Getting good finish on carbide inserts with shallow cuts

[taiwanluthiers]

Have you tried to grind a vertical shear tool with HSS? Its very easy to do so and gives good finish even if you are taking off just a .001" or .002"

https://gadgetbuilder.com/VerticalShearBit.html

Yea I tried to do that, no idea how it works. It looks like a normal lathe bit that's mounted backwards. I tried it and it still didn't give good finish.

 

[Firebrick43]

Yea I tried to do that, no idea how it works. It looks like a normal lathe bit that's mounted backwards. I tried it and it still didn't give good finish.

You put the center of the angled edge on center to the part your turning? You don't turn with the point like a regular tool.

 

[Firebrick43]

Low RPM as well

 

[taiwanluthiers]

We have a winner.
I found these two inserts at a nearby scrap carbide shop. Both of these profiles gave great finish even with shallow depth of cut. I mean I had to spin the lathe at 1800 rpm but still...

 

[Suzuki4evr]

I use wnmg 080404 at high rpm for shallow cuts. The last 04 is the nose radius,not saying you dont,but imcase you did not know. It machines pretty sweet. It has worked for me for years. 080408 also gives a nice finnish at 0.5mm DOC at 750+ rpm.

My 2 cents

 

[Parlo]

The finish you keep getting regardless of the insert type or depth of cut is a result of the play in your machine. If we are honest, we all take the last half thou off with abrasive cloth & scothbrite anyway.

 

[Janderso]

I use TPG inserts, 300 and 400 series; they have a sharp edge and will take light finish cuts.

And, you can save a boat load $$$$ with TPG!

 

[taiwanluthiers]

I'm getting great finish with inserts with a finishing geometry, I just happened to find them at a scrap carbide shop. The only bad part about finishing insert is they cut very poorly at higher depth (anything more than 0.1mm) and while it will still produce a good finish at those depth, they will spit out ribbons that are sharper than a samurai sword that bird nests the lathe.

Edit: The sharp ribbon problem can be remedied by lowering the feed rate...

 

[erikmannie]

If one can’t make it happen with HSS or carbide, I saw Abom79 using one of these in one of his videos:

High budget:

or

Metabo RBE 15-180 SET Tube Belt Sander - 602243620

Description Powerful Tube Belt Sander to process even larger stainless steel pipes Large wrap angle of 270° for seamless surfaces and quick work progress Metabo Long-life motor with patented dust protection for long service life Vario-Tacho-Constamatic (VTC)-Full Wave Electronics with...

bakersgas.com

or low budget:

3/4 Inch X 20-1/2 Inch Pro Mini Angle Belt Sander

Adjustable angle and articulated sanding arm

www.eastwood.com

or

https://www.amazon.com/SPTA-Professional-Stainless-Polisher-Burnishing/dp/B01HB22E76

or

Computer Parts, PC Components, Laptop Computers, LED LCD TV, Digital Cameras and more - Newegg.com

Newegg.com offers the best prices on computer products, laptop computers, LED LCD TVs, digital cameras, electronics, unlocked phones, office supplies, and more with fast shipping and top-rated customer service. Newegg shopping upgraded ™

www.newegg.com

Electric:

CS Unitec PIPE-MAX Weld Seam Grinder/Pipe Sander Kit Electric

CS Unitec 38502A PIPE-MAX Weld Seam Grinder/Pipe Sander, Electric, 110V, 950-3500 rpm Combination grinder and pipe belt sander and polisher. 1710 Watt, 15 amp Grind, blend and polish pipes, handrails and flat surfaces up to 14" diameter.

www.aaabrasives.com

One wonders how safe this is to use on a lathe:



I think this is the one that Abom79 had:

CS Unitec KING-BOA Round Tubing Sander 38810U

CS Unitec KING-BOA Round Tubing Sander 38502A

xpabrasives.com

 

[kmanuele]

Most carbide inserts seems to have a depth of cuts at which you will get a good finish, and for most inserts it's always more than 0.5mm. That means if I want to take 0.1mm off I'm out of luck and will get crappy finish. Are there inserts that allows me to take shaving passes and still get good finish?

I'm machining annealed 4140. The surface finish gets better if it's hardened, but in the annealed state it seems the only way to get a good finish is to basically take large passes.

Some folks have used inserts designed for aluminum in mild steel. They have a very sharp edge and look like they could take a shallow cut. See image. Not sure about strength of that edge though.

I've tried some finishing (-ff )inserts, but they still have a rounded edge before the chip breaker like most carbide inserts. So there is still a minimum depth of cut.