edge planing

[Paul Kierstead]

I have no data to support this, but it seems to me that a cambered joint introduces a gap just where we don't want one. Granted, the gap is small, still it's there, and I'd rather just to without a potential joint failure cause.

Well, there are a lot of combo's to be considered. First off, on a conventional sized edge joint (in the 3/4" ballpark), the amount of camber is extremely small unless you are jointing with a scrub plane. It would normally be well under 0.001". However, if the joint is clamped, the edges will certainly crush a little and eliminate even that very small gap; if you leave a very very small hollow in both directions and clamp, you are practically guaranteed a very tight joint with a fair minimum of clamping. If you are doing a rub joint, I think the rules might change a little, although again, the hollow is extraordinarily small, so who can say. The bottom line is that it works; it is possible to over analyze it.

Traditionally you'll see a lot less joints depending on glue strength alone in positions where strength was required.

 

[Paul Chapman]

The bottom line is that it works; it is possible to over analyze it.

Traditionally you'll see a lot less joints depending on glue strength alone in positions where strength was required.

All very true. In over 30 years I've never had an edge joint fail. But then I always use biscuits or plywood loose tongues. So whether it's skilful planing, or the biscuits and loose tongues, I'll never know. But I must be doing something right :wink: :lol:

Cheers :wink:

Paul

 

[woodbloke]

Paul K wrote:

possible to over analyze it.

Hmmm...my thoughts exactly. As ever, we all have our different ways of doing things and find ways that work for us. Onto our 6th page on this thread, eagerly looking forward to the 7th, 8th, 9th etc .......note to self, must remember not to fall asleep at the keyboard :roll:

Paul C - me and you the same, been doing this woodworky stuff for a few years and I've never had a long edge joint fail - Rob

 

[Scrit]

......been doing this woodworky stuff for a few years and I've never had a long edge joint fail - Rob

Well the one hand planed butt joint I can recall failing was on the maple chopping block I made for my kitchen. And that lasted 25 years until it started to open at the ends, but even then it was just the one joint (out of 6 or 7). Hardly surprising that it did start to fail because it's had a fair bit of abuse and moisture over the years. Oh, and that was glued with UF glue and I seem to recall that the joints were slightly sprung as well.....

FWW concluding that a sloppy joint will fail before one that fits properly, well there's a surprise :roll:

Scrit

 

[engineer one]

surely what everyone is forgetting is the strain imposed by clamping/cramping the board edges. :roll:

as i read the bits and pieces, not least DC 'imself guvnor' he suggests that the clamping process flattens the middle "hollow" section, and as has been said it is a miniscule amount :?

paul :wink:

 

[Alf]

Hmm, I just had a thought. If you don't get your blade edge absolutely square and then match plane, don't you end up with risking (miniscule) gaps on the edges of the joint? Tempting to bring up the argument that a theoretically square edge is probably actually a bit cambered too, but not my thing so I'll leave that to anyone who wants to argue it. Anyway given that, isn't it arguably easier and less risky doing individual edges with a cambered blade 'cos not only don't you have to worry about the mythical idea of an absolutely square edge on your iron but also any gap caused by the camber should end up within the joint and thus unseen?

Speaking for myself it doesn't bother me either way 'cos I don't worry about the camber introducing a gap of anything but theoretical difficulty, but for those folks who do worry about it I thought I'd just, well, add to your worries... Ah. Erm... Sorry, didn't really think this through perhaps... #-o

Cheers, Alf

P.S. Re: falling asleep. We could just sum this thread up as "if it works, it's right" - but then you could do that with most discussions and the forum would get awfully quiet...

