Lathelopnik: Feeling things out

"MM54" (mm54mk2) 07/07/2020 at 21:30 • Filed to: Lathelopnik

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It’s been years since I ran any sort of machine tool so I’ve been spending a little time both knocking the dust off my very-limited abilities and feeling out what my new-to-me lathe can do.

The usual surface finish disclaimer applies, blah blah blah (and yes it’s hanging out of the chuck like a diving board... for experimentation I couldn’t be bothered to get the live center out

One thing it can do is a 0.050" depth of cut in random steel (at a very slow feedrate, but still) with a less-than-stellar tool (the grinding of which is one of those things I need to work on...). It isn’t exactly happy to do it , but at the same time it doesn’t seem exceedingly strained to do a much more aggressive cut than I’d typically consider which is a good sign. A good cutting oil probably would help.

PyroHoltz f@h Oppo 261120 > MM54 07/07/2020 at 21:51

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Don’t forget to brush up on your YT TOT.

I liked this one:

MM54 > PyroHoltz f@h Oppo 261120 07/07/2020 at 22:24

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I should watch more of his stuff, seems quite agreeable

sn4cktimes > MM54 07/07/2020 at 23:15

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Replace as much of your HSS tooling with carbides as you can. You’ll make bigger passes with better surface finish. The live centre would also help finish quality and the dimensions quite a lot.

I wish I had a bench top lathe at home. I used the one at my job all the time. That and the mill. It wasn’t the best mill. Awful to dial in, and the z axis was garbage. But those problems could be worked around in a pinch. If you went REALLY slow you could pull about +/- 0.0002” accuracy.

415s30 W123TSXWaggoIIIIIIo ( •_•))°) > MM54 07/07/2020 at 23:28

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The lathe is one of the most important inventions in all human kind, without it we wouldn’t have much today.

BaconSandwich is tasty. > MM54 07/08/2020 at 00:10

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His stuff is hilarious.  It’s the little touches - like the hidden “subscribe” in almost every video.

MM54 > sn4cktimes 07/08/2020 at 16:04

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Indexable carbides would be nice but until I have a particular use for them I don’t feel much need to spend the money when I have a handful of HSS blanks and a grinder :) I have a live center but in the above I wasn’t going for a quality, just curious how it would handle a notably aggressive cut.

And hey - a lousy mill is way better than no mill!

MM54 > 415s30 W123TSXWaggoIIIIIIo ( •_•))°) 07/08/2020 at 16:21

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I’ve seen that thumbnail dozens of times but it’s so vague (what’s a “1751 machine” and why should I care?) and bordering on clickbait by the name I’d not watched it. Very interesting!

sn4cktimes > MM54 07/08/2020 at 18:04

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50 mil is a pretty good depth with HSS tooling. Were you u sing coolant or just dry? Some juice might help. If you were using a power feed maybe turn the IPM rate down a bit to compensate for lack of turning torque / speed.

I know on my lathe tests I hogged up to 0.250" a pass with a carbide (with coolant. It’s not needed, but it keeps the part cool for dimensional accuracy of measurements, and time was a factor ) and then did my final passes with proper rotational speed but the SLOWEST feed rate the lathe would give me. Surfaces were so shiny. Then hit em with a Scotch Brite pad to get them gleaming.

That’s about as far as my lathe knowledge gets me. Good luck, I’ve always found getting a good grind VERY tricky. But I did see some very interesting “ things” in the machine-shop that the actual machinists came up with. Quite a few were for brass though.

And yeah, shitty mill always > no mill!

MM54 > sn4cktimes 07/08/2020 at 18:21

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I gave it a drop of wd40 since there was some handy, otherwise it was fairly dry (I think it all burned off). There’s only one slower power feed on here, which is only .0005/rev slower. This is more than I’d actually ask of it to make a part, but it’s good to know it’s (about) the limit.

.250 in one pass is crazy, that’s moving some material! Pretty sure this machine would have stalled out by .100" in steel.

Thanks!

sn4cktimes > MM54 07/09/2020 at 02:24

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250 was 50 more than we were “supposed” to take in a pass. But we only had 2 hours to make a rather complex pump-shaft and we got graded via vernier micrometers in the 0.0001” range. For every +/- .0002” off you lost a point out of ten for every graded dimension. Maybe a little ridiculous for a Millwright... but whatever. R ipping it down FAST left more time to get tight tolerances.

I actually got the best mark in class on that one. Including someone who was also a 1st year M achinist apprentice. I was pretty stoked. The instructors commented on my use of coolant At the time as it made a colossal mess. But they later noted it kept the dimensioning accurate. Most of the guys didn’t account for thermal contraction. So while they made the part and it was smoking hot they were bang on. Then it cooled before getting marked and shrank up.

Not sure how “ splashy” it’d be, but maybe you could set up a little coolant pump from an aquarium pump or something small and cheap. It would extend tool life and prevent galling from the heat.