Thread: Biscuit Joints Glue or not to Glue

You used to be able to get biscuits that were made from plywood type material that were quite strong. Then all of a sudden they started making them out of crappy particulate stuff that you can snap quite easily in your fingers.If your doing a 45 degree mitre joint these particulate ones are useless.Unless of course you trust the glue to work on 45 degree end grain,...I wouldn't. Biscuits are handy though when glueing boards together lengthways, much easier than dowelling. They are really only used to hold the boards on the same plane when clamping as far as I'm concerned, the strength is in the glue not the biscuit.
I have found that the usual Harron biscuits(and dowells) you get at your average hardware store seem to be a very tight fit in the slot my cutter makes and are usually sanded on a flat surface first so they dont have to be forced into the slot(however this might be different if you live in a drier climate). If you had to force them in then you probably would get the lumpy bits mentioned in earlier replies.

Originally Posted by artful bodger

You used to be able to get biscuits that were made from plywood type material that were quite strong. Then all of a sudden they started making them out of crappy particulate stuff that you can snap quite easily in your fingers.If your doing a 45 degree mitre joint these particulate ones are useless.Unless of course you trust the glue to work on 45 degree end grain,...I wouldn't. Biscuits are handy though when glueing boards together lengthways, much easier than dowelling. They are really only used to hold the boards on the same plane when clamping as far as I'm concerned, the strength is in the glue not the biscuit.
I have found that the usual Harron biscuits(and dowells) you get at your average hardware store seem to be a very tight fit in the slot my cutter makes and are usually sanded on a flat surface first so they dont have to be forced into the slot(however this might be different if you live in a drier climate). If you had to force them in then you probably would get the lumpy bits mentioned in earlier replies.

There are biscuits and there are biscuits. Lamello are the best and very, very strong; especially in the shear plane. Haron are adequate, at least they make them out of compressed beech. Bix is a very popular Australian brand and are best used as firelighters. They are milled from solid timber with the grain at 45 degrees as they should be, but for some reason they chose a species of wood so weak it beggars belief. Take a handful of Bix biccies and toss them on the floor; one or more will actually break! The little Triton biccies, being Made In Aus are no better. Both of these can be snapped in the hand with bugger all effort. Unfortunately I once bought a box of a thousand Bix and it'll take me forever to get rid of them as I only ever use them for alignment, like butt jointing Tas Oak boards to make panels

I have long suspected that those with the lowest opinions and worst experiences of biscuit joinery have only ever seen crap biscuits used or the joint was for the wrong application. Or both.

Oh, if your boards are at least 3/4" thick and you join them dead centre the chances of the biscuit "telegraphing" through to the surface is very remote. Go for broke. And what the other guys have said about gluing all the surfaces is good, get plenty of glue onto the biscuit itself and make sure the slot and all mating surfaces are coated. There are special Napoleon's hat-type glue dispensers which get glue right into the slots. A glue with a long-ish working time really helps here until you can learn to do glue-ups really quickly!!!

Originally Posted by Chief Tiff

There are biscuits and there are biscuits. Lamello are the best and very, very strong; especially in the shear plane. Haron are adequate, at least they make them out of compressed beech. Bix is a very popular Australian brand and are best used as firelighters. They are milled from solid timber with the grain at 45 degrees as they should be, but for some reason they chose a species of wood so weak it beggars belief.

That, Chief tiff, is an in interesting observation. My recent tests with Bix bikkies were to glue up some pieces of 75 mm X 20 mm boards at right angles, as one would for a frame (and panel) type joint. All the joints failed when the timber split, just at the edge of the bikkie, as we would expect. None of the bikkies failed, except for a couple where the edge of a bikkie was torn off as the wood split.

Makes me wonder if you got a crook batch. As you suggested, when the primary aim is alignment, bikkie strength is not a big deal, but there are many other applications where strength is important.

Nevertheless, I followed up your suggestion on Lamello, and saw their cutter. Was very excited until I saw the cost, over $2,100 on e-bay. Pass. However, the bikkies look like they are worth investigating. From where do you get yours?

BTW, I've used bikkies on 1/2 inch ply and MDF without any telegraphing, but not on 1/2 inch wood ... so thanks to the posters for the "heads up".

Originally Posted by John Samuel

Makes me wonder if you got a crook batch. As you suggested, when the primary aim is alignment, bikkie strength is not a big deal, but there are many other applications where strength is important.

Nevertheless, I followed up your suggestion on Lamello, and saw their cutter. Was very excited until I saw the cost, over $2,100 on e-bay. Pass. However, the bikkies look like they are worth investigating. From where do you get yours?

I bought those Bix biccies about 6-7 years ago; I've still got a few hundred kicking around. My local cabinet hardware store in Bundy sells them loose and they are exactly the same, and I know they are relatively new stock because the store goes underwater whenever Bundy floods (Google image Taylors Hardware Bundaberg)

I used to buy Lamello biccies through UK E-bay but I haven't bought any for years now as I find Haron are adequate for my needs and are available from the Big Green Shed. I did see them on a stall at the 2004 Melbourne TWWS but I wouldn't have a clue who was actually selling them. The reason I bought those BIX was because I had run out of Lamello and deliberately chose to buy Australian Made rather than Proudly Made in the USA/UK/Darkest Peru. One day I'll learn .

I wouldn't use biscuits in a panel under say 16 mm thick if it were a polished feature, what I have seen happen where they are to close to a surface , say within 4 mm or 5 mm or under that, is a few months down the track the moisture that was in the glue dissipates and the biscuit shrinks back . I only use them in gluing up tops as an alignment aid and have seen shallow set biscuits shrink back and show up all the way down the top joints very clearly under a polished surface .



Cheers Rob[/QUOTE]


I said this before, thinking a bit more about it ..
I think that the 16 mm is safe

I think the times I did see it telegraph through, the Biscuit would have been under the polished surface about 3mm maybe 4mm .
Near or under 12mm is getting dangerous not 16mm as I said before.

I have only ever used the Bix brand as well , I've never been unhappy with them .

We were putting some in today and I was thinking of this thread.
Sometimes when putting the biscuits in they can be a bit of a tight fit , they can need a bit of a tap ,but if the mallet is tougher a wood than the biscuit, the edge of it can be damaged which leads to problems fitting what I am gluing on. The other problem is tapping them in can shoot the glue out of the hole each side going all over the place but at worst even in my hair. quite a few times Ive discovered this at home well after the glue is dry .

So I made this Biscuit Bumper a few years ago. soft Douglas Fir used on the wide flat to catch the shooting glue.

Rob