start through the 2nd side. I don't see a benefit to set up for drilling, turn turn the part for milling, then turn back to the first setup to drill 2 more holes, any idea why they would do, or recommend this? https://colfaxtactical.com/docs/Fire...%20a%20DRO.pdf RogerN does anybody make plastic unfinished lowers, just for machining practice? It would seem like a shame, and expensive to be using trashed lowers for the next aluminum casting project. Real AR-15s and M-16s have 7075-grade uppers and lowers. You can't cast that with home hobby equipment. I've read that some of the aftermarket is using 6061 for lowers. But the people making those comments probably don't really know. Yield strength of 6061 is roughly half that of 7075. 6061 is a wrought grade, but it can be cast without doing anything special. I meant once you bungle a partially made lower, you're finished, and it's just expensive scrap metal, of a useless shape probably only good for tossing into the aluminum scrap pile for some backyard casting. It seems like a shame. Well, it is a shame, but I wouldn't toss a high-zinc alloy, which also has around 1.5% copper, into a pile I was going to use for backyard aluminum casting. Zinc and copper will hake it hard to make a casting without internal shrinkage voids. -- Ed Huntress Neither would I . I'd toss it into the pile for ZA alloy casting . Ed , where did you acquire your knowledge about casting and alloys ? Some of the stuff you've posted is directly opposite what experience and hobbycasting yahoogroup has taught me . -- Snag Cast 5 ingots and a pulley this am ... |
Machining Question
On Mon, 8 Apr 2013 21:55:22 -0500, "Terry Coombs"
wrote: "Ed Huntress" wrote Real AR-15s and M-16s have 7075-grade uppers and lowers. You can't cast that with home hobby equipment. -- Ed Huntress You're wrong Ed , I've melted and cast 7075 in my home foundry . Now what I can't do is heat-treat and forge it at home . I'm not sure what's involved with forging , though I'm pretty sure Al is worked cold . Might have to carry a billet up the road and see what my neighbor can do with his trip hammer ... Heat-treat requires some expensive precision equipment though . Well, you may have gotten lucky, or you may have a casting with sub-surface porosity and segregation. The closest casting alloy to 7075 is 713.0, and it has less than half as much copper as 7075. And a fraction of the strength. If they could cast 7075 versus using 713.0, they surely would. But I hope you got lucky. -- Ed Huntress |
Machining Question
On Mon, 8 Apr 2013 22:04:03 -0500, "Terry Coombs"
wrote: "Ed Huntress" wrote in message .. . On Mon, 8 Apr 2013 19:24:51 +0000 (UTC), Cydrome Leader wrote: Ed Huntress wrote: On Mon, 8 Apr 2013 17:14:22 +0000 (UTC), Cydrome Leader wrote: RogerN wrote: I'm close to milling my AR lower receiver, this "95%" machined receiver needs a pocket for the fire control group and 3 holes cross drilled for 2 pins and a selector/safety. I found some instructions for machining the pocket using a DRO, they recommend drilling the selector switch hole, machining the pocket then drilling the trigger & hammer pin holes. Why not drill all 3 cross holes in that 1 setup and then machining the pocket? I would think the drill bits might be more likely to walk as they start through the 2nd side. I don't see a benefit to set up for drilling, turn turn the part for milling, then turn back to the first setup to drill 2 more holes, any idea why they would do, or recommend this? https://colfaxtactical.com/docs/Fire...%20a%20DRO.pdf RogerN does anybody make plastic unfinished lowers, just for machining practice? It would seem like a shame, and expensive to be using trashed lowers for the next aluminum casting project. Real AR-15s and M-16s have 7075-grade uppers and lowers. You can't cast that with home hobby equipment. I've read that some of the aftermarket is using 6061 for lowers. But the people making those comments probably don't really know. Yield strength of 6061 is roughly half that of 7075. 6061 is a wrought grade, but it can be cast without doing anything special. I meant once you bungle a partially made lower, you're finished, and it's just expensive scrap metal, of a useless shape probably only good for tossing into the aluminum scrap pile for some backyard casting. It seems like a shame. Well, it is a shame, but I wouldn't toss a high-zinc alloy, which also has around 1.5% copper, into a pile I was going to use for backyard aluminum casting. Zinc and copper will hake it hard to make a casting without internal shrinkage voids. -- Ed Huntress Neither would I . I'd toss it into the pile for ZA alloy casting . Ed , where did you acquire your knowledge about casting and alloys ? Some of the stuff you've posted is directly opposite what experience and hobbycasting yahoogroup has taught me . Mostly as Materials Editor at _American Machinist_. I had to study basic metallurgy for a couple of years to be able to handle the tech papers coming in from Alcoa, U.S. Steel, and so on. I'm hardly an expert but I know the sources. I'm very curious about what the hobbycasting group is saying that's directly opposite. Does it concern 7075? It's notorious for having lousy corrosion resistance. There are some 7xxxx alloys that are much better, but not 7075. As for copper in aluminum, it makes it extremely hot-short and prone to porosity. That's why welding 2024 is not recommended except by some specialized techniques. It cracks like crazy, and if it happens not to crack today, it may in a couple of weeks, as the HAZ age-hardens. Anyway, what is opposite? -- Ed Humtress |
