Machining SS Lapping plates

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valleyboy101

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Yesterday I bought 4 stainless steel lapping plates from my favourite machine store. They a 8" dia. x 7/16 thick and had a previous life lapping silicon wafers to a specified thickness.
I plan to use them on my rotary lapping machine, but first I have to cut a recess on the bottom side to fit the mount on my machine. The recess needs to be 5" dia. x .140" deep. Tonight I chucked the first one in my lathe and started cutting. Sudden realization - This is some Tough Stuff, I've got problems!
I took the edge off my last carbide insert and then set up a HHS left hand turning bit (i'm turning from the centre out).

It does cut, but at 130 rpm, extremely fine feed, and a .020 cut I get a high pitched howling vibration from The 3/8" square bit. The finish is however beautiful and smooth, but I hate vibration.
I think tomorrow I'll increase the rpm on the inner part of the cut and lower it down to 130 rpm. about half way out.
I am using a 13" Colchester which doesn't normally have vibration problems.
Any suggestions?
Like should I forget the HSS and just use new carbide inserts etc.

Any advise would be appreciated.
Michael
I
 
Try wrap the protruding part of the bit tightly with electrical tape.Should dampen
the vibration.It has worked for me.My two cents

Ariscats
 
I finished the last one the other night. The secret was a new corner on the triangular insert for ever plate and a higher speed.
Thanks.
Michael
 
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