Here’s the goal:
My first challenge was finding the material to make it out of. Pretty much any plastic would work. Even so I called around and had a hard time finding a reasonable price on anything less than a large sheet. I originally though mcmaster was too expensive, at $20, it turned out to be my cheapest option. The piece I got was a 12″x6″x1″ block of HDPE.
First (not shown) I used a table saw to cut the stock to the correct height. After that I milled off the depressed area on the top. I’ve never machined HDPE before, it cuts great! Nice clean shavings and no melting!
I decided to tackle the radius for shoulder surface next. This was going to be the hardest part, so I wanted to get it out of the way early, lest I ruin the part when it’s almost finished. My plan is to attached the work piece to a board and mounted the board such that it can pivot around the center point of the radius. That way I ccan sweep the part under the endmill in an arc.
The pictures a bit blurry, but you can sort of see the center point I drilled on the left side of the board. The radius is 6″.
The drill bit sticking out of the board is the pivot point. I locked the end mill 6″ out from that point.
It worked! The cutting was a bit rough, in retrospect I should have done a rough cut with a bandsaw first so I didn’t have to plow through so much material.
The next step is to make the cutout in the center. The vertical and horizontal slots were easy enough.
The diagonal slot was harder. I can’t make a straight cut diagonally on the mill, so I have to somehow fixture the part at an angle. ..I don’t really want to make a jig for this one cut.
I thought about it for a bit and realized that if I cut the corner off now I can use the scrap piece to hold the part at the right angle like so:
The diagonal slot and the tapered front are parallel, so it works out.
To keep the pieces from slipping I put a threaded rod through both pieces. (I quickly viced the piece and drilled the bolt holes first).
And cut. mrrrrrrrrrrrrrr. The quarter inch endmill isn’t long enough to do the whole depth at once so I had to flip the piece after this and make the other half of the cut.
To finish the stock up, I put a 5/8″ endmill on the lathe and used it to counter-bore the bolt holes. Because the centers were already drilled plunge cut went really easy.
Looks awesome! That’s one part down. The right bolts hadn’t come in yet, but I really wanted to get it mounted so I scavenged some bolts from around the shop.
Next up: mounting the ak47 grip.