Shouldn’t the face behind the cutting edge of a bit be flat? Am I making an incorrect assumption? Not sure if you can tell from the photo, but my diamond credit card file is only making contact along the inside edge and the outer edge. It would take me a half day to flatten this all the way and get a fresh edge.
Replies
Not a router bit expert...
I have always thought so, however, it is not actually necessary in order for the bit to cut. What is needed is a clean edge and it looks like you have achieved this.
If you think about it, a Japanese chisel has a hollowed out back to help with sharpening. Maybe that is the case with your router bit?
I believe (and hope) that you'll never have a feed speed that would interest the inner part of the bit. Realistically just the the first 0.1mm is doing the cut.
Consider when sharpening that you'll reduce the diameter of the bit, but that's no way around that.
I don’t think the carbide is hollow, it’s looks like your card is riding on a ridge at the junction of the body and carbide, try moving the card away from the inside corner especially at the bearing end.
Bingo.
Please remember, honing the back, (flat portion) of a router only helps minimally. Router bits really can't be sharpened, it changes their size and/or profile. Honing the back can remove some debris and freshen the edge a bit but that's all.
I started sharpening mine after reading an article like this one:
https://www.highlandwoodworking.com/careandsharpeningofrouterbits.aspx
Turns out diamond is harder than carbide.
I've always kind of choked on the idea that router bits cannot be sharpened. The last bit I bought was $93! I understand that it is possible to change the diameter/dimension of a bit slightly by sharpening. However, until my work achieves a level of precision where that might make even the slightest difference, (read here - that's NEVER going to happen!), I'm not going to worry about it.
This is typical for most bits I've touched up with a diamond card: they often have a belly. With the speed and power of a typical router it doesn't really matter whether it's flat to mechanic's levels or not. So I just shine the area right next to the cutting edge and it works.
Contrary experience to edwardxweber . . . I send my Whiteside and other high end bits in for sharpening. If you gather a few and send them in a flat rate box the shipping is inconsequential and the results are great.
Yes, straight bits of a specific diameter will return undersized but there is plenty of use for these and a few bucks is a fraction of their original cost for a "new" bit. Matched sets cannot be matched anymore but, a Roman ogee, chamfer, or raised panel that is a few thou less in diameter makes little difference in actual use.
You have to make smart decisions on this. I have a load of Woodcraft or Peachtree bits that I got for $5 each during a sale or at a show. These get used and tossed. A $75 Whiteside, Freud, or Amana bit gets sharpened many times.
Not contrary, exactly what I said.
Sharpening decreases the cut diameter, period.
Whether that bothers you or not is a totally different question.
Also, honing the back flat as most people do is not at all the same thing as sharpening the bevel, as is done in most professional sharpening services.
It would be like sharpening your bench chisel by only honing the backside, all you're doing is making the whole thing thinner.