Help, biscuit joint shows 0.010" glue line on one side

[Clark Magnuson]

http://www.sawmillcreek.org/attachment.php?attachmentid=175830&d=1293866864
http://www.sawmillcreek.org/attachment.php?attachmentid=175831&d=1293867397
http://www.sawmillcreek.org/attachment.php?attachmentid=175832&d=1293867419
I am trying to make a 22" long by 20.5" wide by .75" thick cabinet bread board cutting board.

I have a bunch of 1x10 [.75" x9.25"] rock hard maple cut in 24" lengths.

To practice joining, I took two pieces of scrap and ran them the the Delta DJ-15 jointer with one board getting it's top run against the fence and one board getting it's top away from the fence in case I did not have the fence and blades perfectly square.

I cut three biscuit joints over the 24" length with a Porter Cable plate jointer model 555.

I glued up with Porter Cable size 20 [24 x 58mm] biscuits and Tightbond II glue.

I jointed the outside edges and then ripped down the middle a piece of old growth Douglas Fir 1x4 take off decking in half to insulate the clamps from the work.

The joint looked tight on top and the joint looked very flat when compared to a straight edge.

But when the glue was hard and I took the work out of the clamps, scraped off the glue beads and belt sanded, there was a ~ .010 glue line gap on the bottom. The sander takes out glue faster than it takes off Maple, so there is a ~ .010" trough as well.

This crevice is not good for food preparation.

Should I plan on filling gaps with some product?
Is there a way to avoid gaps?

Thanks in advance.

[keith micinski]

Two suggestions. I always use the same face for reference on every machine. If your machine isn't set up square then stop what your doing and get your machine setup right. A lot of people say that the machines don't have to be setup to as tight of tolerances as all of the digital gauges allow these days and I say those people are over 50 and can't be helped. The day I started getting all of my digital do-hickies and setting all of my machines up properly is the day my life got a lot easier. Admittedly you can build some mighty fine work with old machines that are setup by eye, but it takes a lot more skill and a lot more time to do it. Every thousandth of error you take out of the machine is another thousandth you can be wrong by and still have a piece turn out nice. The other thing I would suggest is when you clamp a glue up like that put two clamps on top of the board to counteract the bottom three. I would guess that the gap is on the face of the board that was facing up in the glue up.

[keith micinski]

As far as the gap, if it is a cutting board cant you just keep the gap on the bottom and make it a one sided cutting board. That one side should last longer then your going to be cutting I would guess. I don't think anything as far as a filler goes is a good idea on a food prep surface.

[Chuck Wintle]

i would rip it in down the glue line, rejoint the edges, test fit the pieces checking for flatness and no gaps and finally recut the slots for new biscuits and reglue. What I noticed during one of my glueups was one of the biscuits was a little tight and became "stuck" while the clamps were being tightened to bring the wood together. It caused a small gap to remain such as the one you have.

[Nelson Howe]

I agree that dividing your clamps top and bottom should help eliminate the gap. I don't agree about always jointing off the same face. I'm no expert, but reversing faces seems like a simple solution for a just in case problem, no matter how careful you are with your machines. It also seems that biscuits aren't necessary for strength in that joint, and I don't find them precise enough (maybe my biscuit jointer has too much slop?) to rely on for perfect board alignment anyway.

Nelson

[Terry Welty]

+1 for all the above, Set up your jointer accurately, table saw down the glue line, re-joint, check, re-glue, re-clamp. I wouldn't use the biscuits either.

[Chuck Wintle]

+1 for all the above, Set up your jointer accurately, table saw down the glue line, re-joint, check, re-glue, re-clamp. I wouldn't use the biscuits either.

I have heard biscuits add a lot of strength to a woodworking joint...is this wrong?

