Well the new lathe was ordered and delivered a few weeks ago and I now have it up and running. That means it is time to make some chips. I upgraded from a 7x12 HF mini lathe to a PM 1030v. I know thats still a small lathe to most but this thing is a monster to me.
Heres a picture of the lathe.
First I will touch on some of the tooling I am using.
I use mostly carbide tools for turning as I haven't yet mastered the art of grinding a turning tool. They never have come out quite right but maybe after a few dozen more tries, the well. I also ground an internal and external HSS threading tool. I am using carbide tipped boring bars, an inexpensive center drill set, a few HSS drill bits, a 5/8x24 tap, and a chop saw rigged up to act as a band saw.
Here are some of those tools with the 1.5 and 1.25 inch 303 stainless stock freshly cut.
Here is my "band saw" rigging.
Here is the threading tool before grinding.
And after grinding.
Onto some chips!
I decided this one would mount to a muzzle brake because I wanted to switch between a few rifles but I didn't want to deal with thread protectors and I also like shooting with brakes when I don't have a can on. My other suppressor mounts directly to the muzzle threads, which is fine, but I wanted something a little different for this one. It uses a 20 degree locking shoulder to index it in the can and utilizes .900x24 threads to attach to the mount.
I started with a piece of 1.25" stainless in the 4 jaw, dialed it in pretty close (getting perfect for this part doesn't matter. Then faced it and turned down a bit. I turned down some so I could check the alignment later with the dial indicator.
Once faced and turned it was drilled with a center drill, then through drilled with a .375 drill bit. Slow, a good bit of oil, and lots of clearing chips. Then it was drilled .65" deep with the .5" drill bit, then opened to the final diameter with a boring bar. I think that was about .58".
Then it was threaded with the 5/8x24 tap, soaked in oil, 2 full turns then a half turn back to break the chips. These threads were a little shallow, looks like I overshot it a bit with the boring bar. Still plenty of thread engagement, and I made two to start with anyway.
Next, I turned down a mandrel to mount the brake to so I could ensure concentricity. Doing this in the 3 jaw was fine since any eccentricity was taken care of while it was turned down.
Here is a picture of that mandrel. It looks like I forgot to take a picture after I threaded it.
Then mounted the brake blank. I checked the concentricity of the part I turned down. My .001" dial indicator was hardly moving, I think the tiny bit of vibration in the needle was just the surface finish.
And turned down to correct diameters.
Cut the locking shoulder with the compound.
Cut some 24 tpi threads.
Thats it for the brake for the moment. Though its worth noting this isn't exactly how I machined everything. I cut the inner threads and locking shoulder of the endcap/mount first so I wouldn't have to break down the set up and introduce eccentricity. I just thought the brake was a more fitting place to start the post.
So for the mount, it uses 24 TPI to thread into a 1.5" OD and 1.37" ID tube. There are .5" of threads on the outside and roughly the same on the inside. It uses the same 20 degree shoulder and .900x24 internal threads as the brake.
Started by facing off a piece of 1.5" stainless. In the 3 jaw it was out by about .005". Thats fine for this, all of the important parts will be indexed off the internal threads and they will be square.
Center drilled, through drilled with .375" drill, then .5".
Then stepped up to .750" drill. Lots of chips.
Then bored to the inner diameter. I can't remember exactly what it was, in the .850" region.
Then got it set up to cut the internal threads. I ground the tool at an angle like that because then I could grind away less for clearance and hopefully it would be more rigid. No idea how much difference it made but it cut well.
Threads look good.
Cut the locking shoulder.
Chamfer on the outside for aesthetics and weight.
That was it for the mount by itself. Next it was threaded onto the brake to be used as a mandrel. Doing this all in one set up ensures that the threads are parallel to each other and concentric to the center line of the lathe, which in turn will be the bore. I checked the runout after mounting and it had gone down from .005" to .003 to .004.
Once mounted, I turned the outer diameter to the thread major diameter and shortened it to the correct length. Squaring off both shoulders is very important for this part. This picture was right when I shortened it over the internal threads and they popped off.
Threaded. I needed to use a wider thread relief at the end.
Finished parts showing the threads and fit. They were so tight a marred the finish a little getting them apart. That should buff out later though.
Then onto the end cap. It is very simple, just .35" of threads, .085" thread relief, and a .375" hole right in the middle.
Started with a piece of 1.5" stainless and faced it.
Cut the diameter to the major thread diameter.
I ground a parting tool and used that to make a relief cut. I had never done an parting operations before this. My old lathe couldn't handle it but this one took it like a champ. A little bit of chatter but it cut well.
Threaded and ready to be drilled.
Drilled.
Boring out the inside. Boring depth was .5" total. I left a bit of a shoulder on the inside because I wasn't super careful with my thread relief depth and I was worried I would go to thin and the thing would come apart.
Then I parted it off with said parting tool I ground. You can see the little chips it was making. I think I was going a little to fast because as I got deeper, the chips got better and it cut better.
Post parting mess. Cleaned that up before continuing.
I flipped the endcap around, using a strip of aluminum from a Dr Pepper can to protect the threads. I don't know if thats the right way to do it, but it worked.
Faced it off to clean up from parting.
A little chamfer to match the mount.
Then I cut a little chamfer on the inside just for looks.
Thats all I have so far. I had a 1.5" 316 stainless seamless tube to use for the main body but while I was dialing it in, I found out it is no good. Warped, ovaled, distorted, anything but round and consistent. So I will be ordering a new tube to use, I will probably stick with 316 stainless since I don't think Titanium would stand up to my uses, as per the design thread. I still need to thread the tube and make the baffles and spacers.
I am open to comments, advice, and suggestions. I like to learn from others mistakes rather than my own if I can. Saves me time and money
