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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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#1
Posted to rec.crafts.metalworking
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Grinding a round cutter?
I'm making a hand-held tarp grommet setting tool I can use on a
ladder, with dies that screw together. I can grind the shank end of a drill bit into a radius form tool and hold it tilted forward but it won't cut very deep before the shank rubs, although the resulting shallow ellipse is likely good enough for this job, I'll find out how well it flares, rolls and crimps the tubular rivet when the tool is complete. If it doesn't work I know a guy who can modify this kind of stuff until it does. Drill shank cutters work better on round pulley grooves for wire cable than for cuts into the flat end of the bar. Is there some simple geometric way to grind an accurately circular convex radius lathe bit that I may have missed? Concave radius forming bits are easy to shape with a tapered Dremel stone marked at the intended size. The taper provides clearance so the bit can be clamped flat to cut a true circular arc. A General drill bit grinding fixture might be the right sort of tool if it could clamp the lathe bit flat and was sufficiently rigid. I can't really justify the cost of a new punch grinding fixture and haven't found a used one. http://tool.wttool.com/tools/Punch%20Grinding%20Fixture --jsw |
#2
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Grinding a round cutter?
"Jim Wilkins" wrote in message
... I'm making a hand-held tarp grommet setting tool I can use on a ladder, with dies that screw together. I can grind the shank end of a drill bit into a radius form tool and hold it tilted forward but it won't cut very deep before the shank rubs, although the resulting shallow ellipse is likely good enough for this job, I'll find out how well it flares, rolls and crimps the tubular rivet when the tool is complete. If it doesn't work I know a guy who can modify this kind of stuff until it does. Drill shank cutters work better on round pulley grooves for wire cable than for cuts into the flat end of the bar. Is there some simple geometric way to grind an accurately circular convex radius lathe bit that I may have missed? Concave radius forming bits are easy to shape with a tapered Dremel stone marked at the intended size. The taper provides clearance so the bit can be clamped flat to cut a true circular arc. A General drill bit grinding fixture might be the right sort of tool if it could clamp the lathe bit flat and was sufficiently rigid. I can't really justify the cost of a new punch grinding fixture and haven't found a used one. http://tool.wttool.com/tools/Punch%20Grinding%20Fixture --jsw Lathe ball cutter mounted on a grinder? Past the pivot you get a convex tool, inside the pivot you get a concave tool. |
#3
Posted to rec.crafts.metalworking
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Grinding a round cutter?
"Bob La Londe" wrote in message
... "Jim Wilkins" wrote in message ... I'm making a hand-held tarp grommet setting tool I can use on a ladder, with dies that screw together. I can grind the shank end of a drill bit into a radius form tool and hold it tilted forward but it won't cut very deep before the shank rubs, although the resulting shallow ellipse is likely good enough for this job, I'll find out how well it flares, rolls and crimps the tubular rivet when the tool is complete. If it doesn't work I know a guy who can modify this kind of stuff until it does. Drill shank cutters work better on round pulley grooves for wire cable than for cuts into the flat end of the bar. Is there some simple geometric way to grind an accurately circular convex radius lathe bit that I may have missed? Concave radius forming bits are easy to shape with a tapered Dremel stone marked at the intended size. The taper provides clearance so the bit can be clamped flat to cut a true circular arc. A General drill bit grinding fixture might be the right sort of tool if it could clamp the lathe bit flat and was sufficiently rigid. I can't really justify the cost of a new punch grinding fixture and haven't found a used one. http://tool.wttool.com/tools/Punch%20Grinding%20Fixture --jsw Lathe ball cutter mounted on a grinder? Past the pivot you get a convex tool, inside the pivot you get a concave tool. I saw a Holdridge cutter at a school shop auction, with several other bidders standing around it and drooling. IIRC it went for over $600. I suppose I could make a base for a lathe compound, which wouldn't be nearly as hard to wash clean after the grinding as the whole lathe. On my South Bend the center of the tool post slot can travel from about 1/4" beyond the compound's center of rotation (between the 90 degree marks) to slightly less than 1.5" back from it. I'd have to mill a custom tool post block to position the end of the bit anywhere near the pivot. For similar effort I could make a bit holder for a 5C spin index and also grind angles on threading bits. The grommet set worked on the first try so I don't need to modify the roll crimp guide. A 1970's brass grommet rolled up perfectly, new import ones from HD cracked and spread flat but remained tight in the tarp after a two man tug-of-war. --jsw |
#4
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Grinding a round cutter?
