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  • Lock Miter Router Bits

  • Video
  • Reviews
Make frames, boxes, right angle
and parallel angle joints.

2 flute, carbide tipped. To join materials at 90° by cutting a 45° miter and a perfect matching tongue & groove glue joint. This joint not only increases mechanical strength, but also increases glue surface area and automatically aligns parts. Set-up blocks sold separately below.

Lock Miter Instructions (PDF)

Set-Up blocks sold separately below.

Lock Miter Router Bits
Item # Thickness
of Stock
Large Dia. Shank
Set-Up Block Price  
#5547 3/8 to 1/2" 1-3/8" 1/4" #9750 $35.50
#5548 1/2 to 3/4" 2" 1/4" #9751 $37.50
#7847 3/8 to 1/2" 1-1/2" 1/2" #9750 $36.50
#7849 1/2 to 3/4" 2" 1/2" #9751 $41.95
#7850 1/2 to 1‑1/8" 2-3/4" 1/2" #9753 $47.50

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MLCS lock mitre router bits

all customer reviews and ratings

Average Customer Rating: (11 reviews)
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DIY Homeowner (3/5), Feb 10, 2021

By Mike Breunig (Tucker Ge US)

Initial practice with the lock miter bit found a risk of damage to the stock when the large low speed bit encounters wood grain at non-optimum angles. With practice and less valuable stock it could be useful, however I am going to use less hazardous joinery on my kitchen cabinet project where paint can hide exposed stock end grain.

Fast setup, perfect fit (5/5), Aug 6, 2020

By Jim Stutzman (Spokane Wa US)

Although skeptical at first, I was amazed at the simplicity of setup using the setup block on 3/4" and 1/2" pine & poplar boards and 1/2" birch plywood. Initial test cut in 3 multiple passes gave a perfect fit on each test.

My first real project, a stand for the MLCS Dovetail Jig #9094,found under the MLCS Projects heading, came out perfectly. Rock solid joinery, square, tight fit. These bits save time in mitering and a none slip glue-up. Recommended !!

Lengthy set up process (3/5), Jun 2, 2020

By Peter A Butzin (Tallahassee FL US)

I bought a lock miter bit from another vendor a few years ago. I sent it back because it didn't work for me. And, it didn't work because the vendor provided no instructions regarding its use.

When MLCS had a sale recently, I decided to try again after reviewing the fairly detailed instructions provided on line.

To save others grief, I found the best instructions in the following YouTube video:

After following the instructions to the letter, I can't fault the bit, which provides clean miter joints. But it takes as much set up as my Leigh DR4-Pro dovetail jig. (I bought the lock miter bit in the hopes that I could shorten the set-up time.)

The bit works great, but only for those who follow the set-up steps. I had to run several passes on scrap stock before the alignment was "just right".

The next time it will go somewhat quicker, but still takes over an hour to set up and run test passes.

I rate the product a 3, only because of the set-up process.

P.S. I purchased the set-up block, but it didn't save me from having to carefully follow the instructions in the YouTube video.

setup is everything (4/5), Dec 29, 2019

By James Fisk (Kennebunk ME US)

I used this to make legs for a 10"w x 36" long x 11" deep cypress planter out of 7/8" stock that my wife wanted 36' high on casters. Needed the setup block, customer service, which was great, they even emailed articles, and many, many test pieces later got perfect lock miter joints and solid legs.

AWESOME!! (5/5), Nov 3, 2015

By Michael Barsky (Philadelphia PA US)

Picked this up today, because I needed to assemble a banister I made out of 4 raised panels, that were 6 1/2x28. I was skeptical about it working on a long surface, but man was I surprised. I got back to the job set the bit up in table and ran two pieces. Perfect the first time, incredibly easy to set up. I ran two of the pieces through on edge in three passes, both sides. Ran the other two through face up in three passes. They slid right together and were perfectly square. These are a must have for me now!!! Love it!!

