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It's all new to me. Todays adventures in Facing, turning, and parting. I'd love some input?

Noltez

Noltez

Member
Grab your coffee or beer and have a seat, and listen to the story of a rookie gettin' his feet wet.

I finally had free time to start making actual chips with this old lathe (SB 10K). I'd scratched out a few things with some scraps but it was time to learn how to work it. My QCTP was fitted. I've bought a half dozen tool holders. And now I had some CR bar stock (1.5") in 6" lengths to learn on. Chucked one up in the 3 jaw, set middle gear, and faced off the cut. Having 6" sticking out was a little unnerving but there was no drama. Swap end-to-end and face the other side, then unwrap the brand new HSS center drills for setting up the tail stock support. Neat! Now I've got my bar supported.

Up next was actually turning. This lathe has power feeds and a gearbox, and I'm getting a feel for what does what. Tried a many different settings on the gearbox, each at a few different depths of cut. I found a few settings that will cut cleanly between 20 and 30 deep. I previously chucked up a piece of 3/8 scrap rod I had and even played with threading. Although I don't have the right tool bit for it, it was satisfying to see the lathe cut a screw thread. Not a useable one, but until now I've only seen this on the youtubes!

Lastly today I tried parting, and was not what I'd call completely successful. I wanted to part it in the middle. I'd set the lathe on the slowest belt speed plus back gears engaged to turn the 1½" material. I have a new (Amazon) HSS 3/32" x ½" parting blade in an Accusize AXA tool holder. I'd properly aligned it with centerline with a dead center in the chuck, and it lines up with the tailstock live center too. Some light oil and... nothing. It just rode up against the stock. Pushed harder, and it just wouldn't cut. The tool angle is pre-set by the tool holder. I'm definitely on centerline. I'm applying oil. Very weird. The oil is parting like Moses is going for a walk. Watched the Blondiehacks video again, I decided to cut my own angle with my bench grinder. Quinn touts the Tee-shaped carbide tools. I put a slight concave to the underside, and slightly relieve the sides to barely a trapezoidal shape. I also tried 3-in-1 instead of light machine oil. This works much better and starts rolling chips off. I got about a ½" in and it starts chattering. I tighten the gibbs, check I'm sharp, make sure my tool post is square and snug. More chattering, and then it binds. Belt comes off, bit is slightly damaged. Refit & sharpen, a few more rolls and it binds again. And again, and again. Each time the belt is thrown. I walked away. Went for a long hike. I came back to try again. Last straw was when I bound & knocked the stock out of it's live center support. As learned as the cut gets deeper I have to speed up the rotate to keep the surface speed appropriate. VFD folks; I am envious! Also noticed the far side of my cross slide (carriage?) is slightly lifting off the ways when I'm cutting. Adjust those gibbs too. Now the compound mount lock screws aren't strong enough to keep the unit from rotating when I'm tightening the tool post top nut. Tighten those further than I liked. We're okay now.

I finally got down to the last 1/4" and the tool went under the stock. Everything jammed, lost the belt again (10+ times now). Backed off the tail stock, opened the chuck, and the part is jammed onto the parting blade. Used a flat blade driver to wedge it open. No idea how. Rechuck the part but now the 3" section being parted is not inline. I used a soft face mallot to try to center it, but in the end I just grabbed it and worked it until she broke free. I now have two 3" chunks of metal. On the up side; I faced off the left overs with no issues. So I've got that going for me, which is nice. But oh my... what a day.

Questions from today;
What kind of cutting oils are you using for parting, or in general? I was just using light machine oil, then 3-in-1 (which actually worked well at first).
Should I try and find a thinner kerf parting tool? A Tee-shaped profile one? Carbide tipped?
Is it worth paying to have a riser block made to eliminate the compound? I don't need it while I'm learning.
Anyone fit an X-axis DRO to a South Bend 10k?

I would love to hear any practical tips on making this easier. I expect to use HR and CR steel quite a bit. I feel like it shouldn't have been so
 
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You mention that the width of the parting tool might be a problem... what is the width you are using?

I use sulfated cutting oil diluted with lighter, cheaper oil. T profiles wedge profiles or flat profiles, they all work fine.

The SB lathe is failrly light (or do you have a 'heavy 10?) so you cannot cut aggressively. Parting on a light lathe takes time.

My 12" lathe is pretty light too. I used to have a lot of problems parting until I made a height standard. If you are as little as .003 high, or .006 low, you will experience a lot of problems on a light lathe. I now set my height .002 below centre, and a lot of my problems went away. Despite what a lot of guys believe, using a centre to set the height is a crap shoot. If you have a really heavy or rigid lathe it works fine. When you are just starting out, even the ruler method to get your tool height works better.

