What tool / cutter setup do you use to turn rifle barrel shanks?

L

LVLAaron

New member
What's your setup to turn rifle barrel shanks?

I have a number of CCMT style inserts and parting blades that I feel comfortable with... and they work. But I'm fairly new to this and wondering... If I were to set a barrel back 1 thread, or just wanted to take a few thou off a shoulder to clock a barrel - what tool would you use?
 
There's a zillion recommendations out there that will work well but I use the following:

ISCAR SWAPR-1414-06 Toolholder #3730108
ISCAR WPEX-060402IC908 Insert #5505996

These were long ago recommended by Speedy Gonzales for turning tenons. He originally recommended un-coated but ISCAR discontinued them and I switched to the IC908. I could tell no difference in the way they performed and the coated may even last longer. I'd have no problem skimming a few thousandths off with these. They cut easy and leave a great finish. I've been using them since at least 2008.

Oh, and thank you Speedy for a fine recommendation. Someone was listening ;)
 
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Louis.J said:
I just use HSS Steel bits that I have ground for all such related work.
Click to expand...

Carbide only works well when you have a solid enough setup to take deeper cuts.
HSS is more than adequate for typical gun work.
Carbide lives and dies by heavy cuts to remove heat in the chips.

Shaping and hardening (followed by some tempering) HSS is not all that difficult.
Barrel threads are not really all that large in the scheme of things.
Often around 8 per inch V threads.

Make sure the setup is solid.
Chatter really messes up smaller threads.
 
Carbide only works well when you have a solid enough setup to take deeper cuts. Disagree.
HSS is more than adequate for typical gun work. Okay, true.
Carbide lives and dies by heavy cuts to remove heat in the chips. Again, disagree.

People keep repeating this stuff over and over but it doesn't make it true. Once upon a time it might have been true but there are plenty of modern carbide inserts that work well with light cuts and are capable of removing small amounts of material at a time. They don't need to "take deeper cuts" nor do you need to take "heavy cuts to remove heat in the chips". I and many others have been using modern sharp carbide effectively for many years in smaller machines just fine. Now you may need to find the correct insert/s to do so but I assure you it exists and it has for quite some time.
 
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WSnyder said:
Carbide only works well when you have a solid enough setup to take deeper cuts. Disagree.
HSS is more than adequate for typical gun work. Okay, true.
Carbide lives and dies by heavy cuts to remove heat in the chips. Again, disagree.

People keep repeating this stuff over and over but it doesn't make it true. Once upon a time it might have been true but there are plenty of modern carbide inserts that work well with light cuts and are capable of removing small amounts of material at a time. They don't need to "take deeper cuts" nor do you need to take "heavy cuts to remove heat in the chips". I and many others have been using modern sharp carbide effectively for many years in smaller machines just fine. Now you may need to find the correct insert/s to do so but I assure you it exists and it has for quite some time.
Click to expand...

The grain in carbide, a sintered material, is also far larger than the atomic spacing in HSS alloyed steel.

Lighter weight equipment often lacks the rigidity to adequately support carbide cutters.
One of my many 'side jobs' was providing instrumentation for metal working setups that measured vibration under cutting loads.

We accounted for everything from bearing clearance vibration, to flex in the shaft of lathe tools.
Shorter reach is better.
We could detect the smoother operation of a 3-pase motor compared to a single phase motor.
 
I use a carbide CCGT insert from Sandvik - it has an .008 nose radius and a chip breaker. Leaves an excellent finish at around 700ish for the tenon, and then I crank it up to 1200 for the shoulder after I do a .004 (.008 total doc)plunge to make up for the radius of the nose.
HSS pre-ground arthur warner threading insert real slow like upside down away from the headstock in a mesa tools goose neck tool holder.
carbide insert made for aluminum on a boring bar for my cone and crown at about 1200rpm. No burrs and a mirror finish with a little viper's venom
 
Crown cut with HSS and polished for cast bullet benchrest use. Polishing is required to be able see the lube star left on the face of the muzzle.

 
I've been fighting this same fight and had basically completely ditched HSS some yrs back (only after spending a couple grand on tool grinding equipment)

So I'm mostly a carbide insert guy now, feeling that with modern tooling the ONLY downside to the newer carbide inserts is that dratted radius on the end.

So I tried something else today :)

I was fitting a timed suppressor/brake and wanted contact at 4 points..... ie slip-fit on two radii and solid butt joints at two points with .001 of Paul Mauser style crush between front and rear abutments. And clean inside radius' at the rear abutment surface makes things wikkid easy.

I have a "pocket microscope" for inspection of porous finishes

I resurrected 6 beautifully ground (MANY hrs) 5/8 "threading bits" with looong slim offset tapers and spent a couple hours dressing edges and tips. Cut myself twice't. And made needle tips and razor edges which passed inspection under high magnification.

And promptly wrecked them.

You couldn't SEE the wrecks but when dialing in my offsets I got misreadings and under 60X could easily see chipped edges, knocked off corners.

