It all depends on how fast you like to run. Stainless or even 4140 doesn't require the use of carbide for cutting or threading if the surface feet is kept reasonably low. In fact, you can obtain better surface finishes at slow speeds with HSS cutting tools when they are ground right.

Now, with all that said, carbide is a little more convenient in terms of aquiring inserts such as thinbits or numerous other models available. Carbide used to be quite expensive and if you weren't running at high speeds, became a little hard to justify. Now with the prices getting down much more reasonably, it's easier to make the change to carbide.
In short, threading barrels on a manual lathe can be done quite easily with either one, and will produce fine results. HSS might have somewhat of an edge due to it's toughness, where is carbide tends to be much more brittle. This comes into play when working with a manual lathe, rather than a CNC where the speeds and feeds are much more controlled.

I use hi-speed for all my threading.....it's so much easier to grind and besides it'll take slow going when you are threading to a shoulder.

Carbide likes to have a lot of surface feet!!

Triggerguard1,

Thanks for the reply. I run pretty slow on my lathe when I'm cutting threads, have found my 80 RPM speed produces a better finish then either my 42 or 150 RPM gears. At least on 1 to 1 1/16" diameter barrel shanks.

I was fitting a few muzzle brakes today and was having some problems with the stainless steel "pushing" when I was opening up the brake for proper cailber diameter.

My proceedure is to drill out the bore of the brake to around 0.020" undersized and bring the hole to final dimension with a reamer, cutting roughly 0.010" per side.

These reamers are brand new and my feed rate was very slow but still the stainless pushed out and formed a lip on the exiting side of the hole as the reamer passed through.

Am I doing something wrong? Should I be drilling closer to final dimension?

Thanks for your opinion!

50

Carbide is the way to do things in industry.
I always feel like I am doing everything for the first time and the carbide always breaks.
So I always use HSS or Cobalt.

Maybe if I was going to turn a barrel blank down to a #1 taper I would try my carbide bits again.

Are You tring to feed the tool in straight?

It should be fed in at the same angle as the right side of Your cutter. Use Your compound. The left side should do all the work until the very last cut. That way You can slope the grind of your threading tool down and away from the cut, like a "chip breaker" on a production cutter. I do all mine that way, and my threads come off the tool shinning.

I use both Hss and carbide indexable inserts.When I use Hss for SS ( It works beautifully) I use a Diamond tool holder ( as advertized In Home Shop Machinist) it really works beautifully. There is a great book by an Englishman named Martin Cleeve that I got about 20 years ago and I think is still in print. Cleeve describes many different ways to cut both internal and external threads. I've tried them all and they all work beautifully. He describes exactly how to grind your HSS tools using a grinding wheel not a belt sander. I usually cut at 60-80 rpm and take multiple .005 to .010 cuts . While watching the threads when I get close, I take .003 cuts and finish at .001.
Most machinists set the compound at 29 degrees and depth the threads by advancing the compound. You can also cut threads by setting the compound to 90 degrees or parallel to the bed and advancing the cross slide .010/cut and the compound .005/cut. These two changes are made before each cut is made. When this is working properly, the SS comes off the tool with a very pleasing hissing sound and the threads are absolutely pristine to look at. No chatter, galling . Just picture perfect. This gives me great pleasure when cutting barrel threads as you can get an extremely fine fit that only can help the final accuracy. -Rob

One thing that no one has talked about is cutting oil for stainless.

Stainless will require different cutting oil than chrome moly.

The last stainless barrel I installed, I went thru all of my four different cutting oils until one of them worked the best.

You will never guess what it was, Good old lard, yes pig lard. Got clean chips and even breakup of the chips and good cutting action. You just really have to clean it well when done.

Also remember to apply antiseize to the threads when screwing the barrel into the action.

James Wisner
Custom Metalsmith