DBS-22 Grinding Issue

[Ric Albano]

Ken,

I am actually having a Tool & Die guy use the 4 facet bits i grinded for him to test.  I will let you know next week the results

Ric

[Ken S]

Ric,  I'll be curious to read what he thinks.

Ken

[Elden]

Ken in regard to your question, I believe your assumption of a pilot hole is correct as long as it of sufficient size to contain the chisel point or chisel edge. Of course, the said bit needs to be properly sharpened.
Some excellent reference material about drill bits are found at:

http://www.youtube.com/watch?v=rUMTJ9GZIC8&feature=endscreen
http://www.youtube.com/watch?v=hJItj_ISurY
http://www.youtube.com/watch?v=cqn2VPGYA9c
All 3 are by tubalcain

and:

http://www.youtube.com/watch?v=5n0PgLuSISE
by machiningmoments.

Elden

[Elden]

The "acid" test of a drill bit is in the chips (actually shavings) that come out while drilling.
1. Are there 2 of them (1 from each cutting edge)?
2. Are they equal (the same size ie thickness, width, not length)
If there are not 2 or are of different sizes, you do NOT have an ideal symmetrical drill bit. However, you can purposefully offset the center to increase the size of the hole. The above videos that I listed, cover this well.
This assumes all the other factors (angles, clearances, etc.) are correct which with the DBS they should be.
If one chip is smaller or not there, then that tells you that cutting edge has been ground off a little bit more than the other.

Elden

[Ken S]

Excellent post, Elden.  I have actually watched the you tubes before, but the time watching them again was well spent.  I like Tubal Cain, and the other guy is very informative, too.  I second your recommendation for them.

Good comments about the chips. Yes, that's the acid test.

Ken

[Ric Albano]

Ken,

I am sharpening some bits for a local Tool & Die Co this weekend.  I'll let you know maybe next week the outcome

Ric