miter lock bit,,,

[jeff oldham]

maybe im doing something wrong,,i have had 2 of these bits bought from amazon,,one which was 1/4 shaft and bent,,which i sent back,,then i reordered a 1/2 in shaft one,,,and used a backer board in both cases and maybe im doing something wrong but these are really dangerous bits,,,one bent and the other would not cut the material all it did was raise up,,,,if anyone can tell me what im doing wrong or the results they have had with this bit it would be appreciated,,,,if you watch the you tube videos on these bits you dont see these problems,,,

[Mel Fulks]

The larger ,approx. 4 inch diameter shaper cutters work much better. If you are getting a lot of tear out ,you can stop that by rounding
over the corner that will be removed...with a “round-over “ bit run with “ climb-cut” ,pocket knife , or even sandpaper.

[Brian Runau]

maybe im doing something wrong,,i have had 2 of these bits bought from amazon,,one which was 1/4 shaft and bent,,which i sent back,,then i reordered a 1/2 in shaft one,,,and used a backer board in both cases and maybe im doing something wrong but these are really dangerous bits,,,one bent and the other would not cut the material all it did was raise up,,,,if anyone can tell me what im doing wrong or the results they have had with this bit it would be appreciated,,,,if you watch the you tube videos on these bits you dont see these problems,,,


Jeff, I used to make drawer boxes with these vs dove tails and apart from getting it set up so I get the right joint overlap, they did work for me. When you machine are you going with or against the grain of the wood? I used a Freud bit. I had to make a sled to do the vertical cut on one piece for the mating pair. If memory serves me one runs through flat 90 degrees and the mating half runs through on the sled vertical. Could you show us pictures of your set up and how you are running them in the router? Brian

[al ladd]

I did a run of boxes in difficult material once a few years back with lock miters. I precut with something like a bevel miter on the table saw first to minimize the material removal from the router bit, and that made for a much more relaxed, accurate router cut.

[Ray Newman]

Lock miter bits are probably one of the biggest PITA bits to set up, but a set up gauge will really help! The below gauge was designed by a member of this board and works very well: https://www.infinitytools.com/lock-miter-master-jigs

[Thomas McCurnin]

+1 for Ray's comment. I tried to use one once and spent an afternoon for set up. Never again.

[Alan Lightstone]

Yup. Get the Infinity version with the setup gauge. Makes all the difference.

Still a PIA, but looks nice when completed.

[Dave Sabo]

The infinity setup jig works with just about any lock miter bit. It is not exclusive to infinity’s version.

[jeff oldham]

what would the bevel setting be on the table saw for precutting the miter

[Jay Rasmussen]

Is it a quality cutter? I have Woodcraft brand, cuts very cleanly. I haven't used it in a while but don't remember any problems.
Do you have any photos of your setup?

[Jim Becker]

what would the bevel setting be on the table saw for precutting the miter

45º. Do keep in mind that pre-cutting the miter to make the cut less work for the lock-miter tooling can get you into complicated sizing calculations if you need to have a "box" of a particular dimension. The reason being that there are portions of the profile that stick out farther than the bevel. So you have to cut long for material relief to pre-bevel. It may be easier to pre-cut with the lock miter tooling but holding back the material slightly before making a final pass at full depth. That's likely relatively easy for the horizontal cut with the material on the table, but harder for the vertical piece which really does have to be supported by a jig/fixture for best results.

I have the good Infinity cutter and setup block. Despite that, I got frustrated with the touchy setup and to-date haven't pursued it much at all.

[Mel Fulks]

Jeff, round off the bottom corner. That will stop the small tear-out and big flying pieces.

[jeff oldham]

thank you mel,,,very helpful

[Jim Becker]

Jeff, round off the bottom corner. That will stop the small tear-out and big flying pieces.
That's an excellent idea, Mel. Thanks!

[Mel Fulks]

That's an excellent idea, Mel. Thanks!

I worked in a large custom mill ,about 3 years, that had a shaper mitre head. But all the guys there ripped 45 degree and just nailed and
glued. Obviously they got a lot of complaints from buyers. I asked them to buy a mitre head and they told me they had one! But they
“didn’t work, tore out big pieces”. I showed them it did work. The basic idea of climb cut rounding before making difficult cuts was once well known.
Im pretty sure it was killed by safety stuff . I did the rounding on the shaper with the feeder on the highest speed, so it didn’t add any
time to do the rounding . Far less time and material are used than getting the material out 3 or 4 times ! And then trying to patch them up.
The climb cut rounding can be done on the highest feeder speed ...yes the one you have to switch the gears to use.

[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.