Lathe tools

[CNCadmin]

OK what lathe tooling advise can you guy's give. I have a 7x10 lathe and plan on cutting steel and aluminum. What type of cutter's and brands sould I get?

[DLMACHINE]

7X10 -- sounds like a chinese mini lathe. For aluminum use HSS and for steel use carbide. Buy the cheapest you can find and grind the shape you want on a bench grinder, you can sharpen them as often as needed. High priced tool holders and inserts are nice but most won't fit your lathe and you won't be able to feed fast enough to really take advantage of them.

[HuFlungDung]

What DLMachine said!

Carbide insert tool holders for lathes are largely negative rake, so you can take advantage of double sided inserts. However, really small inserts are mostly single sided anyway. But, these negative rake inserts take more power to cut with, and likely this would require more rigidity than your machine possesses.

However, carbide inserts come in quite a variety of chip-breaker styles, this is referring to the shape pressed into the top of the insert. Some inserts have enough of a groove pressed into the top that they are actually positive rake, and this makes them more free cutting.

For your roughing cuts, it is nice to be able to use carbide inserts with a chip breaker groove. I wonder if your lathe would handle a T221P insert? This is an equilateral triangle, with a 1/4 inch inscribed circle (a circle this size will contact the three edges). Kennametal makes some mini screw on toolholders that use these inserts.

For general utility, I have always preferred the 60 degree triangle insert. It allows a certain freedom of tool approach, and yet has a small enough point radius to help reduce the incidence of chatter. Square and 80 degree rhombus shapes are stronger, but tend to chatter more.

For finish cuts though, you might as well take DLMachine's advice and grind all your own tools. I do even yet, when doing manual lathe work. I usually take a slightly worn out triangle insert, and grind a gullet hook in the top, grinding down far enough to remove the worn edge of the insert. I have a narrow rim natural diamond wheel with a 1/16 radius to do this. Buy your wife for one of these diamond wheels for your anniversary

This gives the tool something like 25 or 30 degree positive rake, but is very delicate and only good for a max of .005 depth of cut. However, the finish is very accurate and smooth.

HSS is not to be ignored. Excellent work can be accomplished with properly ground tools, but chip control (meaning chip breaking) is difficult (nigh on to impossible).

[Bill C]

Well too, you must also keep in mind that there are different types of carbide inserts. That is, different hardness and structure for specific materials; an insert for stainless will be quickly destroyed by cast iron and vice-versa. You will have to have a 'supply' if you intend to use carbide indexable cutting tools and they are all different.

Use high speed steel with a percentage of cobalt and you can walk up to a standard pedistal grinder to sharpen it.... It hurts to throw away an insert that appears OK but will not cut to any finish. High speed tooling will always be the standard standby and the best for a home shop. There are Micro 100 tools that will cut case hardened steel.

Bill C.

[ToyMaker]

CNCadmin:

Check out the MiniLathe Site for a wealth of information about Asian 7x(10, 12, 14) lathes. Complete "care and feeding" including appropriate tooling and sources.

robotic regards,

Tom