[glenn bradley]

If your faces are flat and there is no gap in the joint on one side but there is on the other, your face to edge joint is not perpendicular. If the gauges you are using to setup your jointer are declaring a true 90*, set them aside. Joint two edges of some face jointed material and lay them on a known flat surface with the edges together. You should have no gap regardless of orientation. If you have a gap, adjust your machine till you solve that. Then just for curiosity's sake you could check the machine with your gauges and see how far out of true they are.

+1 on solving the current problem by ripping and re-gluing. Many folks here (me included) get glue ready edges off the tablesaw. As mentioned, some folks scoff at getting your machines adjusted to within Nths of an inch or degree. I am not one of them. I'm in the over-50 crowd (I thought we didn't trust anyone over 30. Its 50 now? :D) and can say that taking the time to really dial your machines in tight pays you back in saved time and material 10 fold.

[Mark Rakestraw]

No argument from me that your machines should be set up properly, but Nelson's point about not referencing the same face off the jointer fence is a good standard practice. What that means is if you're looking down on the unglued joint run the board on one side of the joint through the jointer with the "face" against the fence and the board on the other side of the joint with the "backside" of the board against the fence. Whatever error there may be in the 90 degree setting of the fence will now cancel itself out.

[Peter Pedisich]

Clark,

I've dealt with this before by placing a track-guided saw (ANY type) with the blade splitting the glue line, and rip away - the resulting halves should mate nicely for a new glue-up.
Good luck!

Pete

[Bill Orbine]

I have heard biscuits add a lot of strength to a woodworking joint...is this wrong?

Sure the biscuit makes the POOR panel joint strong.....especially like the one with gap problem shown above. In reality, with a good joint the biscuits aren't necessary because glue is stronger than the wood. In this case such as above, I only use the biscuits for alignment and I do not use glue on the biscuits.

[Ken Fitzgerald]

Clark....does the gap occur the entire length of the board or just in a small area?

The reason I ask...your tactic of swapping faces should have canceled out any differences in the jointed edges not being at 90º. I am wondering if the gap could have been caused for a couple possible reasons: 1) a biscuit hole wasn't machined deep enough or 2) the board warped after being cut or 3) the board wasn't flat after glue up if the joint runs the full length of the board.

I have never had a biscuit joint hold a board apart during glue up but I have not paid enough attention when cutting the biscuit slot and wound up with a really loose slot and on another occasion I ended up with one that would not align well as it wasn't 90º to the jointed surface. These were obvious operator errors on my part.

If you have some more scrap, it might be worth another attempt.

[Terry Welty]

hmmm... no glue on the biscuits... is that to avoid biscuits swell that could cause the jointed board to swell? Just curious.

[John Coloccia]

It can swell enough to telegraph through the board, actually, and you get a little bump. It's frustrating because you sand away the bump, and then it shrinks and you end up with a little low spot. I personally don't use biscuits anymore, not for this reason, but I just don't find them all that useful.

[Clark Magnuson]

OK, I ripped the glue joint.
MY 28 year old Delta contractors saw with Jet fence and Harbor Freight blade did anything but cut straight.
The jointer with opposite fence sides looked like it made a straight cut.
I glued again without biscuits this time.

After a half hour, I pulled it out and scraped down the joint. Both side look like no gap, except for ~ 1" where the gap is ~ .001", probably from operator error at the jointer.

So it looks like I had success, but why?
Was it the lack of biscuits?

[keith micinski]

It might have been operator error the first time. I have been glueing stuff up for over a decade and I still get nervous when it comes time to glue everything up. I haven't had any major catastrophes yet but I am always on the look out for them.

[Chuck Wintle]

OK, I ripped the glue joint.
MY 28 year old Delta contractors saw with Jet fence and Harbor Freight blade did anything but cut straight.
The jointer with opposite fence sides looked like it made a straight cut.
I glued again without biscuits this time.

After a half hour, I pulled it out and scraped down the joint. Both side look like no gap, except for ~ 1" where the gap is ~ .001", probably from operator error at the jointer.

So it looks like I had success, but why?
Was it the lack of biscuits?

Clark,
Double check the biscuits when clamping...there should be no gap.

