roubo is kicking my....

[Josh Bowman]

I'm building a Roubo bench with a 4 inch maple top. The top has to have 4 mortises cut that are 2-1/2x5x2 deep. They are huge. I started with an electric router, bushing and template until I ran out of bit at 1 inch. That was easy and accurate. Then I went to drilling and chopping. I must be doing something wrong, or it's just the nature of this beast. It's taken me all evening just to chop out the other inch of just one. Any recommendations?

[Rick Erickson]

Josh, get a spiral upcut bit with a bearing. Now that you have some of the mortise cut you can now ride the walls of the mortise with the bearing and set your bit further down.

[Scott Cardais]

Would a Fortsner bit help to remove the bulk of the mortise? You may have to resort to a power drill or drill press but that seems like a good option.

Hope this helps.

Scott C.

[Todd McDonald]

Hitting a knot does not help much. I used power drill with forstner then cleaned up with sharp chisels.

Keep chopping.

Todd

[harry strasil]

Don't try to chop too much at a time!

[george wilson]

I generally use 2 tenons instead of 1 huge one. It helps keep the mortises in the top of the bench from becoming more fragile around the corners close to the edge of the top.

The benches I made and used for many years in the musical instrument maker's shop had an outer tenon right on the edge of the bench like a dovetailed tenon. There was another,rectangular tenon coming through the top of the bench,like the dovetail tenon did,from the inside edge of the leg(s). This was after some benches in Diderot.

[Rick Erickson]

Josh, give this video a look. He does exactly what you are trying to do.

http://rogersfinewoodworking.com/blog/2009/06/29/rww-44-the-roubo-undercarriage/#more-186

[Richard Magbanua]

The mortises in mine kicked my butt last summer. Just drill a bit further than you need with a forstner or bit and brace, get a big chisel, a mallet and your iPod. Take a little at a time until you remove what's not needed. It goes quicker than expected after a while.

[Michael Peet]

Josh, I just started my Roubo build over the weekend and I am already dreading the mortises. It's funny because I literally woke up in the middle of the night last night with the thought to use a router to hog out most of them.

Let us know what finally works for you -

Mike

[Graham Wilson]

I am with George that two mortises would be better than one. Tools that would help, a larger forstner bit, a home-built depth stop and a mortise chisel. Technique is to cut the cross-grain with the chisel and scoop with the grain. Pare the sides.

[Matt Benton]

Just bought my first Brace a few weeks ago. It is by far the fastest hole-drilling tool I've ever used, and that was before I had the bits sharpened...

[Wilbur Pan]

I went with two mortises to attach the legs to the top for my workbench build, which you can see in progress here (http://www.forums.woodnet.net/ubbthreads/showflat.php?Cat=&Number=4088180&page=0&view=collapsed&sb=5&o=&fpart=all&vc=1). But saying that two mortises would have been better isn't going to help Josh much right now.

I tried a variety of methods chopping big mortises for my workbench, both for the benchtop mortises to receive the leg tenons, and for the stretcher/leg connections. The fastest is to drill the waste and chop and pare the sides, but a regular electric drill is going to have problems drilling that deep, unless you drill out in layers. If you have a brace and bit, the drilling will go a lot faster. You can get a surprisingly large amount of torque with a brace and bit, and you'll quickly see that it is more powerful than a handheld drill. The downside is that you'll have to be careful that you are paring the sides square.

The second technique I tried was to use a 1/4" mortise chisel to go down the sides of the big mortise, and then waste out the middle with a brace and bit and chopping. This has the advantage of easily making the walls of the mortise square, and you also don't have to be as careful drilling out the waste since you'll have already done the sides. But this method will be slower overall.

Making sure that your chisels stay sharp will help a lot as well.

[george wilson]

Yes,he can't put air remover in his big mortise!

[Graham Wilson]

You could always use a nice through mortise like this joint:

http://img263.imageshack.us/img263/1166/option.gif

from Wood Joints in Classical Japanese Architecture (http://www.amazon.com/Wood-Joints-Classical-Japanese-Architecture/dp/B000ZKPGGI/ref=sr_1_1?ie=UTF8&s=books&qid=1269363661&sr=8-1). The nearest piece would be the workbench top. Similar to the joint shown in the French workbench built by Roy Underhill (http://www.pbs.org/woodwrightsshop/video/2700/2705.html).

[george wilson]

Graham,that IS ALMOST the joint I used on my workbench in 1970,except that the mortises are the same width and thickness. The outside one was dovetailed as you show. That joint is in the 18th.C. Diderot encyclopedia.

P.S. the Diderot joint IS NOT TAPERED like the one you illustrate.

[Paul Incognito]

You could always use a nice through mortise like this joint:

http://img263.imageshack.us/img263/1166/option.gif

from Wood Joints in Classical Japanese Architecture (http://www.amazon.com/Wood-Joints-Classical-Japanese-Architecture/dp/B000ZKPGGI/ref=sr_1_1?ie=UTF8&s=books&qid=1269363661&sr=8-1). The nearest piece would be the workbench top. Similar to the joint shown in the French workbench built by Roy Underhill (http://www.pbs.org/woodwrightsshop/video/2700/2705.html).

It took me a full week to wrap my head around the "puzzle tail" that Underhill shows in his video. Now you go and throw this at me.
You can come rock me to sleep tonight. :)
Seriously, Junior posted this joint in response to something I posted a while ago. I'd love to see how this joint is made and assembled.
Sorry to hijack your thread Josh.
PI

[Josh Bowman]

Josh, I just started my Roubo build over the weekend and I am already dreading the mortises. It's funny because I literally woke up in the middle of the night last night with the thought to use a router to hog out most of them.

Let us know what finally works for you -

Mike
Micheal,
I found a 3 inch bit at MCLS. I hope to use it to hog and flatten the bottom. I'm still sore from the chopping just 1 inch of the 1st motise. The router did a fine job on the first inch, The only spiral bit I had was a 1/4" and I found my Stanley 70 with Veritas 1/2" chisel did a fine job hogging and smoothing the bulk. And a lot less noise and saw dust. Just used the electric router to do the out line with a bushing and template.

[Harlan Barnhart]

I would rough it out with a router, just short of the lines and finish with a chisel. I just finished a door project with 24 mortises 7/8" wide, 2 1/2" deep and 10" long in white oak. Here are some pictures of the jig I made.

[Graham Wilson]

It took me a full week to wrap my head around the "puzzle tail" that Underhill shows in his video. Now you go and throw this at me.

Underhill calls it a rising dove-tail joint and the Japanese one I showed is a variation. Both pins will have the same rise angle making it possible to connect the impossible looking joint. Watch the linked video near 5:30 and look at his Drawings (pdf) (http://uncpress.unc.edu/woodwright/images/Underhill_Guide_excerpt.pdf) of the single rising dovetail.

[Paul Incognito]

Underhill calls it a rising dove-tail joint and the Japanese one I showed is a variation. Both pins will have the same rise angle making it possible to connect the impossible looking joint. Watch the linked video near 5:30 and look at his Drawings (pdf) (http://uncpress.unc.edu/woodwright/images/Underhill_Guide_excerpt.pdf) of the single rising dovetail.

Thanks Graham,
I think I got it.
The tenon in the back of the Japanese version is similar to the tenon on the back leg of Underhill's Rubo bench, cut at the same angle as the back of the tail. Correct?
PI

[Brian Dormer]

If you are just trying to hog out material - a LONG drill bit would be the easy way out. If you are a purist - a big auger bit in a brace-and-bit is a "purist" solution. Since you've already admitted to using a router - chuck a big, long bit in your beefiest hand drill (a 1/2" drill would be ideal) and have at it. Clean up with your chisels. And don't forget - nobody but you will ever see the inside of those mortises - how neat you make them is entirely up to you.