Quality Control for Square Doors

There's a lot involved in getting five-part cabinet doors to come out really square. October 9, 2006

I have a two man shop and I have been making raised panel doors for about 6 months. As I assemble the five piece door, which includes glueing, clamping (JLT cabinet door clamp), and pin-nailing, the door does not finish as a perfectly square door. I think my problem is that I rip my stiles and rails with a table saw and it is hard for them to be straight. Do you think that if I purchase a straight line rip saw and cut my stiles and rails on it, my doors will finish perfectly square? What do you suggest?

Forum Responses
(Cabinetmaking Forum)
From contributor A:
Check your set-up (you probably have). After you cope your rails, are the ends 90 degrees? Check the pattern cut for snipe.

From contributor B:
I would say that more than likely your problem is not in your rip cut, but rather in your crossgrain cuts as contributor A mentioned. It only takes a your rails being a tiny bit out of square for it to multiply and put your doors out of square 1/8" or more depending on their size. Triple check the cope cut for square after you shape the ends of your rails. I had the same problem a few weeks ago. I use a Panelcrafter coping sled and my split fences were out of parallel a tiny bit, which pulled the end of the rail away from the cutter, giving me an out of square cope cut. It will definitely take some investigating and trial and error to figure it out, but I would start by looking at the cope cut. I would also encourage you to clean up your ripped edges by sending them through a planer or widebelt sander.

From contributor C:
Your cope is probably slightly out of square, which will result in a parallelogram instead of a square door. Most semi-affordable straight line rip saws only straight line one edge. If you don't have a jointer, that's what you need.

From contributor D:
Our coping sled will produce square doors only if you twist it slightly counterclockwise while pushing it thru the shaper. Not a real problem if you warn employees about it, but as the other posters seem to agree, it is the most likely cause of the problem. The plumbness of your table saw will have an effect on the flatness of the doors, i.e., the stiles drooping up or down when checked with a straight edge. If the saw is angled slightly, even running it through a planner or sander might not square it up.We have employees check the diagonals after clamping as a safety check, as well as using a straight edge to check for flatness. Good luck with your doors, you got some good advice from the first poster.

From contributor E:
A featherboard on your table saw will help keep stock straight against the fence when you rip it, but like others said, this is most likely not your problem. Someone above mentioned a jointer. A jointer alone does nothing to insure two edges of a board are parallel Ė you have to joint and rip.

I'd bet your coping setup is the culprit. The fence on your shaper is not as important as making sure that the angle of the part as it sits in your coping sled is square. Also, if you use scrap pieces behind your parts to prevent blowout, make sure they're absolutely straight (parallel) too. Check your coping sled hold-down clamp, too. Parts can slip imperceptibly during cutting.

From contributor F:
I use a machinistís square to check for square cuts on the cope cut. What kind of fixture are you using to cut your copes? I can cut square with just a miter gauge, but I screw a backer to it, and I put some PSA sand paper on the wood backer. This keeps the piece from moving as it is being cut. I would say that one of the biggest problems guys have cutting copes is that the piece moves. Pay attention to it. As you put the square up to it (not a framing square), you can see what happened as you pushed it through the cutters. It could have been moved towards the cutters as it went through. It will taper back, away from the front of the cut. If you did not hold it tightly, it will taper away from the front because the cutters pushed it away. And if you have any slop in the miter gauge, this will cause inconsistencies, too.

I just bought a cope cutting jig for the guys to eliminate some of these mistakes. We found some inconsistencies here, too. If you squeeze the handle and push it towards the fence, the piece can move. Just watch yourself when you are making these cuts. It takes practice doing it right! Just running pieces through the shaper doesn't make you good. It just means that you have run a lot through the shaper. Think like a machine - everything done the same way every time. This will develop consistency.

Another area where tolerance may creep is when you run the door material. Measure the width at the beginning of the cut, and the end of the cut. If your fence is not adjusted right, your material can be cut at a taper. I use a fixed fence on the backside of the material (front side is being cut), and a powerfeeder that pushes towards the back fence. It's a very good system and you get consistent results.

