Biscuit Thickness vs Biscuit Jointer Blade Kerf

[charlessenf]

OK, I've a biscuit jointer and a bag of Vermont American #20 Biscuits.

To me the Kerf on the Jointer is too large (wide/thick) and the pocket created with it too large for the biscuits.

But what do I know, right!

So, I thought to ask here before touching my project with this Jointer blade.

I measure the biscuits and they look to be right on 1/8" inches thick.

The pocket cut by my jointer looks to be about 3/16"

When I place the biscuit in the pocket, it's sloppy.

Now, I know they aren't supposed to be a tight fit or required hammering into place - but I thought they were supposed to help with registration.

I am attempting to join two pieces of MDF along a 29.5" edge to another 29.5" edge that will be reinforced with 3/4" wood screwed and glued across and underneath the joint - a counter top project

QUESTIONS:

1. Is the kerf too large at 3/16" ?
2. Is the Biscuit supposed to fit Loose, Snug, Tightly?
3. Is the biscuit supposed to help align the pieces joined?
4. Given that the work is MDF, can I use regular ANSI/HPVA Type II Water Resistant Wood Glue (Gorilla non-foaming Wood Glue)
5. If not the glue (above) is there a prefect adhesive for such a task?

If you've a biscuit jointer that performs differently, please share the details and kerf size (esp.)

Thank you for taking the time to read this.

 

[JimD]

If the slot is 3/16 it is too large. I have not used Vermont American biscuits but I have used several other brands of biscuits and have never seen a significant difference. My jointer is an old Skil and the slots that it makes require me to push hard or, more often, tap the biscuits into the slot. I think that is the normal fit.

Your wider slots could be a technique thing - you might want to try different ways of using your tool - but I have seen reviews where they mentioned oversize slots as an issue with some biscuit jointers. My guess is the blade is wobbling a bit relative to the wood.

 

[Roy G]

Charles, is the blade on your jointer 3/16" thick?

Roy G

 

[patlaw]

The "standard" biscuit dimension is 5/32", or so the Rockler catalog says.

 

[Berta]

Just pointing out that biscuits are a bit smaller in thickness because they are made to swell up when the glue is introduced so they will be perfectly tight in the joint.

 

[gator]

Berta is correct as to thickness. As to the slot being too long: it is long on purpose so that after joining the two workpieces you can adjust them so the registration marks can be aligned perfectly and clamped. If the slots were exact length and you missed cutting the slots by a gnat's whisker the pieces would not be able to be aligned.

George

 

[Jeff]

Biscuit joiner blades and wood biscuit dimensions are standardized. Most blades are 4" diameter and about 5/32" t (0.156" t). See #20 biscuit dimensions in the table. Also see pic #3-the slot is a bit longer than the biscuit length so there is some wiggle room for alignment.

https://en.wikipedia.org/wiki/Biscuit_joiner

 

[Volksdad]

QUESTIONS:

1. Is the kerf too large at 3/16" ?
2. Is the Biscuit supposed to fit Loose, Snug, Tightly?
3. Is the biscuit supposed to help align the pieces joined?
4. Given that the work is MDF, can I use regular ANSI/HPVA Type II Water Resistant Wood Glue (Gorilla non-foaming Wood Glue)
5. If not the glue (above) is there a prefect adhesive for such a task?

Charles:

1 no. The slot needs to be wider than the biscuit. When the joint is done it will be tight. The biscuit swells with the application of a water based glue. The pressure of the swollen biscuit along with the glue strength makes the strong joint.

2 it should be loose when dry and slightly snug when glueing up. Biscuits are made with compression and heat to remove the water. If you want to see what the biscuit looked like before the process, iron it with steam. It will swell right back to its original shape. Because Wood is organic and because humidity and temperature varies, compressed biscuits will vary slightly in thickness. When I am joining with my biscuit joiner if the dry biscuit Is snug In the slot during my dry-fit then I throw it into the trash. Once a biscuit swells it does not “unswell”. You cannot recompress them.

3: yes. It will when dry if you cut the slots properly. To align two boards, I will work on a clean flat surface. Clamp the board flat on the surface and use the base of the joiner to align the slots. I don’t like using the flap and cutting slots “freehand”.

4: That is what I would use.

5: I think you have the perfect adhesive.

HTH

One last piece of advice. I think that you should do a test of a biscuit joiner joint with two pieces of MDF and one biscuit. It doesn’t need to be 30 inches long-just two little 5 inch long pieces. Make your Slots, put glue in both slots ( not on the biscuit) and clamp them together. Wipe your squeeze out and come get it an hour later. The biscuits swell and lock the joint in about 20 minutes. Your glue should be set in an hour or so.

