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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
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Machining 0.250 inch square hole?
On Jul 18, 6:27 pm, "David Anderson"
wrote: Any ideas how to machine a 0.250 x 0.250 inch square hole in 1/4 thick low-carbon steel (only two required). Tolerance minus zero plus 0.002. Begin with a drilled hole. I have a die filer also a small shaper but a good set up seems unlikely. Maybe a home-made broach? Thanks for any ideas. Dave I've often thought about making up a toolholder for my shaper that would allow mounting a bit in line with the ram movement axis. You could use, say, a 3/16" square bit and feed it into the corners. For a hole that small in mild steel, though, you can probably get away with drilling the corners, then drilling out the center, and then forcing through a 1/4" tool bit with a press or with a hammer. Grind the tool bit straight across and sharp, or even better with a bit of back rake. Might have to back up the workpiece to keep from blowing out the edges. I've also considered chucking a tool bit into a spin index and then using my surface/T&C grinder to grind the end of a tool bit to round, and extend the round back along three corners - thus making a broach which would cut one corner at a time and thus be a lot easier to drive. Then one with two corners for the second pass, etc. For a tool bit of only 1/4" I'm not sure it would be necessary. John Martin |
#2
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Machining 0.250 inch square hole?
John Martin wrote:
I've often thought about making up a toolholder for my shaper that would allow mounting a bit in line with the ram movement axis. Â*You could use, say, a 3/16" square bit and feed it into the corners. Something like this: http://www.motor-manufaktur.de/werkstatt/10_keyways/en_index.html And yes, you could quite easily get the 0.05mm tolerance. Nick |
#3
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Machining 0.250 inch square hole?
On Jul 19, 2:29 pm, Nick Mueller wrote:
John Martin wrote: I've often thought about making up a toolholder for my shaper that would allow mounting a bit in line with the ram movement axis. You could use, say, a 3/16" square bit and feed it into the corners. Something like this: http://www.motor-manufaktur.de/werkstatt/10_keyways/en_index.html And yes, you could quite easily get the 0.05mm tolerance. Nick Nice job. I thought of making a holder to replace the lantern toolpost and take a HSS tool bit at 90 degrees, and not worry about any relief. For longer cuts, though, I can see that having the 5 degrees clearance makes a lot of sense. John Martin |
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