 

[Scrit]

I've come to the conclusion that making the decision to move to machining the joints (with a dead flat blade) was a good thing after all. Less to fret about, methinks..... :roll:

Scrit

 

[Alf]

a dead flat blade

"dead flat"?! BB'll be all over you like a rash for calling anything dead flat. I mean for heaven's sakes, Scrit, there are engineers present. 8-[

Cheers, Alf

 

[Scrit]

What should I say - straight and flat within acceptable engineering tolerances? :wink:

Scrit

 

[Paul Chapman]

isn't it arguably easier and less risky doing individual edges with a cambered blade 'cos not only don't you have to worry about the mythical idea of an absolutely square edge on your iron but also any gap caused by the camber should end up within the joint and thus unseen?

I think the main difficulty with planing the boards separately is making the edge of both boards exactly 90 degrees to the side. Planing them together completely does away with this problem. By comparison, I think honing the edge of a blade straight (it doesn't have to be absolutely square with the side because you can adjust it with the lateral adjusting lever) is a doddle.

Cheers :wink:

Paul

 

[Nick W]

It's a fallacy that Engineering is all about accuracy. Really it's all about approximations that are good enough to be got away with. Sometimes those approximations need to be pretty accurate, sometimes, but not often. Stuff can be made to exacting tolerances, but that's not usually necessary, nor financially viable. Just because you can make surfaces square to within .001 of a degree and flat to within .1 of a thou doesn't mean you have to, or that you should.

Remember people, the bad news is that it has to good enough, the good new is that it only has to be good enough.

 

[pam niedermayer]

What's happened to Jeff Gorman's site? He's even blocked the Wayback machine. I went there to pick up the link for that great page on using cambered blades, but most of the old pages are missing.

Pam

 

[Paul Kierstead]

What's happened to Jeff Gorman's site? He's even blocked the Wayback machine. I went there to pick up the link for that great page on using cambered blades, but most of the old pages are missing.

Yes, I noticed that a couple of weeks back. Very sad. I hope he chooses to put them back up at some point; I always found them a useful resource and used them fairly often.

 

[dunbarhamlin]

Match planing with a straight edge blade only requires that the abutted arris of the two boards follow a straight line. Off true, or even wind (about the center) won't affect the match. For a sprung joint, I suppose the ideal shape would be a catenary curve no deeper than a shaved smidgen.

Amusing thought - if could introduce alternating riples of extreme wind centered on the common arris, would get an interesting interlocking joint. Have seen a squared version somewhere, think, in foil or plastic components. Hmm

 

[engineer one]

honest guv i only wanted to plane the edges,not get into the paranormal :roll: :lol: :twisted:

paul, who's now struggling again with dovetails see elsewhere :wink:

 

[Skip J.]

honest guv i only wanted to plane the edges,not get into the paranormal :roll: :lol: :twisted:

paul, who's now struggling again with dovetails see elsewhere :wink:

Hmmmnn.. I guess that would make this the "deep end"......

 

[dchenard]

It's a fallacy that Engineering is all about accuracy. Really it's all about approximations that are good enough to be got away with. Sometimes those approximations need to be pretty accurate, sometimes, but not often. Stuff can be made to exacting tolerances, but that's not usually necessary, nor financially viable. Just because you can make surfaces square to within .001 of a degree and flat to within .1 of a thou doesn't mean you have to, or that you should.

Remember people, the bad news is that it has to good enough, the good new is that it only has to be good enough.

I agree, as long as we don't use this as an excuse for sloppiness... :roll:

DC

 

[Anonymous]

snip
Have seen a squared version somewhere, think, in foil or plastic components. Hmm

Lego? Yeeah thats a good idea.

cheers
Jacob

 

[dunbarhamlin]

Maybe it is time to le'go of the bone.
No, really - remember being amused by it, but can't think where (and no it wasn't stickle bricks either)
Looking along the join from one end to the other, in cross section it would first look like a scarf with the right board uppermost, transitioning to a straight butt, then scarfed with the left hand upper most and back again. Might only be practical with power though.

 

[bugbear]

a dead flat blade

"dead flat"?! BB'll be all over you like a rash for calling anything dead flat. I mean for heaven's sakes, Scrit, there are engineers present. 8-[

Cheers, Alf

And woodworkers who've learnt enough to know what engineers think :twisted:

BugBear