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Drawbore mortise and tenon offset, 1/16" vs 1/32"

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Blog entry by ceshelman posted 01-21-2022 05:55 AM 660 reads 0 times favorited 4 comments Add to Favorites Watch

I have been working on a Stickley 406 Morris Chair for my son. This is my first mortise and tenon chair build. I decided to keep the joinery as close to Stickley’s as possible. In looking at pictures of original and current Stickley Morris chairs, I saw that the mortise and tenon joints were all doweled. I am guessing that these are more specifically drawbored mortise and tenon though I have no proof. Long story short, I decided to drawbore the mortise and tenons on my chair. But the more I researched drawbore mortise and tenon joints, the more apparent it became that there was no consensus on the amount to offset the tenon hole. Most sources seemed to recommend 1/16” others 1/32”. So I decided to test them to see for myself.

The footstool joints I decided on 1/4” downs, so that is what I tested today. I will do this same test with 3/8” dowels which I plan to use on the chair itself. Common opinion appears to be that the size of the dowel on furniture joints does not really matter. But for aesthetic reasons I am going with 3/8” dowels on the main chair.

Ok, on to the test. The chair and footstool are all quarter sawn white oak so that is what I did the test with.

I rived the dowels to make sure the grain was straight. Not really necessary on oak but figured it could not hurt.

Then ran the dowels stock through the dowel place starting a 3/8” and worked down to 1/4”, hitting each diameter twice to make sure the dowel was clean.

I used the leg I messed up as my test stock. I drilled the holes in the leg and then the tenons on the drill press. The plan was to have one tenon hole offset 1/32” and one offset 1/16”. Ended up more like 3/64” and 1/16”.

I did use suspender and a belt and glued the tenon with TBIII. I also used TBIII in the dowel hole for a lubricant… way too much lubricant on the first dowel. The first dowel I covered with glue. Mistake. The second on I just put a small drop in the hole then hammered the dowel in. Worked like a dream.

Dowels are in.

Used a flush cut saw to trim the dowels and sanded them up.

Final results:
The 3/64” dowel went in noticeably easier. And the down appears to have seated better. The 1/16” appears to have distorted the dowel very slightly so it does not seat quite as well. There is no discernible difference in the strength of the joints. Neither has any movement and bot are tight and seamless.

Conclusion:
I will be going with the smaller offset for the 1/4” dowel joints. At least with this dowel size, this appears to make the better joint.

-- “Whether you think you can, or you think you can't--you're right.” - Henry Ford



4 comments so far

View EarlS's profile

EarlS

5513 posts in 3806 days


#1 posted 01-21-2022 11:48 AM

If you are using glue then you really don’t need to draw bore the dowel. Put some glue on the dowel, pound it in and clamp the joint. My understanding of draw boring is the you don’t have to use glue and it pulls the joint tight so you don’t need to clamp it either. Seems like a lot of extra work to use both methods.

-- Earl "I'm a pessamist - generally that increases the chance that things will turn out better than expected"

View ceshelman's profile

ceshelman

9 posts in 138 days


#2 posted 01-21-2022 04:53 PM



If you are using glue then you really don t need to draw bore the dowel. Put some glue on the dowel, pound it in and clamp the joint. My understanding of draw boring is the you don t have to use glue and it pulls the joint tight so you don t need to clamp it either. Seems like a lot of extra work to use both methods.

- EarlS

Agreed, you don’t need glue on the tenon or the dowel with a drawbore joint. However, the dowel does need some kind of lubricant. Wax or glue both work, so I chose glue. And I’m a belt and suspenders kind of guy. Paul Sellers used glue in his drawbore video as did most of the other videos I watched. Not because it was necessary, but because there was no drawback to doing so and it will make the joint stronger.

Also agreed that clamping is not needed and I didn’t clamp these joints. That is one of the best parts of the drawbore joint, even if you use glue there is no clamping and waiting for the glue to dry as the joint is permanently clamped. The drawbore, in my opinion, is actually not much more time consuming than a regular mortise and tenon when clamp time is taken into consideration. Plus, the dowel ends add a nice aesthetic to the piece.

Thanks,
Carl.

-- “Whether you think you can, or you think you can't--you're right.” - Henry Ford

View EarlS's profile

EarlS

5513 posts in 3806 days


#3 posted 01-21-2022 05:52 PM

In all honesty, I’ve probably made more than a few inadvertent drawbore dowels just because something shifted or didn’t quite line up when it came time for final assembly.

-- Earl "I'm a pessamist - generally that increases the chance that things will turn out better than expected"

View splintergroup's profile

splintergroup

6945 posts in 2680 days


#4 posted 01-21-2022 06:09 PM

Nice test Carl!

One of those joint reinforcement techniques that while probably unnecessary with a properly fitted joint and modern adhesives, it’s not much extra work, highly functional, and decorative so why not.

My thoughts are that as long as there is some offset, the dowel will act as a drawbore. More offset for softer dowels and project wood, less for harder. Go too far and the chances of breaking something increases (obvious woodworking adage 8^)

Good luck pulling that joint apart if it ever needs repair! (like that would ever be necessary 8^)

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