Forstner lube

[Gramps' shop]

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 t o recall seeing a demo where the guy used a light brush on of WD-40. The l ast 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

[G. Ross]

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.

[woodchucker]

Larry, you are probably not feeding fast enough #1, try candle wax, at least if you light it, it will be a candle.;-) no seriously, I use wax sometimes, but I find burning a result of not feeding fast enough. I used to think my friend abused his tools as he always pushed the things to the point of bogging down, but he never burned anything, so there was something to his madness... __Now that you have smoked the bit, take it out, sharpen it__, then try again with more feed speed.

[Lew Hodgett]

---------------------------------------------------------------------------- "woodchucker" wrote:

----------------------------------------------------- SFWIW

Cerritos college, in their WMT courses teach to feed forstner bits as fast as possible to prevent heat build up and resultant burning.

It works for me.

Lew

[CW]

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

+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++= Forstner bits have no clearance so they create a lot of heat. Go very slow and use paraffin wax for lube. Pull it out of the hole frequently to clear chips and apply more wax.

[Leon]

If using a bit larger than 1" you are probably turning too fast.