Line Boring Bit Sharpening

Careful sharpening will renew the bits and preserve bored-hole accuracy. October 11, 2007

My line boring machine bits have dulled. I was going to replace them for $13 each. I know the sharpening service I use will sharpen them for $3 each, but I am concerned that the diameter will be affected. Do you sharpen them or toss them and get a new set?

Forum Responses
(Cabinetmaking Forum)
From contributor B:
I assume you are talking about a brad point bit. These are sharpened on the end and this does not affect the diameter of the bit.

From the original questioner:
They are brad point. Thank you. I would also add that the tips (all 3) are rather worn. Will the sharpening restore them all?

From contributor B:
If sharpened correctly they should be as good as new. That's the purpose of the set screw in the end. This will enable you to set all the bits to an equal length.

From contributor F:
I want to interject that improper sharpening of a drill bit can change the diameter of the hole it bores. The bit's diameter does not actually change, but rather the bit's center point is ground slightly off center, causing the bit to run eccentrically as it enters the material. I have heard of machinists purposely sharpening this way to get an odd sized bore. I post this only as information. You shouldn't think twice about having your bits sharpened properly by a professional sharpening outfit.

From contributor J:
Why bother sharpening? For less than $7 a piece (depending on size) you can buy new carbide tipped bits. Not worth the time in my opinion.

From contributor L:
Don't be shy of sharpening them, but check them when they come in and buy yourself one set for the machine and one set to be at the sharpening shop, and maybe a couple of extras for broken bits. Set aside a binder for others to change the bits and set the set screw at your determined length. Buy a quality digital caliper around 125.00 up; they give you repeatable measurements.

From contributor W:
Integra Tooling had them for $7 each last time we replaced a set.