Gunsmithing parting tool vs. hack/band saw for cutting barrel?

300sniper

300sniper

Gunny Sergeant
Full Member
Minuteman
Jan 17, 2005
3,438
26
Greenwood, Ca
#1
i have seen a very good write up on the negatives of using a parting tool to remove the excess barrel length but i can not find it now. i believe he was using a microscope to look at the grain structure of the barrel after using both methods.

does anyone know where i can find this write-up?
 
#3
Re: parting tool vs. hack/band saw for cutting barrel?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: DebosDave</div><div class="ubbcode-body">Just curious, but if you clean it up after either method, would it matter which you use?

</div></div>

if that write-up surfaces, from what i remember, the grain structure of the steel actually changes around the cut when using a parting tool. i am mostly curious how far away from the cut the material is affected.
 
#4
Re: parting tool vs. hack/band saw for cutting barrel?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: 300sniper</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: DebosDave</div><div class="ubbcode-body">Just curious, but if you clean it up after either method, would it matter which you use?

</div></div>

if that write-up surfaces, from what i remember, the grain structure of the steel actually changes around the cut when using a parting tool. i am mostly curious how far away from the cut the material is affected. </div></div>

It has a simular effect as a tubing cutter has on any type of pipe or tubing. It pushes the metal in as it cuts. The problem is knowing when you have all of the displaced metal cleaned up and removed. Band saws and or hack saws remain the best way to cut a barrel off.
 
#6
Re: parting tool vs. hack/band saw for cutting barrel?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: 300sniper</div><div class="ubbcode-body">i think the write-up actually had some pictures of the grain structure under a microscope. that is what i am really after. </div></div>

I think that would be the only way to determine where the displacement / distortion stopped.
 
#7
Re: parting tool vs. hack/band saw for cutting barrel?

This story would tell me that either someone needs to learn how to sharpen a parting blade, or facing 101 needs to be introduced.

Part them off and face them down, facing from inside out. Never seen it not work, but I have seen a few marks that took some serious elbow grease to remove with a draw file and sandpaper because they spun inside the jaws of a vise during the cut-off operation or were clamped on saw filings.
 
#8
Re: parting tool vs. hack/band saw for cutting barrel?

There is a certain amount of tearing when using any parting tool, but who cares, the barrel muzzle needs to be trued and then the crown cut. By the time you have accomplished that much, there is no way you will find damage left by the parting tool.
 
#9
Re: parting tool vs. hack/band saw for cutting barrel?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: triggerguard1</div><div class="ubbcode-body">This story would tell me that either someone needs to learn how to sharpen a parting blade, or facing 101 needs to be introduced.

Part them off and face them down, facing from inside out. Never seen it not work, but I have seen a few marks that took some serious elbow grease to remove with a draw file and sandpaper because they spun inside the jaws of a vise during the cut-off operation or were clamped on saw filings.

</div></div>

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Dan Carey</div><div class="ubbcode-body">There is a certain amount of tearing when using any parting tool, but who cares, the barrel muzzle needs to be trued and then the crown cut. By the time you have accomplished that much, there is no way you will find damage left by the parting tool. </div></div>


so what you guys are saying is that you have seen the results of a parting tool on the grain structure of the barrel after using a parting tool and it is the same as when it is cut with a hack or band saw? i remember seeing something totally different. <span style="font-style: italic">that</span> is what i am looking for.
 
#11
Re: parting tool vs. hack/band saw for cutting barrel?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Dan Carey</div><div class="ubbcode-body">No it won't look the same, nevrtheless, it makes no difference what it looks like at that point. </div></div>

and if it ends up choking the barrel near the part? the whole reason i am looking for this write-up is to clear up some of this information.
 
#12
Re: parting tool vs. hack/band saw for cutting barrel?

I talked with Tim North at length concerning this very topic several months back. The general consensus among builders he had spoken to was to saw the barrel off. Being a barrel manufacturer as well, he had tried numerous techniques to cut barrels. Part off tools were not his first choice.
 
#14
Re: parting tool vs. hack/band saw for cutting barrel?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: DebosDave</div><div class="ubbcode-body">Bill Calfee </div></div>

crazy.gif
 
#15
Re: parting tool vs. hack/band saw for cutting barrel?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: 300sniper</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: triggerguard1</div><div class="ubbcode-body">This story would tell me that either someone needs to learn how to sharpen a parting blade, or facing 101 needs to be introduced.

Part them off and face them down, facing from inside out. Never seen it not work, but I have seen a few marks that took some serious elbow grease to remove with a draw file and sandpaper because they spun inside the jaws of a vise during the cut-off operation or were clamped on saw filings.

