Precisely setting up the Freud 99-034 Lock Miter Bit regardless of thickness

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Blog entry by CTBlankenship posted 02-28-2015 12:26 AM 5438 reads 5 times favorited 11 comments Add to Favorites Watch


Just to let you know, three months ago I was a woodworking novice … seriously novice. So green in fact that I did not realize it is completely impossible to setup one of these bits with a Lowe’s Bosch Adjustable Router Table. So, I purchased some JessEm products and a Wixey Digital Height Gauge with Fractions. I then began the process of working with a lock miter bit. I started with a Katana Lock Miter Router Bit (#17850) and their setup block (#9755). The problem being that the block is setup for only ½” and 11/16” stock. I work with varying stock thicknesses. So, this was no solution for me. Next I purchased the Freud 99-034 lock miter bit and the Sommerfeld ‘s Easy Set Up Jig for Freud Bits. This is one quality tool as it works with 8 Freud bits and accommodates stock thicknesses from 23/32” to 1-3/16” in increments of 1/128th of an inch. I thought I had it made. However, I did not. It was very, very close … but not precise enough to risk 5 board feet of Mahogany ($4.90/bf * 5 bf = $24.50 plus a drive to Gibsonville, NC to replenish my inventory). There has to be a way to do this precisely, for any given material thickness.

The Way

I researched dimension information about the 99-034 and could find nothing, so I borrowed my son’s (a mechanical engineer) caliper (1/1000” accuracy) and got to work.

Step 1: Obtain accurate dimensions of the bit itself

I ran the bit through the router table with the fence set so that the entire profile of the bit registered on the plywood. I also referenced the 99-034 instructions and found the exact center point of the bit. Then found the following:

A. Total Bit Height: 1.160”
B. Bit Height above center point: .650”
C. Bit Height below center point: .50:
D. Thickness of 11/16” stock: .6875”
E. Center point of 11/16” stock: .34375”


Step 2: Calculating bit height

Just by trial and error I determined that the approximate bit height for 11/16” stock was .975”. However, that was not close enough. When performing the test (see below) the height difference was still noticeable.
Notice that when you raise and lower the bit height, the distance that remains constant is the bit height above the center point of the board. What varies is the distance below the center point of the board to the top of the router table. So, the bit height has to be:

.650” + (.50” – ½ of the material thickness)

Or, for my situation

.650 + (.50-.34375) = .80624”

I knew I had it when the result was very close to .975 but just a little bit higher.

Step 3: The Test

1. Go to Lowe’s and ask for four of their thick paint sticks
2. Rip two of them to the exact thickness of your material
3. Set the fence close to the point where the fence face meets with the top of the material thickness.
4. Run a stick through the bit and adjust the fence so that the bit just barely kisses the upper edge of the stick.
5. Do the same with the second stick.
6. Flip one stick over and fit the two together.
7. For me, I achieved a perfect alignment for the very first time.



A perfect setting and not one expensive piece of wood harmed in the process. Comments welcome …

11 comments so far

View pintodeluxe's profile


5328 posts in 2532 days

#1 posted 02-28-2015 12:44 AM

Wow, I guess having an engineer in the family changes everything. I have Rockler’s version of the locking miter bit, and it works well. I didn’t measure anything, just eyeballed it with a scrap block. Readjust the bit height as needed until the fit is correct.
I know some people say it is a difficult bit to set up, but I didn’t find that to be the case.

-- Willie, Washington "If You Choose Not To Decide, You Still Have Made a Choice" - Rush

View dustyoldman's profile


22 posts in 964 days

#2 posted 02-28-2015 01:30 AM

Just remember wood is not metal , and temperature and humidity play a big roll in joining pieces together, also the built in tension from a tree growing . I have had boards that were perfect twist and bow even when cutting them and after glue up .

View CTBlankenship's profile


8 posts in 927 days

#3 posted 02-28-2015 06:01 AM

I was WRONG … just ask my wife … it happens all the time!

I began reviewing the process all over again and viewed the same problem from a different perspective. If I start with the bit height at .650 … this places the center line of the bit at router top level. Next, to position that bit center line at exactly the centerline of the board … divide the thickness of the board in half and raise the bit that amount.