Review of lock miter bit (4/5), Oct 28, 2015

By ralph (Harrisburg Pe US)

I have just finished using the one that I had purchased and have had terrific results. It is so much easier and effective for making the 90 degree corners on all pieces of wood. It takes some time to work with, but once you become familiar with it, the router bit produces fantastic results. All of the corners are square and very strong.

limit the glue (5/5), May 22, 2015

By tom siegel (Charlevoix MI US)

Test cut in 12" long dry oak was absolutely perfect. Found the set up guide blocks useful.

Lept to a 7 foot long cut in walnut for box beams for a king size bed. Absolutely loved an earlier review suggesting leaving 1/16th or so in thickness when milling your own stock. I used a drum sander to remove the excess after the miter .. avoided risk of snipe on the planer .. got a knife edge.

Had early problem with glue-up. The tongue and groove, when using a single bit and single fence setting, are apparently so tight, there is little to no room for glue squeeze out .. especially in a 7 foot long joint.

Resorted to gluing only the 45 degree flat surfaces, leaving the tongue and grooves dry. Much better fit. Got the minimum desired squeeze out at the 90 degree inside and outside edges making for a very tight looking edge.

In my project, with the box frame still in three sides, I glued in some ribs to make up for any loss of strength I caused by not gluing the tongues and grooves.

strong drawer joint (5/5), May 31, 2013

By Ken Rupkalvis (San Antonio TX US)

I used this bit to make many drawer boxes for a very large desk. It's rock solid after glue up and very square off the router. I found the setup block helpful in that it cut setup time significantly.

Nice Joint (5/5), Oct 24, 2012

By John McCormick (Spring Te US)

I too used this bit to make table legs because I did not want to show a glue joint down the piece. I was very happy with the outcome. The setup block was nice but not 100% necessary.

Also, if you are milling your own wood to thickness, I recommend that you leave a sixteenth or so on the thickness before routing the lock miter. This way, you are not producing a sharp edge to ride on the out feed fence. Mill to final thickness after the miter has been routed.

Best of all, the joint produces a near perfect 90 degree joint with little effort. Just make sure to clamp it tight.

Very Versitile (5/5), Sep 5, 2012

By Paul Smith (Altoona PA US)

If you want to build a table leg made from 4 pieces of wood this is the answer. Used it to make legs for a Craftsman design dining room table. Many of my woodworking pals thought the legs were solid, but I explained how this bit works and a couple added this bit to their collections. Also, this is a great bit for making drawer boxes. The front, sides and back interlock and make a joint of unprecedented strength. Also, the set-up block is a near necessity for accurate joints. There are alternative set-ups but the block is easiest.

Avid DIY (5/5), Aug 5, 2012

By Paul J Schneider (Red Lodge MT US)

I have used this product and found it to be very useful, and would recommend it to anyone wanting a secure joint in their woodworking. The video is most helpful.

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  • Set-Up Blocks for Lock Miter Bits

  • Reviews
Save time, effort and wood.

The pre-cut joint profile allows quick, proper height adjustments with accurate setup everytime. The size of the set-up blocks varies: #9753 is 3‑3/4" x 1-1/2", #9750 is 4" x 1‑7/8", #9751 is 3-3/4" x 1‑7/8". They're manufactured from ultra high molecular weight polymer. Items #9750 and #9751 are for 1/2" and 3/4" stock. Item #9753 is for 3/4" stock only. Instructions included. Note: The joint may need to be fine tuned after the first cut to get a perfect fit.

Set-Up Block for Lock Miter Instructions(PDF)

Set-Up Blocks for Lock Miter Bits
Item # Set-Up Block Profile Price  
#9750 Set-Up block for lock miter bits #5547 & #7847 $12.95
#9751 Set-Up block for lock miter bits #5548 & #7849 $12.95
#9753 Set-Up block for lock miter bits #7850 $12.95

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MLCS set-up blocks for mitre bits

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Average Customer Rating: (6 reviews)
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Easy-peasy (5/5), Aug 6, 2020

By Jim Stutzman (Spokane Wa US)

Very quick set-up, dialed in within 10 minutes on a cheesy HF router table. My tests and project turned out far better than expected. A very useful aid.

