The Home Machinist!

Ok, got a stainless steel Brutus Denali blank from Gunparts. .50 cal, 1:24 twist, and 1.25" diameter

What advice can anyone offer ( loaded question )
for turning this barrel to a different profile. I assume light cuts and some sort of coolant flow? any thing, as far as coolants you'd stay away from?? what Speeds/feeds/carbide? or HSS, you'd suggest

. I have access to a Howa lathe 24" swing 8' on center.. so getting it to fit the lathe is no problem! I've never turned stainless, so I'm curious as to what you all would say!!??

Respect Always
Metalshaper/Jonathan

A great deal depends on the alloy that was used in making the barrel. It would be useful for you to make mention, and to find out if you don't know.

Stainless, in particular the 300 grades, are not hard, but they are tough---they resist machining (all but the free machining grades). They respond better to light feeds with positive rake, although if you have enough horsepower that may not be true. I would expect that with a lathe the size of yours, power won't be an issue. Negative rake would serve you well, again, depending on the alloy.

If you don't have the capability of straightening the barrel after it has been altered, I suggest you give this serious consideration before jumping in. Chances are good that the barrel will move a little.

C2 carbide is generally recommended for stainless. It will also respond well to HSS, but knowing how to grind the tools is important.

Because the cut is long, running coolant can be in your favor. Stainless tends to cut hot, due to its toughness. The expansion that results can be troublesome unless you keep close watch on tailstock pressure. Allowed to go beyond reason, it's possible for the barrel to bow under pressure.

Harold

in the muzzel breaks that ive installed on stainless, there usually isnt too much differance in cutting between the 4140 and the 416c stainless, like the previous response said alot depends on the alloy, i usually take fairly light cuts, no more than .020 at a time, but with what your doing i would contact a compentant machinist and see how they would go about it,,, ive always used indexable carbide tooling,,,

One would hope it is 416. It is the best machining of all the stainless alloys. It can be machined just about as easily as mild steel, with much better finishes and no tearing. It is truly a pleasure to machine. It responds exceedingly well to large cuts with coarse feeds, assuming the tool configuration is correct. C2 carbide, or HSS. Note that it is magnetic.

Harold

I have an e-mail out to Pedersoli and Gunparts, so I see if i can pin down the alloy? it sticks in my mind it is a 400 series, but will wait for their answer to be sure.

the tapered barrel has a 7/8th x 18 tpi section and just ahead of that an area that measures 0.947-.948 for about 1.5: then the barrel jumps to 1.10 for about 4" then tapers to the muzzle at .086.

here is a link to it:
http://www.gunpartscorp.com/catalog/Det ... li&catid=0


what I'm thinking of doing is turning off that 1.10 section and making it a straight 0.947 out until the normal taper takes over?? in this 50 call barrel, it would still leave me a wall of about .2235,
<which is thicker than the wall on my 15/16ths ML barrels??>

So what do you think??

Respect Always
Metalshaper/Jonathan

I have considerable experience in machining, but none as a gunsmith. I'll defer to those that have such experience.

Harold

What are you making with that barrel? A muzzleloader? It's too small in my opinion for a .50 BMG which is always what I think of when hearing .50 cal.

What are you making with that barrel? A muzzleloader? It's too small in my opinion for a .50 BMG which is always what I think of when hearing .50 cal. >>>>

Yep I'm building something in the way of a ML!
I normally lean towards a Mule ear or Underhammer percussion, but build whatever suits me at the time? this gun I'm considering, may end up as my Brother's Elk gun??

Respect Always
Metalshaper/Jonathan

ML--OK.

The last barrel I worked on was a stainless Shilen select match for my AR match rifle and I was astounded at how nice it cut, even full length cuts.

George,
Any idea what alloy is preferred for barrels? Some of the stainless alloys machine far better than mild steel, so that you found it easy comes as no surprise. Given a choice, I'd go with 416, which machines exceedingly well, and can be heat treated by conventional methods. Not being a gun person, I don't know if that's in keeping with desired qualities of barrels, however.

Harold

416 is the most common stainless alloy used for gun parts including barrels.

George,

Thanks for the info! I'm assuming this to be a 416 SS barrel.. I have to say it's quite a mystery, as gunparts swears it's a Denali? but the gal I traded e-mails with at Pedersoli, adamantly defends that D.Pedersoli never made stainless Denali's???

when compared to a pic of the carbon steel Denali barrels.. they have the exact shape and measurements??? So go figure! They did make another gun that used some of the same compnents, so It may be from that rifle instead??

I need to finish up this P.I.T.A Underhammer I'm building now... so I can move on to my new Muley and this SS gun.

Respect Always
Metalshaper/Jonathan