[Mike OMelia]

+1 for all the above, Set up your jointer accurately, table saw down the glue line, re-joint, check, re-glue, re-clamp. I wouldn't use the biscuits either.

+1. Gluing with biscuits is optional for smaller work. Its the bigger items that bisuits really help out on. Always dry fit (without the bisuits) to be sure you won't have joint problems. Also, make sure your biscuit depth is adequate... that can also cause gapping (but a strong clamp should compress a 0.001" gap due to a shallow bisuit cut). Finally, reversing clamps, top and bottom, plus adding a stabilizing board, top and bottom can help for thiinner boards.

Good luck,

Mike

[george wilson]

YOU NEED TO PUT HALF THE CLAMPS ON THE TOP SIDE OF THE BOARD!!!! Putting them all on 1 side causes the boards to spring upwards,opening the joint on 1 side. Suggest you pay attention to this in the future.
Your 2 little clamp down clamps may not be enough.

This,in addition to making sure your edges do align with each other before gluing.

I always do a "dry run" before committing to glue.

[Kent A Bathurst]

YOU NEED TO PUT HALF THE CLAMPS ON THE TOP SIDE OF THE BOARD!!!!

1] Absolutely alternate clamps: top-bottom-top-bottom. Put as many clamps on as you can fit.
2] I always joint glue edges by using alternate faces [if I understand correctly]. I take an adjacent pair of boards, and fold them up like book leaves, and joint them that way. Even if the jointer fence is out of square, the joint still aligns perfectly. Of course, my jointer fence is square to 4 ten-millionths of a nanometer :D - I use one of George's $82,000 machinist squares for setup :p :p :p.
3] AFAIK, biscuits add no strength to an edge-glue operation over and above what the "naked" glue up has. The theory is that it helps with alignment, but there is enough "slop" built into that system - by design - that it is not a silver bullet. I do not have a good reason why I still have my plate joiner - haven't used it in 10+ years [should sell it, I guess]. I found that it adds just one more alignment operation to the task, and has the potential to cause more problems than it solves. IMO - don't use it for this task. Great for plywood casework ass'y, or attaching face frames to cabinets, etc.

Less is more, in this instance.

[David Thompson 27577]

I have heard biscuits add a lot of strength to a woodworking joint...is this wrong?

Technically, it is correct.

In practicality, it is wrong. A well done joint -- in this case long grain to long grain (board edge to board edge) -- with virtually any of today's glues, will be stronger than the surrounding wood. Although the biscuits might add something to that, it's still stronger than the surrounding wood. So what's the point of adding that extra strength?

And biscuits can cause problems. I've seen cases where they can be seen through the surface of the finished piece, as a football shaped buldge. And if not done just right, they can hold the joint open.

And biscuits do not help with alignment. Period.

[george wilson]

Biscuits really don't ensure good alignment,for sure. They fit too loose in their mortises (initially) to help. By the time they swell,the other glue has dried,and the work is in clamps,anyway.

Generally,I stay away from new fangled things like biscuits,and DEFINITELY "loose tenons". However,I had to make a very LARGE dining table for my wife's family,and did use biscuits. It may depend upon what kind of glue you use,and how much water it contains,but I haven't had and bulging problems from the biscuits. I used brown carpenter's glue IIRC. Good thing they didn't bulge,I used some very nice,wide curly maple boards for the top.

P.S.: The only reason I have a biscuit joiner is that I got a nearly new one pretty cheap. Otherwise,I'd have had to use splines. I didn't because the 8' X 16" wide maple planks were too heavy to wield on the saw,and I didn't have a side cutting router bit on hand. I seldom build furniture,mostly tools and guitars.

[Pat Barry]

Clark,
I looked very closely at your pictures and think that the gap is actually on the top side of the glue up (unless your clamped photo is re-created). The gap on the top is what I would expect since the bottom side is restrained by the pipes and because the cauls are ever so slightly lower than the boards you are clamping, therefore the force from clamping will cause the boards to be forced up. I would recommend not using any more force than needed to close the glue joint, checking it very carefully before walking away from it, and adding a couple clamps to the ends, with cauls to hold the boards flat.

