# Using Miter Lock Bit Question



## sailmike (Jun 7, 2011)

I recently acquired a miter lock bit and was making some test cuts to get some practice with it. My first cut didn't turn out so good (see pictures. This site turned the pictures sideways.). I'm guessing I need a zero clearance fence to avoid all that nasty chipout. The wood is baltic birch plywood from Rockler.


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## woodnthings (Jan 24, 2009)

*looks to be a low cost/cheap bit ....*

That bit would probably not give great results in plain hardwood, let alone Baltic Birch plywood. Plywood, even with the best of bits won't be easy to cut without splintering. because the grain keeps changing 90 degrees to itself. On hardwood it at least runs one direction ... along the length which makes splintering minimal.

I don't think a zero clearance plate would make that much difference, but it won't hurt to experiment. Also make progressively deeper cuts. Also, you may have to "climb cut" to avoid splintering, and that's a bit dangerous. I would just make a 45 degree miter on the table saw and use a spline for strength and positioning.


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## J_L (Apr 22, 2014)

Some plywoods are more prone to tearout then others. A zero clearance fence would help for sure. Are you using the plywood as just a test piece or are you looking to use plywood with the lock miter?


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## Sawdustguy (Dec 30, 2008)

That is really bad chip out.. It looks like some pretty poor quality plywood to me. Is that the piece that you cut flat on the router table or the piece you cut vertical against the fence? 

I have a lock miter bit but have not used it with plywood yet.


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## sailmike (Jun 7, 2011)

That was the piece that was vertical. The piece that was flat on the table came out fine with some tear out at the ends, which I expected. The plywood is good quality baltic birch from Rockler. I plan to work with a lot of 1/2 and 3/4 inch plywood.


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## GeorgeC (Jul 30, 2008)

If you are using a lot of plywood and want to continue this joint then you need to find a much better bit. Or find another joint.

George


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## Toolman50 (Mar 22, 2015)

I think one of the problems is you are trying to cut too much in one pass. It’s too much on this plywood. And by the way, this does not look like Baltic Birch Plywood. But I’m looking at a picture. 
Here are a few things to try. 
1. Measure your depth if cut in total and score a line all across the top with a knife against a straight edge where the router bit should end. 
2. You can also add masking tape across the board starting at the line you just cut laying the tape inside your line. 
3. Make your cut in 3 increments with the final cut cutting less than 1/4” deep. 

After tying this, please report your findings.


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## Sawdustguy (Dec 30, 2008)

I don't think making a lock miter joint can be done in multiple passes. One piece is fun outside face up on the table and the other piece is against the fence with the inside against the fence. Changing either depth of cut or the position of the fence will change the relationship of the pieces and the joint will not fit together and make the outside corner.

You need to run both pieces with one setup of the bit and fence.


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## GeorgeC (Jul 30, 2008)

Sawdustguy said:


> I don't think making a lock miter joint can be done in multiple passes. One piece is fun outside face up on the table and the other piece is against the fence with the inside against the fence. Changing either depth of cut or the position of the fence will change the relationship of the pieces and the joint will not fit together and make the outside corner.
> 
> You need to run both pieces with one setup of the bit and fence.


You could do it, but it would take a lot of work. You would have to make numerous cuts with scrap materials to get the final setup correct.

It would not be worth it.

George


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## Rebelwork (Jan 15, 2012)

Are you using a feather board on the router table to keep the board flat. When I've ran them any air between board and table top led to tear out. Kind of a finicky setup...


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## Sawdustguy (Dec 30, 2008)

GeorgeC said:


> You could do it, but it would take a lot of work. You would have to make numerous cuts with scrap materials to get the final setup correct.
> 
> It would not be worth it.
> 
> George


Exactly what I was driving at in my post.


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