Grinding HSS Lathe Tools

G

Gene Beggs

Active member
Today, I ground a new lathe tool out of 3/8" Rex 95. I ground in the seven degree relief under the leading edge then ground the point relief less than ninety degrees so it would get up into corners. When it came time to grind the chip breaker, I wondered how it would work if I just left the top of the tool flat; no chip breaker. :eek: I was surprised and delighted to find that it worked great; perhaps even better and it's so easy to sharpen. Only two surfaces to grind instead of three. But I probably won't be doing many more now that I've discovered the Diamond Tool Holder. It has only ONE surface to grind and it works GREAT!! :D

At this stage in life it doesn't take much to amuse me. Give me a grinder and some tools to sharpen and I'm happy as a lark. :p

Later,

Gene Beggs
 
Gene, be aware that taking cuts with a zero or negative top rake you can induce surface stresses in the workpiece. Stresses in rifle barrels are not good!
 
The DTH is a very nice cutting tool and works as advertised. There is another option for guys who have indexable tooling. The Arthur Warner Tool Company of Latrobe, Pa. makes HSS inserts for any tool holder. Mike Warner will custom grind inserts for any tool. When the insert gets dull, all you have to do is, turn it upside down on a wet stone and rub it in a circle for 30 seconds and it's even sharper than when new. You never have to touch the sides to re sharpen. His threading insert cuts the nicest threads at low speeds.

www.arwarnerco.com
1-724-539-9229
 
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Warner has a kit with a right hand, left hand and boring bar with 5 inserts for $130.

American made.

Just what I was looking for.

Jim
 
JerrySharrett said:
Gene, be aware that taking cuts with a zero or negative top rake you can induce surface stresses in the workpiece. Stresses in rifle barrels are not good!
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Jerry, I should have mentioned that I do not take heavy cuts on my little 13-40 Jet lathe. When I'm machining a tenon, the first cut reduces the diameter by only .050, which of course is only taking a .025 depth of cut. As I get near the final diameter, I reduce the cut, taking only around .005 to finish.

Then comes the threads which I also do with shallow cuts. After the threads are cut to final depth, I take a final skim cut of about .003 off the top of the threads which removes any burrs and finally polish with 320 wet or dry paper and Cratex. I don't feel this procedure induces any significant stress in my barrels. It may be that when using a big lathe and taking heavy cuts, the absence of a chip breaker might induce more stress in the work but since I do only light stuff, I don't think leaving the top of the tool flat causes any problem.

The fact that I'm lazy is probably the MAIN reason I want to omit the chip breaker. This way I have only two surfaces to grind. After grinding the front relief and the point on the grinder, I hone the radius of the cutting tip by hand with a diamond hone to about an .035 radius. All this is well and good, and I wish I had known this long ago before I discovered the Diamond Tool Holder because with it you only have ONE surface to grind! :D

Just yesterday morning, Huckeba and Tucker were down at my shop trying out the Diamond Tool Holder. Guess what? :eek: They both said, "Order one for me."

I wish I was making money off this stuff but I have no vested interest. I just like to share good things that I discover with my friends. :)

Later,

Gene Beggs
 
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Gene Beggs said:
Jerry, I should have mentioned that I do not take heavy cuts on my little 13-40 Jet lathe. When I'm machining a tenon, the first cut reduces the diameter by only .050, which of course is only taking a .025 depth of cut. As I get near the final diameter, I reduce the cut, taking only around .005 to finish.


The fact that I'm lazy is probably the MAIN reason I want to omit the chip breaker.

I wish I was making money off this stuff but I have no vested interest. I just like to share good things that I discover with my friends. :)

Later,

Gene Beggs
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Gene, it is not the amount of cut (DOC-depth of cut) that induces surface stress it is the amount of pushback the cut produces that induces stress.
 
JerrySharrett said:
Gene, it is not the amount of cut (DOC-depth of cut) that induces surface stress it is the amount of pushback the cut produces that induces stress.
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Jerry, does the chip breaker behind the leading edge of the tool reduce pushback? Sort of like a sharper bow of a ship cleaving thru the water easier?
 
Gene

A properly ground chipbreaker will tend to let the tool slice the metal instead of wedging it off.

Also, you want the radius of the chipbreaker to have as good of a finish as you can put with your grinding wheel, simply to reduce friction as the shaving curls over the surface.

I got some bad news from one of our tool supplyers a while back. They said that Crucible will cease the manufacture of REX-95 HSS, and as soon as stocks are depleated, it is gone. REX-95 has been the go-to general purpose HSS in our shop for years. It is the only thing we use in our Portable Boring Equipment.........jackie
 
Gene Beggs said:
Jerry, does the chip breaker behind the leading edge of the tool reduce pushback?
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If you are talking about an adjustable chipbreaker like commonly used on carbide insert holders, the answer is no. Only metal being directly removed from the workpiece can cause surface stresses. A slicing action, in the case of a positive rake cutter, can remove material without inducing stress.

A neutral or negative rake cut can and does induce stress partly because it is causing work hardening among other forces. This surface work hardening, which is not constant, is the chief culprit. That is why a neutral or negative cut must be run at higher surface footage to be efficient. It also requires much more horsepower per unit of metal removal.

Try slicing a ripe tomato with the sharp edge of a knife, then try making the next slice by slowly moving the knife. Then use that same dull edge and use a fast chopping action.
 
jackie schmidt said:
.

I got some bad news from one of our tool supplyers a while back. They said that Crucible will cease the manufacture of REX-95 HSS, and as soon as stocks are depleated, it is gone. REX-95 has been the go-to general purpose HSS in our shop for years. It is the only thing we use in our Portable Boring Equipment.........jackie
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Jackie, there is still plenty of HSSCo coming out of Communist China and Mexico.....but then who has the market captured on Cobalt?

Thanks folks for letting your Congressmen get by with this crap...among other craps they are screwing the US economy with!!!
 
jackie schmidt said:
A properly ground chipbreaker will tend to let the tool slice the metal instead of wedging it off.

Also, you want the radius of the chipbreaker to have as good of a finish as you can put with your grinding wheel, simply to reduce friction as the shaving curls over the surface.

I got some bad news from one of our tool supplyers a while back. They said that Crucible will cease the manufacture of REX-95 HSS, and as soon as stocks are depleated, it is gone. REX-95 has been the go-to general purpose HSS in our shop for years. It is the only thing we use in our Portable Boring Equipment.........jackie
Click to expand...



Thank you Jackie,

Good information. I guess I'll go out tomorrow and see if I can find some extra Rex 95 tool blanks. There IS a difference in the way it cuts compared to some I have used.
 
Zebra13 said:
Gents,

Does the REX-95 require special wheels for grinding?

Justin
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No special wheel required to grind Rex 95. I grind it on my old six inch Craftsman, which still has the original wheels on it. I think they're aluminum oxide. Left side is course and right one is fine.

Gene Beggs
 
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