are drill bits equally hardened throughout

[balddave]

hey, i recently had to cut down a 7/16 drill bit to about half it's original length and then resharpen it (couldn't fit a full lenght bit and drill in the space) anyhow, my reshrpening skills have provided adequate results in the past(just doing it by hand), but this thing wouldn't cut and just dulled away, could it be that these drill bits are only hardened at the tips? i'm really curious

thanks a bunch boys

[Alistair Hosie]

Ideally you should be able to continue sharpenning drills till there is very little of the drill left depends perhaps on the quality of the drill.Alistair

[aboard_epsilon]

Think if you get the tip too hot during the regrind and then let it air cool ......then the tip would end up soft.
all the best..mark

[CCWKen]

I've resharpened broken bits and they've worked.

[Timleech]

The drill web thickens as you get towards the shank, so you'll need to thin the point especially if you don't have a pilot hole.

Tim

[DR]

Some drills are hard through out, others are obviously soft on the shank.

Have you noticed how chewed up some bits are from slipping in chucks?

[psomero]

do you use a drill point gauge to check your work when grinding?

also, check the web thickness as timleech suggested.

[jfsmith]

My cheap drill bits are soft in the shanks, my good ones that get a lot of care seem to be harden through out.

Jerry

[PeteM]

Assuming it's a decent brand drill bit, and properly treat heated and sharpened, I'd say Tim has the right idea. Thin the Web. It's also slightly possible, with all the work to cut it down to size and sharpen a thick-webbed drill, that it was inadvertently tempered.

[spkrman15]

Bdave,

I would venture to guess that the web is too thick and that maybe you heated up the drill bit too much as you were sharpening it. I always keep some water beside me. I count to three as i sharpen and then dunk the bit in the water. If you can not hold it in your hand it is way too hot.

Spkr

[wierdscience]

Dunk the bit in water,then grind until it boils off.If you go the other way you risk micro-cracks and spider webing on the cutting edge shortening it's life in use.

If it's a HSS bit grinding to red heat and then air cooling won't effect the result much since HSS has a high red hardness.

A good bit should be useable for two thirds the length.