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.
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.
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.
Everyone has their own methods, after doweling the doors for several years now
I would not go back to doing them without. The trick is to make drilling your holes accurately which takes some time to get the right set up.
lots of good advice from the previous posts.
i don't have a proper dowelling setup but often use dominoes (as long as possible, often 8x80) to reinforce these joints in cabinet doors- especially when they have a glass panel or are particularly large. telegraphing has not been an issue. otherwise glueing in the panel (unless it's solid wood of course!) increases the doors integrity quite a bit.
Telegraphing is usually the result of sanding
the face before the glue dries.
this can happen easily with biscuits that hold
a lot of glue, it swells the wood around it
and shrinks back after sanding the face smooth.
I've never had dowels telegraph but if you're
concerned, just allow it to dry a couple of days
before sanding the frame flat.
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.
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?
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,
How strong does it really need to be?
I've used coped joints and 3/8" doweled
frames in cabinets and furniture for over
35 yrs now and never had one break.
If someone breaks one of these, they're
abusing the cabinet.
Vice have you ever reglued a door with a dowel you won't ever have to.
We used to use a 3/8" dowel till we got a doweling machine now we use an 8mm dowel both work great.I wouldn't ever build a door without one.
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