Wednesday, November 24, 2010

More machining on the bolt......

Okay, so I had already turned down the outer end on the bolt in anticipation of machining the locking lugs on the bolt. The original Holmes design calls for machining 3 male lugs on the bolt. I have seen a few designs, such as the serbu BFG.50 that use only two lugs. There doesn't seem to be a whole lot of difference between the two, at least not when it comes to functionality. So, I went into my CAD system and sketched out the lug system, printed it out and glued it to the bolt face. From there I took a punch and outlined all the areas that needed to be milled out.
I had an old lathe headstock laying around that was still functional but had been replaced due to age. I made a set of mounts for the lathe headstock that would allow me to bolt it to the milling table. The headstock of the lathe had a locking stud and with that locking stud there are indicator holes every 6 degrees. I set the bolt up in the chuck on the old lathe headstock and used that as a dividing head of sorts. From there I just supported the opposite end of the bolt directly below the area being machined and then went to milling it out alternating between a 1/2" cobalt end mill and a 1/4" carbide end mill.

No, the wood is not what's supporting the bolt in those pics. There's actually a set of machined steel blocks under the bolt supporting it.

After a couple hours of cussing and milling, rotating and milling, and a whole lot more cussing, I had a more-or-less machined bolt. I wasn't real happy with the finish the end mills left (the cobalt one was getting dull and the carbide one was chipped pretty badly.), so I made sure and left about .01 inch of material on the area being machined so that I could fine tune the bolt with a file and some sandpaper. That was an exercise in insanity all by itself.

For those who are looking closely, you can tell this was indeed built in my garage, as you can see my weedeater in the background of one of the pics.

And.......after a short trip back to the lathe to take a couple thou off the outside of the bolt, this is what it looks like so far...
More on the bolt later. For now, it's on to the chamber and the actual tube receiver.....


  1. Yep, I got here from Unc's site but now that I've seen your work I'm hooked. I'm a wanna be fabricator myself but your stuff is so far above my head I'm getting the bends.
    Fantastic stuff. I'll be following with great interest.

  2. Thanks for the kinds word, and thanks for stopping by!

    I'm no fabricator, just a redneck with too much spare time and some power tools.

    Stop by again sometime!