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Arbo
03-24-2004, 07:59 PM
I have a project which is baffling me. I need to modify a cast iron step pulley, reducing the bore size from 15/16 to 5/8" My plan is to bore to one inch, plug the bore with one inch CRS and silver braze it in, and then rebore to 5/8". That's the easy part...how do I cut the internal keyway in the resulting blind hole?

John Stevenson
03-24-2004, 08:06 PM
Machine the plug first to just under 5/8", plane the keyway in by using a parting type tool on it's side and taking very small cuts rack it thru the hole in the plug.
Then bore the pulley, press and braze in and final bore the 5/8" hole.
You may have to just clean the keyway up slightly with a needle file when you have done.
Second way is to drill a crosshole in the plug before pressing and brazing in, then bore the 5/8" hole.
Use the crosshole to allow the side mounted keyway tool to run into for chip relief.

John S.

[This message has been edited by John Stevenson (edited 03-24-2004).]

mochinist
03-24-2004, 08:17 PM
Could you use a round key instead?

SGW
03-24-2004, 10:41 PM
What John said. I've also done it by making an appropriate "shaper" tool out of drill rod, putting it in the milling machine (locking the spindle against rotation) and nibbling out a keyway using the quill feed lever.

If you try this, make the tool pretty thin -- not over 1/16" wide. It takes an amazing amount of force to plane off chips!