</div></div>

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Dan Carey</div><div class="ubbcode-body">There is a certain amount of tearing when using any parting tool, but who cares, the barrel muzzle needs to be trued and then the crown cut. By the time you have accomplished that much, there is no way you will find damage left by the parting tool. </div></div>


so what you guys are saying is that you have seen the results of a parting tool on the grain structure of the barrel after using a parting tool and it is the same as when it is cut with a hack or band saw? i remember seeing something totally different. <span style="font-style: italic">that</span> is what i am looking for. </div></div>

I'm simply saying that I've parted off tens of thousands of parts in CNC and manual lathes that required tolerances far beyond the scope of the firearms industry and it is a waste of shop time to justify doing it any other way, unless an excessive amount of material must be removed.

The most precision turned parts in the world are parted off every day. To think that it is somehow wrong to do it, simply because its a barrel, or that you're going to effect the grain structure enough to effect accuracy is a bit off.

When you're holding tolerances of +/-.00005, they get parted, all day and every day.


Leave the sawing to the loggers.
 
#16
Re: parting tool vs. hack/band saw for cutting barrel?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: triggerguard1</div><div class="ubbcode-body">

I'm simply saying that I've parted off tens of thousands of parts in CNC and manual lathes that required tolerances far beyond the scope of the firearms industry and it is a waste of shop time to justify doing it any other way, unless an excessive amount of material must be removed.

The most precision turned parts in the world are parted off every day. To think that it is somehow wrong to do it, simply because its a barrel, or that you're going to effect the grain structure enough to effect accuracy is a bit off.

When you're holding tolerances of +/-.00005, they get parted, all day and every day.


Leave the sawing to the loggers.
</div></div>

and that is exactly why i want to review the write-up, so i can make up my own mind if there may be a better way of doing things.

since i was only looking for the write-up and you chimed in with your experience, maybe you can answer what i was looking for in that write-up. if you had a cylindrical part similar to a rifle barel that you had to hold the bore tolerance to +/-.00005" (or even .0001") in 416r, how much material would you allow for a facing cut after parting? if your parting cut left .010" for a finish facing cut, would the bore dimensions not change at all? .020"? .100"?
 
#17
Re: parting tool vs. hack/band saw for cutting barrel?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: triggerguard1</div><div class="ubbcode-body">
300sniper said:
triggerguard1 said:
Leave the sawing to the loggers.
</div></div>

Agreed. What a load of bollocks. If you don't use a parting tool correctly, perhaps, but I'm sure theres those who manage to use a hammer the wrong way to pound a nail and reckon a boot heel does a better job.
Click to expand...
Click to expand...
 
#18
Re: parting tool vs. hack/band saw for cutting barrel?

Typically, in CNC situations, I'll leave .010-.020" for facing cleanup. That is dependent on the material that I'm running though and the geometry of the tool I'm using.
Some tools need only .002" to make a nice finish in certain materials, where others need as much as .020" to get the chip cleared correctly to achieve the best finish.
Tool nose radius and chip breaker have everything to do with this, as well as material.

A lot of the lathe work on manuals that I do, I'm usually grinding my own tooling, thus chip breakers are rarely employed and the nose radius I leave nearly razor sharp at times, but again, that's depending on what I'm up to.

For facing the crown, I like a nose radius of about .003-.007 either from an insert, or by my own grinding on brazed carbide. .010 is plenty, but sometimes I'll take two passes for the last tidbit of finish.
My recess will vary from .075-.140, depending on my mood, alignment of stars, and what have ya. That cut can be done with a larger tool nose radius, allowing more aggressive material removal and less chance of breaking off the tip.

416 can be easier to work with than a lot of mild steels, but more often than not, people get scared because its stainless. Coatings can be your friend and I routinely run 416 at 800-1000 SFM on my milling machines.
416's biggest problem in a turning application is the murky finish that you'll sometimes get, which I've been told is due to the sulfur content. 304, 303, 1018 and 4140 can all be turned like a mirror easier than 416, but it can be done, it just takes some experimenting.
I've had some of the biggest machining characteristic changes occur in 416. You're cutting along and everything is great and then you switch to a new certified heat and it all goes to hell in a hand basket and you're back to square one.
One thing I learned for sure was, no matter what you're making, never use 416 from Taiwan. My customer sent me some of that crap and I literally scrapped $30,000.00 worth of otherwise good parts due to the material self destructing during the machining process. I had to eat it, since I was charging for the machining only and they picked up on the tab for the material.
Costly cheap route in the end.
 
#20
Re: parting tool vs. hack/band saw for cutting barrel?

416 can vary from vendor to vendor, no doubt, btdt. Carpenter and Crucible make the most homogenous stuff..I find the internal machining of 416 vs CM lends to longer tool life, better surface finish prior to polishing..But 4140-45-50 does machine very well on lathe processes..
 
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