# 45 degree locking miter



## jzimba (Jan 11, 2012)

What Is the best method to router 45 degree edges that lock together to form a 90 corner?


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## jlord (Nov 16, 2009)

jzimba said:


> What Is the best method to router 45 degree edges that lock together to form a 90 corner?


Welcome John.
This bit is a little fussy to set up. Leave your material square, the bit will cut the miter. Here is something to read on this.

http://www.mlcswoodworking.com/shopsite_sc/store/html/smarthtml/graphics2/TM26-29lockmtr0911.pdf

Video
http://www.mlcswoodworking.com/shop...ges/bt_lockmiter.html#lock_miter_video_anchor


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## jw2170 (Jan 24, 2008)

Welcome to the router forum.

Thank you for joining us, John.

A 45degree chamfer bit will cut the mitres in thinner stock. What thickness is your stock..


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## paduke (Mar 28, 2010)

I am a lock miter fan Make sure you have a tall fence square to the table


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## Drew Eckhardt (Aug 2, 2008)

jlord said:


> Welcome John.
> This bit is a little fussy to set up. Leave your material square, the bit will cut the miter. Here is something to read on this.
> 
> http://www.mlcswoodworking.com/shopsite_sc/store/html/smarthtml/graphics2/TM26-29lockmtr0911.pdf


A measurement based approach to lock miter setup is much simpler especially since setup errors are doubled due to how the joint works and even .005" matters.

To get in the ball-park, you're looking to have the center of the bit (halfway down the mating edge of the male finger on each piece) line up with the center of the wood. Then set the fence so a flat piece of scrap laid across the top of the work intersects the bit.

Run one piece through face up and mark it "A". Run one through face down and mark it "B".

Mate them and measure with your dial caliper (I like a slightly bigger set where the jaws usually reach correspondingly farther) across the high parts and divide the measurement by 2. This is how far off your height setting is. If "A" is high the bit is low so raise it by that amount. If "B" is high the bit is high so lower it. Note the first attachment - height isn't set right yet.

If you're setting based on measured bit height you'll get a perfect joint after two sets of pieces. Maybe another try or two if you have to hassle with backlash in the router height adjustment mechanism and read its scale.

Fence depth setup works the same as height except you cut the pieces vertically against the fence. Use shim stock or feeler gauges to space your fence out from the stop blocks or to move the stop blocks away from the fence. If you move just one end the fence will move half the distance from the bit.

Other caveats are 

1) Your wood must have uniform thickness since the bit indexes off the inside surface.

2) You want to make 2-3 passes with the last at 1/16" to prevent tear-out. Clamp a pair of stop blocks to your table behind the fence in its proper location and space the fence out for initial cuts.

3) You want to run a piece through behind your work to prevent tear out.

4) The bit wastes the entire height of the stock so you want to stick a straight edge to the top with double sided tape to guide it.


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## bobj3 (Jan 17, 2006)

hi


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## jlord (Nov 16, 2009)

I have those Bob & they do save time with setup's.


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## RJM (Apr 11, 2010)

Router Table SOP "Setting Router Bit Height on Work-in Turn Bits"    Page 1

Router Table SOP "Setting Router Bit Height on Work-in Turn Bits"    Page 2

Router Table SOP "Setting Router Bit Height on Work-in Turn Bits"    Page 3


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## paduke (Mar 28, 2010)

Robert thats a great link. Luv the playing cards.


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## fixrite (Apr 5, 2011)

I will be using that card trick in my sawdust making shop. thanks Robert


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## Jack Wilson (Mar 14, 2010)

One method that has been over looked is the spline method. I have attached a photo to help my poor explanation. All you need for tools is a table saw, 1st cut all your sides to length with a 45* so it forms the box you want. Then set your blade, (still at 45*), to about 3/8" depth. Then set your rip fence to about 5/8" away from the blade, I use a starting block so that the cut is not trapped as I run my stock thru. Now run your stock thru the blade so that you create a kerf in the 45* faces you just made. At this point if you set your corners all together you should have kerf in each corner thats about 1/8" x 3/4". Now set the saw blade to 90* and rip a spline the width of your saw blade, and just under the 3/4" that your kerfs should be. Now glue the kerfs and install the spine, then clamp.


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## otherguy (Jan 19, 2012)

paduke said:


> I am a lock miter fan Make sure you have a tall fence square to the table


Agree with this, I didn't have one and it made doing the vertical pass harder. Aslo my router table fence slipped, I had to clamp a board behind it to make sure the setting stayed where it should


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## bigrigger61 (Jan 24, 2012)

I don't want to butt in, but Freud has a baby lock miter bit, and for another 30 bucks, comes with a setup guage. The baby will start at 3/8 and go to 3/4! Will post later as the mailman is delivering a guage soon!


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## jlord (Nov 16, 2009)

Here is some setup jigs that also helps setup the lock miter bit.

Ezset For Freud Bits-Sommerfeld's Tools For Wood

Sommerfelds Easy Set Up Jig-Sommerfeld's Tools For Wood


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## jruimy (Jan 14, 2012)

What a great tip! Thanks, Robert. Will be trying it this weekend.


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