Thread: How much back bevel?

I've also got some curly spotted gum. I was planning on buying a Metabo Duo ROS to finish it.

I'm no expert (I seem to be saying that a lot lately) - I'd just go with 60 - 70 degrees effective angle as that's what HNT Gordon seem to use.

Try PMing apricotripper or searching back through the threads he has started, he put up a comprehensive thread a fair while back on back bevelling.

Edit: I think I'm thinking of this thread here, maybe check it out them send PM for more info.


Cheers...................Sean

Have you tried a scraper on it?

Thanks Scooter, did a bit more searching and found another thread by apricotripper that was helpful for the first question. Good little guide for making a very low angle back bevel guide too

Still have no idea about the second question though.

Originally Posted by silentC

Have you tried a scraper on it?

Don't have one, this being the primary reason for experimenting with back beveling. On the other hand would a bevel up attempt with the iron primary bevel ground to <20 degrees work?

I'm sure someone has tried it.

I made my scraper from an old saw blade. It's a very handy tool to have and the finish is like glass. Great for removing tear out and machine marks but not so good for flattening or removing lots of material.

Silent, scrapers are only for whiley old farts like you and me

Ah, I misunderstood, I though you meant a scraper plane. Either way the tearout generated with the No.4 plane bevel down is almost 1mm deep. Not suited to a hand scraper me thinks. When I said a mess.... I meant a MESS!

You can tell us from the rest by the crooked thumbs

They can be made to cut quite aggressively. I used mine the other day to remove some tearout lovingly introduced by my thicknesser. Probably not 1mm deep but still pretty nasty. Might be worth a try before you muck up one of your good plane blades

BTW regarding backbevel, I've got a spare #4 that has a 15 degree back bevel. I haven't spent enough time with it to really test it out but it seems to cut a bit better in some situations compared to the one with the 5 degree bb. The back bevel is only a couple of mm. I don't think it needs to be any more - not sure, one of the other guys will know for sure.

Originally Posted by silentC

...The back bevel is only a couple of mm. I don't think it needs to be any more - not sure, one of the other guys will know for sure.

My thinking is the same. It make sense to me for the back bevel to be <1mm deep so that the chip breaker can be positioned the same way on the iron. Of course this also limits the geometry change so it won't effect adjustments much either. I've got a spare iron and the smaller I make the back bevel the easier it is to remove later too

I'll take a couple of pics on the timber tonight so you can see what I'm talking about.

kman, I think the backbevel only needs to be very small, read < 1mm. Sure I saw that somewhere.

Originally Posted by kman-oz

To my mind the only practical and in-expensive way to do this is with a back bevel on the plane iron.

Hi Dave,

I don't know whether you ever see the UK magazine "Furniture & Cabinet Making" http://www.thegmcgroup.com/ccp51/cgi...f=1010FC#thumb In the May 2007 issue there was an excellent article on this by David Charlesworth, which covered the subject very comprehensively. Well worth reading if you can get hold of a copy.

Cheers

Paul

Thanks to all who replied, you've been a big help. I'm happy to say the back bevel operation was much more sucessful in both the No.4 and 5 planes, with only the slightest tearout at 15 degrees and only a few furry bits at 25 degrees. I also had a go at hand scraping the surface using the plane iron from a No.6 (2 3/8") and the result was very nice indeed. Still no sure how to get that gloss back, but I'm infinitely better off.

Thank you all again! Now I'm going to attempt to build a high-angle smoother/scraper plane

P.S. As soon as I get my camera back I'll provide some shots of the result.

I thought I'd update this thread with newer results since the last attempt at some curly timber; further refinment of the back-bevel operation has made me question the need for a HA plane at all.

The last back bevel I tried on the No. 5 plane used a primary bevel of 25* and a back bevel of 25* for a total iron cutting angle of 50*! Some research tells me this may be too high, so I've tried a few different configurations since then with even better results. First I left the back-bevel and ground a primary bevel of 20*.... smoother but no less effort to plane, i.e. lots of energy expended. Next I tried the back-bevel at 20*.... no less smooth, but less effort to plane. So, progress then?

In further iterations of this process I've now got both bevels at 15 degrees for a total iron cutting angle of 30 degrees, or roughly the same as a standard primary bevel with an additional micro bevel. Results: much easier to plane with only the slightest degradation of finish using a deep cut. Wind the blade back a little for a see-through thin shaving and the finish is almost perfect; nice semi gloss with no tear-out at all. A quick once over with some 1200 grit silicone carbide paper and Tung oil reveals a beautiful patina.

It seems that this method only really suffers when I attempt to take more than a medium to thin shaving. When attempting a heavy shaving the tear-out comes back and it becomes increasingly difficult to eliminate chatter, presumably because the un-supported edge has become considerably longer due to the very low primary bevel angle.

I'm not sure how much interest there is in this department, but in the interest of sharing knowledge (this is a forum isn't it ) I've added this for future reference for other cheapskates like me.