what am i doing wrong?
Re: what am i doing wrong?
The opposite I think. Forstner bits clear chips poorly. No clue about the glazing. Sounds shiney to me. Shiney is usually good, no?
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Re: what am i doing wrong?
I would think shiny outside good, shiny (burned) inside bad. You want it smooth, but not shiny.
Cheers,
Rob
Rob
- KurtHuhn
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Re: what am i doing wrong?
m.c. wrote:KurtHuhn wrote:What's the disadvantage of a glazed wall?
And what's the difference between a forstner bit and a spiral bit as far as mortise drilling is concerned? Does the forstner bit clear chips more efficiently than a sprial bit?
Glazed wood is burned wood. It's also very unstable in moist environments since you've squashed the fibers rather than cut them. In a mortis it could expand to the point where the stem would be near impossible to remove.
Forstner bits are very poor chip-clearing bits. A standard twist drill bit is much better at clearing chips. When I use a 5/16" forstner bit for a mortis, I usually only advance the bit one rotation of the tailstock feed at a time, clearing the chips in between.
Re: what am i doing wrong?
Thanks. I did some experiment last night. Yes, clearing the chips is a must! Otherwise the bit squeaks badly in the hole. And being slow is the key, both RPM and advance! However, I still find some slight taper when measuring it with the calipers, about 0.2mm-0.3mm in difference between mortise rim and bottom. I will experiment more to figure out.