Machine a Cotter to lock a sliding part to a shaft

[jjr2001]

This is a part that will be used in an up coming project but I think this cotter and sliding shaft system
could be used in many applications in the home shop.

Cotter may refer to: Cotter pin, a pin or wedge used to fix parts rigidly together.

I did not invent this but I implemented it a bit different than the example I used to make it from.
It will lock a part to a shaft and prevent it from rotating or slipping. In my case I am using
it to lock a rail block to a vertical shaft. It could also be used to make an adjustable sliding table or dolly
for a photographic rail or a table on a machine tool.

The cotters are 3/8 diameter brass with 1/4-20 threads on each end of both.
The holes for them are drilled and reamed first in the block. Then the large 3/4" hole is
bored and reamed with the cotters installed and fixed with the 1/4-20 nuts and washers.

After the shaft (3/4") has been lapped to the vertical post the nuts are removed and the
front end of the cotters have the threaded ends removed. The neat thing here is that with
one 3/4" hole you are making the 3/8" radius on each of the cotters at the same time.
I like that, 3 functions done with only one hole drilled!

The cotters are then lapped for a fine sliding fit. The yoke is installed on the cotters and they
can now be used to clamp the rail block to the vertical post.


Cheers, JR