Some questions about my lathe

BigAppleRanch · Mar 5, 2020

Hey y’all! I recently picked up a (1912?) prentice brothers 14” lathe. I’ve been slowly working on making it more user friendly. I just recently replaced the lantern style tool post with a QCTP, and I’ve slowly been picking up some tooling here and there. Today, my boss asked me to turn something down for him and I agreed. I had played around with the lathe off and on since I acquired it, but this was the first time I had dimensions, and tolerances to deal with. I ran into a few issues that I’m a little confused about.

- no matter what I did, adjusting tool angles, speeds, bite size etc... I couldn’t get the chips to break. The whole time I only got long razor sharp ribbons of steel. What can I do to try to fix that?

-depending on the pass, it was either smooth with a beautiful finish, or it was noisy, with a terrible finish. I wouldn’t do anything different from one pass to the other, and for some reason it would just start chattering and produce a terrible cut

- my cross slide seems to have a ton of backlash in it. There is an indicator dial on the crank, but it moves 4-8 hash marks (thou) before the sled moves. Is there anything I can to to tighten this up?

I was turning mild steel with a carbide brazed rh turning tool. The tool was one from a kit I got on amazon. Very cheap.

crossthread · Mar 5, 2020

Unless you have an insert or a tool bit with a chip breaker profile, what you are seeing is normal. Your second issue with poor finish could be a lot of things. The heel of the tool could be dragging if your bit is too high. You could have a chip sticking to the bit if you aren't using the right or enough lube. If it were me, I would ditch the cheap brazed bits. Get some HSS blanks and grind them so they work for you. A little more back rake and a change in the radius might very well help. You may have a lot of slop in your cross feed. Lathes with conventional crossfeed screws and nuts often if not always have some slop. Learn to back off on the crossfeed and take up the play in the in feed direction only.

janvanruth · Mar 5, 2020

BigAppleRanch said:
Hey y’all! I recently picked up a (1912?) prentice brothers 14” lathe. I’ve been slowly working on making it more user friendly. I just recently replaced the lantern style tool post with a QCTP, and I’ve slowly been picking up some tooling here and there. Today, my boss asked me to turn something down for him and I agreed. I had played around with the lathe off and on since I acquired it, but this was the first time I had dimensions, and tolerances to deal with. I ran into a few issues that I’m a little confused about.

- no matter what I did, adjusting tool angles, speeds, bite size etc... I couldn’t get the chips to break. The whole time I only got long razor sharp ribbons of steel. What can I do to try to fix that?

-depending on the pass, it was either smooth with a beautiful finish, or it was noisy, with a terrible finish. I wouldn’t do anything different from one pass to the other, and for some reason it would just start chattering and produce a terrible cut

- my cross slide seems to have a ton of backlash in it. There is an indicator dial on the crank, but it moves 4-8 hash marks (thou) before the sled moves. Is there anything I can to to tighten this up?

I was turning mild steel with a carbide brazed rh turning tool. The tool was one from a kit I got on amazon. Very cheap.

did you try to use the tolls straight out of the box?
better start with hss

dalmatiangirl61 · Mar 5, 2020

BigAppleRanch said:
- my cross slide seems to have a ton of backlash in it. There is an indicator dial on the crank, but it moves 4-8 hash marks (thou) before the sled moves. Is there anything I can to to tighten this up?

The slop in the cross slide is normal, for a machine of that age, its actually pretty good, I've seen far worse. As stated above, always take the slack out. Get some HSS blanks and grind your own, and if you need to know how the book "How to run a lathe" will show you, and teach you just about anything else you need to know to get started.

MilGunsmith · Mar 5, 2020

When you grind the HSS tools, you can use a dremel to grind a chipbreaker in just past the cutting edge. If possible, avoid backing off on the crossfeed between cuts, that way the slop is taken up at the beginning of cutting and dosent reappear. Also get in the habit of pulling on the toolpost after each adjustment to ensure that there is no slop.

johnoder · Mar 5, 2020

mild steel with a carbide brazed rh turning tool

You need to study up on tool geometry (why a cutting tool works). With store bought crap used-as-is you may as well try to get a finish with a stick of key stock

Ever look in such as this?

http://vintagemachinery.org/pubs/1617/5795.pdf

ph

BigAppleRanch · Mar 6, 2020

Thanks for the link to that book! I’ll be sure to read it. This is all great information!! Thank you guys!

rons · Mar 6, 2020

BigAppleRanch said:
-depending on the pass, it was either smooth with a beautiful finish, or it was noisy, with a terrible finish. I wouldn’t do anything different from one pass to the other, and for some reason it would just start chattering and produce a terrible cut

I was turning mild steel with a carbide brazed rh turning tool. The tool was one from a kit I got on amazon. Very cheap.

What is your depth of cut?

I use those types of bits. If the carbide chips I grind the edges of the tip and reuse the bit, many times until only a small chunk of
carbide is left. I have as set of tool holders that take inserts but often the carbide brazed bits are there for the roughing out work.

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Some questions about my lathe

BigAppleRanch

Plastic

crossthread

Titanium

janvanruth

Titanium

dalmatiangirl61

Diamond

MilGunsmith

Stainless

johnoder

Diamond

BigAppleRanch

Plastic

rons

Diamond

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