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Dowels in cope and stick joints6/1
I am considering using dowels to aid in strength in some cope and stick hard maple cabinet doors.
The infinity cutters I have give a 3\8" tenon, which is not quite what I would prefer depth-wise on the larger and glass doors.
I do not want to invest in any new tooling at this time. Also, I would be glad for the extra ease-of-alignment the dowels would provide.
The doors are to be 3\4" thick, 2 3/4" wide rails and stiles with solid wood panels.
Should I be worried about the dowels "telegraphing" through the finish?
Possibly dowel thickness would be the important thing.. 1\4" 5\16, 3/8?
Any input is appreciated.
Vince I have been making cabinet doors as you describe with the 3/8 tenon and have never had any issue in 10 years. Mostly oak and maple and birch hardwood. Numerous large doors for pantrys also. I think the dowels are not needed. I am trying to get new tooling with longer tenons but only because I think they look a little better.
I'd bet the dowels would cause you more problems than they would solve. As long as you have a nice slip fit on your cope/stick they will hold fine.
That is reassuring guys.
What is the size relationship we want between a mortise and tenon? My cutter is making the tenon 6-7 thousandths less than the mortise opening.
That's pretty lose. Is your set adjustable? Most have some way of shimming to adjust fit. .004" should be max for most fits. .002 will give a nice sliding fit and keep from wiping too much glue of when slid together.
1 dowel 3/8"x 2" per joint. Once you have a good set up you will wonder why you never used the dowel before. So much easier to assemble.
Interesting Al. Do you ever notice an imprint telegraphing through the door where the dowels are located?
Larry, I can put shims in between the rail set to give a larger tenon. So is a tenon 3 thou less than mortise the goal? I though I read somewhere that a bit more space is preferable for a strong yellow glue joint.. like 5 to 6 thou.. I could be wrong.
Vince, We may be splitting hairs here. If your joint has some friction when you slide it home that's probably a good fit. It shouldn't take a lot of force.
As for the doweled cope, it may be stronger if perfectly executed but it may also harm the fit by off setting the tenon to one side so all the slack is on the other and the tight side gets its glue wiped off. At any rate strong enough without the extra step. Want it stronger yet? Put two dowels in.
I used to travel fixing other peoples equipment. You wouldn't believe some of the terrible cope & stick joints that some of the big operations put out. Brazed tooling, that had been horribly sharpened way to many times, was a big problem.
The scientific answer to your question is destructive testing. Take one of your 3/8" coped doors and drop it on the ground on the corner. Take another one and securely clamp the stile to a workbench push on the other stile door until it breaks.
Our Freeborn sets are 1/2". I would not trust a 3/8" tenon on a glass muntin. The 1/2" allow you to use space balls or the equivalent. The cabinet door companies typically use 5/8" or some metric equivalent.
It also depends on the wood. If you think about it the tenon is not the weak part. The long grain of the profile is the weak part. I remember having all kinds of trouble profiling vertical grain cedar for some project. The shaper would rip the profile off occasionally. If the panel was a wee bit thick it would likewise break the back of the profile. In some ways the deeper the groove the weaker the door.
If you are doing ply or mdf panels, glue them into the stile and rails. We've been doing this for over 30 years.
Dowel does not telegraph through. No different than doweling a frame together.
lots of good advice from the previous posts.
Telegraphing is usually the result of sanding
This is what draws me to wood working; so many intricate (potential) problems to solve.
I agree that dowels could cause a lot of trouble in relation to a cope and stick joint if they were not indexed to within a couple thousandths.
As far as destructive testing goes, sounds fun, but I never seem to have the time to do that sort of thing, especially while trying to learn so much on the finishing end.
I will need to dowel the large glass doors for sure. The standard doors have solid panels with space balls; the larger ones of these could use a bit more strength as well.
I will get some 3\8" drill guides and make some clamp blocks for quick and accurate alignment. One 3\8" x 2" dowel should give me peace of mind on the larger units.
Thanks everyone for the honest input.
I used to teach a weekend long beginning course in mortise and tenon joinery. We all made several cabinet door type frames, no panels. Some were coped with integral tenon, some were square edge with longer tenons, and some were cope and stick with a long tenon. We did dowel joints with a funky jig, nothing to proud of in the final result.
On the second day, we destroyed one of the frames we made the previous day. They were all amazingly strong (excepting the dowelled joints), and taught the students a good lesson on putting two pieces together in proper fashion.
The governing factor to strength is surface area of glued joint, as seen by destructive testing.
Except the dowel joints?? Explain!
One of my old school craftsman guys used to put (2) 1/4" dowels in all of his door and face frame joints. He had built a dedicated low tech mortiser back in the 60's and was still using it when he passed away in 2008.
I wouldn't use a 3/8" dowel in a 3/4" piece of wood. Regardless if it was edge gluing boards or a door joint.
That makes sense. It seems like the 3\8"tenon is not so bad, with many people using them alone. I will just dowel the glass doors since I am using custom trim cleats (not silicone) to hold the glass in.
What glass does everyone use in their doors? 1\8" tempered? Un-tempered?
Tempered, lawyer protection! Cost is very little more and the glass company delivers every week.
We use laminated
I took one of the 3/8" cope and stick doors apart, just breaking it with slow pressure over the edge of the work bench. (Most of the door on the bench, pushing down on the stile).
The door was 15" wide x 23.5" tall.
The surrounding wood broke. Looking at it, I agree that 1\2" tenons would not be much stronger. They might make the doors go together flat a little more, they might make it possible to do deeper profiles, but when it comes to strength, if you get a good fit between the parts, and fill it with glue, the groove breaks along the whole length of the stile.
While doweling the joints would only make them stronger, I am skipping them on this project.
The real question is,
Are you talking about doors with a profile on the inside edge, or shaker/mission style where the tenon itself is the only long grain glue joint?
For cope and stick with a profile, there is plenty of good glue surface with a shorter tenon. For a simple square stub tenon alone, a longer tenon/deeper groove gives you more glue surface area.
Vice have you ever reglued a door with a dowel you won't ever have to.