Machining Question
Gunner Asch wrote:
On Mon, 08 Apr 2013 20:02:47 -0400, "Steve W." wrote: Richard wrote: On 4/8/2013 4:06 PM, Ed Huntress wrote: Snipped - just to show it's technically possible... Something is strange there. I'd have to dig out my ASM book to check, but 7075 has low corrosion resistance overall and is not recommended at all for marine environments (or salty sweat, one would assume). 6061 is somewhere in the middle. I wondered about that too. What's the story here? Current Mil spec is 7075 - T6 The original design called for either a 6 or 7 series alloy. The 6 was cheaper and easier to work with so that was what ended up being used. The problem is that between corrosion and thread deformation the spec was re-written to 7075 - T6 being the "correct" alloy to use. I have shot both and other than knowing the alloy due to the makers you couldn't tell any real difference. 6061 is still used by a few companies and with the design of the AR the strength in Civilian use isn't an issue. However if you plan on needing to depend on the rifle in real combat where you may be using it as a club, hammer or whatever, the 7075 has the edge with regard to wear and tear. I have used both forgings and solid billet as a starting point. With forgings you are limited as to what you can add/subtract. With billet you can have fun. I machined in a solid trigger guard, milled my logo in 3D on the side, and a few other tricks. Could you machine one out of a stainless steel block? Already been done. There are a few companies that already sell stainless lowers. I did one out of 416 just to see what it took. It will be the only one I ever do as well. It machined very well but even when I thinned areas down to reduce weight it's still pretty hefty. Does make the .308 a lot nicer to shoot though. I have been tossing around the idea of making one out of steel though. Thinking of areas like the sides of the mag well for skeletonizing... Anyone with a mid sized mill can handle the job. If you buy some guides you can even use a good drill press! -- Steve W. |
Machining Question
On Tue, 09 Apr 2013 00:19:34 -0400, "Steve W."
wrote: Gunner Asch wrote: On Mon, 08 Apr 2013 20:02:47 -0400, "Steve W." wrote: Richard wrote: On 4/8/2013 4:06 PM, Ed Huntress wrote: Snipped - just to show it's technically possible... Something is strange there. I'd have to dig out my ASM book to check, but 7075 has low corrosion resistance overall and is not recommended at all for marine environments (or salty sweat, one would assume). 6061 is somewhere in the middle. I wondered about that too. What's the story here? Current Mil spec is 7075 - T6 The original design called for either a 6 or 7 series alloy. The 6 was cheaper and easier to work with so that was what ended up being used. The problem is that between corrosion and thread deformation the spec was re-written to 7075 - T6 being the "correct" alloy to use. I have shot both and other than knowing the alloy due to the makers you couldn't tell any real difference. 6061 is still used by a few companies and with the design of the AR the strength in Civilian use isn't an issue. However if you plan on needing to depend on the rifle in real combat where you may be using it as a club, hammer or whatever, the 7075 has the edge with regard to wear and tear. I have used both forgings and solid billet as a starting point. With forgings you are limited as to what you can add/subtract. With billet you can have fun. I machined in a solid trigger guard, milled my logo in 3D on the side, and a few other tricks. Could you machine one out of a stainless steel block? Already been done. There are a few companies that already sell stainless lowers. I did one out of 416 just to see what it took. It will be the only one I ever do as well. It machined very well but even when I thinned areas down to reduce weight it's still pretty hefty. Does make the .308 a lot nicer to shoot though. I have been tossing around the idea of making one out of steel though. Thinking of areas like the sides of the mag well for skeletonizing... Anyone with a mid sized mill can handle the job. If you buy some guides you can even use a good drill press! Id not mind having a lower someday. Though given the prices of the upper Stuff..it would likely remain a door stop. ARs are quasi legal here in California..but they have to be neutered with a 10 rd mag and a bullet button etc etc Gunner |
