How To.. line up a router bit more mortise or dado?

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Forum topic by Holbs posted 09-16-2014 09:49 PM 1074 views 0 times favorited 6 replies Add to Favorites Watch
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1878 posts in 2053 days

09-16-2014 09:49 PM

I cut 42 1/2”x2” mortises with my Router Mortise Jig for a lunchbox planer / jointer fliptop table with 4’ stowaway infeed and outfeed table project that i’m in the middle of. I really should start a blog on this. Due to errors I made, I had to reset the router for different tasks. I learned precious placement of the router bit to match identical measurements of previous mortise should not be done by the eye alone. Even with the use of dial caliper, 0.4mm pencil marks… my double floating tenon is off a hair enough to cause concern by 1/16” or so. I think I will be ok for this utilitarian project, but this leads me to when it comes time for fine furniture precision cuts. I know I will create one of those router dado jig for precision. But when it comes to using router bits at precise measurements down to 0.010” or so, how do you go about it?
I do admit, I own the Microfence router jig that does 0.001” measurements. But even with it’s use, the end result is using the eyes to zero in which I am finding impossible.
Maybe I should start using my marking knife. But when I watch other wood workers on youtube for precise cuts, they just use a #2 pencil and haphazardly start cutting. End result: perfectly mated pieces.

-- The Carpenter Bee is derived from the Ancient Greek word wood-cutter

6 replies so far

View johnstoneb's profile


2938 posts in 2197 days

#1 posted 09-16-2014 10:35 PM

Have all your pieces cut and make the joint cuts on the same setup. For example have all you legs cut out then cut all the mortises at the same time.

-- Bruce, Boise, ID

View TheWoodenOyster's profile


1317 posts in 1959 days

#2 posted 09-16-2014 10:39 PM

You gotta do them all at once. Never ever reset you router between identical joinery pieces if possible. But, if you are talking about how do you set it in the first place, I just do trial and error with scrap until it works, then I knock them all out. I have been pleasantly surprised by how unscientific setup can be as long as the pieces are identical. Pencils and marking knives get me where I want to be. But I always test with a scrap first.

-- The Wood Is Your Oyster

View Richard's profile


1916 posts in 2714 days

#3 posted 09-16-2014 10:49 PM

You just got the right answer 2 times in a row , batch out all the parts that need a paticular setup then go on to the next setup and test each one first.
Unless you are useing a CNC system you are Never going to get the same setup twice in a row unless you are very very Lucky. And really even with CNC you have to place the parts correctly in the machine to get the Exact Same Part on a second run.

View lateralus819's profile


2241 posts in 1913 days

#4 posted 09-16-2014 11:11 PM

I use a V groove bit to center my other bits. Works well.

View Holbs's profile


1878 posts in 2053 days

#5 posted 09-16-2014 11:47 PM

ahhhh. lateralus…. v groove bit. now, that might help a bunch. gonna have to try that. maybe make one of those centerline jigs to help with pin pointing exact center for a pointed bit. i like that :)

-- The Carpenter Bee is derived from the Ancient Greek word wood-cutter

View timbertailor's profile


1594 posts in 1448 days

#6 posted 09-17-2014 04:12 AM

Take a straight edge and clamp it to some scrap wood and cut with your router using the bit you plan to use. Now, take a piece of Birch plywood and cut it to the width of the cut you just made. Now, you have a jig that is the exact distance you need to measure from the bit edge to the straight edge guide.

I keep several of these jigs marked with the bit and diameter they are associated with on hand. Makes cutting a daddo quick and exactly where I need it.

I do the same for my circular and jig saw.

-- Brad, Texas,

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