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Metalworking (rec.crafts.metalworking) Discuss various aspects of working with metal, such as machining, welding, metal joining, screwing, casting, hardening/tempering, blacksmithing/forging, spinning and hammer work, sheet metal work. |
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Roughing out 4" hole in .750 thick aluminum.
I have a task which requires boring four 4" holes in .750 plate aluminum,
with 10 plates in total to do. I have a boring head and / or flycutter, so the finish cut will be no problem, it is just going to be a real chore to rough them out I suppose. Short of using a jig saw (which I am not convinced would work too well) what would be the best way to approach this task? I would like to use the milling machine for the roughing, so that I can rough the hole, then finish bore in 2 steps. Would a trepanning tool be the best bet? If so, can someone suggest a particular model, keeping in mind this job is meanial, therefore tooling costs are a concern. Thanks in advance, RB |
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Roughing out 4" hole in .750 thick aluminum.
Good point...
Have 10x50 table vertical milling machine, do not have cnc, nor a rotary table. Will look into the holesaw type cutter, did not think they made one that big, RB Starrett makes holesaws to 6". Others probably do also. John Martin |
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Roughing out 4" hole in .750 thick aluminum.
I should have looked before inserting foot in mouth...
thanks, RB "JMartin957" wrote in message ... Good point... Have 10x50 table vertical milling machine, do not have cnc, nor a rotary table. Will look into the holesaw type cutter, did not think they made one that big, RB Starrett makes holesaws to 6". Others probably do also. John Martin |
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Roughing out 4" hole in .750 thick aluminum.
I find drilling small holes in the kerf really helps on the chip clearance
with holesaws in aluminium. If I had that mill, I'd be tempted to put a trepanning tool together and try that. Brian "Bob Swinney" wrote in message news:AVTXa.73038$YN5.55452@sccrnsc01... Ryan sez: "Will look into the holesaw type cutter, did not think they made one that big,.." They do, though. Not too long ago I cut a 4.5 inch hole in a piece of 3/4 inch mild steel plate. I'm not saying it was fast. The main thing is to keep the chips from accumulating in the kerf. Blow or brush them out frequently. Wear safety glasses if you blow - hi-velocity chips are just so much shrapnel. Bob Swinney "Ryan" wrote in message ... Good point... Have 10x50 table vertical milling machine, do not have cnc, nor a rotary table. RB "Torsten" wrote in message ... Depends on what tools you got. A cnc could just cut out the center. Manual machine maybe cut it out on a rotary table. Other option would be a holesaw type of cutter single or multyflute. A lot will depend on your machinery and tools. "Ryan" wrote in message ... I have a task which requires boring four 4" holes in .750 plate aluminum, with 10 plates in total to do. I have a boring head and / or flycutter, so the finish cut will be no problem, it is just going to be a real chore to rough them out I suppose. Short of using a jig saw (which I am not convinced would work too well) what would be the best way to approach this task? I would like to use the milling machine for the roughing, so that I can rough the hole, then finish bore in 2 steps. Would a trepanning tool be the best bet? If so, can someone suggest a particular model, keeping in mind this job is meanial, therefore tooling costs are a concern. Thanks in advance, RB |
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Roughing out 4" hole in .750 thick aluminum.
Brian wrote: I find drilling small holes in the kerf really helps on the chip clearance with holesaws in aluminium. If I had that mill, I'd be tempted to put a trepanning tool together and try that. I've never done one quite this big, but before I had CNC, I did set up to trepan out some 2.5" or so holes. At very low RPM, it cut long, stringy chips that were mostly pulled up out of the hole, so chip clearance was not a big problem. It went through on power feed rather quickly. I just ground a special tool to use in my boring head. Jon |
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Roughing out 4" hole in .750 thick aluminum.
Ryan
Roughing out 4" hole in .750 thick aluminum. I have a task which requires boring four 4" holes in .750 plate aluminum, with 10 plates in total to do How big are the plates? Bob AZ |
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Roughing out 4" hole in .750 thick aluminum.
In article , Ryan says...
I have a task which requires boring four 4" holes in .750 plate aluminum, Holesaw. Get the best bi-metal blade you can, mount it up in a bridgeport, and use WD-40 for the cutting fluid. Retract feed frequently to blow out chips. You can cut from both sides, just pick up the pilot hole from the first side. Jim ================================================== please reply to: JRR(zero) at yktvmv (dot) vnet (dot) ibm (dot) com ================================================== |
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Roughing out 4" hole in .750 thick aluminum.
