Dressing hole saws

[surlypud]

So one can apparently do a bit of grinding to the teeth on a cheap hole and suddenly achieve much better cuts and tool life. I have only see very brief mention of this and I would love some more detail about how it is done and if it really does work better. I included a photo from Brent Steelman's flickr stream where he basically says a much as my first sentence.

Any advice appreciated.
-Chris

6942224138_15d19aa685.jpg

[jaredjerome]

I tried this the other day and it worked awesome. However, it was with a fine tooth set, so of course I decide to cut some stainless and killed a couple of them.

I'm going to try it again with some regular hole saws and see how it works.

[ToddFarr]

It looks like the teeth have just been ground down at a slight relief angle, I'm guessing that the 5 deg he's describing.

Before


After

[jaredjerome]

I didn't really read the part where you asked how, oops.

In another pic on his stream he says he just hits them on a grinder or sander, can't recall. I just hit them one quick pass on a bench-type grinder and it was good to go.

[Alistair]

I used 8 degrees for the relief angle and did it on a bench grinder,




Also, perhaps overkill but I also got all the teeth height +/- 0.001 using a height gauge, with the hole saw sitting on a surface plate for checking. Mark the high teeth with a sharpie and hit them with the wheel another skosh.

For "real" milling machines this may not be necessary but on my benchtop machine having a tooth or two standing proud by too much caused snagging issues, breaking teeth.

Alistair

[ToddFarr]

Make sure you do add the a little relief though, don't want to be dragging any more metal over the surface than you have to.

[surlypud]

Make sure you do add the a little relief though, don't want to be dragging any more metal over the surface than you have to.

Thanks guys!

So that looks to answer my next question which was going to be "5 degrees from what reference point?" So based on your drawing and Alistair's post, I looks like I need to not only have relief from front to back but also from inside to outside?

[Alistair]

Thanks guys!

So that looks to answer my next question which was going to be "5 degrees from what reference point?" So based on your drawing and Alistair's post, I looks like I need to not only have relief from front to back but also from inside to outside?

Yep, front to back only.

Alistair.