"Jim Wilkins" fired this volley in news:nlmtao$igv$1
@dont-email.me: I saw a Holdridge cutter at a school shop auction, with several other bidders standing around it and drooling. It's a gorgeous tool, and does precisely (and well) what it was designed to do... turn radii. I owned the 9" lathe version for about 15 years; bought it for only ONE project, and it paid for itself in one project. But, I ended up using it almost never after that. Finally sold it for about $600 about three years ago. But BOY, I sure did PAY more than that for it, new! urk! Lloyd |
#5
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Grinding a round cutter?
On Thu, 07 Jul 2016 20:50:25 -0400, Jim Wilkins wrote:
The grommet set worked on the first try so I don't need to modify the roll crimp guide. A 1970's brass grommet rolled up perfectly, new import ones from HD cracked and spread flat but remained tight in the tarp after a two man tug-of-war. Are the import ones brass? If so anneal them and see how they fold. |
#6
Posted to rec.crafts.metalworking
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Grinding a round cutter?
"Unk" wrote in message
... On Thu, 07 Jul 2016 20:50:25 -0400, Jim Wilkins wrote: The grommet set worked on the first try so I don't need to modify the roll crimp guide. A 1970's brass grommet rolled up perfectly, new import ones from HD cracked and spread flat but remained tight in the tarp after a two man tug-of-war. Are the import ones brass? If so anneal them and see how they fold. Yep, my plan is to buy some more, place their heads in shallow water and anneal only the tubes with a propane torch. My small stock of the good old ones that roll up smoothly won't be wasted on outdoor tarps. I cut the roll-up groove with a round 5/32" HSS boring bar bit blank. The squared-off drill bit shank which isn't as hard as the fluted end stayed sharp long enough to cut the washer side recess in the W1 tool steel blank but I had to carve the deeper rivet side with the 5/32" bit. I tried to copy the cast iron punch and die that came in the old kit. Drill bit ends held up well enough to cut aluminum pulley grooves to fit the rope and cable. Had they been a common fractional size I could have milled the semicircular groove with the side of an end mill. I used a half-round convex lathe bit hand-ground to visually match the right sized hole in a drill bit gauge to groove a steel spring winding mandrel. The resulting groove looks round but I wouldn't trust it as a ball bearing race. --jsw |
#7
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Grinding a round cutter?
On Fri, 8 Jul 2016 09:29:58 +0000 (UTC), Unk wrote:
On Thu, 07 Jul 2016 20:50:25 -0400, Jim Wilkins wrote: The grommet set worked on the first try so I don't need to modify the roll crimp guide. A 1970's brass grommet rolled up perfectly, new import ones from HD cracked and spread flat but remained tight in the tarp after a two man tug-of-war. Are the import ones brass? If so anneal them and see how they fold. A whole lot of the imports are brass-plated FEmutt. My lovely set from HFT is such, but they work fair to middlin'. -- "Government is not reason; it is not eloquent; it is force. Like fire, it is a dangerous servant and a fearful master." --George Washington |
#8
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Grinding a round cutter?
Jim Wilkins wrote:
I saw a Holdridge cutter at a school shop auction Schools hold auctions? That's good to know, I never knew that. I hear that many schools have 3-D printers, now. |
#9
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Grinding a round cutter?
wrote in message
... Jim Wilkins wrote: I saw a Holdridge cutter at a school shop auction Schools hold auctions? That's good to know, I never knew that. I hear that many schools have 3-D printers, now. It was a going-out-of-business sale, since manual skills are irrelevant in our brave new post-industrial society. --jsw |
#10
Posted to rec.crafts.metalworking
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Grinding a round cutter?
