Yeah older machines really get the tapers banged up. Especially when the tools you're putting in and out might weigh 20 pounds. We used to regrind the tapers on the big mills every 3-4 years. Those were MT6 and MT7. NMTB50 seems to take a lot less of a beating as long as it's kept clean.
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Originally posted by Bented View PostMany 50 old machines have clapped out spindle bores as well, the radial drill pictured above has a difficult time holding a tool against gravity (-:
Oyeah,, hand raised high.
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Normally at work we use brazed tools for everything as there is only a few of the cheap, harbor freight style triangular inserted tools there. Well I was cutting on some 6061, and no matter what I tried I could not make a nice chip using that tool without a chip breaker. Then one big nasty chip snagged my dial indicator and drug it in to the chuck, breaking it. I finally resorted to one of the dull triangular tools and that broke a chip nicely. I should be getting me a nice MWLNR with some iscar IC907 TF inserts soon, which I adore.
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Originally posted by reggie_obe View Post
Well that sucks, hope it wasn't one of your best.
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I've already dulled off a brazed carbide tip on a P-type parting blade. Did some googling to refine my setup. It seems that the parting blade would randomly "dig in" and either stall or snap. It takes the edge off the tip, now I need some diamond tooling to resharpen... No real reason that I could see, but I had the carriage locked. I moved the toolpost over towards the center of the compound. And I "locked" the compound itself by tightening the gib screws. So far, its going a bit better. Thank goodness those blades were double ended. Mat'l is bog-standard A-36 structural, 2" dia. Running in back gears at 80 RPM. The part is 6" long, fully in the 4-jaw, and using the live center on the outboard end.
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I've always been under the impression that supporting the outboard end when parting off was a "no-no", since the parted off piece can then bind the tool rather than come off. Yes? No?"A machinist's (WHAP!) best friend (WHAP! WHAP!) is his hammer. (WHAP!)" - Fred Tanner, foreman, Lunenburg Foundry and Engineering machine shop, circa 1979
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Originally posted by The Metal Butcher View PostSupport it until you are about through.
EDIT to add: my favorite blade is 3/32x1/2" x 4" long, the holder puts it at the proper angle. The cutting tip is on dead center. I changed the lathe over to power cross-feed and tried various feeds -- ended up using the slowest. But it still cuts pretty good. ALSO I keep my hand on the clutch knob now. I can "feel" when the blade is trying to dig, and the machine is laboring. And I can back off the clutch for a bit.. Reminding myself that is is a clutch, not an on-off switch.Last edited by nickel-city-fab; 02-18-2021, 11:29 AM.
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That is an issue with those lighter lathes.
Nicole, try this if you don't mind: move your toolpost as far right as it will go and angle and back the compound out to where a vertical line coming down from the blade is within the cross-slide ways, and preferably near center. Might help.
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Originally posted by The Metal Butcher View PostThat is an issue with those lighter lathes.
Nicole, try this if you don't mind: move your toolpost as far right as it will go and angle and back the compound out to where a vertical line coming down from the blade is within the cross-slide ways, and preferably near center. Might help.
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Originally posted by nickel-city-fab View Post
Thanks, I will try that. I already have the tool post moved, but I have not tried changing the angle on my compound. Being lazy, I normally leave it at 30 deg. Will report back after I try again. So that the blade tip has iron and not air under it, right?
30° is fine if you can back it up enough to get the blade inside. Turning it 90 you now have the narrower width vs the length, so there is something to be said against that as well. Like all things, it's a balance.
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Originally posted by Bented View PostIf the part has a bore and is short in length you may place a plug past the finished bore held with a center into the rough hole and part off multiple pieces without loading them in Z.
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