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jwoitasek
09-13-2002, 12:05 PM
Hey Fella's
Heres a bunch of questions.

cemented carbide lathe tools:
on I guess lower quality tool bits ( new )
they appear to cut fine but I still have to finish the surface with emery or the like.

looking at the surface with a low power microscope.
you can deffinately see the grind pattern.
would there be an advantage to polishing the cutting surface?
Are carbide ment to be really sharp?
edges?
does it matter?
is the only thing to polish carbide, diamond?
or can you use like mold honning stones?
I am working with 316 stainless right now and was wondering if I would gain anything by polishing the carbide surface.
cutting back on the finishing would deffinately save time.

Thanks to all.
JRW
In the near future when affordable i will install coolant on the lathe, So as you can see this is machined dry.

t&cgrinder
09-13-2002, 02:05 PM
If I understand your question you are concerned the finish on your carbide tool is leaving a bad finish on your parts.

The finish on your part will be affected by your sped and feed along with the nose radius of your tool. If you are needing a ground finish then leave matterial and grind the finish.

Most carbide cutting tools will have grind marks. I generally have told people over the years to get a silicon hone and put a 45 degree bevel on the cutting edge. You do not want a sharp corner. Carbide is brittle and will chip. Only a couple of thousandths.

If you are looking at the cutting tool edge you should be looking for chips in the cutting edge and edge wear rather than grind marks.

Paul

Rotate
09-13-2002, 02:07 PM
JRW,

I don't believe polishing the surface will do any good. However if the grind pattern has left visible grooves, then this grooves would affect the cutting edge. Check the cutting edge for any irregularities. The edge should be made as sharp as possible. You can use either diamond or green stone to hone the carbide.

Frankly I don't like cemented carbide for lathe. Consider using carbide inserts. I think they are more economical and you'll have better choices in terms of size, coating, and quality.

Albert

burnlast
09-13-2002, 11:34 PM
I have cut tons of 316.It may not be your tooling.316 stainless has a very bad tendency to weld to tools (hss & carbide).You didn't say if you were machining dry or with some kind of cutting fluid.Try some coolant or cutting oil.

BURNLAST!!!!!!!!!

C. Tate
09-14-2002, 12:19 AM
If you are only making one or two pieces then use HSS and make it as sharp as you can. 40 sfm and .006-.008 ipr with a .015 nose radius will produce a good finish. If you have to do a lot of cutting go to an indexable tool and an insert that has positive geometery. You can run the indexable faster but it requires more rigidity. If you go with HSS use flood coolant or lots of oil you do not want chip welding on the cutting edge which is number one cause of tool failure and poor finish with stainless steels. If you cannot flood the indexable run it dry partial cooling of carbide is much worse than no cooling at all it can cause thermal fracturing on the cutting edge. I cut stainless everyday and have never gotten a good turned finish with brazed tools.

Thrud
09-14-2002, 06:03 AM
Mr. Tate has it in one go. I would suggest that the brazed carbide tools are not your best solution for doing better work at home - they are handy for taking the skin off of cast iron and rust or scale.

A better soulution for you may be to look into the purchase of some T-15 HHS tools from www.arwarnerco.com (http://www.arwarnerco.com) - these will give you far superior finish compared to what you have now even with interrupted cuts and stainless steels. These tools are T-15 inserts that have three cutting edges, as one wears out it is turned. Their tool holders for these are quite reasonable (a kit of 5 toolholders and ten inserts is a tad over $100). They also advertise in HSM/MW.

If you have Armstrong toolholders then consider getting the T-15 Bits (also from A.R. Warner) - they are tough to grind but hold their edge longer even weh used to cut high temperature alloys.