Muzzle threading help needed.

[raven7usa]

I see you have a G4003G, same as me. Your compound should be set at 60 1/2 degrees to give you a true 29 1/2 degree angle to the part you're threading.

 

[6literZ]

Here is an attempt from today.

This is .500-32 and I was able to get the thread pitch diameter to .4872" with a pass feeding in .001" on the cross feed and then a few spring passes.

I sharpened my 60* cutting bit on a wet stone to a nice fine finish.

I also cut at 200rpm. That kept me on my toes!!




I don't have any muzzle devices free to check fitment, but I believe it would be a good fit theoretically.

 

[6literZ]

When you set the threading tool with the fishtail, simply pull the tool back and see if it follows the angle in the fishtail. I only thread straight in when internal threading, because my compound won't swing around to do it. Checking with a protractor is a great idea, then mark something so you can repeat it.

WD40 is not cutting oil. Go to Home Depot or Lowes and by some dark theading oil in the plumbing section, preferably Rigid brand.

Thank you for the info, I haven't checked lowes for cutting fluid, but was SOL at Fleet Farm.

I see you have a G4003G, same as me. Your compound should be set at 60 1/2 degrees to give you a true 29 1/2 degree angle to the part you're threading.

Ok, that is a great help! I was checking online for where I read that. I'll adjust my compound.



On the topic of protractors to check the angle of the compound; I have been eyeing up a stainless steel machinist protractor, what does everyone use?

 

[chips&more]

I have not read all of the above. If I’m repeating I apologize.
1) If you put in a relief you lose an alignment feature when you screw together the male and female parts. That little shoulder with step helps alignment of the two adjoining parts. Of course this is only true if the two parts are machined correctly with tight tolerances at said connection. I think this is very important.
2) Threading up to a shoulder is not difficult. And it greatly helps if you only feed the cross slide for thread depth. Do not feed the compound. Just feeding the cross controls the exact placement of the cutter in the longitudinal direction (no creeping to the left). Just set-up an indicator or similar noting carriage travel. Set the cutter for a minimal distance/spec from the shoulder and zero your indicator.
3) If threading under power makes you nervous, then it can all be done with hand power. Just takes a little longer.
4) Good Luck, Dave.

 

[Holescreek]

What can I do to get smoother cuts?

Make sure your tool is sharp and on the center line of the part. Even though you had the compound set, you still need to use the side of the fishtail gauge lying against the side of the part to align your threading tool square to the barrel. You were kicking up burrs so either the tool height was off or it was not ground correctly. I use Rigid brand high sulfer thread cutting oil (used for pipe threading). Sometimes you need to make more tan one pass at a depth to ensure that the cutter didn't push away. When I'm getting close to finished I run sandpaper over the threads and take a spring cut to clean the threads out before I measure with a pitch micrometer. There's nothing wrong with Mauser barrel steel, you just need practice.

 

[Holescreek]

I have not read all of the above. If I’m repeating I apologize.
1) If you put in a relief you lose an alignment feature when you screw together the male and female parts. That little shoulder with step helps alignment of the two adjoining parts. Of course this is only true if the two parts are machined correctly with tight tolerances at said connection. I think this is very important.
2) Threading up to a shoulder is not difficult. And it greatly helps if you only feed the cross slide for thread depth. Do not feed the compound. Just feeding the cross controls the exact placement of the cutter in the longitudinal direction (no creeping to the left). Just set-up an indicator or similar noting carriage travel. Set the cutter for a minimal distance/spec from the shoulder and zero your indicator.
3) If threading under power makes you nervous, then it can all be done with hand power. Just takes a little longer.
4) Good Luck, Dave.

I disagree with #1. If you make the shoulder behind the relief square it provides the perfect surface to tighten up against and the 2 or 3 threads immediately in front of it aren't doing any work anyway. You can design brakes to tighten against either the muzzle or the shoulder depending on the application, I've made dozens of specialized brakes both ways.

Here is my current project, threaded with a relief and the brake screwed up against the shoulder. No "barrel on the lathe" O.D. sizing was required. This brake is in stainless steel. I have a matching brake made from barrel steel that fits identically but will take parkerize:

 

[chips&more]

I disagree with #1. If you make the shoulder behind the relief square it provides the perfect surface to tighten up against and the 2 or 3 threads immediately in front of it aren't doing any work anyway. You can design brakes to tighten against either the muzzle or the shoulder depending on the application, I've made dozens of specialized brakes both ways.

Here is my current project, threaded with a relief and the brake screwed up against the shoulder. No "barrel on the lathe" O.D. sizing was required. This brake is in stainless steel. I have a matching brake made from barrel steel that fits identically but will take parkerize:

I disagree with #1. If you make the shoulder behind the relief square it provides the perfect surface to tighten up against and the 2 or 3 threads immediately in front of it aren't doing any work anyway. You can design brakes to tighten against either the muzzle or the shoulder depending on the application, I've made dozens of specialized brakes both ways.

Hi holescreek, you have every right to disagree with my statement. And I will disagree back at you. The shoulder does lock in angular alignment but it does not help with parallel misalignment. With your method, the ramping of the angle of the threads when tightening would be your only means for parallel alignment. If you had a nice fitting shoulder that would be your positive contact for that alignment direction. Good Luck at your projects… Dave.

 

[6literZ]

Practiced some more thread cutting. I am using a cutting fluid now, and have also tried setting up my dial indicator temporarily indicating off the carriage.

I also have been practicing cranking out the cross slide as well as throwing the half nut lever simultaneously when the dial indicator hits a certain spot.

I've also cut right to a shoulder, as seen here. Although I cheated and put a chamfer on it just in case.





And here is the wobbly dial indicator. Where can I purchase a mount that will attach to the ways of my g4003g and clamp the dial indicator. I've seen plans, but I don't have a mill yet.



Thanks again.

 

[dave2176]

Enco has a mag base part number ME625-0440 or ME505-1852 both reasonbly priced. Should do the trick.
Dave

 

[Andre]

I would try using an upside down threading tool, with some back rake, and run the lathe in reverse at maybe 600 RPM. The faster speeds and back rake might help with a cleaner cut, but I have never tried that. Running it in reverse and feeding away from the chuck allows you thread at fast speeds without crashing into the shoulder.
Motor oil is an okay substitute to cutting oil, but don't breathe the fumes and use a respirator or ventilation system if possible.

And yes, I do believe that old barrel steel is not the best.