Turning mandrel change

[Apollo]

I want to make the turning mandrel on my K&M neck turner a tad smaller.(less diameter) Reason; it will then match up with my turning mandrel on my Sinclair turner - which means they would all would match up (.001 under) with my Sinclair expander.
I would do the work on a mini-lathe. What would be the best material to use? Is there a sandpaper available that would work? Or...is this something left to professionals? I could sleep in a Holiday Inn if that would help.

Stanley

 

[mike in co]

if a ss mandrel... (if carbide no answer..send it back and ask for a new dia..)
the clue is to get the same finish and the desired dia...
take it slow...
320/400/600 and then polish with crocus cloth......

if it is .001 or less dif start with 600 and go slo..when close change to polishing...
let it cool before measuring...

mike in co

 

[Al Nyhus]

Jason, I've polished quite a few mandrels down to size in my mini lathe. Most of my .30 cal. mandrels are Sinclair .338 mandrels turned down and then polished to final size. Standard sheets of wet and dry cut into strips would tear too easily. Had the best luck using 3M crocus cloth cut into strips starting with 220, then 320 and finally polishing with either 440 or 600 with Marvel Mystery Oil as a cutting lube. Most any light machine oil (3 in 1, etc.) will do. Keep the abrasive moving and don't stay in one spot too long. It takes a bit of time to polish off a thou. or so on the Sinclair mandrels...haven't done a K&M, though.

Good shootin'. -Al