I am pretty new to woodworking; one of the first tools I bought, for woodwork, was a biscuit jointer. I have used it a lot in the past year, however, I have trouble aligning the top surfaces of boards. In other words there is always about 1/16th of a difference, the boards are never flush when I glue them. Am I doing something wrong or is this the nature of the beast.
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Replies
Couple of things to check:
* Are you referencing off the same plane (e.g., the top)?
* Is your fence mis-aligned? Put a piece of plywood down and see if the fence accurately references against it.
* Be sure to hold the fence and depth guide right to their reference surfaces.
I am referencing the same surface, if the joiner was mis-aligned, how would it cause the boards not to be flush?
mgill,
There are a few things that could be causing this. How do you register the tool to the work, with the fence, with the base on a flat surface? Do you always have the work piece face up or down depending on how it is registered to the tool? It could also be the tool itself. Some are much more accurate than others. What brand is it?
It can also be your technique. If your jointer has play in the slides you have to compensate for it by keeping your wrist locked and insuring that you push the tool straight in to the work.
There also may be that much slop in the biscuit slots themselves. When you are assembling the pieces can you align them before they are clamped? Do you use cauls to hold the pieces flat when clamping?
There are so many variables here that we should narrow it down a little. It may be a combination of things as 1/16" sounds like quite a bit.
Rob
What is a caul?
mgill,
It is a board with a slightly convex curve cut in it that is clamped across the pieces you are gluing on the top and bottom to hold them flat. I may have the spelling wrong. How about the other things I asked?
Rob
I hold the board over the end of my workbench and but the tool (Porter-cable) fence on the top of the board and the part where the saw blade comes out flat with the edge I want to join.
I am mindful to make sure I don't twist the tool while cutting.
I'll have to check to see if they line-up before I clamp them, maybe I have a clamping problem.
mgill,
Try clamping the piece face down on a flat surface and using the bottom of the jointer as a reference. This only works on boards thicker than 3/4" for the most part as the slot will be 3/8" up from the bottom of the jointer. This will allow you to use both hands on the jointer.
I have the same jointer and I have noticed that you can move the boards up and down slightly with the biscuit in place. Did you understand my explanation of a caul?
Rob
Most everyone has already hit all the points I can think of, but one still sticks out for me, something I did and almost pulled my hair out trying to find out what I was doing.....make sure your biscuit joiner isn't resting on the bench, make sure the tool is resting only on the board you are cutting. I ended up hanging my boards over the end of my bench so my joiner would cut the slots while sitting only on the board, and my misalignment problems went away. Most of the time the tool body is thicker than the material you cut a slot into so the bottom of the tool sitting on the bench makes the board not sit high enough, not as high as it should. Might be worth a look.
My students often have the same problem. Instead of holding the tool by the top handle and the motor, put left hand down over the plate to hold it in position. Get the motor up to speed before pushing it in to make the cut. My students, holding the top handle, would often slightly rotate the tool up a bit when pushing in. Also be sure your stock is hanging over the edge of the table when using the tool. Sometimes the setting of the fence is higher than the thickness of the stock and the result is that the table becomes the reference. As such, any sawdust or chips on the table would lift the tool up a bit and result in inconsitant cuts.
Part of the problem is that the low end plate joiners, and the low end biscuits, are not terribly precise, so that small variations in how they are held to the board can cause variations in the outcome. I'd bet that using the Lamello Top 20 would reduce the differences to nil. But that machine costs about $700. (There is the economy model Lamello that is more like $415.)
If it doesn't really aid alignment, there is no reason to use a plate joiner on edge to edge joints since it doesn't strengthen the joint. They're good for quick and dirty right angle joints however and earn their place in the shop in that respect.
Here's a quick and easy test you can do to help determine if it's the biscuit joiner or your technique that's at fault. Take two of the boards you slotted on the ends, insert biscuits into one of them, and then push them together end to end. If they line up, then it's your technique that's at fault.
I've found, when joining plywood 90 degrees to another piece (I'm unsure if this is what you're attempting to do), that alignment problems crop up with I try to balance the jointer's fence on top of the 3/4 inch edge of the ply. If the jointer is rotated at all out of perfect perpendicular the pieces are out of alignment.
By using two top reference surfaces (slotting the ends of two pieces), the top surfaces should line up when biscuited. If they don't, you might have a slipping fence, bad biscuits, or something else the matter.
Zolton
I found they don't help much with alignment, either, but not as bad as yours (more like 1/32"). The problem I've found is that the biscuits are not consistent - some of them are too loose; they expand unpredicably, etc.
Maybe the super-expensive Lamello system does better; its proponents claims it does. On the rare times I bother with alignment aids for panel glueup now, I use a router slot cutter to make slots for a spline.
A 16th isn't bad. You can smooth that with 80 grit or a well tuned #4 bench plane.
One thing I try to do is find a surface that's flat and true.. like my table saw.. and then hold the board down flat to the table with one hand.. as I plunge the joiner blade into the board with the other.
All the potential problems have been raised already. Just to summarize:
1. Make sure nothing is interfering with the way you reference the tool. This is more common than you'd think, even with experienced operators.
2. Make sure the biscuits are a tight fit in the slot. I use Lamello bicuits only, because the thickness is reliably uniform. Cheap biscuits often have a lot of variation in thickness.
3. Check that there's no slop in the fence you're using. The rack-and-pinion type often cause problems because they go slightly out of parallel with the blade. The only solution if you've got a sloppy fence, aside from getting a better tool, is to avoid using it as much as possible - put the reference face down on a flat clean table and rest the tool on the same surface. This limits the applications but for flush connections it's usually OK.
David Ring
http://www.touchwood.co.il/?id=1&lang=e
Rarely ever have I been able to attach two flat pieces of wood perfectly with a biscuit joiner. Some sanding is usually involved. My suggestions - 1. Be sure the surface on which you are placing the glued wood is good and flat. 2. Use a rubber mallet to gentle tap the pieces level after they are clamped 3. Plan on putting something heavy on the two pieces of wood while the glue is drying. The clamps have a tendency to buckle the wood at the joint unless something heavy is holding both pieces flat to the table. It would be nice to have a large sanding machine that you could run the piece through after the glue has dried because it would fix those issues quickly. But of course they cost an arm and a leg and take up a lot of room. One last thing, when I first got my biscuit joiner I built a mobile stand for my band saw using nothing but biscuit joints. Clearly it was a poor choice for such a job but I wanted to explore the limitations of the biscuit joiner, and using it over and over again on one project helped me to understand it a lot better.
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