Machining Question
On 4/8/2013 11:19 PM, Steve W. wrote:
Could you machine one out of a stainless steel block? Already been done. There are a few companies that already sell stainless lowers. I did one out of 416 just to see what it took. It will be the only one I ever do as well. It machined very well but even when I thinned areas down to reduce weight it's still pretty hefty. Does make the .308 a lot nicer to shoot though. I have been tossing around the idea of making one out of steel though. Thinking of areas like the sides of the mag well for skeletonizing... Anyone with a mid sized mill can handle the job. If you buy some guides you can even use a good drill press! What does that do to the weight??? |
Machining Question
On Tue, 09 Apr 2013 00:04:40 -0500, Richard
wrote: On 4/8/2013 11:19 PM, Steve W. wrote: Could you machine one out of a stainless steel block? Already been done. There are a few companies that already sell stainless lowers. I did one out of 416 just to see what it took. It will be the only one I ever do as well. It machined very well but even when I thinned areas down to reduce weight it's still pretty hefty. Does make the .308 a lot nicer to shoot though. I have been tossing around the idea of making one out of steel though. Thinking of areas like the sides of the mag well for skeletonizing... Anyone with a mid sized mill can handle the job. If you buy some guides you can even use a good drill press! What does that do to the weight??? It would center it nicely..and by the time folks get done putting all the lasers, launchers and other sundry bull**** on them...shrug...a steel lower really wouldnt be noticed too much. Gunner |
Machining Question
On Mon, 08 Apr 2013 21:56:51 -0700, Gunner Asch
wrote: On Tue, 09 Apr 2013 00:19:34 -0400, "Steve W." wrote: Gunner Asch wrote: On Mon, 08 Apr 2013 20:02:47 -0400, "Steve W." wrote: Richard wrote: On 4/8/2013 4:06 PM, Ed Huntress wrote: Snipped - just to show it's technically possible... Something is strange there. I'd have to dig out my ASM book to check, but 7075 has low corrosion resistance overall and is not recommended at all for marine environments (or salty sweat, one would assume). 6061 is somewhere in the middle. I wondered about that too. What's the story here? Current Mil spec is 7075 - T6 The original design called for either a 6 or 7 series alloy. The 6 was cheaper and easier to work with so that was what ended up being used. The problem is that between corrosion and thread deformation the spec was re-written to 7075 - T6 being the "correct" alloy to use. I have shot both and other than knowing the alloy due to the makers you couldn't tell any real difference. 6061 is still used by a few companies and with the design of the AR the strength in Civilian use isn't an issue. However if you plan on needing to depend on the rifle in real combat where you may be using it as a club, hammer or whatever, the 7075 has the edge with regard to wear and tear. I have used both forgings and solid billet as a starting point. With forgings you are limited as to what you can add/subtract. With billet you can have fun. I machined in a solid trigger guard, milled my logo in 3D on the side, and a few other tricks. Could you machine one out of a stainless steel block? Already been done. There are a few companies that already sell stainless lowers. I did one out of 416 just to see what it took. It will be the only one I ever do as well. It machined very well but even when I thinned areas down to reduce weight it's still pretty hefty. Does make the .308 a lot nicer to shoot though. I have been tossing around the idea of making one out of steel though. Thinking of areas like the sides of the mag well for skeletonizing... Anyone with a mid sized mill can handle the job. If you buy some guides you can even use a good drill press! Id not mind having a lower someday. Though given the prices of the upper Stuff..it would likely remain a door stop. ARs are quasi legal here in California..but they have to be neutered with a 10 rd mag and a bullet button etc etc Gunner Bullet button? Remove 333 to reply. Randy |
Machining Question
On Mon, 8 Apr 2013 17:14:22 +0000 (UTC), Cydrome Leader
