Biscuit Shrinkage dents

[Clarence Miller]

Norm Abram quit using biscuits because after the glue lost all of its moisture and the biscuit shrinks leaving a dent. Have any of you had this happen in non televised experiences?

[Tom Giles]

If you allow penty of drying time before you sand you won't have dents. Might not be possible if you're a pro but a hobbiest should have the time to allow complete drying.

[Pat Barry]

Yes - I actually did. It was my first experience with biscuits - after watching a few of Norm's projects. It really bummed me out when the top developed those dents. It was red oak, 3/4 inch boards edge laminated with biscuits. I won't use them for this type of application again. I think it isn't needed for edge lamination. If you do need to do it, make sure that the biscuits are biased toward the side of the top that won't be seen. Keep as much material between the biscuit and this finished surface as possible. JMO

[Sam Murdoch]

Keep as much material between the biscuit and this finished surface as possible. JMO

That is the secret to success - keep biscuits at the center of 3/4" stock or slightly lower. I have used many thousands of biscuits in all kinds of application and only had the divets materialize once. That was on a table top that I had so much trouble developing the proper finish/color that I sanded it down 3 or 4 times pretty hard. Got to close to the biscuits - probably within less than a 1/4". The lamello biscuits that I prefer are very dimensionally stable - shrinkage or swelling is very rare. I have found that on occasion using biscuits that have not been stored in a sealed container that they seem tight as I dry fit them in the slot. In that case I throw a handful in the microwave for a bit until they are no longer swelled. Sometimes it just best to toss the biscuits that start out to tight. Again, I have only seen the divets once.

Biscuits don't add much joint strength to an edge to edge glue up but they do help to keep surfaces aligned which make gluing up and cleaning a top to flat much easier. These days though, I admit that I no longer use biscuits for glue up alignment, rather I use Festool dominos. They are much more precise. I use biscuits exclusively however for attaching face frames to cabinets - excatly because they are not precise but that they allow a little play.

[Charles Lent]

I've had them in a pine table top and had to make it over again. If you glue the biscuits in softwood and finish sand the surface of the boards before the moisture from the glue can equalize with the rest of the board you will get dents. This can even happen when you just join two softwood boards with glue and no biscuits if you finish sand the board before the moisture in the seam can equalize with the rest of the boards. To keep the dents from happening again I have stopped putting glue on the biscuits, only the seam and stopped surfacing the joined boards until a week after the glue-up . I only glue the edge of the boards and use the biscuits dry for alignment purposes only. It works for me.

Charley

[Bob Wingard]

YUP ... the "dents" aren't from the biscuits drying ... they are from the user flattening the surface while the biscuits are still swollen from the moisture in the glue ... THEN ... when they do dry out, they recede slightly, and you have the dents. Give them a little time to dry out, and they are fine.

[Van Huskey]

My experience is the same as Bob's, that said I have all but given up using biscuits for other reasons.

[HANK METZ]

Use a #0 biscuit installed dry, plenty of alignment meat and no possibility of pucker. Norm is widely credited with promoting biscuit use but he too had a learning curve and the effects of not centering and surfacing too soon was quickly discovered by him. Once he realized it's first purpose in life is alignment, the method rapidly gained acceptance in his shop; coupled with pocket screwing it's been a mainstay of his for years.

- Beachside Hank

[Don Jarvie]

Iv'e used biscuits for years and never had this happen. I'll have to keep this in mind in the future.

[Curt Harms]

I've never had it happen but I haven't used biscuits in solid wood much, either. They work pretty well for things like reinforcing mitered corners in sheet goods cabinets or attaching face frames.

[John Coloccia]

Use a #0 biscuit installed dry, plenty of alignment meat and no possibility of pucker. Norm is widely credited with promoting biscuit use but he too had a learning curve and the effects of not centering and surfacing too soon was quickly discovered by him. Once he realized it's first purpose in life is alignment, the method rapidly gained acceptance in his shop; coupled with pocket screwing it's been a mainstay of his for years.

- Beachside Hank

That was my first thought reading this thread. I see no reason the biscuit needs any glue on an edge glue up.

[Mike Monroe]

Never has happened to me, biscuit denting that is.

[John TenEyck]

Same here; thousands of biscuits overall, hundreds in hardwood - never had any shrinkage dents.

[Steve Griffin]

Same here; thousands of biscuits overall, hundreds in hardwood - never had any shrinkage dents.

Not a single problem here either, and that's using about one one or two 1000 count boxes a year.

The only glue that I put in the slot is the glue that happens to drip in from gluing the edge. Even for situations where they are used for strength, not just alignment. Also, I wonder if using dry wood and biscuits in a dry climate helps--there can't be too much glue which doesn't dry up overnight just like the edges of the wood.

I never use them for simple glueups which are manageable with good technique. But there are times when I wouldn't trade my biscuit jointer for all the ice cream in the world--like a when I assembled a 7"x 12" x 24' beam wrap on the ceiling a few weeks ago.

[john lampros]

I'm with Bob, I've used thousands of biscuits and never had that problem but I've been aware of it so I let critical pieces like table tops etc dry overnight and postpone finish sanding for more time. Some have been high gloss rubbed out finishes so it would have shown. And I coat the biscuit and the slot very well if I have the time. Its a machine, it does what it does. and like every other machine its the thing holding the handle that makes all the mistakes. a domino works on the same principal and is subject to the same thing although they have somewhat different purposes so you should still be aware of this phenom.