If you have a mill it is pretty easy to make a riser block.

Get a some aluminum and practice on that first, and develop your technique. parting cold rolled is harder to work with because of all the internal stress in it. as you cut, the stress is released, and it moves, sometimes with unfavourable outcomes.

Lastly the relief angle should be about 7 degrees. the smaller the relief angle, the more pressure you need to cut the metal. on a small lathe it makes a noticeable difference...

So start slow, and go slower as you get closer to the end of the cut.
 
I recognize some of those issues:
1. Don't be afraid to increase the rpm. I know the conventional wisdom is back gear and slow but on my King1022 I now spin at anywhere from 300 rpm (for mystery steel) to 1500 and up for aluminum. This is using a 2mm carbide grooving/cutoff insert. For HSS cutoff I go less rpm but still higher than conventional. My experience with parting off improved considerably when I took the advice to go a bit faster on rpm, and keep feeding in. A bit nerve wracking at first but the tool needs some pressure to keep it in the cut.

2. Cutter going under the work, I would suspect that your spindle bearings are not tight enough. OTOH you are parting between centres which will never work. Generally loose spindle bearings are also a root cause of chatter.

3. I have never parted off between centres, it doesn't seem like a way to success. Once the part gets too small diameter it will bend and pop out. If I need to part something in the middle as you are trying I use my horizontal bandsaw and then chuck the part to clean up the face.

To quote Smith from Advanced Machine Work (1919): Tool is used close to chuck jaws, no more than 1 diameter from chuck lest it catch and break.

(If you contact TOBARApprentice, he has some very good texts available on machining, written by local Niagara region shop teachers). Derek is not too distant from you.

Gerrit
 
Also don't be afraid to get rid of the compound, you need it only for cutting shortish tapers. For threading it is not needed unless you are into deep threads. In EU this is the norm, feed straight in. This table gives you the depth of cut and # of passes for threading this way:

1625227802305.webp


Gerrit
 
Lots of good suggestions in previous posts but I'll just add a little. Parting is a very demanding operation on a smaller lathe. Even mrpete222 on Youtube often hacksaws a part rather than using a parting tool. Just saying.

Successful parting needs everything tight and square. Cross-slide gibs, compound gibs, headstock bearings, etc. Adjusting all these things will also pay dividends in other operations due to reduced chatter and whatnot so it really is worth doing.

Also need a sharp, properly ground tool. Can you take some detailed pictures of your HSS blade? Did you hone the cutting surfaces?

Re binding and diving, your chuck might be part of the problem if the jaws are even slightly bell-mouthed or the chuck is just worn out. Is it an older chuck? Again, detailed pictures of the jaws might help. If you chuck up stock and can slip a 1-thou feeler under the outboard edge of any of the jaws, that's bell-mouth.

I've attached an old magazine article that I found somewhere. It provides a good summary of overcoming common parting problems. It helped me.

Craig
 

Attachments

You shouldn’t use the tailstock when parting off. With the short lengths yore working with you really don’t need the tailstock anyway. With 1.5” stock you can have up to 9” stickout from the chuck with no support.
The deeper the cut the more tendency for the sides of the tool to bind. The stock and tool is heating up and expanding in the kerf. For deeper cuts I often back off and cut the kerf wider. The last little bit is where you get the most tendency to ride up on the tool. It’s way easier if there is a hole down the center. Parting off pipe is a breeze.

I read somewhere that one of the problems with parting is too slow of speed and that you should just run normal speeds. That seems to work for me. It seems to be easier to get a steady cut going than at slower speeds. It takes a bit of practice to get a feel for when it’s time to back up and clear all the chips. Doesn’t always work but that’s where slipping belts can save you.

My SB 9A may be marginally stiffer than your 10K but not by much.

Happy parting
John
 
Years ago I worked with an old school machinist that was a machinist in the days before carbide tooling.
I was telling him about the problems I had parting wit my 10K South-Bend lathe.
He took my parting blade and heated it with a mapp gas torch and then peened the cutting edge
so it was wider than the rest of the blade then ground it so it had a slight radius on both sides
of the cutting edge. It worked way better and I have used it for years only sharpening it with a diamond file.

He told me never heat high speed steel with an acetylene torch as it carbonizes it making it brittle.
I also learned that high speed steel does not loose its hardness unless its heated white hot.

parting.jpg
 
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Johnwa said:
You shouldn’t use the tailstock when parting off. With the short lengths yore working with you really don’t need the tailstock anyway. With 1.5” stock you can have up to 9” stickout from the chuck with no support.
...
Happy parting
John
Click to expand...

