Question about cutting mortices in end rails

[Mike Pittenger]

Hi all

I'm building a blanket chest and using floating mortises (first time). This requires double mortices for strength and I"m struggling with them in the rails. The rails are 5/4 lumber (1 x 2.5"). With such a small surface I'm having a hard time clamping the boards so they don't move with the router. I have a small, single screw clamp.

Any suggestions for jigs or methods?

Thanks

Pitt

[Frank Drew]

Pitt,

Mortising end grain is one of the great features of horizontal slot mortisers, but it's much harder with a hand held router. You might make a jig that incorporates wood all around and flush with your workpiece's end surface, giving the router a broader and more stable surface on which to ride.

You might also (re?)consider integral tenons.

[Chris Fournier]

You are making floating tenons, not mortises. I can't imagine any blanket box needing doubles unless they were lead blankets!

I have done what you are doing many times and it is easy as pie. You need to use a guide bushing on your router and make a fixture that has a 90 degree fence attached to it that you use to clamp it to the end of the work piece. Time consuming (20 minutes) but safe and predictable results are the outcome.

282620You can see that you design the amount of work surface required and the operation is sure and steady with your router properly supported. I use a spiral upcut bit and have my vacuum running to suck up the chips after each pass. I like to take a full depth plunge at each end and then remove 0.25" per pass.

[Mike Pittenger]

Thanks Chris - you're correct, of course, re: mortise. I've never used floating tenons before. Do you use a collar with the template, or do you need a bit with a bearing?

[Chris Fournier]

Thanks Chris - you're correct, of course, re: mortise. I've never used floating tenons before. Do you use a collar with the template, or do you need a bit with a bearing?

Use a collar and you have chip clearance. Use a bearing and you'd destroy the jig.

The jig is easy to make, I make it in 5 pcs. The mortise portion is 4 pcs. I cut the mortise portion to make the right width, ripping it on the TS, then I cut this ripping in two and lay it in between the two cheeks. Carefully glue this up flat, clean it up and you're on your way. The 5th piece is the 90 degree fence.