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Reply by weathersfuori

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Posted on Joinery for bar stools

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weathersfuori

96 posts in 1585 days


#1 posted 05-16-2017 07:27 PM



weathersfuori,

As already mentioned, I would be concerned that pocket screws, even in conjunction with glue, could result in a joint that weakens over time. The glue joint where the legs will meet the rails would be an end-grain glue joint which is not very strong; screws would do most of the work. If you elect to assemble the stools with screws, driving the screws through the leg and into the rails could be faster and easier and maybe stronger, since some long screws could be used.

An alternative joint to the mortise and tenon joint would be a lap joint. But in making this joint, ensuring that the dado in the legs is not too deep would leave enough material in the leg to support weight. Since the dado is filled with a rabbeted rail, any strength lost due to material removed to from the dado should be at least partially recovered when a snug fitting rabbeted workpiece is glued into the dado. The lap joint could be reinforced with a dowel. Angling the dowel slightly could make the joint a bit more resistant to coming apart.

My preference for the joinery on a chair or stool is mortise and tenon. Cutting the mortise is perhaps the most challenging milling with this joint. The router and properly sized straight bit and a well-thought out mortising jig could give consistent and accurate joints relatively quickly and economically. Here are a couple of YouTube videos that illustrate versions of the router mortising jig. I am sure a YouTube search for router mortising jigs would bring forth more videos.

Mortising router jig using the router fence…

https://www.youtube.com/watch?v=mKZJyBuqYIs

Mortising router jigs using guide bushings…

https://www.youtube.com/watch?v=9TyLVBmrAVA

Rockler’s Beadrock system would work but would require precise setup to get a pair of perfectly aligned mortises in a leg pair. Since I have not seen this jig, I am not sure how easy or difficult it may be to obtain accurately positioned mortises. The loose tenons that mate with the mortises would be required. Thus I doubt that this option is as economical as it may appear since either the Beadlock router bit or Beadlock loose tenons would have be purchased; but I suspect it would do the job, well.

The most economical method for cutting mortises is with the drill press and a chisel. However careful set up is needed to get corresponding mortises in proper position in the workpieces. Obtaining mortises that are all the same size, which would make cutting tenons easier, could be difficult and would require some careful chisel work.

I try to generally adhere to a standard where the two walls of the mortise and the thickness of the tenon each are no less than 1/3 the total thickness of the material, especially if the mortise is in ¾” thick stock. Also, since wood glue is a poor gap filler, cutting the tenon to fit the mortise snuggly produces the best results. Snug to me means the tenon slips into the mortise by hand and the un-glued tenoned workpiece remains in place when handled. This snug fit means the wood glue has little, if any, gaps to span.

- JBrow

Thank you for going into so much detail! This is very helpful- great analysis of all the options and the strengths and weaknesses of each, literally. I had thought about lap joints as they would certainly be easiest with the tools I have at my disposal, but I am all in on the M&T using the drill press and a chisel. I’ve seen many of the jigs that you mention, but I feel like with my experience level there are too many ways for me to mess them up. With the chisel I feel like I’ll have a little more control of the result. Thanks again- huge help.


I recommend mortise and tenon for most
chair applications. The Miller Dowel system
may be worth looking at in addition to the
Beadlock.

I ll note that when drilling out the waste
in mortises care should be taken to chisel
the sides of the mortise carefully so they
are parallel. It s easy to get carried away
with the chisel. A “drift” can be made,
just a stick of wood the the width of the
mortise to use as a gauge for the right
width.

- Loren

This is also tremendously helpful- the drift sounds like a great time saver as it will help test the mortise quickly.


Worst case the ryobi forstners at Home Depot aren t too bad.

I have a little cube of ebony I used as a guide to keep the sides true. Or close enough. It s a pain on the short side but I trim that side of the mortise when test fitting.

- TheFridge

Like the idea of the ebony as a guide! I’ll have to come up with something similar- sounds really helpful.

-- Weathersfuori, Texas, www.facebook.com/f5creations


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