biscuit joiner gluing question

[Howard Pollack]

Hi- I'm not sure how to glue joints together using my new biscuit joiner. Do folks glue just the biscuits, or do you glue the whole length of the joint? Thanks. -Howard

[Kirk (KC) Constable]

Glue the entire length of the joint. Most folks will make sure there's some glue in the biscuit slots. I don't worry about it too much because I feel like they're more for alignment than strength...and some glue's gonna sneak down in there as you spread it on the edge(s) anyway.

KC

[Mac McAtee]

I have to respectfully disagree with KC. You want glue on the biscuits and on the joint. If you'll look at the biscuits you'll see that they have been compressed just a little bit. When you put glue on them they swell back up and help lock the joint together. Yes, they do help align the joint but their main purpose is to add strength to the joint and they won't do that unless they are glued and swelled up to fill the slot.

[Bob Reilly]

Have to agree with Mac

[Kevin Gerstenecker]

I have to agree with Mac. It is important to get the Biscuits and the Slots glued for the Biscuits to be most effective. While some will argue that they don't add much strength on butt joints, such as panel glue ups, they do their job on "T" type joinery. I was very sceptical when I first starting using my Plate Joiner, so I did a little experiment using pine. I cut slots in the edges of 2 boards, then dunked the #20 Biscuits in water and put them in the slots. After about 15 minutes, you couldn't pull the boards apart..............I finally got them apart, but it was a struggle. The Biscuits DO swell up and hold, just as advertised! While I rarely use them for edge joints when doing panel glue ups, they do have their place, and I use them whenever the need arises.

[Mike Evertsen]

I glue the joint the bisquit & the slot I don't over do it but enough to make a good glue joint without alot of squeeze out after a few joints fail you'll get it right,,,,

[Ron Meadows]

The myth that biscuits add strength to a joint, especially a long grain one, is quite funny. With the cure strength of modern woodworking glues the wood surrounding the joint are the failure points of a joint, if by some remote chance a falure occurs.

The only place that biscuits add strengh to a joint is in short grain, i.e. miter, joints. Don't go leading the guy astray and filling him full of mythes and stories of hocus pocus

Ron

[Kirk (KC) Constable]

I know I may be a minority of one...that's why I said 'most people...'

KC

[Steve Clardy]

I glue the whole thing, biscuit and joint. Whether or not the buscuit actually strengthens the joint, I haven't given it much thought. I use them mainly for alignment. Steve

[Eric Apple - Central IN]

Wow a range of advice... Use them and see if you like them. If so, use them all the time....

PVA,EVA glue on biscuits and in the slots... For long grain on edge, there is usually plenty of stength without a biscuit... But, put glue on the biscuit and in the slot anyway if you are using biscuits. You will add strength due to the 45 deg. orientation of the grain in the biscuit and the panel will not break at the joint. Ever wonder why when you purposfully split cut offs of glued panels they often snap near the glue line ? The grain is interrupted and the wood weaker at that point. For lamination glue ups on the face side, there's so much surface that you won't benefit in strength from anything. But biscuits can stop the panels from slinding around.

On short grain, the biscuits add the most strength. In fact they add a lot, and double/triple biscuits can be used very sucessfully to join large panel door frames such as exterior doors.