It didn't look 'right', and I know this is a forming job so you want to really support it. I certainly bit off too much lol.

YYCHM said:
You're not the only one that finds parting off to be a challenge....
https://canadianhobbymetalworkers.com/threads/9-sm-utilathe-restoration.1671/page-4#post-17579
It was an on going challenge to me until I stopped using the headstock/tailstock centers for tool height reference and started using the metal ruler method. I don't have a QCTP yet, but making a dedicated parting tool post helped.

Craig
Click to expand...

I'll look into this. I raised and lowered the tool on my QCTP several times and eventually, after sharpening it on a coarse stone wheel started to get a good roll coming off it. Trial and error got me 90% of the way though.

terry_g said:
...so it was wider than the rest of the blade then ground it so it had a slight radius on both sides
of the cutting edge. It worked way better and I have used it for years only sharpening it with a diamond file.
...
Click to expand...

Yep! I used my grinder to mimic that shape. I mentioned Quinn (Blondiehacks) prefers the Tee shaped parting tools and has tips for aligning them. I used the side of the stone to cut a relief under and to both sides of the parting edge. It's not pretty, but it was working. Curious what oil you're using?
 
Don’t hesitate to use the band saw. Cut it, chuck it back up and reface the end. Parting off became a lot easier when I upgraded to a 1300 lb lathe.
 
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When I was having problems parting, I'd use the parting tool to remove .100, and then use the groove as a guide to bandsaw the rest off, and reface it later...
 
I for one would like to hear the pros and cons of using parting tool blades with inserts in comparison to your standard HSS blades.

Secondly there must be a better light oil than way oil or WD40 more specifically with name brand, perhaps you are one who mixes your own concoction so lets hear what that might be.
 
I bought a gallon of sulfated cutting oil years ago and use it 50/50 diluted with 30W detergent oil. The dilution is partly to save money. The other reason is to thin it to use in a pump oiler.
 
Dabbler said:
I bought a gallon of sulfated cutting oil years ago and use it 50/50 diluted with 30W detergent oil. The dilution is partly to save money. The other reason is to thin it to use in a pump oiler.
Click to expand...

Hey Dabbler although I haven't tried it my thinking is somewhat the same although I want to stay away from strong odors in our attached garage/shop because the supervisor complains loudly. Nose like a hawk. LOL

So here's an idea I have in mind, using mineral oil which you can purchase at any drug store as the the basic carrier then mix that with a 20 weight non detergent oil although I'm unsure of amounts ie: 2 or 3 parts 20w to 1 part mineral oil. Baby oil should also work but then it's perfumed. Mineral oil is just a non-odor liquid paraffin, should work. What say you to this, any suggestions as to mix ratio?
 
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Tool geometry is generally better with inserted parting blades vs HSS ones.

The tool holder for the insert is skinnier than the insert itself - less chance of it binding in the kerf as the cut progresses deeper and things heat up and expand - closing the kerf and thus having a tendency to pinch the blade shank. Also, the insert is relieved backwards from the cutting edge. The red arrows are not parallel (yes, the insert has the front left corner chipped and is u/s).
E8FCD31D-1A87-422C-BBA7-94DF01543F96.jpeg


There is no kerf relief on an HSS blade - unless you grind one in it. Blades have a tendency to pinch unless you use a kerf widening strategy (as has been described above, I believe). The two arrows are parallel.
760EA745-FD40-40CE-8CE6-CFD86950B06D.jpeg


For cutting fluid I have had good success with the water soluble stuff from PA. I use it straight on all drilling and cutting ops on all types of metals.

https://www.princessauto.com/en/cutting-oil-coolant/product/PA0008034012
 
Dusty said:
So here an idea I have in mind
Click to expand...

There's a reason that sulfated oil is used as the base. It lubricates under extreme pressure, which is very good for cutting steel.

For brass I use wd40 with 10% sulfated oil and aluminum100% WD40. For stainless I use 100% sulfated, and brush it on.

Use as little as possible and draw the smoke out using an exhaust fan. My garage is detached, so I get a pass.
 
Dabbler said:
There's a reason that sulfated oil is used as the base. It lubricates under extreme pressure, which is very good for cutting steel.

For brass I use wd40 with 10% sulfated oil and aluminum100% WD40. For stainless I use 100% sulfated, and brush it on.

Use as little as possible and draw the smoke out using an exhaust fan. My garage is detached, so I get a pass.
Click to expand...

SMOKE: Lordy no then our fire alarm will go off and I'll be in deep ka ka. I'm not the only one conscious of order issues just think of all the members running basement shops. Happy wife happy life.
 
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