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9" SM Utilathe Restoration

Things are not going very well at all...…… Geepers, I'm only trying to part off 1/4" wall 1 3/4" pipe here.

BrokenBlade.JPG


This is what's left after breaking the blade 3 times now. I don't think I have managed to make a single pass with out some disaster happening.

SoClose.JPG


Things seem to be going really well and then BANG. On my last attempt the blade broke, the tool post was spun and the work piece dislodged itself from the chuck:eek:

Strange.JPG


This is really strange..... look at that finger of metal that appears to have peeled into the center. It' a good 1/16" thick. There was 1/16" to go to part off.

One thing I have notice now is the power of the machine. When things were going sideways on my mini it would stall, indicating it was time to sort the problem out. This machine just keeps turning until something fails. With NO warning to boot.
 
Did it go bang just as the tool was coming through to the the inside wall? Is that what you mean by finger of metal?
 
PeterT said:
Did it go bang just as the tool was coming through to the the inside wall? Is that what you mean by finger of metal?
Click to expand...

No where near breaking thru the ID. The tool slot is .139 and the ID is .124. That finger of metal measures 0.062 thick.

FINGER.JPG
 
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YYCHobbyMachinist said:
Things are not going very well at all...…… Geepers, I'm only trying to part off 1/4" wall 1 3/4" pipe here.

View attachment 6527

This is what's left after breaking the blade 3 times now. I don't think I have managed to make a single pass with out some disaster happening.

View attachment 6528

Things seem to be going really well and then BANG. On my last attempt the blade broke, the tool post was spun and the work piece dislodged itself from the chuck:eek:

View attachment 6529

This is really strange..... look at that finger of metal that appears to have peeled into the center. It' a good 1/16" thick. There was 1/16" to go to part off.

One thing I have notice now is the power of the machine. When things were going sideways on my mini it would stall, indicating it was time to sort the problem out. This machine just keeps turning until something fails. With NO warning to boot.
Click to expand...
I had no idea this was going to cause you this much grief. I’m sorry this isn’t as simple as I thought it was going to be for you
 
Chicken lights said:
I had no idea this was going to cause you this much grief. I’m sorry this isn’t as simple as I thought it was going to be for you
Click to expand...

No worries. It's all part of the learning process. New machine, new stuff to sort out. I hope the shims I cut on the band saw and PHS work for you, they ain't pretty.

Craig

P.S. Wait until you start turning...… You'll find out. There's more to it than meets the eye. But it's fun, fun, fun.
 
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I don't quite understand your dimensions. What is the annular (wall) thickness you have to part through (for example 0.250) and how much depth of cut did you get in before problem? Like half way = 0.100 or 3/4 way like 0.200, or close to the bore ID like 0.245. Whats the .062" measurement, does it coincide with your blade thickness for example?

Is the green arrow showing breakthrough of the tool into the ID or you just happen to lay a chip there?

What I'm getting at is, if you are 'nearly' through the annular thickness (red line depiction) and the blade is just starting to peek through in one area of the ID, then its plausible that this is the snatch & grab point. Thic could be because the ID is slightly irregular but a big culprit could be if you have backlash
 

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Just eyeballing, but this looks pretty close to your full wall thickness no?
Again, is green arrow pointing to breakthrough of parting slot to ID?
 

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Sorry, I slipped a digit here. The ID is 1.25 and I had parted to 1.39. So had 0.07 to go before break thru. I've noticed there is a lot of backlash on my cross slide. Gibs need adjustment?
 
PeterT said:
Just eyeballing, but this looks pretty close to your full wall thickness no?
Again, is green arrow pointing to breakthrough of parting slot to ID?
Click to expand...

Yes, but like 0.0625 too soon, and the piece peeled back looks just that peeled. I don't get it? So the pipe ID might not be concentric with the OD? To add to the confusion, I had mounted the pipe on the chuck using the ID as the gripping surface.
 
YYCHobbyMachinist said:
Sorry, I slipped a digit here. The ID is 1.25 and I had parted to 1.39. So had 0.07 to go before break thru. I've noticed there is a lot of backlash on my cross slide. Gibs need adjustment?
Click to expand...
I'm not an expert but I think that backlash is likely the problem. I think that the cutter is grabbing into the work and pulling the cross-slide forward--that's why the cutter broke through into the interior. However, that depth of cut is too much...so something has to give.

How much back rake do you have on the parting tools? Less back rake should mean the tool won't be as likely to self-feed. Does the tool holder hold the blade level or does the blade cant up to the work? If the latter, you probably don't need to grind any back rake into the tool.

Are you SURE you're on centre? You should be able to do a facing cut (say on aluminum) and not leave any nub.

How much wear is there in your cross-slide screw and nut? On my lathe, the cross-slide (and compound) feed nuts are made from brass and are intended to be replaced when worn. My screw has a bit of wear too but replacing the nut reduced the backlash to around a third of the original. Then with the gibs adding a bit of drag, it usually behaves.

Craig
 
Yikes.... I pulled the cross slide off to have a look at the screw and nut.

CROSSSLIDESCREW.JPG


The nut is pretty darn loose and the screw doesn't even look like an acme thread in the middle. Pretty much shot I'm thinking.

Why would that screw wear like that on a brass nut?
 
The brass or bronze nut picks up “dust” particles and acts as a lap.
That looks a lot like my Southbend xslide screw. Replacement screw sections and nut used to be on eBay but I can’t find any right now. For the Southbend the old screw had to be cut off and a new section spliced in.
 
If those are the originals,, change them out with the ones you got from the old lathe. During my Lathe reconstruction making a new cross slide nut and compound nut took almost 0.050" of play out of the lathe and makes a world of difference in performance
 
Brent H said:
If those are the originals,, change them out with the ones you got from the old lathe. During my Lathe reconstruction making a new cross slide nut and compound nut took almost 0.050" of play out of the lathe and makes a world of difference in performance
Click to expand...

Ya, the imaged depicts the screw that was delivered with my machine. I installed the screw and nut you sent me from the parts machine and WOW 210% better. I can't feel any lash in the cross slide now. Good call on your part for sending it to me, I didn't think I needed it. THANKS!!!
 
I have bought Acme thread ready rod at a Bolt Supply House in Red Deer so I'm sure you can find some in Cowtown. the nuts are available as well but they are steel (can probably be jury-rigged to work as well) Your brass might hopfully be in good enough shape to re-use with a new chunk of ready rod tho.
 
Looks like you got fixed up while I was typing. is your brass cut crossways thru the threads? the one on my lathe is and there is a set screw that pulls the threads together a smidge so that a small bit of backlash can be adjusted out of it.
 
Good work Craig!
That will help a lot. Make sure now that your parting tool is adjusted spot on centre or just a hair high as buddy in the video suggests to keep the tool from pulling in.

is your cross feed screw 8 tpi x 9/16 left hand? I think it was ?
 
One word of caution when parting, and I forgot to mention it at the outset. your tool should be set about .001 or a 'little' more ABOVE the centre line. This is exactly the same problem as the 29.5 degree angle for threading - it is insurance. If you are at the centre line or below, the tool will pull into the work - no matter how good your screw is. you want the tool to always be pushed away from the work.

I went from having no success at all at parting to clean, quiet parting with just this one change.

[edit - we posted at the same time!]
 
Dabbler was bang on when he said give the whole top end a good push pull to see what's what in terms of movement. I had no idea the slide was that loose.

Cross feed nut is not split, so no means of adjustment.

Cross feed screw appears to be 10 tpi LH 0.497"
 
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