leeko
Stainless
- Joined
- Jun 30, 2012
- Location
- Chicago, USA
Hi all,
I'm looking for some advice on troubleshooting my lathe's accuracy. I had noticed that the lathe fairly consistently cuts less than what I dial in on the crossfeed, and had just assumed that the dial was not correct for the lathe. But, last night I put a dial indicator on the crossfeed and found it corresponded to the dial, but not the actual cut.
- The lathe is a lodge and Shipley 16" selective head
- I've tried with both hss and insert carbide, held in a QCTP. The cutters are on centre height
- the lathe was levelled a couple of months ago
- gibs are reasonably tight
- The current workpiece is a piece of 2" stainless, with <2" stickout from the 3-jaw chuck. No tailstock support.
- The turning cut goes well and leaves a nice finish
There is a slight taper in the part OD dimension, usually <0.001". I attribute this to the loose rear bearing (out of shims, needs new insert shells). I'm not too worried about the taper.
What is weird, though, is that the lathe consistently takes off less metal than is dialed in. For example, I dialed in 50 thousandths per side (100 thou off the diameter), and verified it with the dial indicator. I made the cut, and the resulting part OD was 1.906".
I made a smaller cut, 0.012", and it took off 0.010".
Any suggestions for what might be going on? I had initially thought maybe something on the compound or tool holder might be slipping under the pressure of the cut, but then I would expect more variation along the OD of the part. Similarly, if the spindle was being allowed to push away from the cutter because of the loose rear bearing, wouldn't that also create a taper?
Any suggestions are greatly appreciated. Thanks in advance,
Lee
Sent from my SM-N920T using Tapatalk
I'm looking for some advice on troubleshooting my lathe's accuracy. I had noticed that the lathe fairly consistently cuts less than what I dial in on the crossfeed, and had just assumed that the dial was not correct for the lathe. But, last night I put a dial indicator on the crossfeed and found it corresponded to the dial, but not the actual cut.
- The lathe is a lodge and Shipley 16" selective head
- I've tried with both hss and insert carbide, held in a QCTP. The cutters are on centre height
- the lathe was levelled a couple of months ago
- gibs are reasonably tight
- The current workpiece is a piece of 2" stainless, with <2" stickout from the 3-jaw chuck. No tailstock support.
- The turning cut goes well and leaves a nice finish
There is a slight taper in the part OD dimension, usually <0.001". I attribute this to the loose rear bearing (out of shims, needs new insert shells). I'm not too worried about the taper.
What is weird, though, is that the lathe consistently takes off less metal than is dialed in. For example, I dialed in 50 thousandths per side (100 thou off the diameter), and verified it with the dial indicator. I made the cut, and the resulting part OD was 1.906".
I made a smaller cut, 0.012", and it took off 0.010".
Any suggestions for what might be going on? I had initially thought maybe something on the compound or tool holder might be slipping under the pressure of the cut, but then I would expect more variation along the OD of the part. Similarly, if the spindle was being allowed to push away from the cutter because of the loose rear bearing, wouldn't that also create a taper?
Any suggestions are greatly appreciated. Thanks in advance,
Lee
Sent from my SM-N920T using Tapatalk