# using a 45° Lock Miter Bit



## allthunbs (Jun 22, 2008)

Some time ago I bought a Lee Valley 45° Lock Miter Bit (part number 16J75.08.)

This past week I saw the perfect opportunity to experiment with this little gem and see what it would really do.

I used 7/16 th birch plywood and the 1/4" shanked bit. The router is a full blown Hitachi M12V table mounted with a solid fence. I followed the instructions that were published on their web site. 

The choice of birch plywood (the cheapest I could find) is the wrong stuff to use with this bit. As I ran the material through the bit, the top edge (the thin edge) of the wood began to collapse as it pressed against the fence. This led to an interesting "waveyness" in the cut as I struggled to correct for the weakness in the plywood. I then did the mating joint in the other surface but using a high fence and again the same thing happened. The result was a less than spectacular joint. 

Perhaps in a stronger wood or with some sort of supplementary support for the area being cut would yield better results. For example, when doing critical cuts that have to be perfectly even across the face, I use a squared up block of heavy 2x4 (about 100 yrs old so the dimension is real) to hold the piece against the fence with even force across the entire face. That block might provide support for the weak edge thus giving an even cut. I'll have to leave that experiment to someone else. 

Once all of the pieces were cut squarely I did a trial fit. All of the other parts were off a bit because of the "adjusting" I had to do with the lock mitre bit. Using a rather large mallet and a whole bunch of very strong clamps, I eventually _forced_ everything to comply. 

I would welcome someone else's observations on this bit. It has every potential of being an excellent problem solver but I haven't realized it yet. It is also highly likely that my inexperience might have caused some of the problems, but I'm not sure which.


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## bobj3 (Jan 17, 2006)

Hi AT

The key in using this type of bit is to use some other stock that is put in place with double sided carpet tape....

You can see a demo how to use the bit on the MLCS web site, great demo...

Once you see the How-To video you will get it.. and your joints will come out just right with plywood....

http://www.mlcswoodworking.com/shopsite_sc/store/html/smarthtml/pages/instruct.html

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## allthunbs (Jun 22, 2008)

bobj3 said:


> Hi AT
> 
> The key in using this type of bit is to use some other stock that is put in place with double sided carpet tape....
> 
> ...


Right on. I got two chunks of information in the same response. I'd seen references to mlcs before in the posts and couldn't figure out what people were referring to. Now I know. Thanks for the link.

As for the information, right on. Too bad you weren't handy before I started cutting the corners. They're assembled now and they're going to stay that way but one learns by a variety of ways - one of which is their errors - and, perhaps, the errors of others. Thanks for the help and the experience.

Allthunbs


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## bobj3 (Jan 17, 2006)

You'er Welcome AT

That little trick works for just about any bit that removes the tip of the wood or to say bits without bearings the norm or if you are not using the bearing as a guide setup... 


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