When I posted the .806 amount I must have been in some parallel universe. The actual bit height for 11/16” stock is 11/16 / 2 + .650 or .99375”. A Wixey height gauge makes the rest simple.

To be even more precise, place your board on the router table and measure the height … one would think that the height would be the same as the stock … however, on my router table the 11/16” stock came in at .70” ... .650 + .350 = 1.0 … pretty close to .99375.

DustyOldMan: Yea … wood is unpredictable … however, I buy the planed lumber and season it for a couple of months, then I cut out the rough pieces and sandwich them in between two vacuum press cauls for a couple of days, then make the cut to final thickness … repeat the caul process and then joint and glue. I make sure that all of the rings arch in the same direction (towards the outside of the box). I’m in hopes that the 45 degree lock miter joint is so strong as to prevent much movement. Of course, this is when I’m working with real wood for a special humidor … I’m particularly partial to marine grade 13 ply 18mm plywood … which is more dimensionally stable than real wood.

View playingwithmywood's profile


320 posts in 1316 days

#4 posted 02-28-2015 06:35 AM

very interesting reading but this really brainy gentleman from NC also was conflicted with this issue and he came up with a jig and then found someone to make it

i bought it and nailed it the first time I used it

View botanist's profile


167 posts in 3258 days

#5 posted 02-28-2015 01:50 PM

I’d kill for $4.90/bf mahogany…

View CTBlankenship's profile


8 posts in 927 days

#6 posted 03-02-2015 05:17 PM

PlayingWithMyWood … you just make my day … this is exactly why I post such things … frequently there is always a better solution. That user name can be construed a different way … you are a funny guy!

Botanist … .... I attached a price list for you that may illustrate the price difference to which you refer. These people ship using UPS and standard trucking … although shipping can be expensive.

View playingwithmywood's profile


320 posts in 1316 days

#7 posted 03-04-2015 05:08 AM

glad I did not offend you by pointing out the product after all your time on calculations

the guy that designed those also designed the I-box for box joints that Incra sales

how far are you away from the hardwood store….

View CTBlankenship's profile


8 posts in 927 days

#8 posted 03-04-2015 03:46 PM

106 miles or 1h 40 min … I go there to replenish my Spanish cedar and mahogany.

The shipping uses UPS if the lengths can stay below 4 ft. and under a certain weight. But, I haven’t used that yet. This is a nice drive on a Saturday for the wife and myself.

I took the plunge and bought the RTJ400 (Leigh) for box joints, dove tails and half blind dovetails … it is an engineering wonder.

No offense at all … as a matter of fact, I’m primarily going to use that tool to set the fence since the calculations are exact and I can set the height exactly using the Wixey height gauge. It is amazing how just one small variance (either wobble or bit/fence setting) and mess up a 45 degree lock miter. If I had known these two facts before trying to use that bit I could have saved hundreds on wood.

View CTBlankenship's profile


8 posts in 927 days

#9 posted 03-23-2015 12:54 PM

Just an update … I purchased the “Infinity Tools Lock Miter Master Jig – For 5/8” – 1-3/16 Lock Miter Setup and used it to build a router bit box (just as a test). The settings were spot on (fence and bit height) the first time through … no adjustments necessary.

It is interesting to note that the calculations previously mentioned (.650 + 1/2 the thickness of the material to be mitered) is also correct. The jig set the bit height to .998” ... the calculation set it to 1.02”.

This jig is worth its weight in gold. Which, if you do the calculations (weight to actual price of gold) the pricing is probably pretty close.

View playingwithmywood's profile


320 posts in 1316 days

#10 posted 03-25-2015 01:33 AM

This jig is worth its weight in gold. Which, if you do the calculations (weight to actual price of gold) the pricing is probably pretty close.

LOL…. Well glad you got it and like it….. I think it is a good investment that will only increase in value…

here is a article about the gentleman that designed the lock miter jig and the Incra I box

View thpalex's profile


2 posts in 553 days

#11 posted 02-13-2016 10:50 AM

Thanks for the helpful discussion, was pretty helpful to me.


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