Sloppy-Fitting Biscuits
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A primer on what's too loose, too tight, and just right. February 25, 2005
Question
I recently bought a biscuit machine, after thirty years in business. It has a Dewalt blade. I made some slots with it and inserted some biscuits I had picked up somewhere over the years. (They were some other brand than Dewalt). The biscuits slip into the slots, but have play in them. Is this normal?
Forum Responses
(Cabinetmaking Forum)
From contributor E:
They will have some play, but there shouldn't be an excessive amount. The beech will absorb water from the glue and swell, which will take up the slack and tighten the joint.
From contributor D:
I also have the DeWalt biscuit cutter. I get my biscuits at Home Depot, which are made by Porter Cable and fit a little loose. I was concerned at first, so I did some sample pieces. You have to make sure you get glue into the biscuit cut out on both pieces. After the joint cured overnight, I ripped it on the table saw right down the joint. Sure enough, those things do expand and make a good, tight joint.
From contributor J:
I also have the DW and PC biscuit machine. I use the PC biscuits also. Once I have them in shop for a short time, I wind up having to sort them because bunches wind up tight. Usually I pile them up and then chuck them in the microwave for about 20 seconds or so, so they dry out a little and fit better.
From contributor I:
I find the Lamello, Kaiser, and Virutex brand biscuits are more consistent and of a better fit.
From contributor L:
Nuke 'em, eh? I've got to try that. I separate my biscuits into loose and tight depending on the type of fit I need for a particular job. Thanks for the insight.
From contributor J:
The other thing I found that helps is to keep the biscuits in a Ziploc bag. This helps keep them dry. I use the cheap plastic food containers to hold the baggies, which really does keep them under better control.
From contributor C:
I'm in hot and humid Florida (well, most of the year). I store my biscuits in zip-lock bags in the air-conditioned office, and also nuke them when necessary. Just be careful with the microwave. Those biscuits really get hot when the moisture boils out!
From contributor H:
I have started using a Kreg pneumatic pocket cutter and my biscuit machine is collecting dust. I have not found an application where it cannot be substituted.
From contributor J:
Biscuits sure as heck make alignment of parts to pocketscrew together nice and easy, especially glueups.
From contributor R:
I had the same problem with a DeWalt biscuit cutter. I had my saw man take a little off the sides of the cutter, and they all fit perfectly now. I'm thinking that the DeWalt must have a little more runout than it should, since we had the same problem with two DeWalts.
I still like the Virutex better. I bought one when they first came on the market, and it still works well.
The comments below were added after this Forum discussion was archived as a Knowledge Base article (add your comment).
Comment from contributor A:
I did what contributor "R" did and reduced the width of the cutter slightly and now the biscuits are nice and snug instead of sloppy. I also measure each biscuit with a digital micrometer and write the measurement in pencil on the side of the biscuit. It makes things go a lot easier. One thing you might consider is taking the silica packets that come in vitamin bottles and putting them inside the containers in which you store the biscuits; you'll see that they will shrink over time. I've seen them shrink up to at least .004 of an inch.