So I'm back to carbide inserts, "smallest radius I can buy"........ and plunging that dadblamed inside radius
 
Did you harden and temper the HSS tools?
It makes a huge difference in their life.
The availability of diamond surfaces for sharpening hardened
HSS tools allows very fine edges to be created.
 
brickeyee said:
Did you harden and temper the HSS tools?
It makes a huge difference in their life.
The availability of diamond surfaces for sharpening hardened
HSS tools allows very fine edges to be created.
Click to expand...

No, I have never done this. And I do like it because it would allow me to do bulk grinding without a constant spray of water.

So please give me your opinion..... If I were to grind a bit to shape taking care to never let the points and edges get more than blue-hot. Then heat to a dull red and water quench...... then polish and anneal back to straw?

Anneal back to tan?

Brown?

Then stone/polish back to sharp edge using cold methods.....

is this what you propose?
 
BTW, when I say "stone/polish" I do in fact use diamond-coated metal lapping boards. I have 12-15 large and flat diamond impregnated surfaces ranging from 320 grit to "6000" grit

I'm very adept at "sharpening" stuff....
 
Which grade of HSS did you actually have.
I personally have allot of time on my hands and now being retired also no in hurry to get anything done.
I have tried the carbide inserts but they are just not up to my own quality of workmanship.
 
Louis.J said:
Which grade of HSS did you actually have.
I personally have allot of time on my hands and now being retired also no in hurry to get anything done.
I have tried the carbide inserts but they are just not up to my own quality of workmanship.
Click to expand...

I don't know.... some say 'cobalt' or 'HSS' most are unmarked
 
I use a mix, but for a tenon probably HSS

About 3/4 of my cutters are HSS of one kind or another - All quality e.g. Rex aaa, Cleveland, etc. The import stuff is a minefield of uneven quality - some is great, some seems like mis-labeled 12L14... The time I spend grinding a cutter is worth more than the blank, so I'll pay a little extra for 'insurance'. I reach for HSS nearly all of the time that I want a superior finish. The exception being threading, where I have found some terrific and inexpensive inserts that are as good as anything else I've used. I have used some of the sharp carbide and it definitely cuts just fine, but if I'm using HSS I can tailor the cutter to the cut (size, shape, my tools, etc) and that's a hard combo to beat, imo.

I stone or hone only a few cutters - mostly form tools. Don't lose sight of the forest for the trees - your goal is a good finish, not on the cutter, but on the work - put down the microscope and see how it cuts!

GsT
 
GeneT said:
......- put down the microscope and see how it cuts!

GsT
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LOL!!

It was still cutting nice and mirror smooth, it'd just lost .002 of side-cut..... buggered my offset.

You know how it's nice to use the same tool to set tenon length?? Actually, nice to use the same tool for the entire tenon except threading? In this case I was timing the brake by slicing a couple thou off the end of the "tenon" (actually the muzzle), then move over .894 to reset the abutment shoulder slowly sneaking up on it two-three thou at a time when my touch-offs started to get wonky and I found that the cutting edge had been damaged by the sideward plunge into the root of the abutment shoulder. When it happened the second time I chickened out and finished with a bit like the one Rubicon Precision recommends above.


I've tried to do the same thing using a carbide threading bit and had the same problem..... for some reason that 60* threading bit running directly into the root and pulling/cutting out to face the abutment shoulder is really hard on the bit. I can't see the clearance problem except that the carbide threading bit has a small vertical drop at the tip so I'd used a clearance ground HSS cutter slowly at 360RPM
 
Louis.J said:
Which grade of HSS did you actually have.
I personally have allot of time on my hands and now being retired also no in hurry to get anything done.
I have tried the carbide inserts but they are just not up to my own quality of workmanship.
Click to expand...

HSS is available in an insert format for some grades.
Sort of the best of both worlds.
An insert that is HSS.

We used to make receivers and transmitters that had a stack of slices.
Each major function (Command/control interface, LO slices, mixer slices,
power amp slices (for TX) etc.
Slices where typically about 3 inches by 5 inches and as thick as required.
Lots of isolation and shielding.
We would start with an aluminum billet slight large enough to make a slice.
Then hog it out.
Sometimes from only one side, sometimes both sides.
Stack the pieces up with RF tight joints and through bolt the stack together.

Cut surfaces had to be clean and smooth to make an RF tight joint.
Nickel plating on all surfaces.
Gray epoxy paint on exterior except mating joints and connector locations.
Sometimes silver filled conductive gaskets.
HF to UHF was about 3 in. X 5 in. by 6 inches tall.
Blind mate command / control / reference oscillator input on one end, RF in/out on the other face.
SIGINT / ELINT grade equipment.
As many as 127 receivers in a system.
 
alinwa said:
BTW, when I say "stone/polish" I do in fact use diamond-coated metal lapping boards. I have 12-15 large and flat diamond impregnated surfaces ranging from 320 grit to "6000" grit

I'm very adept at "sharpening" stuff....
Click to expand...

I was spoiled for many years with access to tool room quality machinery.
We had a couple lathes and milling machines in their own temperature controlled enclosures
off in a corner of the larger tool room.

My first meeting with the "tool room supervisor" was when the need arose for higher precision
for making tools and cutters.

He had already decided on the need for better temperature control on a few machines.
Together with my Chief Mechanical Engineer we created what the super wanted.
It worked better than any of us could have dreamed.
 
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