I think I shouldn't try to adjust anything in my lathe for now ...

[wquiles]

I have been debating checking the pre-load on my PM1236 lathe now that it has been in service for about 18 months or so, but I think that based on what I found today, I am just going to leave it alone for now. And checking the lathe was not my goal today - that was just an accidental result of the work today ...

This all started when I was making heatsinks for the "D" body. Sometimes I make them, sometimes I buy them, but today I wanted to make several of them for use in projects.

I started with a bar of 6061 Al, 1 and 3/8" dia, and the part sticking out of the chuck is close to 9 inches, so I used my Royal live center to keep things steady:

I then cleaned up the OD with my PCD insert and Accu-Lube, spindle speed of about 900 rpm, by hand (no auto feed):

I then proceeded to leave the "lip" in the heatsink, and turn down the body section to close to 1.347" OD. I did a deep cut in between each one to delineate each one. I used the same tool, and did all of them (8 of them) one right after the other, and used the DRO to stop at the same OD for each part:

I then cut them all up in the metal band saw (commercially available heatsink on top for illustration purposes):

Since I have a lip with a slightly larger OD, it is hard to hold in the chuck, so I took a small section of a D mag (I wonder where I can find some scrap pieces .......) and I slightly turned the ID to allow a press fit of these new heatsinks, so that I could then clamp on the "ring" and grab the heatsink inside the ring without having to worry about the chuck damaging the finish. Kind of a poor mans custom collet:

I then press fit each of the heatsinks to clean/true the bottom side - the "collet" worked perfectly:

The thing was that all 8 heatsinks fit pretty well in the "collet" ring, so I though that the OD was probably very close, even though I turned the piece over 9 inches:

So I figured that although I did not try to test the accuracy of the lathe on purpose, this was as a good time as any to check things out. So out came the micrometer ...

And after testing all of them, I found a variation of only 0.00080 over the 9" or so:

So unless I hear otherwise from you guys the real experts (Barry?), I am leaving my lathe as is for now, and will keep using it without worrying about needing to adjust something.

Will


PS
For those wondering, this is the ID of the collet:

And yes, I missed the target OD by about 1 mil too large - I will have to lightly sand those to fit , although of course that is always better (and easier) than adding metal back

 

[gadget_lover]

Re: I think I am leaving my lathe alone for now ...

Thank goodness that your lathe is working so well.

I thought at first that you had taken sick. Broken bones, illness, some strange disease.

Leaving it alone. yeah, Right.

Daniel

 

[wquiles]

Re: I think I am leaving my lathe alone for now ...

Thank goodness that your lathe is working so well.

I thought at first that you had taken sick. Broken bones, illness, some strange disease.

Leaving it alone. yeah, Right.

Daniel

Daniel,

My most sincere apologies. Yes, all is well, and thank God I am healthy. And yes, I "will" keep working on the lathe/projects/etc..

But everything else being the same, I probably should change the tittle to something that would have a less negative meaning

Will

 

[ninemm]

Re: I think I am leaving my lathe alone for now ...

Ditto. I was not looking forward to reading this thread. Worried about a horror story. Glad to know you're not leaving your lathe alone due to injury.

 

[wquiles]

Tittle changed. Sorry about that guys

 

[ninemm]

Tittle changed. Sorry about that guys

No worries! Those parts turned out nicely. I wonder if I'll ever be able to work a lathe one day. Seems pretty complex for someone who is not naturally good at math/numbers.

 

[precisionworks]

So unless I hear otherwise from you guys

If it isn't broken, don't fix it :thumbsup:

FWIW, I would have made those parts just a little differently ... extend only enough past the jaws to make one part at a time, which eliminates the need for tailstock support. The problem with a long rod, even with tailstock support, is the deflection of those parts in the middle of the rod. A follower rest would eliminate that, but most followers would mark the soft aluminum.

Once the correct tool setting is found for the OD you want, turn one sink, part, extend the bar (without moving the tool location) turn & part again, etc. If you watch a CNC lathe with a bar puller, that's exactly how they make a part like this.

 

[KC2IXE]

If it isn't broken, don't fix it :thumbsup:

...snip...

Once the correct tool setting is found for the OD you want, turn one sink, part, extend the bar (without moving the tool location) turn & part again, etc. If you watch a CNC lathe with a bar puller, that's exactly how they make a part like this.

+1 and more

What is real interesting is to watch someone using a turret lathe that knows what they are doing for bar work. Picture "manual CNC without curves" - some wild tools made over the years. Setup can be a royal pain, which is part of why CNC rules for a lot of stuff - that said, for real long runs, turret lathes and/or screw machines can be amazing

 

[wquiles]

If it isn't broken, don't fix it :thumbsup:

FWIW, I would have made those parts just a little differently ... extend only enough past the jaws to make one part at a time, which eliminates the need for tailstock support. The problem with a long rod, even with tailstock support, is the deflection of those parts in the middle of the rod. A follower rest would eliminate that, but most followers would mark the soft aluminum.

Once the correct tool setting is found for the OD you want, turn one sink, part, extend the bar (without moving the tool location) turn & part again, etc. If you watch a CNC lathe with a bar puller, that's exactly how they make a part like this.

Thank you - good idea. I will definitely try this method next time :thumbsup: