Jointer tolorence's?? Question/Advice

[Pierre]

Hey folks,

How picky am I supposed to be for jointing. I'm gluing up some oak for a table top that will be about 7 feet long. I'm using an 8 inch busy bee machine. As I hold up two piece's to the light, I'll see small small gaps that are easily closed during glue up in the middle. Is this normal?? or should I be more concerned with the infeed and outfeed tables. I've spent hours trying to realign the tables and still little gaps. The gaps I'm referring too are about 1/16. How much should I depend on the gap filling properties of the glue??

Hope this is a decent question in this group..

Pierre in Ottawa.

[Doug Miller]

Not that much, that's for sure. A gap of 1/32" in the center is not harmful; some argue that it's desirable, because it makes the glue joint less likely to separate at the ends. But a gap of 1/16" is too much.

You may have your jointer knives set a bit too high. They should be just a hair higher than the outfeed table, just a couple thousandths of an inch.

Do a Google search on this newsgroup for jointer adjustments. IIRC, this was discussed in some detail within the last few months, and several posts had some excellent advice.

Great question, actually.

-- Regards, Doug Miller (alphageek-at-milmac-dot-com)

Save the baby humans - stop partial-birth abortion NOW

[Mike G]

Ideally you should be able to stack one board on the other and see no light. I usually shoot for the ideal since it means less stress in the joint.

I suppose a little light might be ok but certainly not 1/16 of an inch. In relative terms I wouldn't consider that a little gap, I'd consider it a gaping hole.

As for gap filling abilities. Most common glues don't have any and what they do have provides no structural strength. Epoxy or the like may do the job but they won't take stain and, in a gap like that, will look like hell.

I'm not familiar with a busy bee but if it is a jointer and you can't get the joint so you can't see light either there is something wrong with the jointer set up, your procedure, or both. A properly jointed board has a flat face. Not partly flat, not almost flat, just plain flat. When you put two flat faces together there will be no light.

Accuracy in any joint tolerances can be summed up easily. The closer you get to perfect the easier the project will go together and the better it will look. The further off from true the joints are the harder it will be to stick things together and the sloppier it will look. After that it is up to what the individual woodworker's threshold for a good looking project is.

[FOW]

You should be able to press your joints together by slight hand pressure. 1/

[Mike G]

True for most joints, dovetails, box, etc. You certainly don't want the so tight you have to bang them together. And it is true that some like to have the smallest of gaps in the middle of an edge joint so, when clamped close, there is tension on the ends of the joint. The part most subject to separation over time. I can go either way on that one but usually try to go with the no gap thing

[Preston Andreas]

If you have wide boards, then you have to use a lot more clamping pressure to pull it together. This means you have the correct clamping pressure where there were gaps, but there may be excessive pressure elsewhere in the glue up making the overall strength of the glue up weaker. I have had that problem and a resulting weak joint was the result.

I use a 4' starrett straight-edge to adjust the beds on my Delta 8" jointer. When I hold two boards together, there is only a glimmer of light through the joint.

The only gap filling glue with strength would be epoxy.