I have to make 4 m & t joints on a chair seat. Tenons I make on the table saw and have no trouble making them dead centre. For mortises I usually make a jig and use a plunge router. I haven’t figured out a way to assure the mortise is dead centre. Any suggestions other than simply measuring and trial and error?
Edited 1/3/2008 9:13 pm ET by willy
Replies
What about routing the mortise from both sides and then make the tenon to fit what might be a slightly larger mortise?
Edited 1/3/2008 9:52 pm ET by dherzig
Hello , they make a router base that has guide pins ( or bearings ) that thread into the base ( on opposing sides ) which leaves the router bit in the middle . Using the pins as guides put 1 pin on each side of the stock , before plunging you should be able to slide the router back & forth easily , also the bit will be perfectly centered over the work piece . You could probably make your own base for this as easily . Just attach a stop on one end and cut your mortise .
You are right. I had forgotten about those. It has been so long since I used my router, I lost track of some of the attachments.
Excellent point, herz. That's what I'll do.
I made a test m & t joint using your suggestion, and of course it came out a perfect fit. I cut the tenons using a crosscut sled and lay the rail flat on the sled, a secondary back stop + a block with a set screw and I cut one side then the other and it's dead centre. If I have a number of tenons to cut, I will set up the dado blades to reduce the time. Thanks again herzig.
There is always some iteration whether you're tuning the tenon or the mortice.
Notwithstanding, an edge guided mortice can be auto-centered x taking a cut from both sides of the work. No changes in router position on the guide rods or the slop in the guides with respect to the work allowed , for this to happen.
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