Lock Miter bit size choices

[Dean Moldenhauer]

All,
I am in the market for a Lock Miter bit. Based on my experiences thus far, I am most likely to buy one of the Whiteside offerings.My question is, which of the two sizes would make the most sense?
Whiteside offers one that is 2" diameter and cuts the joint in 1/2" - 3/4" stock (Model #3362). They also offer one that is 3 1/8" diameter and cuts the joint in 1/2" to 1 1/4" stock (Model #3360).
I will most likely be using this primarily for boxes with nominal 3/4" stock - sometimes 1/2", so the 3362 bit would most likely work; however, buying the 3360 bit would allow me to do thicker stock if the need were to arise.
Seems like a no-brainer to go with the one that will work with 1/2" - 1 1/4" stock, but I wanted to poll the Sawmill Creek population to see what your experience is. Are there drawbacks to the larger bit that I am not thinking about? I realize I couldn't use it on stock <1/2", but I don't think that will be an issue.

In case anyone wonders, because of the difference in bit size/mass - I will be using this on a table-mounted 3 1/4 HP router.

Also, have any of you used the Lock Miter Master jigs? Are they really helpful in the setup (which seems to be the major drawback to these bits/joints). I don't mind spending the money for the jig if they're really helpful.

Thanks,
Dean

[Jim Becker]

I bought the larger one as well as their magnetic setup jig. Do note that you need to build a jig to hold material vertical for one side of the cuts.

[Dean Moldenhauer]

Thanks, Jim. I hadn't made it that far yet, but figured that would be the case. I'm using the JessEm table and TA fence, as well as the Mite-R-Slide II. I will have to do some noodling around on that setup to see what I might be able to rig up for the vertical pieces.

So, what are your impressions on the magnetic setup jig - big help or so-so?

Dean

[Mike Cutler]

I have the larger one as well. I also have the Infinity setup jigs to set them up.
Th jigs are nice and make it quicker to set the bit up. I use them in combination with a dial indicator. The setup jigs will get you within 10-20/1000th's pretty easily. the dial indicator will get you perfect.
There are many videos on using this bit, and the setup necessary. Make a nice carrying jig fixture for the material. This bit put's a lot of pressure on the material and will try to force it up and away from the fence. If your purpose is primarily the corners of boxes, I would make a horizontal and vertical coping sled. (There used to be a video of a guy using a Delta Tenoning jig for the vertical piece.)

[Dean Moldenhauer]

Thank you, Mike. I will be doing some video searches later tonight.
The other $64,000 question is about use of this bit with plywood. My research has been somewhat limited so far, but I have read some negative comments about using this bit with plywood. Does anyone have experience with this and are there tips for maximizing success and minimizing tearout? I assume the usual recommendations apply re: use of a follower board, but I assume that is a bit of a challenge with the vertical cut?

Dean

[Mike Cutler]

I tried it once on plywood and it didn't work out for me. Others may have a better solution for plywood use.
This is actually a pretty big bit. I run it in my shaper at 10,000rpm. I have the larger Whiteside bit. Someday, If I ever use one enough, I'll get a lock miter shaper cutter.

[Mel Fulks]

You lose some chunks with plywood, but not enough to prevent alignment. Some strength is lost ,but that might not matter for some jobs,and you can add some glue blocks inside for insurance.

[Dean Moldenhauer]

Thanks, Guys. After a small amount of reading, I am also considering the lapped miter bit set. Looks like it might be a good compromise - maybe a little bit of strength sacrificed, but (presumably) easier setup and looks like a better choice for plywood.

Thanks again,

Dean

[Mel Fulks]

Dean, I have my own easy set up method ,so I have not bought that easy set-up jig . But it gets rave reviews, I wouldn't sacrifice the strength of the standard model for any reason other than the other one being better for a particular job.

[Charles Lent]

I was never happy with the amount of tear out that I got when using the lock miter bits and I have the Lock Miter Master set up jigs. I've even tried making the cuts in several passes, using spacers to limit the depth of cut. So I went back to mitering my boxes and using cross grained full length splines. It takes me a little longer because of the added steps, but I like the results much better.

I use my tenon jig on my Unisaw to make the thin cross grained spline stock on both ends of a donor board. Actually the resulting tenon becomes the waste and I keep the thin waste from making a tenon as my spline material. Then I chop them free using my miter saw with a stop set up.. Mitering of the box corners is done on my Unisaw, which also makes the thin spline cuts. I use a Wixey angle gauge to set up the saw to exactly 45 degrees for this. For me, the "old way" still works better, but is much easier to do now, using a digital blade angle gauge.. Mine is a Wixey.

I think a lock miter bit that has more cutting surfaces would work better, but I could never find one. I think a 3 or 4 blade bit would improve the quality of the cuts and reduce the tear out, but I'm not a router bit designer. If I find one I will likely buy and try it.

Charley

[Rod Sheridan]

I use the lock mitre cutter for Arts and Crafts legs.

I does it a good job, however I use a stock feeder with it.

The flatness of the stock, table and fence is critically important for this type of operation...........Regards, Rod.

[Mel Fulks]

Charles, there is a way to stop the tear out. Use a 3/8 round over on the edge that will be mitered. Make that a "climb cut",feeder can be on the highest speed. Then set up the mitre cut with feeder on a normal speed and run material in standard manner. Don't let the mitre cuts make a sharp point ,leave a small flat. That will disappear in the sanding and
normal slight easing.