"Ryan" wrote in message news:
Short of using a jig saw (which I am not convinced would work too well) I have done stuff like that with a drill and file, a pain. a jigsaw is fine on metal, though even on alluminium i use proper hacksaw blades, the things they sell for metal are overpriced and the few I have been given were crap - still Sandvik don't know how to make a hacksaw blade anyway;-). Yes i modified the jigsaw so i don't have to grind a bayonet on the blades. I chop out bit's for motor bikes with a jigsaw and 1/2" plate is no problem, i cut blanks like your on about and get circles within a 64th without any problem. The way I cut a hole like that is. Scribe the circle and drill some holes -equally spaced about the inside of the scrap bit- big enough to get the saw blade through, four or five holes will be enough. Criss cross the waste with the saw till some big bits fall out. Then cut almost to the circumferance[scribed line], cutting at an angle to the radius and keep making cuts like this all the way around the inside of the circle, cutting at an angle to the radius. The plate should look like a cross between a negative of a circular saw blade and an odd comb at this stage. Then repeat the above bit, cutting at the opposite angle to the radius, so the bits fall out and your left with a round hole with little bit's to file or bore out. It's very simple and with a jig saw you can get very close to a circle, or any other shape you want. the number of cut's you make 'at an angle' will determine how long it takes, go around the circle once making say eight cut's, this will get the big pieces out and then repeat with the cuts closer to get closer to a round hole. The only thing to watch out for is the foot of the jigsaw marring the surface, it isn't to bad if you make sure you don't get swarf under the foot. They cut much better at slowish speeds, don't push to hard the hss blade will chop through the cheapo rear blade support. cut dry, wet lubricant will just make a mess. When you want to make a straight cut try a woodworkers circular saw if you haven't used one on alli you will be suprized how good they are... -- richard |
#9
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Roughing out 4" hole in .750 thick aluminum.
You might try "treepanning" ( I think that is spelled right !)
just a thought, Ron "Michael" wrote in message .. . Ryan, i did an almost identical job, 10 pieces in 1" AL, except i was cutting an arc rather than a complete hole. As others have suggested, i used a hole saw in the mill at a low speed (not because of theoretical cutting speeds but because its a bit of a hairy cut to make). There was enough clearance in the saw to cut the 1" at one go (3.5" hole saw) Here's a caution for you....Most of the hole saw arbours I could find or were presented to me by tool store counter help do not hold the saw rigidly which it must be to use on the mill. Starrett's A17-12 does hold the saw rigidly, or make your own. I'm no hole saw expert, but i speculate that the most common app for hole saws is blasting through wood on a construction site, i guess ease of changing blades matters more than a little wobble. you'll get probably the worst finish ever created in your shop, so buy a smaller dia hole saw and finish up with a boring head. in my limited experience, these hole saws are not precision cutters, then again maybe i bought the wrong one. the set of the teeth seem incorrect leading to a lot of rubbing on the outside dia of the saw and the butt weld of the rolled portion is visibly out of alignment. its only going to be cutting on a few teeth so feed was determined by feel. oh well, that's what the boring head is for. hope it helps "Ryan" wrote in message ... I have a task which requires boring four 4" holes in .750 plate aluminum, with 10 plates in total to do. I have a boring head and / or flycutter, so the finish cut will be no problem, it is just going to be a real chore to rough them out I suppose. Short of using a jig saw (which I am not convinced would work too well) what would be the best way to approach this task? I would like to use the milling machine for the roughing, so that I can rough the hole, then finish bore in 2 steps. Would a trepanning tool be the best bet? If so, can someone suggest a particular model, keeping in mind this job is meanial, therefore tooling costs are a concern. Thanks in advance, RB |
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Roughing out 4" hole in .750 thick aluminum.
This is the best advice.
Use eye protection someone else said and is the only thing I can add. "jim rozen" wrote in message ... In article , Ryan says... I have a task which requires boring four 4" holes in .750 plate aluminum, Holesaw. Get the best bi-metal blade you can, mount it up in a bridgeport, and use WD-40 for the cutting fluid. Retract feed frequently to blow out chips. You can cut from both sides, just pick up the pilot hole from the first side. Jim ================================================== please reply to: JRR(zero) at yktvmv (dot) vnet (dot) ibm (dot) com ================================================== |
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Roughing out 4" hole in .750 thick aluminum.