On Fri, 8 Jul 2016 15:08:59 -0400, "Jim Wilkins"
wrote: wrote in message ... Jim Wilkins wrote: I saw a Holdridge cutter at a school shop auction Schools hold auctions? That's good to know, I never knew that. I hear that many schools have 3-D printers, now. It was a going-out-of-business sale, since manual skills are irrelevant in our brave new post-industrial society. --jsw A school nearby did that around 25 years ago. They auctioned off three 9" SBs that looked like they had been used as horseshoeing anvils. -- Ed Huntress |
#11
Posted to rec.crafts.metalworking
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Grinding a round cutter?
On 08/07/16 20:20, Ed Huntress wrote:
On Fri, 8 Jul 2016 15:08:59 -0400, "Jim Wilkins" wrote: wrote in message ... Jim Wilkins wrote: I saw a Holdridge cutter at a school shop auction Schools hold auctions? That's good to know, I never knew that. I hear that many schools have 3-D printers, now. It was a going-out-of-business sale, since manual skills are irrelevant in our brave new post-industrial society. --jsw A school nearby did that around 25 years ago. They auctioned off three 9" SBs that looked like they had been used as horseshoeing anvils. I see ex school stuff come up in the UK at various places like ebay and condition seems to depend on what it is, CNC stuff seems to have seen little use and often the use is on easy stuff like plastic so the machines are in very good order. As you say though the "ex school" on manual machines may sound like they have seen little use but in reality they have been used and abused by trainees and suffered beyond their years as a result. I remember in Wichita votec the first year evening class was used to prove you could use the machines, mainly knackered Rockwell Lathes and BP mills and only after that did you pass on to the other workshop with the nice machines. Regarding machine usage at the end of my first year doing a mechanical engineering degree we had to do some practical skills of various sorts such as machining and some electrical and electronics. I had been doing machining since about the age of 12 - 13 in junior high and so had covered it all before but discussed threading with one of the lecturers and he mentioned a guy a year or 2 before who hadn't been paying attention and set the machine for manual threading at over 1000 rpm and engaged the halfnuts and bang crash, IIRC he said it scrapped the lathe, the guy was in shock and got sent home to recover for the rest of the day. I guess far more happens to manual machines that just chew them up a bit rather than scrap them but many ex school lathes seems to have been in the wars. |
#12
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Grinding a round cutter?
"Unk" wrote in message
... On Thu, 07 Jul 2016 20:50:25 -0400, Jim Wilkins wrote: The grommet set worked on the first try so I don't need to modify the roll crimp guide. A 1970's brass grommet rolled up perfectly, new import ones from HD cracked and spread flat but remained tight in the tarp after a two man tug-of-war. Are the import ones brass? If so anneal them and see how they fold. Annealing the tube helps a lot. |
#13
Posted to rec.crafts.metalworking
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Grinding a round cutter?
On Fri, 8 Jul 2016 15:08:59 -0400, "Jim Wilkins"
wrote: wrote in message ... Jim Wilkins wrote: I saw a Holdridge cutter at a school shop auction Schools hold auctions? That's good to know, I never knew that. I hear that many schools have 3-D printers, now. It was a going-out-of-business sale, since manual skills are irrelevant in our brave new post-industrial society. After we're all gone, they'll realize just how badly they need us; when it's too late. -- "Government is not reason; it is not eloquent; it is force. Like fire, it is a dangerous servant and a fearful master." --George Washington |
#14
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Grinding a round cutter?
On Fri, 8 Jul 2016 10:40:38 -0700 (PDT), wrote:
Jim Wilkins wrote: I saw a Holdridge cutter at a school shop auction Schools hold auctions? That's good to know, I never knew that. I hear that many schools have 3-D printers, now. Blink....blink...most..most...most schools hold auctions, or have an outside company come in and hold auctions. http://www.tlcauctions.com/ --- This email has been checked for viruses by Avast antivirus software. https://www.avast.com/antivirus |
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