Biscuits Versus Dowels

      Which is stronger — and does it matter? Cabinetmakers exchange views and information. July 9, 2005

Question
I'm currently constructing boxes with veneer core plywood. I use biscuits and screws. My question is, would using a construction borer with dowel construction be as strong as biscuits and screws in the veneer core plywood?

Forum Responses
(Cabinetmaking Forum)
From contributor W:
Why bother with the biscuits? We have been stapling/screwing for years without a single problem due to strength.



From contributor M:
I agree with Contributor W. We build mostly with 3/4" melamine, but a small percentage with plywood and mdf too, as in glass door and open cabs.


From contributor S:
To the original questioner: Yes, if not stronger and faster, too. If your dowels are 30mm - 35mm, and they are inserted horizontally, you will have the advantage of surface area and sheer strength. Add to that confirmats (sometimes called metal dowels) and glue, you will have joints that will not fail. Having used both, I have a limited use for biscuits. Dowels are much more accurate and a construction boring machine is much faster.


From contributor A:
I'm with Contributor S. Dowels are stronger and faster, but you need the right equipment. Clamping can be frustrating without a case clamp. I have changed from biscuits to dowels to dado construction done on a CNC.


From contributor L:
It seems either method is fine if properly done. We've used biscuits, confirmats and dowels, and they all have their place. Dowels require exact machining and a case clamp to work well. If you don't get it clamped up very quickly, the glue will set too soon and be torn loose in late clamping.


From contributor G:
Dowels do not make a stronger joint than a biscuit, and they also do not have more surface area than a biscuit. A 1/2" diameter dowel would have to be 5-9/16" long to have the surface area of a #20 biscuit.
Splining dowels to allow glue to escape the hole decreases their usable surface area even further.

Half of the surface area of a dowel is end (short) grain, while biscuits maximize long grain surface area. In many joints, dowels serve only to align the parts, and rely on the surface glue of the two mated surfaces for the majority of their strength. Dozens of easily located technical articles demonstrate this. Biscuits outperform dowels in wood, particleboard, and mdf.

John D Wagner in Fine Woodworking:
T and G joint, glued,no reinforcing: 1250 pounds to destruction
T and G joint, with 2 each 1/2" by 5-9/16" dowels- 1800 pounds to destruction.
Butt joint, Two #20 biscuits: 2700 pounds to destruction.

More technical information is available here: http://journals.tubitak.gov.tr/agriculture/issues/tar-04-28-5/tar-28-5-2-0311-1.pdf
See table seven.

At any rate, dowels might be strong enough. They might be faster and you might like them better. It's easier to drill a hole than a biscuit slot. But to answer the question that was asked, I would answer no.



From contributor T:
If you have the proper machinery, dowels are more accurate and much faster. However, for cabinet construction in most small custom shops, either one is total overkill. Use a couple 1 1/2" staples to tack your sides to your bottoms, and then drill a #6 pilot hole and use 2" x #6 course drywall screws. I have been in the cabinet business for 21 years and have never had a single failure. So to answer your question, biscuits are stronger then dowels, but both are overkill.


The comments below were added after this Forum discussion was archived as a Knowledge Base article (add your comment).

Comment from contributor A:
Though a biscuit will never break, the wood around it will collapse with the right force. It’s not all about surface area. Dowels go all the way through the wood making them much stronger.



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