wrote: RogerN wrote: I'm close to milling my AR lower receiver, this "95%" machined receiver needs a pocket for the fire control group and 3 holes cross drilled for 2 pins and a selector/safety. I found some instructions for machining the pocket using a DRO, they recommend drilling the selector switch hole, machining the pocket then drilling the trigger & hammer pin holes. Why not drill all 3 cross holes in that 1 setup and then machining the pocket? I would think the drill bits might be more likely to walk as they start through the 2nd side. I don't see a benefit to set up for drilling, turn turn the part for milling, then turn back to the first setup to drill 2 more holes, any idea why they would do, or recommend this? https://colfaxtactical.com/docs/Fire...%20a%20DRO.pdf RogerN does anybody make plastic unfinished lowers, just for machining practice? It would seem like a shame, and expensive to be using trashed lowers for the next aluminum casting project. Buy a 0% forging, make a mold from it using bondo (autobody filler) then make some machinable wax castings from that. Screw it up, just remelt the wax! Remove 333 to reply. Randy |
Machining Question
Randy333 wrote:
On Mon, 08 Apr 2013 21:56:51 -0700, Gunner Asch wrote: On Tue, 09 Apr 2013 00:19:34 -0400, "Steve W." wrote: Gunner Asch wrote: On Mon, 08 Apr 2013 20:02:47 -0400, "Steve W." wrote: Richard wrote: On 4/8/2013 4:06 PM, Ed Huntress wrote: Snipped - just to show it's technically possible... Something is strange there. I'd have to dig out my ASM book to check, but 7075 has low corrosion resistance overall and is not recommended at all for marine environments (or salty sweat, one would assume). 6061 is somewhere in the middle. I wondered about that too. What's the story here? Current Mil spec is 7075 - T6 The original design called for either a 6 or 7 series alloy. The 6 was cheaper and easier to work with so that was what ended up being used. The problem is that between corrosion and thread deformation the spec was re-written to 7075 - T6 being the "correct" alloy to use. I have shot both and other than knowing the alloy due to the makers you couldn't tell any real difference. 6061 is still used by a few companies and with the design of the AR the strength in Civilian use isn't an issue. However if you plan on needing to depend on the rifle in real combat where you may be using it as a club, hammer or whatever, the 7075 has the edge with regard to wear and tear. I have used both forgings and solid billet as a starting point. With forgings you are limited as to what you can add/subtract. With billet you can have fun. I machined in a solid trigger guard, milled my logo in 3D on the side, and a few other tricks. Could you machine one out of a stainless steel block? Already been done. There are a few companies that already sell stainless lowers. I did one out of 416 just to see what it took. It will be the only one I ever do as well. It machined very well but even when I thinned areas down to reduce weight it's still pretty hefty. Does make the .308 a lot nicer to shoot though. I have been tossing around the idea of making one out of steel though. Thinking of areas like the sides of the mag well for skeletonizing... Anyone with a mid sized mill can handle the job. If you buy some guides you can even use a good drill press! Id not mind having a lower someday. Though given the prices of the upper Stuff..it would likely remain a door stop. ARs are quasi legal here in California..but they have to be neutered with a 10 rd mag and a bullet button etc etc Gunner Bullet button? Remove 333 to reply. Randy Kali semi-auto guns are supposed to have "fixed or not readily removable magazines" So the bullet button was born. Instead of the normal magazine release there is a small release button that requires the tip of a bullet or similar to depress. http://bulletbutton.com/ -- Steve W. |
Machining Question
Richard wrote:
On 4/8/2013 11:19 PM, Steve W. wrote: Could you machine one out of a stainless steel block? Already been done. There are a few companies that already sell stainless lowers. I did one out of 416 just to see what it took. It will be the only one I ever do as well. It machined very well but even when I thinned areas down to reduce weight it's still pretty hefty. Does make the .308 a lot nicer to shoot though. I have been tossing around the idea of making one out of steel though. Thinking of areas like the sides of the mag well for skeletonizing... Anyone with a mid sized mill can handle the job. If you buy some guides you can even use a good drill press! What does that do to the weight??? Adds about 8 oz. to the bare lower compared to a "normal" lower. -- Steve W. |
Machining Question
Pete C. wrote:
Cydrome Leader wrote: Pete C. wrote: Cydrome Leader wrote: Ed Huntress wrote: On Mon, 8 Apr 2013 17:14:22 +0000 (UTC), Cydrome Leader wrote: RogerN wrote: I'm close to milling my AR lower receiver, this "95%" machined receiver needs a pocket for the fire control group and 3 holes cross drilled for 2 pins and a selector/safety. I found some instructions for machining the pocket using a DRO, they recommend drilling the selector switch hole, machining the pocket then drilling the trigger & hammer pin holes. Why not drill all 3 cross holes in that 1 setup and then machining the pocket? I would think the drill bits might be more likely to walk as they start through the 2nd side. I don't see a benefit to set up for drilling, turn turn the part for milling, then turn back to the first setup to drill 2 more holes, any idea why they would do, or recommend this? https://colfaxtactical.com/docs/Fire...%20a%20DRO.pdf RogerN does anybody make plastic unfinished lowers, just for machining practice? It would seem like a shame, and expensive to be using trashed lowers for the next aluminum casting project. Real AR-15s and M-16s have 7075-grade uppers and lowers. You can't cast that with home hobby equipment. I've read that some of the aftermarket is using 6061 for lowers. But the people making those comments probably don't really know. Yield strength of 6061 is roughly half that of 7075. 6061 is a wrought grade, but it can be cast without doing anything special. I meant once you bungle a partially made lower, you're finished, and it's just expensive scrap metal, of a useless shape probably only good for tossing into the aluminum scrap pile for some backyard casting. It seems like a shame. It depends on exactly what you bungle, but most mistakes in the machining can be remedied/worked around to make a perfectly serviceable lower. On the 7075 vs. 6061 thing, operationally it won't make much difference since the AR receiver basically guides parts and have very very little stress placed on it due to the fact that the bolt locks into the barrel extension and no into any portion of the receiver. I believe the first M16s were 6061 and they only changed to 7075 due to corrosion issues in the 'Nam jungles. With the lower forgings running in the $25-$80 range depending on completion state, the financial risk isn't really much more than the financial risk of breaking an end mill or reamer in the machining. hmm, I've not stumbled across the $25 ones, but that would be worth it just for the practice. I haven't looked recently, but that's what 0% forgings were going for last I looked. The 30% TM ones I got for $45 in qty 5+, I think the broached magwell is worth the $20. One key thing is to have a lower parts kit when you start the machining so you can test fit many of the parts as you go before you tear down each setup. It's also helpful to have a regular factory AR for visual sanity check reference, but you can use good pictures as well. On the first one I did I grabbed the wrong drill and drilled the hammer and trigger pin holes oversized. After staring at it and scratching my head for a few minutes I re-drilled the holes a bit larger to give a reasonable size for a bushing, grabbed a piece of brass rod, threw it in the lathe and made a set of four bushings to bring the holes down to the correct size. I assembled the lower with a set of anti-rotation links to act as bushing retainers and all works perfectly, you can hardly even see the bushings under the AR links. nice save. Now it has "bearings". I was examing some sort of German rifle and pretty much any sliding parts had actual bearings, including the ends of torsion springs- they had little metal sleeves acting as rollers. They must have had lots of spare time to come up with all of that. |
Machining Question
Gunner Asch wrote:
On Tue, 09 Apr 2013 00:04:40 -0500, Richard wrote: On 4/8/2013 11:19 PM, Steve W. wrote: Could you machine one out of a stainless steel block? Already been done. There are a few companies that already sell stainless lowers. I did one out of 416 just to see what it took. It will be the only one I ever do as well. It machined very well but even when I thinned areas down to reduce weight it's still pretty hefty. Does make the .308 a lot nicer to shoot though. I have been tossing around the idea of making one out of steel though. Thinking of areas like the sides of the mag well for skeletonizing... Anyone with a mid sized mill can handle the job. If you buy some guides you can even use a good drill press! What does that do to the weight??? It would center it nicely..and by the time folks get done putting all the lasers, launchers and other sundry bull**** on them...shrug...a steel lower really wouldnt be noticed too much. I enjoy watching clowns with laser sights at the range. They are good if you have a spotter and are trying to tame flinch. |
Machining Question
Randy333 wrote:
On Mon, 8 Apr 2013 17:14:22 +0000 (UTC), Cydrome Leader wrote: RogerN wrote: I'm close to milling my AR lower receiver, this "95%" machined receiver needs a pocket for the fire control group and 3 holes cross drilled for 2 pins and a selector/safety. I found some instructions for machining the pocket using a DRO, they recommend drilling the selector switch hole, machining the pocket then drilling the trigger & hammer pin holes. Why not drill all 3 cross holes in that 1 setup and then machining the pocket? I would think the drill bits might be more likely to walk as they start through the 2nd side. I don't see a benefit to set up for drilling, turn turn the part for milling, then turn back to the first setup to drill 2 more holes, any idea why they would do, or recommend this? https://colfaxtactical.com/docs/Fire...%20a%20DRO.pdf RogerN does anybody make plastic unfinished lowers, just for machining practice? It would seem like a shame, and expensive to be using trashed lowers for the next aluminum casting project. Buy a 0% forging, make a mold from it using bondo (autobody filler) then make some machinable wax castings from that. Screw it up, just remelt the wax! Remove 333 to reply. Randy good idea. I make some hillarious measurement mistakes. For whatever reason, the various number of decimal places on measuring tools is what throws me off. |
Machining Question
"Ed Huntress" wrote in message
... On Mon, 8 Apr 2013 22:04:03 -0500, "Terry Coombs" wrote: "Ed Huntress" wrote in message . .. On Mon, 8 Apr 2013 19:24:51 +0000 (UTC), Cydrome Leader wrote: Ed Huntress wrote: On Mon, 8 Apr 2013 17:14:22 +0000 (UTC), Cydrome Leader wrote: RogerN wrote: I'm close to milling my AR lower receiver, this "95%" machined receiver needs a pocket for the fire control group and 3 holes cross drilled for 2 pins and a selector/safety. I found some instructions for machining the pocket using a DRO, they recommend drilling the selector switch hole, machining the pocket then drilling the trigger & hammer pin holes. Why not drill all 3 cross holes in that 1 setup and then machining the pocket? I would think the drill bits might be more likely to walk as they start through the 2nd side. I don't see a benefit to set up for drilling, turn turn the part for milling, then turn back to the first setup to drill 2 more holes, any idea why they would do, or recommend this? https://colfaxtactical.com/docs/Fire...%20a%20DRO.pdf RogerN does anybody make plastic unfinished lowers, just for machining practice? It would seem like a shame, and expensive to be using trashed lowers for the next aluminum casting project. Real AR-15s and M-16s have 7075-grade uppers and lowers. You can't cast that with home hobby equipment. I've read that some of the aftermarket is using 6061 for lowers. But the people making those comments probably don't really know. Yield strength of 6061 is roughly half that of 7075. 6061 is a wrought grade, but it can be cast without doing anything special. I meant once you bungle a partially made lower, you're finished, and it's just expensive scrap metal, of a useless shape probably only good for tossing into the aluminum scrap pile for some backyard casting. It seems like a shame. Well, it is a shame, but I wouldn't toss a high-zinc alloy, which also has around 1.5% copper, into a pile I was going to use for backyard aluminum casting. Zinc and copper will hake it hard to make a casting without internal shrinkage voids. -- Ed Huntress Neither would I . I'd toss it into the pile for ZA alloy casting . Ed , where did you acquire your knowledge about casting and alloys ? Some of the stuff you've posted is directly opposite what experience and hobbycasting yahoogroup has taught me . Mostly as Materials Editor at _American Machinist_. I had to study basic metallurgy for a couple of years to be able to handle the tech papers coming in from Alcoa, U.S. Steel, and so on. I'm hardly an expert but I know the sources. I'm very curious about what the hobbycasting group is saying that's directly opposite. Does it concern 7075? It's notorious for having lousy corrosion resistance. There are some 7xxxx alloys that are much better, but not 7075. As for copper in aluminum, it makes it extremely hot-short and prone to porosity. That's why welding 2024 is not recommended except by some specialized techniques. It cracks like crazy, and if it happens not to crack today, it may in a couple of weeks, as the HAZ age-hardens. Anyway, what is opposite? -- Ed Humtress Not that 7075 is corrosion-resistant , just that it can indeed be cast by a home shop foundry . I've cast a couple of pieces with no problem - in fact it casts nicely and machines well if you chill it in water straight out of the mold then let it age for a couple of weeks . 6061 is very gummy especially when freshly cast , and 356 is sweet to work with . As far as copper in aluminum , we try to avoid it . It does indeed cause problems , mostly in the machinibility of the items . A trace is no problem , but get too much in the melt and you'll find that it's nearly impossible to machine , even with carbide tooling . Some of the best bronzes are mostly copper with small amounts of al , ampco 45 for example my bike rides on swingarm bushings made of it ... and they too are difficult to machine . I'm not set up to weld aluminum , and cannot speak to the weldability of any of the alloys . When I need that knowledge I'll be looking for info ! -- Snag |
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