[Dean Moldenhauer]

Thanks for all the input, gents. I will do a little more research and thinking about my needs before I dive in.

Dean

[Ralph Okonieski]

I have not had success cutting ply with it. Too much tear out. It is only used for poplar or other hardwoods in my shop.

[Dean Moldenhauer]

Thank you, Ralph. Sounds like it's a mixed bag as far as results in plywood - not surprising considering the inconsistency in that type of building material. I'll do some more research but I'm kinda' leaning away from getting this bit considering a) my experience level and knowledge of the things to do to make this bit perform better and b) the fact that most of what I was going to use this for was plywood boxes.

Dean

[Alan Schaffter]

I never tried lock miters in standard ply- too many voids and inconsistent thickness, but Baltic Birch or other better hardwood ply works just fine. I built a book case from Birch veneer ply with poplar (faceframe) from the borg- it was assembled with lock miters- the sides to top/bottom and even the faceframe was joined to the sides/top/bottom with lock miters- that took some figuring out, because if you don't do it right you can't attach the faceframe (hint: the faceframes should be cut in the vertical position)- see photos below.

The Infinity Lock Miter Master is fantastic setup jig for lock miter bits (all brands). I know the guy who designed it and he's a great guy- he also invented the INCRA I-BOX box joint jig which is another option for making boxes. The Infinity website has a very detailed set of instructions for using the jig to make standard and specialty lock miter joints.

All pieces in this photo were joined with lock miters:

http://www.ncwoodworker.net/pp/data/2580/medium/IMG_4439.JPG

http://www.ncwoodworker.net/pp/data/2580/medium/IMG_4435.JPG

[Mike Cutler]

Charles, there is a way to stop the tear out. Use a 3/8 round over on the edge that will be mitered.

I don't use this bit alot Mel, but thank you for that tip. I'll think I'll try it out today for practice.

[Alan Schaffter]

The only problem rounding over a mitered corner in ply is that you reveal a few of the inner plies.

[Mel Fulks]

The only problem rounding over a mitered corner in ply is that you reveal a few of the inner plies.
The round over I referred to is before the lock mitre cut. I've used it mainly on solid woods like maple and birch which can
often have long pieces as much as 3/4 inch wide torn off by the mitre cutter. I think of it as removing a loose thread before it is pulled. It doesn't change the look of the finished work.

[Rick Potter]

Alan,

Who was it that told you the inventor was a really great guy? His wife, maybe? ;)

[Alan Schaffter]

Alan,

Who was it that told you the inventor was a really great guy? His wife, maybe? ;)

Yup, the person who spends his royalties!

[Alan Schaffter]

The round over I referred to is before the lock mitre cut. I've used it mainly on solid woods like maple and birch which can
often have long pieces as much as 3/4 inch wide torn off by the mitre cutter. I think of it as removing a loose thread before it is pulled. It doesn't change the look of the finished work.

There is another technique described in the Lock Miter Master manual, called the off-set lock miter, that allows you to round over the corner when you have a solid wood panel, like a drawer front or faceframe meeting a piece of ply. It drives the miter "around the corner" so no plies are exposed. There are two sets of special set-up marks spaced in 1/8" increments on the LMM that allow you set up the bit and fence to do this. You can also do a double offset- so that you can use corner, square or rounded inserts of the same or contrasting wood. Of course you can cut the corner rabbet in a finished joint as well. You'll also notice, that contrary the claims of most lock miter bit manufacturers, the LMM allows you to use a standard lock miter bit to make a lock miter with stock of different thicknesses. There are some side effects to doing this, but they are not serious.

http://www.ncwoodworker.net/pp/data/2580/medium/Offset_LM.jpg

http://www.ncwoodworker.net/pp/data/2580/medium/IMG_4471.JPG

http://www.ncwoodworker.net/pp/data/2580/medium/IMG_4527.JPG

http://www.ncwoodworker.net/pp/data/2580/medium/Offset.jpg

http://www.ncwoodworker.net/pp/data/2580/00-LMM_Add_2.jpg

http://www.ncwoodworker.net/pp/data/2580/medium/Dual_Offset_Corner-rounded.jpg

[Warren Lake]

I dont see the second one a rabbet will do the same and done it many times then rounded it as it disguises where the line is from the face frame that has been rabetted back there is nothing gained form doing the lock mitre that way that comes to mind first time seeing that. Do you have photos of the first one before you sanded and put the finish on it it looks very good what you have shown in terms of being tight but know that once sanding and finishing can take things up a level or two as well so curious what is off the cutter.

[Alan Schaffter]

I'm not following what you are saying, but with the dual offset setup, you only have one operation, not two. One definite advantage of the offset lock miter illustrated in the first drawing- using a 1/4" offset, you can match up 3/4" solid wood face frames (or drawer fronts) with 1/2" ply sides. I don't have any before shots of the cabinet, but the joints were darn tight- the end result is a function of good milling (bit/fence setup, sharp lock miter bit and steady feed rate) and clamping. With borg ply which has very thin face veneer you don't want to do much sanding to achieve a good corner- you'll expose the next ply.

Though nobody mentioned them, some of the benefits of a lock miter over a plain miter or even a plain miter with spline, is that it requires a single setup/operation, yields a perfect 45°, stays aligned during glue-up and clamping, and has more glue surface for a stronger joint. It is not as strong as a box joint or even possibly a dovetail joint, but it has its place and is just another weapon in your arsenal.