Thread: Back bevelled jointer blades

Haven't tried it, but when I heard him talking about it, I was thinking only a very flat angle of a few degrees, like with a plane blade. Personally I think those angles are all too steep.

Google turned up this: http://www.woodweb.com/knowledge_bas...ling_Tips.html

Wouldn't the back of the blade need to be perfectly flat also?

Does anyone go to that degree with jointer knives?

Not if you back bevel because the back of the blade is not part of the cutting edge any more under that scenario.

Like this one silent?

On the show he did show a picture and it looked like option 3. As he described option 3 gives a scraping action rather than cutting action. Hmm..

Yeah I was thinking 10 degrees but like I said, haven't tried it and that was just what I thought he meant. He doesn't actually say what angle.

But you would need to make sure that whatever angle you use clears the in feed table, you don't want the bottom of the bevel where it meets the back (front) of the blade coming into contact with the timber before the cutting edge.

Also I think the steeper the back bevel, the more force required to push through the cutter. One bloke in that woodweb link mentioned using a power feeder. So it's probably a trade off, like with a hand plane.

Originally Posted by silentC

But you would need to make sure that whatever angle you use clears the in feed table, you don't want the bottom of the bevel where it meets the back (front) of the blade coming into contact with the timber before the cutting edge.

Very good point.



I am really troubled by the concept now. On one hand if the angle is too small then it might make no difference at all. On the other hand, if the angle is too big then the machine has to work a lot harder to crape the wood off.

are you having any troubles with tearout Wongo?

No not really. but isn't it for the more difficult grains?

if you're getting good results why bother.

If it ain't broke don't fix it!

go and make some sawdust instead

Doing a back bevel would be similar to a negative rack on a saw blade. It would reduce tear out, prolong the edge somewhat but it would also compress the fibres in the timber - which could come back and bite you if your finishing technique isn't up to scratch.

I gave it a go on the jointer knives last night. I cut the back of the knife as a very small angle, just like option 1 above. Thne I tried it on a piece of jarrah which has irregular grains and a piece of rosewood. The results were pretty but I wasn't sure whether it was because the knives were newly sharpened. I did feed that I had to push the wood harder but the extra effort is insignificant. I think I will do the thicknesser knives too this time and see how it goes.

Cheers

There's got to be something in it I guess. Otherwise people wouldn't do it. I suppose it's a matter of finding the right bevel angle.

I searched through all my books and couldn't find a single mention of it, including Leonard Lee's sharpening book and my old WW textbooks. Might be a matter of trial and error. Just hope you don't grind all your blades away before you find it...

When you find the best angle, let us know

Silent, I am not sure if I would waste my time to find the correct angel. What is the correct angle anyway?

You know I am not like those who must get the blade angle to the nearest 0.0001 degree. No I am not.