Lock Mitre

[Phil]

Has anyone used a "Lock Mitre" router bit for joining boxes?
Looks like a neat idea.
If I go ahead with this box build https://www.thewoodhaven2.co.uk/threads/saw-blades-cabinet.11100 then it would be ideal.

 

[Jonathan]

I’ve used it a few times, normally clients want dovetails so not much experience with it.
I remember its a little fussy to set up, but quick when it’s set up.

 

[Phil]

I’ve used it a few times, normally clients want dovetails so not much experience with it.
I remember its a little fussy to set up, but quick when it’s set up.

Did you use in a router table or free hand?
The bit is not cheap at ZAR2,600

 

[Eric the Viking]

I have a couple of different sizes - the smaller one has had the most use. The big one I don't think I have ever used in 10 years!

I had limited success in ply because of the opposing grain, making the tongue weaker but it did work.

I think you need a well set up router table, with a solid, perpendicular fence, but I didn’t find it as tricky as I expected. I built a simple auxiliary fence (that slid on the main one) to support the vertical stock, and that worked well.

I like it as a system, because clamping becomes easy for the glue-up. Also, if you have an easily adjustable fence, you can creep-up on the right setting, or do several passes to avoid overloading cutter or router.

Both my cutters were Axminster's "cream" range. I'd like the middle size too, but it's way too expensive to just buy on a whim - need a job that needs it first. You may find Wealden has a better range also. Axy has dramatically cut back their range in recent years.

 

[Spectric]

The setup is easy if you use the Infinity cutter and setup jig.

Lock Mitre Bits – Infinity Tools

These router bits produce strong and beautiful lock mitre joints for kitchen cabinetry, drawers, four-sided planters, boxes, picture frames and much more.

www.infinitytools.co.uk

Lock Mitre Jigs – Infinity Tools

Set up perfect-fitting lock mitre joints in minutes, without frustration or wasted wood.

www.infinitytools.co.uk

 

[Steve Maskery]

IME great when they work, a PITA to set up.
S

 

[Jonathan]

Did you use in a router table or free hand?
The bit is not cheap at ZAR2,600

I used a router spindle in the spindle moulder, but a router table would definitely work.
I don’t think it would be possible freehand.

 

[Trevanion]

I've used a lockmitre spindle moulder cutter a lot over the years for corner covers, beam covers, etc...

Not sure I would use it for box making, whilst the joint will be relatively strong once the glue has set, the actual joint itself could be prone to just shearing across the tongue that's produced when used as an end-grain to end-grain connection. I wouldn't trust it for a structural application, but if you had a plywood bottom that was glued on to the underside completely as a shear panel it would make a decent box for lightweight applications.

The tricky bit is setting them up. I find that it's best to start with getting the height roughly correct and then feeding a sample piece into the cutter and cutting a small piece off and inserting it into the same cut will tell you if you need to adjust it up or down slightly, do this until both pieces are completely flush. Then follow the same process for the depth of cut, though this is much easier to set up once the height is set.

 

[Jar944]

I use it for long miters when just a miter fold won't work or would be a pain to glue up. Pain to setup though.

Works great on pvc that would be a pain otherwise.

 

[Phil]

Thanks chaps for all the comments.

The little beanie sitting on my left shoulder explained very carefully about the cost of the cutter for possibly only a once off use.
"You have #10 and #20 biscuits in stock and 3 slot cutters, so why not use them?"

Good question! Good advice!
Going to need the money for a new pulley on the TS.