Thread: Forstner lube
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G. Ross G. Ross is offline
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Default Forstner lube

Gramps' shop wrote:
I'm boring into some hard end grain using a pretty big forstner bit. This is on a lathe at a pretty low speed. Lot of smoke and heat with the first 1/4 inch, so I thought I'd stop and ask if I should lube the bit. I seem to recall seeing a demo where the guy used a light brush on of WD-40. The last thing I want to do is start a fire on the lathe.

Yes, I should be using gouges for hollowing, but I absolutely suck at this (although I anticipate improvement with practice).

Any thoughts?

Larry


Start with the largest bit you will use and go about 1/4 inch deep.
Change to one 1/2 inch smaller and go 1/4 inch, and so on til you get
to about an inch diameter bit and go as deep as you are going, pulling
it back often. Pull it out and cool with air gun and blow out chips.
Then do the reverse, using the next larger bit. It will cut only a
small part of the hole and create less heat. You have a shallow hole
to start each bit in since there will be no center dimple to hold it.

I measure the desired depth from the flat bottom of each bit and make
a mark on the shaft or even on the chuck with a magic marker so I will
know when to slow down and check the depth of the hole.

When the bit gets hot it expands and chatters when pulling back. I
try to let the bits cool between uses and sometimes touch the sides of
the warm bit with a piece of paraffin wax while it is warm. This
lubes it some.

Use a chuck with a drawbar hole in it and screw a piece of all thread
rod into it with a washer and thumb nut on the other side of the
tailstock. I did not do this when I first started and one day I was
backing out and not paying attention and the Forstner bit stuck. It
pulled the chuck out of the tailstock before I knew it. A spinning
piece of wood with a Jacobs chuck hanging out the end and slamming
into the ways every turn will wake you up in a hurry.

--
 GW Ross 

 Kinkler's First Law: Responsibility 
 always exceeds authority.