Lathe: high feed vs large depth

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Batmanacw

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I'm noticing a trend with my Mulliner Enlund lathe. It seems she doesn't like high depth cuts but higher feed rates seem fine. It doesn't like 0.1" per side on a small diameter but she runs beautifully at 0.010" feed. I know 0.010" per rev isn't crazy high but I'm used to 0.005" on my smaller lathe.

What is a normal feed rate for these mid size lathes?

I'm not trying to take 0.015" per rev like we used to on the big lathes back at the tool and die shop. I just want to get an idea of what you guys run.

TPG322 insert as of right now.
 
I’m usually between 0.005 and 0.010. I’ve found 4140 does not like the lower feed rate and needs to be higher with the inserts I have one hand. I’m mostly CCMT/GT and TCMT/GT in a finishing chip breaker. I haven’t used my TPG inserts much lately since getting the CCMT since that can do facing and turning in the same toolholder.
 
Just to give closure to this thread, I discovered my t nut for the quick change toolpost was too high. It's much more rigid now. The cut quality is really nice with a bit of light oil. I'm stuck with 417 rpm for now.

I'm still very interested in feed vs cut depth. I've always defaulted to lighter feeds, but with my two bigger lathes, I'm going to start going with the recommended feeds for roughing cuts. I've got an app for feeds and speeds.
 
Batmanacw said:
Just to give closure to this thread, I discovered my t nut for the quick change toolpost was too high. It's much more rigid now. The cut quality is really nice with a bit of light oil. I'm stuck with 417 rpm for now.

I'm still very interested in feed vs cut depth. I've always defaulted to lighter feeds, but with my two bigger lathes, I'm going to start going with the recommended feeds for roughing cuts. I've got an app for feeds and speeds.
Click to expand...
Without going too far down the rabbithole, you need to understand that the diameter of your part matters as much as the other two parameters.


.010 per rev at 1" diameter is wholly different than .010 per rev at 4" diameter as the latter will be removing ~8X the material.
 
RaisedByWolves said:
Without going too far down the rabbithole, you need to understand that the diameter of your part matters as much as the other two parameters.


.010 per rev at 1" diameter is wholly different than .010 per rev at 4" diameter as the latter will be removing ~8X the material.
Click to expand...
Whaaasaaaaaaaaaa? No way! :grin:
 
Both my hobby bench top lathes, prefer lower depth of cut at higher feed rates. But since I use a bit heavier lathe, I tend to do heavier cuts also on the mini lathe.

If you take a deeper cut at a lower feed rate, the Feed/Rev will be less and than could result in a better finish. Also the longer and smaller chip tends to break easier. For the tool life it "doesn't matter". Twice the depth at half the feed rate is the "same" wear and processing time.

Once you cut deeper than the tool nose radius, any deeper cuts won't increase the radial tool load so part bending is maxed out. That makes turning to a tight dimension easier if your lathe can handle the load and the part has a decent finish.

The parts can handle more axial load than radial load (it is a pillar). The drawback is that higher axial loads require higher clamping forces that could leave marks on your part.

Thin parts require a very modest depth of cut or they bend.

My priority is getting the dimension right, a good finish and last making chips. That means that I often have to "sacrifice" tool life on my hobby lathes.
 
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