What did you screw up today?

[eKretz]

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.

[I make chips]

Many 50 old machines have clapped out spindle bores as well, the radial drill pictured above has a difficult time holding a tool against gravity (-:

All that have used a big brass hammer to whack the hell out of a mt6 taper drill bit in a spindle raise their hand. I worked a summer job in the high school years where the newest machine was from about 1940. Oldest was 1914 ish. Everything was clapped out junk.
Oyeah,, hand raised high.

[The Metal Butcher]

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.

[reggie_obe]

Then one big nasty chip snagged my dial indicator and drug it in to the chuck, breaking it..

Well that sucks, hope it wasn't one of your best.

[The Metal Butcher]

Well that sucks, hope it wasn't one of your best.

$25 Shars for a reason. Some days I gotta live up to my name ya know.

[nickel-city-fab]

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.

[mickeyf]

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?

[The Metal Butcher]

Support it until you are about through.

[nickel-city-fab]

Support it until you are about through.

Yep, that is what I have been doing. Cut till there's about 1/4" left, then finish the job with the hacksaw. I still need to double check how much play is in my setup though, I've never really checked the machine thoroughly. Will spend the afternoon with an indicator to find out where the greatest movement is.

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.

[The Metal Butcher]

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.

[nickel-city-fab]

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.

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?

[The Metal Butcher]

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?

Bingo. I find that even a slight amount of lean allows the blade to catch and pop under. It certainly helps on pur little Rockwell. I used to have tremendous issues, now not so much. I'm better at sharpening tools though now. It helps a lot of the Sidney due to looseness, it won't part straight otherwise. Mass>tightness IMO.

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.

[Bented]

If 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.

[nickel-city-fab]

If 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.

Cool idea, thanks! It will have a bore eventually but I wanted to part off and rough it out first. Making it into a cats-head spindle chuck, threads directly onto my spindle. Will have enough bar left over to make an ER collet chuck that also threads directly on.

[Bented]

Works well.
If making only one part you can make the plug fit the finished bore and part right into it, the plug is one use only then tossed.