Does the job (4/5), Apr 24, 2018

By Joe Braun (Fort Collins Co US)

Overall I like this bit and the set up block gets you within a few mils accurate. I used it on making 3” thick front floating shelves out of 3/4” MDF. The end result was terrific. This joint requires serious clamping as it is a very close tolerance fit. But the end result is extremely tight miter that finished perfectly.
I tried this with 1/2” Baltic birch ply, poplar and MDF for drawer stock. Unfortunately the tongue it leaves behind is to small and either tore out during milling or cracked during assembly with this thinner material. It’s also way to tight to assemble the drawers. I had to go back to the locking drawer miter bit for that to mill properly and ease the assembly process. The set up block does set up both 1/2” and 3/4” stock. Although I won’t try this with 1/2” stock again

Locking Mitre bit (5/5), Jun 27, 2017

By Carl B (Watertown NY US)

Love the bit and the strength of the joint. However I highly suggest using a backer board to prevent tear out at the rear of your workpiece.

unknown setup block (3/5), Sep 13, 2015

By Anonymous ( )

I am sure the lock miter bit and setup block is a good product. However, I did not know about the set up block until AFTER testing the bit and failed. It would be nice to know about the added cost of a setup up block BEFORE ordering the bit. Why is it not listed as a KIT? Thus only 3 stars.

MLCS NOTE: The setup block is listed right on the page with the bit. We do not include it as part of the package because many customers do not need the block and this helps to keep the price lower.

great cutter (5/5), Aug 19, 2014

By dennis curtis (myrtle point OR US)

just got my lock miter bit today. worked perfectly.. ordered the set up block for 1/2-3/4 stock. block setup made it fast and accurate. save yourself time, buy the setup block..

Non-laminated table legs (5/5), Oct 27, 2012

By John McCormick (Spring Te US)

I got my lock miter bit in a few weeks ago. I have use it to create table legs for a dining table I am making. I didn't want lamination joints showing where I built up the thickness so I used 3/4 inch stock and made essentially column for the legs. They turned out great. I ran a few practice boards and it didn't take me long to figure out it is best to leave the thickness about 1/16 inch from the final thickness just to have an edge to run along the out feed fence.

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  • Two Piece 22-1/2° Lock Miter Set

  • Video
  • Reviews
Carbide Tipped Lock Miter Set

2 flute, carbide tipped 1/2" shank set. The 2 bit system joins material at 45° by cutting a 22‑1/2° miter. Makes a perfect matching, strong tongue and groove joint. Easy set-up. Use for octagonal shapes on corner cabinet, entertainment centers, etc. For 1/2" to 15/16" stock. Set-Up Block sold separately below.

Lock Miter Instructions (PDF)

Lock Miter Router Bits
Item # Thickness
of Stock
Set-Up Block Price  
#7740 1/2 to 15/16" 1/2" #9756 $49.95

Set-Up block sold separately.

Set-Up Block for Lock Miter Set #7740
Item # Set-Up Block Profile Price  
#9756 For two piece lock miter set #7740 (3/4" stock only) $12.95

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MLCS lock mitre router bits

Sorry no videos exist for this product.

all customer reviews and ratings

Average Customer Rating: (2 reviews)
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Lock Miter Bit (5/5), Jun 21, 2017

By Edward Hollingworth (Albuquerque NM )

There will always be tear out on plywood. BUT if u put a backing board on it to protect the thin plywood edge YOU WILL NOT GET BREAK OUT.. you will get a good looking edge, I have used these to make boxes and have never been disappointed.

22-1/2 lock miter bits (3/5), Mar 13, 2017

By Raymond Kiser (Pounding Mill VA US)

Tried bits on plywood and hardwood. Works ok on hardwood but on plywood had lots of tear out, even when taking shallow scoring cuts.

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