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Old 04-13-2005, 11:11 PM   #46
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Ditto on which bit I got. One is simply carved/shaped and the other has a blackish plate mounted to the lower side. The blackish plate is chipped badly so I fingered it was bad but I don't know if I could reshape it or wut?
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Old 04-18-2005, 10:15 AM   #47
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**BUMP**
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Old 04-18-2005, 12:14 PM   #48
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Being a machinist for 15 years, most of what I am reading here has nothing to do with whether the bit is sharp or dull. Lathes with dull bits will produce a nice finish if your feedrate, depth of cut, and rpms are correct. That's saying if the bit is dull, not chipped. I use high speed steel blanks and drill and tap for a circle brand carbide insert with Ticn coating and a .007 rad. It is a triangle shaped insert, so I get three sides to work with, the blank never leaves the lathe, just the insert when it is used up, and I can say that one insert should last about six months if used properly, then I just grab another insert (3.00) and start again. Copper is very soft, and requires feather light cuts with the right rpms to produce a good finish. Never ever back the bit accross the com after you have made the final cut.
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Old 04-18-2005, 03:48 PM   #49
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dude,a dull bit on copper will burnish the surface and create a pitting effect.there is more to it than just speed and feed.i am also a machinist of 16 years.cutting .001 per pass you need a razor sharp bit with a real small tool nose radius.carbide inserts would work if you have a small enough tool nose radius.you really cant compare to what we do in the shop because comm lathes do not brace the armature well.i attempted using a mini tool holder with a very small insert and it didnt do the job very well.smallest radius i could find was .007.plus the cost of carbide inserts makes it not worth it.i get much more life out of a cemented carbide.
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Old 04-18-2005, 04:06 PM   #50
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how can I visual tell if my diamond bit on my lathe needs to be resharpened?

cheerz
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Old 04-18-2005, 05:54 PM   #51
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I have found that my lathe cuts much nicer when I only use 2-2.5 volts from the Pulsar. At aroudn 4 like a 4 cell pack, its not as nice.

I think this is probably better for carbide than diamond because it creates a larger chip, which takes away the heat, instead of just friction. You would be surprised to know how much friction is happening at higher RPM at the feed rate we use on these lathes. Its a fairly slow feed rate, so its not making a chip, therefore its not cutting.

I get a BEUTIFUL finish at 2-2.5 volts taking off .0005 per cut using a pace of aboukt 2-3 seconds to feed the entire length of comm.
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Old 04-18-2005, 05:54 PM   #52
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you can look at it with a jewelers eye loop.you should be able to see if there are any chips in the cutting surface.
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Old 04-18-2005, 06:36 PM   #53
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Quote:
Originally posted by protc3
dude,a dull bit on copper will burnish the surface and create a pitting effect.there is more to it than just speed and feed.i am also a machinist of 16 years.cutting .001 per pass you need a razor sharp bit with a real small tool nose radius.carbide inserts would work if you have a small enough tool nose radius.you really cant compare to what we do in the shop because comm lathes do not brace the armature well.i attempted using a mini tool holder with a very small insert and it didnt do the job very well.smallest radius i could find was .007.plus the cost of carbide inserts makes it not worth it.i get much more life out of a cemented carbide.
I would agree you can burnish copper very easy, but you can also make a good cut as well, I never have any problems at the track or at work. In any regrads I guess it will be up to the individual as to how well they can turn a comm.
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