Thread: Jig needed for lock mitre router bit operation

A square piece with a larger length on the table pushed through behind the work piece will make it much easier. Will give you breakout protection on the work piece as well.

As per NCA's response, but attach a second, larger piece of wood to the backer piece so that the work is surrounded on one side by the fence, on the other side by the extra bit of wood that I am suggesting, and on the exit end of the cut by the backer piece. The added piece acts as a guard and allows you to safely apply pressure to keep the work against the fence at bit level, instead of having to apply it higher.

Ideally you want a 'tall' fence (150mm or so high) around the cutter region, backer at least 150mm square and the same thickness as the material if possible, and outer panel say 225 long (150 attached to backer and 75 to contact work to 75mm wide) by 150 high. You could do the whole thing in MDF if the material was close to a standard MDF thickness. MDF might be a bit tough on the bit when it makes the first clearance cut into the backer, but shouldn't need to cut more than 25mm along the backer after which it is backing the rest of the cuts without contacting the bit, so it will not be continually be in contact with MDF and in a wear situation.

Hope that explains the idea, can sketch for you if needed.

Many thanks for these helpful replies, much appreciated. Will post a pic when I have made it along the lines of the above, and it is in action

Thanks for starting this thread Joe.
I've been watching closely - I was wondering how to do it myself.

Saw this on the web that might help.

http://www.americanwoodworker.com/bl...er-Joints.aspx

A friend bought the Infinity lock mitre set up jig but even using this to set up the lock mitre bit proved to be a real pain. I tried it on the table saw and found the set up much easier. Used a tenon type jig for the vertical piece.

I tried it on the table saw and found the set up much easier.

hi safari, thanks for this reply. Not too sure about what you did on the table saw.

Originally Posted by safari

Saw this on the web that might help.

http://www.americanwoodworker.com/bl...er-Joints.aspx

A friend bought the Infinity lock mitre set up jig but even using this to set up the lock mitre bit proved to be a real pain. I tried it on the table saw and found the set up much easier. Used a tenon type jig for the vertical piece.

Step 5 in the AW article answered my question. I was concerned about the piece ending up like B and rocking. I've saved a copy of the article for reference.

(Not sure about the table saw tip either.)

Re the American Woodworker link, their method is viable for material the size of the pieces in their pics, but that would have to 150mm wider or more. The original question related to working with pieces one third to one half that (50 to 75mm). Parts that narrow are too skinny to safely secure with just a paddle because the paddle will not be supported along its length and can be prone to rocking and loosing grip. The skinny part is also very much more prone to moving off vertical as it is passed through the bit resulting in a spoiled job. The simple jig with a backer block and a cover block to trap the part is much more reliable and safer.

Neat trick about cutting a chamfer on the board ends to reduce the amount of material to be removed though. I think that is what Safari meant about using a table saw, or maybe he is suggesting a splined mitre joint.

Sorry for the delay in replying. What I was talking about is that it is possible to do a complete mitre lock joint on a table saw. As long as you are very careful with the measurement of the cuts (I use a vernier height gauge) everything is successful. I managed a very good joint on the first try.

I got the idea from a very good book called "Collins Good Wood Joints". Well worth the money.

I have included the relevant page from the book. Hope it comes out readable.
PAGE.jpg

Neat approach Safari.