Glen

 

[gator]

One more thing to watch out for when using biscuits is if you are using a very soft wood and/or cutting the slot close to the surface is the swelling nature of the biscuit. You will find in these cases that there will be a slight (in some cases a Very slight) bulge on the surface of the workpiece over the biscuit. You will have to do some light sanding to bring the bulge back down to the surface of the piece.

George

 

[charlessenf]

I want to thank all who took the time to reply and even look up helpful links so I might learn the origin of the Plate Joiner!

For what it is worth, I decided it was my Harbor Freight Tools Joiner that was the issue. Either the KERF on the blade or the 'wobble' of the blade resulted in a slot that was nearly 1/16" greater than the 'standard' biscuit thickness. As such, the biscuits were way too loose to the point of falling out of the slot during a dry fitting.

I found a DeWalt on Amazon Prime for $169 and thought to get it a LOWES instead (Shop Local!) because Home Depot had the Porter Cable 557 for $199 ON LINE but would not factor in my discount if I bought it off their web site. When I got to LOWES, I found they had the DeWalt priced @199 and would honor my discount, but would not Price Match the Net. So, I bought the DeWalt and went home to finish the project. Too late to start so I went online again and figured out that I could get the Porter Cable (one of the few that takes the smaller blade for detail biscuitry) for about eleven dollars more than I paid for the DeWalt - delivered Saturday morning. So the DeWalt goes back. I did try Klingspor, I did not consider the Lomello @ $1,500US!

I think the biscuit should confirm the alignment. From all the U-tube videos I watched (dozens!), it appeared this was the way 'everyone' was using them. I think of them as intermittent little splines with grain in the appropriate direction. Maybe they should be 1/16" loose, but I can't buy that proposition.

There may have been some confusion as to what I meant by the thickness of the biscuit and the thickness of the biscuit slot - I may have said width at some point. I know the slots are longer than are the respective biscuit and this is a feature that affords one a bit of flexibility in aligning the two boards before the glue sets.

Again, thank you for all your help!

Charles

 

[bob vaughan]

The lemon splines, as they were first called, is a European origin gadget. The slot is supposed to be 4mm and the biscuits slightly less. The back end of a 5/32nds drill bit should slide in the slot easily since it should be 3.962 mm. Usually the shanks of drill bits are a thou or two under nominal size.

To measure the slot cut by your biscuit jointer, slip various size drill bits in it until one fits pretty good. Observe the size of that bit. It it isn't a 5/32 bit, then its time to do some diagnostic work.

 

[JimD]

If I ever get a new biscuit joiner it will probably be the PC. All the reviews I've seen place it on the top of the reasonably priced ones. The DeWalt gets good reviews too, however.

I use biscuits for alignment and I am sure it helps a lot but it isn't enough in my experience if the boards are pretty warped. In those cases it helps the mis-match but doesn't eliminate it. I've read that dominos align better but never tried them. That tool is really expensive.

 

[charlessenf]

"If I ever get a new biscuit joiner it will probably be the PC (557)"

I would agree. Mine served me well - bought it off Amazon ($199) last week. The older Biscuits I had were a bit snug - hard to pull them out after a test fit.

So, I bought a jar of DeWalt Biscuits from Lowes and mixed a couple of the old ones (tight fitting) with the fresh ones - somewhat loose-fitting. The TIGHT-FITTING biscuits held the joint together and aligned nicely and I assume the thinner, fresh biscuits went along for the ride.

I am joining MDF and was concerned about swelling. As far as I can tell, there has not been any swelling.

If one can get clamping pressure to hold the alignment until the glue sets, the loose fitting biscuits might be fine. I simply did not have that option as the counter top was as much as 7ft by five feet and I had no flat surface to support it - working on saw horses with boards screwed between them and a foam board to allow the saw blade to pierce the work and not the saw horses.

It appears the have worked out fine - but I am not ready to turn it over yet! Since it will be covered in Formica or similar laminate, I suspect all will be fine - though getting into place when completed will prove 'interesting' or better.

 

[tri4sale]

If I ever get a new biscuit joiner it will probably be the PC. All the reviews I've seen place it on the top of the reasonably priced ones. The DeWalt gets good reviews too, however.

I use biscuits for alignment and I am sure it helps a lot but it isn't enough in my experience if the boards are pretty warped. In those cases it helps the mis-match but doesn't eliminate it. I've read that dominos align better but never tried them. That tool is really expensive.

I got lucky and found a Porter Cable at an estate sale, $20!! what a steal! Spent more on biscuits!!