From contributor G:
I use a JLT door clamp also. We have deleted pin nailing from our routine. We leave the door in the clamp for about ten minutes while performing other nearby work. This gives a much better square. That being said, we also final trim, square and bevel one stile on the slider saw prior to sanding as we do an inset door and it must be very square.

From contributor H:
I donít have a fancy door clamp myself. I pin nail before I clamp with bar clamps. Nailing first keeps it in place until the clamps override the brads and pull the joints tight. I re-square my doors on a RAS that cuts square. I think it is far more important to have the outside of the door square than to fuss over a door stile being 1/16th" narrower on the left side of door. Re-squaring only takes a second and it really speeds up assembly.

From contributor I:
Fabricating square five part cabinet doors quickly and consistently is a devil of a problem. It's not easy. The problem, in your case, could be either in fabrication or assembly - or operator error - is the same person always doing the door fabrication and assembly - or multiple, different operators? You should pursue the solution systematically and change only one variable or operation at a time until the problem is solved. Many folks, in the interest of time, change several variables at once. If they get lucky, they may solve the problem, but they never learn what went wrong. When the problem re-surfaces, and it is, in my experience, often due to the same cause, they may not be able to solve it effectively the second time around.

From contributor J:
The other side of the coin is, even if your rail ends get coped perfectly square, it is still possible to clamp up an out of square door. I have never been able to be certain any frame type of assembly is square when clamped up without using a square!

From contributor K:
I would like to add one more thing. How are you measuring square on your jigs and machine setup? I would suggest Starrett or some other type of high quality square. I have a 6" that has a place in a fitted pocket in a custom made apron I had made years ago, a 12" that is my work horse, and a 24" that is the final authority for most machine set up and jig fabrication. That 6" is a life saver because it is never far from my side. For non 90 and 45 degree angles I had always asked for full scale, cross section print-out from the draftsmen so I can lay up my test cut pieces and compare to what came off their plotter. This also protects me if a contractor doing installation claims something like a wall panel with return is the wrong angle. I can show them their own print out. Hence, a change order request instead of unsatisfactory craftsmanship complaint! Recently I came across a dial based angle protractor that is sold on Grizzly's web site for under $50.00. It is unbelievably accurate and comes with its own case.

From contributor L:
I make lots of doors, and thatís all my company does. The JLT clamp forces at least one corner to be square, so 1) the door is moving after you release it from the clamp, which often occurs with yellow glue and pin nails, or 2) the parts have un-even dimensions in some aspect. If the door doesn't move after it is removed from the clamp, then out of square rail cuts just result in a gap where the rail meets the stile. You can still have a square door with out of square rail cuts.

To keep the door from moving after you release the clamp, try a snug joint (assuming yellow glue). Another solution is Jet-weld hot glue from 3M. The gun is about $650, but you don't have to sink or putty pin nails. It sets in about 30 seconds, time to get the next door ready for the clamp. It's about ten times stronger than your Home Depot variety of hot glue.

If your parts are out of dimension, you either are cutting them to inconsistent length, or most likely you are using the wrong shaping method when shaping the stick profile. When shaping, you should be dimensioning at the same time. Weaver makes a jig that does this. The best solution is to get a Weaver shaper with their sticking jig and if you can afford it, their belt (vs. roller) power feed. With different inserts, you can rip different stile and rail widths. This comes in handy when someone wants raised panel drawer fronts and you need to rip 1-5/8" rails, or someone wants that wide 3-1/4" stile for a lazy susan door, etc.

As a two man shop, your best solution is to find a high quality door supplier who can provide a dozen woods, a dozen edges, several arches, miter doors, etc. that will look professional every time, and free up your time and floor space and capitol. To be blunt, I know what your doors look like, and they don't look good.

From contributor M:

Is your JLT clamp square? The left side of the clamp is adjustable to square it up.