First lathe, tool bits

mikey said:
Really enjoyed your post, Rex. Well written and based on experience.
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Thanks. Doubtless it was overly verbose, but if I'd just said "go get a diamond tool holder" nobody would have believed me!

Reminds me of my favorite expression: "There's no such thing as bad experience." (Assuming you survive!)
 
I thought tangential tool bits were pretty much just for shallow cut finishing work. I have never actually used one, but have watched a few in use, trying for average (and less) depth cuts on light lathes and not succeeding. The only success I saw was with a very light depth of cut and a very slow feed rate, which worked well.
 
What is T15 and is it commonly used in cutters today? I'm curious because I came across a NOS Niagra T15 4 flute end mill with Weldon shank and a curious
ring around the end of the shank. Is T15 better than cobalt for lathe bits and other cutters? (sorry, not trying to hi jack, just saw a mention to T15 earlier in this great thread.)
 
Bob Korves said:
I thought tangential tool bits were pretty much just for shallow cut finishing work.
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Are you confusing a shear tool with a tangential tool holder?

The former is definitely for very shallow cuts (a few tenths to about one or two thou) but leaves a fantastic finish. A shear tool is also very easy to grind, but is still plunged into the work with the tool held normally (radially). Works great for final finishing passes when precision turning. See Conrad Hoffman's article for a description of the sheer tool (about halfway down the page). The chips (shavings) really do look like very fine steel wool.

A tangential tool holder holds the entire bit at a tangent to the work. See the Diamond Tool Holder from Eccentric Engineering. [FWIW, I have no financial interest in the company, but I did have the pleasure of meeting Gary recently — great guy.]

I usually take about 0.040" to 0.060" off the diameter of mild steel with my tangential tool during a roughing pass on my light lathe, but I could probably take a bit more. Some might consider that a shallow cut but I think they've got much heavier direct drive lathes. My belt between the motor and the drive shaft is fairly loose and tends to slip if I attempt a cut much heavier than that.

Here's a video of someone taking what I consider to be reasonably heavy cuts in a variety of material with a tangential tool:

Regards,
--
Rex
 
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EmilioG said:
What is T15 and is it commonly used in cutters today? I'm curious because I came across a NOS Niagra T15 4 flute end mill with Weldon shank and a curious
ring around the end of the shank. Is T15 better than cobalt for lathe bits and other cutters? (sorry, not trying to hi jack, just saw a mention to T15 earlier in this great thread.)
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T15 is a Tungsten high speed steel that mostly uses tungsten for the hot hardness ability. It is an older design of HSS that is not often seen anymore, but I have some. M series HSS uses molybdenum for part of the tungsten amount for hot hardness ability. Molybdenum is cheaper than tungsten, so they moved in that direction. I have zero experience with using my T15 tool bits, but I assume that they perform pretty well. If you can get the end mill cheap, go for it...
http://www.asminternational.org/doc...yNow.pdf/b8f2e317-5089-44bc-a14d-af31f80e33a5
 
I gotta' admit, that tangential tool is pretty slick. I think Tozguy also uses and likes that tool. The only thing I can't wrap my head around is the fact that the geometry is fixed ... no tool bit works for everything. Seems to me that for smaller lathes, you would want the flexibility to reduce cutting forces, no? To do that, you need to alter tool angles and this tool holder/concept will not allow for that. On the upside, grinding the tool bit can't get much easier and that's a big positive.
 
mikey said:
Seems to me that for smaller lathes, you would want the flexibility to reduce cutting forces, no? To do that, you need to alter tool angles and this tool holder/concept will not allow for that.
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The angles are fixed, but I use mine for both soft aluminum and fairly hard steel without issue. I'd probably use a different tool for turning a bunch of Delrin or really gnarly stainless, though. The amazing thing is you can even use it for threading. (The grinding jig lets you grind a 60º angle as well.)

It's not the only tool you'll ever need (you can't grind chip breakers, for example) but it suffices for about 90% of the turning and facing I do. It does tend to generate long chips, but then so do most of the well-ground tools I've made. I never grind chip breakers myself, anyway: speeds and feeds (and a pair of long nosed pliers) suffice for my needs.
 
Rex Walters said:
The angles are fixed, but I use mine for both soft aluminum and fairly hard steel without issue. I'd probably use a different tool for turning a bunch of Delrin or really gnarly stainless, though. The amazing thing is you can even use it for threading. (The grinding jig lets you grind a 60º angle as well.)

It's not the only tool you'll ever need (you can't grind chip breakers, for example) but it suffices for about 90% of the turning and facing I do. It does tend to generate long chips, but then so do most of the well-ground tools I've made. I never grind chip breakers myself, anyway: speeds and feeds (and a pair of long nosed pliers) suffice for my needs.
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What I meant by my statement is that a good tool can enable your lathe to take cuts that a normal HSS tool and probably that tangential tool won't allow. My Sherline lathe is tiny in comparison to a 10" Logan but it will take a 0.050" deep cut in mild steel with the right tool. Your lathe, with the same tool, could easily double that cut.

On the other hand, if it works good enough for your needs then that is really all that matters.
 
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