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Need Help surfacing stainless steel nuts

G

GabrielMB

Plastic
Joined
Jan 17, 2022
Hello everyone,
First, please excuse my lack of experience, i have only very recently bought my first mini lathe so I may very much be overlooking something very simple or making a beginner mistake.
I am a novice ring maker and i have recently bought a lathe in order to speed up to process of doing it with a disc sander.
However, when i try surfacing the nuts, i get a terrible surface finish and a lot of vibration.
I realize the surface of a nut is hexagonal so irregular, but even as that surface is removed with very shallow passes, the nut vibrates like crazy and the lathe motor shuts off very regularly. I am using tungsten cutters with carbide inserts which i make sure to keep cool.
If anyone has any tips on surfacing irregular surfaces and can offer any tips, they would be greatly appreciated.
Thank you.
 
It is possible that a mini lathe may not have the strength to resist cutting forces needed to penetrate the martial.

Possible the mass/weight of a small lathe will not resist the vibration that comes from motors, pulleys and moving mass.

Possibly your cutting tools of bits and inserts are not sharp enough or have the proper geometry (shape).

Interrupted cuts like rounding a hex nut are difficult with any machine and more difficult with a small or lightweight machine.

Often tungsten cutters with carbide inserts ate not super sharer edged so may need more machine strength and RPM to cut effectively.

Converting a manufactured something like a nut may be more difficult and more expensive than just buying the material in a simple form like round stock... or altered round stock, like round stock sent to a manufacturing shop to be drilled.

And the work hardening factor.
 
Your OP couldn't be more vague.
How much of a cut are you trying to take?
What cutter (exact make and model) are you using?
What is the exact material.
 
I am trying to remove the hexagonal shape from the nut (about 1.5 mm cut) and then remove around 2 mm of material. The nuts are 18-8 stainless steel and the cutters are SWGCR04-2 with WCMT2.52 TiN coated carbide.
Thank you.
 
GabrielMB said:
I am trying to remove the hexagonal shape from the nut (about 1.5 mm cut) and then remove around 2 mm of material. The nuts are 18-8 stainless steel and the cutters are SWGCR04-2 with WCMT2.52 TiN coated carbide.
Thank you.
Click to expand...

Post a few pix of your set-up
 
You're using a (very) low power and stiffness lathe, which is the opposite of what you'd like for machining stainless steel. Adding to that, your low-grade carbide tooling just makes things worse.

I think you'll have to accept cutting at very small depths of cut, and maybe using a cobalt (not just high speed steel) ground tool bit, held as close to the tool holder on the carriage of the lathe as possible. This means you'll need a bench grinder and some Youtube study time on grinding lathe cutting tools to get decent results.

Be careful, mind your fingers and eyes - a better lathe is always available, new digits and eyeballs not so...
 
I used a tiny grizzly lathe to turn a bunch of 1/2" stainless nuts and cap screws down to a uniform diameter (including facing the nuts and shoulder so they fit tighter). I used the carbide inserts it came with and had to rotate one every 20 parts or so.

Low speed, low depth of cut, low feed. The power went out while I was working and I finished the part by rotating the chuck by hand.
 
Thank you Milland for your response,
Any recommendations when it comes to cobalt cutters (% cobalt, brand, etc)?
 
Interrupted cuts are difficult and need a better class of lathe than you have. Have you considered St.St. tubing which can be had in different wall thickness. art.
 
GabrielMB said:
Thank you Milland for your response,
Any recommendations when it comes to cobalt cutters (% cobalt, brand, etc)?
Click to expand...

I'd go to Ebay and look for used cobalt lathe bits. That would get you an assortment of cheap "ready to use" (maybe not) bits that would give you an idea of how to grind your own (follow the existing patterns).

Type "used cobalt lathe bits" into Ebay search to see if anything looks promising.

It would be wise to get a decent bench grinder, you'll use it for a lot of shop tasks. Make sure to get quality wheels in aluminum oxide. Others here can give better recommendations on those, but maybe a 60 grit rough and 120 grit fine would be a start.

Don't overheat the lathe bits when grinding them, cool them frequently to preserve their hardness (although cobalt is better in this regard than regular HSS).
 
GabrielMB said:
I am trying to remove the hexagonal shape from the nut (about 1.5 mm cut) and then remove around 2 mm of material. The nuts are 18-8 stainless steel and the cutters are SWGCR04-2 with WCMT2.52 TiN coated carbide.
Thank you.
Click to expand...

You are making the nuts round by chopping the six edges off so they become round.

How are you holding the nuts on the lathe?
How much material is removed in a shallow pass? (How deep is the cutter)
 
winger said:
Slow rpms down and switch to High speed steel. Mini lathe, interrupted cuts, and carbide do not bode well.

Dave
Click to expand...

I would also suggest that given the lack of rigidity such machines exhibit, knocking the corners off by grinding before mounting in the lathe would reduce the severity of the interrupted cut.

Also, if it's a typical "mini" it needs careful fitting (scraping, better gibs, etc.) to tighten up and mounting to a higher mass base will reduce vibration. Basically most of them are considered semi-finished kit machines that need much work to be usable.
 
GabrielMB said:
Hello everyone,
First, please excuse my lack of experience, i have only very recently bought my first mini lathe so I may very much be overlooking something very simple or making a beginner mistake.
I am a novice ring maker and i have recently bought a lathe in order to speed up to process of doing it with a disc sander.
However, when i try surfacing the nuts, i get a terrible surface finish and a lot of vibration.
I realize the surface of a nut is hexagonal so irregular, but even as that surface is removed with very shallow passes, the nut vibrates like crazy and the lathe motor shuts off very regularly. I am using tungsten cutters with carbide inserts which i make sure to keep cool.
If anyone has any tips on surfacing irregular surfaces and can offer any tips, they would be greatly appreciated.
Thank you.
Click to expand...

Why are you dooing this ?
Why not start with round barstock ?
 
rons said:
You are making the nuts round by chopping the six edges off so they become round.

How are you holding the nuts on the lathe?
How much material is removed in a shallow pass? (How deep is the cutter)
Click to expand...

I am using a mild steel expanding ring mandrel and the cuts are about a quarter milimeter deep
 
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