Mortise Jig - Homemade

[Peter Pedisich]

Hi,

This is a homemade mortising jig I designed and built for loose-tenon joinery. Previously I had used a Beadlock jig, but I always wanted to try router made mortises.
I studied plans from Workbench, Fine WW, Popular WW, etc...book articles by Pat Warner, Gary Rogowski, Tage Frid.
I designed it in CAD and had the curved outrigger support arms cut on the CNC at work, but all other parts I made at home. It's mostly 24mm and 27mm multi-ply (Russian birch ply) with a mounting plate of 3/4" mdf. The extrusions are 8020 10 series. I just have to figue out how to mount the edge guide to the linear motion bearings (UHMW). I'll add sliding stops in the t-slots. The reason for no top plate and a outrigger support is to not lose any depth capcity like other jigs, here the wood goes right up to the router base to enable deep mortises.

Capacity is 3.5" thickness, 8.5" width and length varies if it's a rail or stile.

Since I've never made this type of jig before, i'm looking at it like a learning experience, and consider it a prototype. I'll discover it's shortcomings in use and correct them in the final version. Yeah, right! who has time for that, except for jig designers.

I'd really appreciate any comments and criticisms.

Thanks for looking,

Pete

[Peter Pedisich]

some more pics...

[Scott Rollins]

All I can say is WOW! That is a great jig and will handle anything you can throw at it!. I am envious. I made a "woodrat" to do the same thing you are doing. I hope you don't mind my copying some elements of your design in the near future.

[Peter Pedisich]

Scott,

Thanks, I'd be interested in seeing your Woodrat, have you posted about it?
Also, I'll be glad to share any details, drawings, etc, just PM me.

Pete

[Scott Rollins]

I posted it a while ago. It can cut handle a 36" cut left to right under full control with "power feed" to allow climb cutting. It will cut 12" in the "y axis" and up to 15 degrees off axis for dovetails.

http://www.sawmillcreek.org/showthre...light=scottrat

[Peter Pedisich]

After testing it out today, I noticed a problem of the stock moving when mortising in the end of a rail. I kind of thought this might happen, so I drilled a hole and put a clamp through, which held much better.
In the pics you can see where the stock moved and then with the clamp it worked fine.

Please ignore the mortise proportions, it was a test with the only straight bit I have left, a 1/2" P-C bit from the borg. This week I'll pick up some spiral upcut bits.

Any recommendations as to brand and if HSS or carbide are better?
My first project will be in doug fir.

Please be critical I'm looking for input from those with experience.

thanks,

pete

[Neal Clayton]

your design is very similar to the leigh jig, i have one.

a couple of things that would help for stability and ease of setup, that they did to theirs...

a) they have a 'hooked' piece of straight aluminum with a hole in the center that can be butted up against the bottom of the jig, that serves as both a right hand stop and a straight edge (as long as the metal is square and the bottom of your jig is square, the guide has to be square, right?) the hole takes a threaded hand knob to hold it in place. like the picture below...

b) theirs has a top with a large'ish opening which the board being cut goes all the way up against. the router runs inside of the opening. this also serves as a quick square, and with the vertical straight edge and the board butted up against the table top from below, you have the board in a bind on one corner so it can't easily move on you.

i think those two additions would probably make it alot more stable, if movement is your problem.

edit: nevermind, i see now that you have some overlap on your top rail so that the board is stopped at the top, but the vertical guide being 'hooked' on the bottom of the jig would be a good solution still, imo. you could then incorporate free range of movement with your vertical stop, without having to use pre-set drilled holes.

[Peter Pedisich]

Neal,

Thanks for the detailed reply, and the sketchup image. I'm going to study it tonight.

Pete

[John Petsche]

thanks for sharing, great post and jig idea.

[Bruce Wrenn]

HF, yes I said HF sells a set of three (1/4,3/8, and 1/2") spiral mortising bits for about $14+/-. They are often on sale for $12.99, to which you can add a 20% off coupon. A member of another forum who is considered a jointer guru turn me on to them. HfFalso sells a set of three 1/4 spiral bits for a Roto Zip type tool, that do mortises also.

[frank shic]

those aluminum extrusions definitely take your jig out of the realm of slapped together scraps of wood!

[Peter Kelly]

Any recommendations as to brand and if HSS or carbide are better?

Freud carbide up-spiral bits work very well for this type of application. Available at Amazon and others. Also, I'd add another piece of blocking to the other vertical edge of the piece you're milling instead of the clamp. Will do a better job holding your workpiece in place, especially when you're milling something harder then Radiata.

[John Petsche]

great design, thanks.

[Rick Lizek]

I've been using the horizontal slot mortiser and loose tenons for 30 years. First learned of it in FWW but they never expanded on it properly, The ones using 5000 rpm and HSS endmills are much quieter and versatile. The horizontal type will accommodate longer rails and stiles. Go back to the FWW issue with the horizontal slot mortiser using drawer slides and the one later using t track. Bronze bushings or 80/20 with their linear slides are another option. The bronze bushings one is far cheaper. Also has a lot of possibilities for sliding fence options for shapers, router tables and is only limited by your imagination or lack of imagination.

The 1/3 rule for size of your mortise still applies. For the most part I keep tenon material planed to rough size and rip then chamfer the edges (only round them if doing through tenons, decorative) then crosscut to length. I have used all the other methods in factories and custom shop and the slot mortiser is the simplest and most versatile. Good for doweling as well. You are taking something so simple and losing the versatility...

In one of your photos the depth of you mortise doesn't look deep enough. Why wouldn't you make them all the same depth on your rails and stiles????? You not making them the same doesn't make sense to me and makes more work fiddling with adjustments. Again, taking simplicity and making it more complicated.

[Peter Pedisich]

Rick,

You are right, a slot mortiser, either by a top manufacturer or shop-made, is simpler, more versatile, and of course better suited to production work than mine. I never made any claims that mine was anything other than a way to produce mortises with a the Festool router I had purchased just prior to making the jig. I wanted to use the router to make mortices in a home hobby shop, and have great dust collection, it does both very well.
As far as the depth of the mortise, I did state above in the thread to "please ignore the mortise proportions..." as I was just testing it out with the only plunging bit I had on hand. For the door I made I purchased a HSS spiral upcut bit that worked beautifully. They were all the same depth, no fiddling or adjustments, and so I did not take simplicity and make it more complicated.

Pete