Machining new takedown pins - Help please

Markit

CGN Regular
Rating - 100%
61   0   0
Hi all,

Seeking some guidance on a fixture to assist in machining the slots / channel in a new custom oversized pivot pin for my BCL 102.

I am told by SFRC that the front pivot pin is proprietary to BCL so finding an off the shelf oversized front pivot pin is likely not going to work.

Turning the round stock to the correct OD is obviously not the issue using my lathe. I have turned several that I have then screwed up as the problem I am having is machining the longitudinal groove / slot for the detent retention pin.

I do not have a milling machine and have tried to do this using the tool compound using shims (the part rotates and I do not get a uniform cut) as well as the milling attachment I adapted to use with this lathe and am having the same issue with the pin rotating when using a mill end in the chuck.

The only solution I can think of is boring a square bar or old cutting tool lengthwise to the correct ID so the pin fits in, and then machining a wider slot in that square bar to access the pin with a mill end, and drilling and tapping screw holes in the square bar to use set screws to hold the pin in place so I can Mill the slot / groove for the detent.

There must be an easier way.

Anyone have any suggestions?

Many thanks in advance.

Markit
 
Last edited:
If the pin is moving while you are trying to cut, the logical answer is to tighten the damn thing down in whatever you are holding it in.

If you cannot or do not wish to lean on the clamping of the part for fear of marking it up, build the part so that you can clamp it down and turn off the damaged parts later.

I have made a fair few parts, with a great deal of milling, using a Myford 7 inch lathe with a milling slide attachment, and the mill cutter held in the 3 jaw chuck. Not ideal, but possible.

Sorta need better details to get better answers. But it does seem to be an issue of either work holding, or maybe, too heavy a cut being taken.

If you are using one of the low rent vises like a Palmgren, you might find that putting a part of similar diameter at the back of the jaws helps, else the jaws spring a bit and tilt towards allowing the work to escape. Having a stuffing in the back will help keep the jaws parallel.

Strips cut from beer or pop cans work well to allow the hard jaws to grip either your end mill or the work, too, and can reduce or prevent marring.

Or a custom work holding fixture. That can work too.
 
Back
Top Bottom