[Faust M. Ruggiero]

Don't use biscuits on edge jointed boards. They are just another thing that can go wrong. Besides, since they are a loose fit until they swell, they don't even help align the joint. If you are worried about holding the faces even, clamp cawls on the faces with wax paper between the work piece and the cawls. Mark gave you great advice about alternating sides against the jointer fence. I mark the face of my boards with a carpenters triangle then just make sure one edge of a joint is jointed with the marking against the fence and the other side so I can see the mark. It works every time.
fmr

[Chip Lindley]

...A lot of people say that the machines don't have to be setup to as tight of tolerances as all of the digital gauges allow these days and I say those people are over 50 and can't be helped. The day I started getting all of my digital do-hickies and setting all of my machines up properly is the day my life got a lot easier. Admittedly you can build some mighty fine work with old machines that are setup by eye, but it takes a lot more skill and a lot more time to do it.

Keith, you get the results you desire from your digital "do-hickies". More power to you. Speaking of "power" I hope you don't fall out of favor with the "Battery Cartel!" You mistakenly equate non-digital methods of machine setup as inferior. It must be your age. The semi-conductor and printed circuits made "digital" possible. Mass production made digital parts cheaply, but not necessisarily more accurate than their analog predecessors.

I grew up in an analog world, which amazingly measured very very accurately--just perhaps more slowly (and mechanically) A slide rule can do everything a scientific calculator can do, but it takes inherent knowledge, and time.

My old Craftsman dial caliper measures to within .001". Before dial readouts, there were vernier calipers. Before that, just calipers. Machinists made very precise parts with only dividers and a caliper. It was "go" or "no go" referencing a known part. My 0"-1" Craftsman micrometer's vernier measures to .0001" on it's scale, with interpolation.

Speaking of "interpolation", no digital instrument whatsoever is needed to set a jointer fence or tablesaw blade at 90 degrees. The lowly machinist's square does it all. It's amazing, that when that sliver of light disappears between joiner fence or saw blade and the square, a perfect 90 degrees is achieved. Is this old guy lucky or what??

175975

Don't equate age with lack of accuracy. It's just that other means have been employed for Eons before you were born. There are generations who will be totally lost if the batteries in their GPS poop out. Get a compass; learn to read a map!

I am not only wayy past 50, I am past 60! (An Old Hippy who survived) I take your comments from the young perspective they are offered. You cannot possibly see (yet) from the broad perspective we Baby Boomers do! This world would be well-advised to have a Plan B! Just in case the batteries wear out.

Now back to our regularly scheduledTopic:

If stock butts together seamlessly on one side, with a .010" gap on the other. there is an angle other than 90 degrees in effect. Tweaking of the jointer fence or saw blade angle is definately in order. I recommend a decent machinist's square to fix your woes. Use of biscuits and clamping procedures is for another day.

Happy New Year!!!

[Justin Jones RDH]

http://www.youtube.com/watch?v=F3uOkMK4UqM&feature=related

Check out this video 7 minutes in. He explains what others have said about jointing opposite faces for a glue up. Also alternate you pipe clamps- over/under.
Video 2 actually shows the jointing/glue up

[Don Jarvie]

I've never had an issue with biscuits and I use them all the time. Maybe dumb luck but they work, for me anyway.

Enought cannot be said about tool setup. A simple speed square can make sure your jointer is at 90 degrees. I check mine periodically during a project and especially on the final pieces. It can always go out of wack.

When jointing longer, taller boards you need to make sure the board stays against the fence and table across the whole cut. Since this happened at the end you may have slightly moved it off the fence or table and it dipped. You don't notice it until you go to glue up.

If I can I make my glue ups larger than the final size and cut them to size at the end. This provides a bit more room for error.