You could have some gun nut friend let loose on it with his Browning.
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Roughing out 4" hole in .750 thick aluminum.
Jim sez: ..."and use WD-40 for the cutting fluid ..."
I respectively question the logic of using WD-40 as a cutting fluid. Why WD-40? Yeah, I know it is kerosene based but why not use just plain kerosene? I know kerosene is a recommended cutting fluid for aluminum. Or better yet, "Liquid Wrench", also kero-based - it comes in a spray can version also. Are you sure you aren't confusing the washing action (chip removal ?) of spray-can WD-40 with cutting fluid efficiency? Bob Swinney "jim rozen" wrote in message ... In article , Ryan says... I have a task which requires boring four 4" holes in .750 plate aluminum, Holesaw. Get the best bi-metal blade you can, mount it up in a bridgeport, Retract feed frequently to blow out chips. You can cut from both sides, just pick up the pilot hole from the first side. Jim ================================================== please reply to: JRR(zero) at yktvmv (dot) vnet (dot) ibm (dot) com ================================================== |
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Roughing out 4" hole in .750 thick aluminum.
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Roughing out 4" hole in .750 thick aluminum.
"Jon Elson" wrote in message ... William G Darby wrote: I also like the idea of trepanning! You could drill a hole at the center of the hole location and use a bolt through the hole into a Tee slot anchor with a threaded hole to receive it, in order to form a pivot for your plate to rotate on. (like a rotary table) Pick up the hole center and traverse your table two inches away from it (making allowance for the diameter of a slot cutter) Take great care not to let the plate get away on you. Also a bolt with a smooth shank would be best and cut to a length such that it bottoms out and locks up at the right depth. A bar clamped to the plate to provide better rotational control would provide additional safety. This sounds EXTREMELY dangerous! Yes it could be dangerous!!! But I would not use a big end mill and I would not try to hog into a 3/4" cut either. That would be asking for trouble. I would go with a 1/4 slot cutting EM and I would start with about an eighth inch depth and more if the set-up felt right****** OK I just got back from the mill. I cut a 4.25 " dia hole in a bit of scrap half inch plate and once I got the bugs out, it went along fairly smoothly. The first thing I will say is that this method is a lot of work and dangerous, but you do not need much equipment to get a big round hole or disc. I used: 1/2" drill 1/4" slot cutting EM at 5000 RPM one Tee slot nut one 3" piece of 1/2" threaded rod two 1/2" nuts one short heavy coil spring I anchored the threaded rod in the center of the bed in the Tee slot nut. Drilled a half inch hole where I wanted the center of the hole on the plate to be. Then placed the plate over the threaded rod followed by a washer, the spring another washer and two nuts locked against each other. Picked up the center of the threaded rod and did an X move of about 2.25 inches On my first attempt I had set the speed at 5000 but was getting only 1000 RPM. This had the effect of severely shaking the set up and unknown to me the threaded rod slacked off and allowed my center to move enough for me to notice it. On the next and final go I got the RPM up to speed and planted that threaded rod deep enough into the Tee slot nut sos it'll never come out. After that it was clear sailing there was very little rotational pressure on the plate, so it was not in the least difficult to control the rotation. At the same time I was fully aware that the rotation had to be controlled at all times least it be allowed to free wheel. (BAD) )^: So the method is doable, and yes it is dangerous but I at no time was the least bit concerned for my safety. Somewhat like operating anything else: most anything can tear your hands off if you do not know what you are doing or are inattentive. I am including a few pictures of the set-up to you Jon and anyone else that cares to see it. Bill Darby With a 3/4" plate, and a big end mill hogging into a 3/4" deep groove, I doubt you could hang onto it. Trepanning with a hand-carved single-point cutter in a boring head will be a LOT safer, and all you have to do is feed the quill. Jon |
#16
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Roughing out 4" hole in .750 thick aluminum.
Run the saw fast and use plenty of WD40. Peck, and blow out the chips every 1/8". Should take a minute a hole, tops, with a bimetal hole saw. Less time if you use one of those nice carbide hole saws. With aluminum, little need for the carbide unless you want it just for the larger gullets - which is an advantage. Just make sure you're talking carbide teeth and not carbide grit. Doubt that a carbide grit saw would get through a single hole in aluminum before it loaded up. John Martin |
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