miter lock bit,,,

[jeff oldham]

all of these answers are great and i thank each of you very much for your comments and help,,and it has helped me a great deal,,,im kinda like others have said,,it is a pita to set up,,,

[William Chain]

The setup gauge is important - as important is setting up your table with a zero clearance fence, and I use a sacrificial push block behind the stock to discourage the tearout. It'll pay off in the final product. I clamp a zero clearance fence made out of 3/4-in MDF onto my regular fence, with a healthy allotment of featherboards to hold the stock down in all directions. Even properly set up, which is still a giant PITA with the gauge everyone recommends, in my experience the bit makes horrific noises despite cutting nicely. Every time I do use this bit I swear I won't, but if you're careful, the resultant joint is nice. +1 on Jim's recommendation not to precut the bevel, the measurements will end up bending your mind and the lock mitre bit is annoying enough.

[fred everett]

I spent an afternoon setting up a Freud LM bit. I used the setup gauge. Several hrs later I had acceptable lock miters. One project and now the bit sits on the shelf.....I don't think I'll use it again.

[ChrisA Edwards]

I spent an afternoon setting up a Freud LM bit. I used the setup gauge. Several hrs later I had acceptable lock miters. One project and now the bit sits on the shelf.....I don't think I'll use it again.

Pretty much my same experience. I also bought the Infinity Tools Vertical sled to aid in cutting the vertical pieces. That was certainly handy and worked as advertised.

I completed 18 drawer boxes, but have not used this method since.

At the time, I couldn't get one of the (Infinity) setup jigs, so after I got the bit dialed in, I cut the end off the test piece and saved it as my jig for future use, but as stated above, it also just sits in a drawer.

[fred everett]

Pretty much my same experience. I also bought the Infinity Tools Vertical sled to aid in cutting the vertical pieces. That was certainly handy and worked as advertised.

I completed 18 drawer boxes, but have not used this method since.

At the time, I couldn't get one of the (Infinity) setup jigs, so after I got the bit dialed in, I cut the end off the test piece and saved it as my jig for future use, but as stated above, it also just sits in a drawer.

I did the same when I finally produced an accurate test piece. I hate to sound discouraging because I do believe the bits have their place.....perhaps best when left set up in a production situation.

[Alan Schaffter]

For sure the lock miter bit can be a bugger to set and since it is large, a bit intimidating to use.

The setup blocks provided by some bit manufacturers will work, but only if the stock is the exact same thickness as the block. The instructions provided with many of these bits (and in many online videos) at best are confusing, and worst are just WRONG! The process often devolves into numerous attempts at trial and error. What many don't realize or appreciate, is that because the joint is at 45°, any minor adjustment in one direction (bit height or fence position) MUST be accompanied by an adjustment in the other direction. A video by an editor of a major WW mag said of his method it was easy and quick. By the time he was done, it was long. He even admitted, for time considerations, he had edited out a few minutes. He also had to go through a half dozen or more test cuts!

As a few have mentioned, the Infinity Lock Miter Master (LMM) setup jig is a godsend. The LMM works with any stock thickness within the range of the bit. Contrary to the claims of many that it can't be done, the LMM can be used to make a lock miter joint between stock of different thickness, e.g. a drawer with a 3/4" thick front and 1/2" thick sides and back. Likewise, the LMM will work with just about all brands of lock miter router bits and some shaper bits even though the profiles differ. The only exception is bits where the cutting edge is offset, i.e. is a chord not a radius of the bit. In that case the LMM can be used to set the bit height but an extra step is needed to set the fence position. This is all explained in the illustrated manual which can be viewed on or downloaded from the Infinity website.

Like other precision joints, close is just not good enough. You can't be cavalier or slapdash about the setup. Honestly, however, if you are careful, the LMM will allow you to set the bit correctly on the first try. If you careful and feed the stock slowly and consistently you don't need to pre-cut a 45° bevel first. I never do. I have used the lock miter bit to join solid face frames to ply boxes which were built using lock miters also- perfect 45° corners, no reveal, easy to clamp.

Disclaimer: I know the guy who invented the patented LMM (he visits here occasionally.)

[Joe Jensen]

I used one many years ago and it was obviously a pain to set up. Once I used it I failed to see how it was really any better. The little tongues are super fragile and appear to give no strength. I now always do dovetails on drawers and either a blind spline or a Festool Domino for all else. Can anyone show me how a lock miter does anything other than aid in alignment?

[Alan Schaffter]

I used one many years ago and it was obviously a pain to set up. Once I used it I failed to see how it was really any better. The little tongues are super fragile and appear to give no strength. I now always do dovetails on drawers and either a blind spline or a Festool Domino for all else. Can anyone show me how a lock miter does anything other than aid in alignment?

It certainly has its place as do other joints especially when using long miters on table legs, etc.- the advantages- increased glue surface and stronger miter joint over a standard (non-splined) miter, no slippage when clamping, perfect 45° better than typically possible with a TS, both profiles can be cut on a router table with the same setup, works great for A&C legs if you want all faces to be quartersawn with no reveal. I've never found the tongues to be fragile even with ply, but even if a section breaks it is not visible and has little effect on the overall joint.

[mreza Salav]

Not sure why so many have difficulty with setting up these bits. I have one (purchased from LV) and following the simple instructions they have it takes less than 10 minutes to set it up to get perfect joints; yes it requires a few try/tests but you can do the adjustments based on the first cuts easily. I admit I have never tried it to glue stocks of different thickness though. My experience is solely based on using stocks of the same thickness.

[Warren Lake]

old guys did this with two mitres and a spline simple fast and forever. The only advantage I see in the lock thing is that it looks like you only have to clamp in one direction but ive never used them. Maybe there are more.