Help with fitting tenon in round stock mortise

[Michail Kyriazanos]

Hello to everyone

Recently I got a commission for a bed frame that it's going ti have φ50mm legs and mortise tenon joints.

What I usually do is to cut a recess around mortise to fit the flat end gain around the tenon.

This won't be possible in this case so I'm looking for a way to get the end grain curved around the tenon.

I've found only 1 video on YouTube that uses a nice setup but I can't figure out what type of router cutter is used.

You can check it here at 4:35

https://youtu.be/TbW32wDRn1I



Do you have idea how it can be done?
I don't have any sweep gouges to carve it by hand, also I would prefer a machine setup for repeatability.

[Derek Cohen]

Michael, I think the technique you are looking for is to cope the leg and stretcher. I have an article on this when building a Hans Wegner chair, here: http://www.inthewoodshop.com/Furniture/TheChairFittingFrontRearStretchers%28Part2%29.html

Regards from Perth

Derek

[Keegan Shields]

Michail,

The video you posted is the only machined cope I've seen and was the video I was going to recommend. :)

If I needed to do a run of chairs with this joint, I would probably try routing a flat bottomed recess for the tenon shoulder.

Should be a pretty simple router jig where you use the mortise to index the leg to the top of the jig, plunge and route the recessed shoulder, then square the corners of the recess.

I think I've seen this in a YouTube video. If I can find it, I'll post it.

Hope that helps.

[Derek Cohen]

Keegan just beat me to it. Here is a build of mine where I flatten the entry to the mortice instead of coping the tenon ...

http://www.inthewoodshop.com/Furniture/AnotherCoffeeTable6.html

The shoulder of the mortice is levelled with a chisel and rasp ..


http://www.inthewoodshop.com/Furniture/AnotherCoffeeTable6_html_636f48d8.jpg


... until each is a good fit ..


http://www.inthewoodshop.com/Furniture/AnotherCoffeeTable6_html_m78655beb.jpg

http://www.inthewoodshop.com/Furniture/AnotherCoffeeTable9_html_m5bacb16f.jpg

http://www.inthewoodshop.com/Furniture/AnotherCoffeeTable9_html_43990ca8.jpg

Hope this helps.

Regards from Perth

Derek

[John Kananis]

Derek, I'm not finding the complete build on your site and I'm very curious how you shaped the inside and outside corners on that top.

Michail, I think recessing is your best option.

[Jamie Buxton]

Here’s a way to do what the OP wants…
Use a loose tenon. The first step is to cut the mortise in the apron. Then find a drill bit the diameter of the round post which is the leg. Clamp the apron in a drill press, and drill down along the end of the apron. You’ve just formed the curved shoulders of the M&T joint. Glue the loose tenon into the mortise in the apron. Presto you have an apron with a tenon sticking out the end, and shoulders which match the cylindrical leg.

[Derek Cohen]

Derek, I'm not finding the complete build on your site and I'm very curious how you shaped the inside and outside corners on that top.

Michail, I think recessing is your best option.

John, the complete build (and others) is on this index page: http://www.inthewoodshop.com/Furniture/index.html

Scan down the page to “Coffee table for my nephew”. There are several chapters.

Regards from Perth

Derek

[Edward Weber]

I think the OP is looking for this type of router bit
https://www.cooksonhardware.com/product.php/section/8660/sn/6%2F5X1%2F4TC/kw/Trend-6-5x1-4TC-Two-FluteD-Ovolo-10mm-Rad

There are several methods for making this joint

[Derek Cohen]

The issue you will have with router bits is that they need to match the leg circumference. They may be too big an ask. Hence they are handcut.

Regards from Perth

Derek

[Edward Weber]

The issue you will have with router bits is that they need to match the leg circumference. They may be too big an ask. Hence they are handcut.

Regards from Perth

Derek


If you start with the bit, you match the diameter of the leg to the radius of the bit. This is no different from using a floating tenon and matching the drill bit size to the leg or vise-versa.
Here is an example of the floating method

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

[Keegan Shields]

Yep that’s a great idea!

[Brian Holcombe]

Need an undercutting bit with a radius. I end up doing stuff like this fairly often where I will plan parts around common bit sizes.

[Mark Hennebury]

You can grind a router bit to the size and shape that you need, it's not that hard to do.