Kerfmaker - Perfect grooves with no trial and error

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Project by treeman posted 07-26-2009 12:55 PM 74042 views 412 times favorited 127 comments Add to Favorites Watch

If you are like most woodworkers when you make a groove or a dado, you will sneak up on the correct fit through trial and error. This was my standard procedure until I found the Bridge City Kerfmaker.

This item intrigued me so much that I thought I would order one until I saw the price. For many people price will not be an issue but for me, well, I need to watch my budget. I decided that I would attempt to make my own and the pictures you see are the result.

My version is made out of 3/4” Sapele cutoffs I had laying around. It measures 4” long by 1 3/8” tall. This is an ingeniously simple device that removes the trial and error process from fitting dados to the material that fits into them. Basically, you set up the kerf width of your cutter and the material thickness on the Kerfmaker and then make your cuts. The result is a perfectly sized dado with no tweaking.

The last picture is my first test cut using the device. There was no trial and error or tweaking involved. The first try was perfect. This cut was made on my table saw using a standard 1/8” cutoff blade. The cut was made in three passes; the first two established the width of the groove with the last pass cleaning up the middle.

To see how this actually works click the above link and watch the video at the bottom of the page.

127 comments so far

View spanky46's profile


995 posts in 4853 days

#1 posted 07-26-2009 01:34 PM

Very ingenious! Got to have one! You are a craftsman to duplicate this tool as well as you did!

-- spanky46 -- Never enough clamps...Never enough tools...Never enough time.

View Tim Pursell's profile

Tim Pursell

501 posts in 5244 days

#2 posted 07-26-2009 01:36 PM

View kerflesss's profile


182 posts in 4830 days

#3 posted 07-26-2009 01:43 PM

This is awesome. Very nice tool to make on such a simple concept. Well done!

View spanky46's profile


995 posts in 4853 days

#4 posted 07-26-2009 01:53 PM

Treeman, Where did you find the thumb nuts for this tool?
Could you provide exact dimensions of each piece?
Thank you.

-- spanky46 -- Never enough clamps...Never enough tools...Never enough time.

View Innovator's profile


3589 posts in 4876 days

#5 posted 07-26-2009 03:32 PM

Great looking tool, nice job.

-- Whether You Think You Can or You Think You Can't, YOU ARE RIGHT!!!

View BeachedBones's profile


201 posts in 4864 days

#6 posted 07-26-2009 03:34 PM

Sweet little tool, and an excellent job of making your own.

-- You know.... I think that old wood needs to be furniture.

View woodsmithshop's profile


1425 posts in 5008 days

#7 posted 07-26-2009 04:19 PM

great job, the video makes it look very simple, just the way it should be for me. lol
the video says it is for up to 1/2” wide kerf, and 2” wide material, could the tool be made longer to accomadate larger kerfs and wider stock?

-- Smitty!!!

View majeagle1's profile


1429 posts in 4958 days

#8 posted 07-26-2009 04:54 PM

Man O man, can I ever use this!!! What a neat but simple concept. Thanks so much for shareing.

I, like Spanky, would like to know some of the dimensions of the materials used and the source for the

Thanks again…........

-- Gene, Majestic Eagle Woodworks,,

View Charles Maxwell's profile

Charles Maxwell

1110 posts in 5269 days

#9 posted 07-26-2009 05:07 PM

When I examine the lack of quality in my own ‘good enough for government work’ approach to grooves and dados, I have that Sailor mentality, “Sir, we’ve always done it this way!” Now, I can take a step back from my blind, wasteful habits and put this very useful jig to work. Then I can tell my Sailor self, ‘I understand that’s the way you’ve done it before but, this jig will actually do the work better!’ Very useful! Thanks for the post.

-- Max the "night janitor" at

View a1Jim's profile


118321 posts in 5039 days

#10 posted 07-26-2009 05:10 PM

Hey TM
Thanks for sharing this cool tool and your creative reproduction of this neat aid.


View bayspt's profile


292 posts in 5167 days

#11 posted 07-26-2009 05:30 PM

Process blog- Process blog- Process blog This looks great Treeman.

-- Jimmy, Oklahoma "It's a dog-eat-dog world, and I'm wearing milkbone underwear!"

View arw01's profile


55 posts in 5076 days

#12 posted 07-26-2009 05:43 PM

I have sent an email to Bridge City to see if their pre-buy is still open. Those of us who can afford to buy such a clever device, should support the American Made tool maker.

Thank you for the post, it has brought my attention to a device I have added to my buy list!

-- No good deed goes unpunished!

View treeman's profile


208 posts in 4912 days

#13 posted 07-26-2009 05:50 PM

For people who value their time, the “buy” route is the way to go. I am retired and do woodworking as a hobby only. As such, I have to watch my $$ and choose carefully what I purchase. The Bridge City device intrigued me enough to figure out how it works. The challenge of building it intrigued me enough that the prototype was born.

I spent several hours on the drawings (above) and then several more hours deciding how to build it and then several more hours doing the actual build. If I valued my time at $10 per hour; I could have bought several of the Bridge City ones; but… then I wouldn’t have had the satisfaction of building it myself.

View Christopher's profile


576 posts in 5382 days

#14 posted 07-26-2009 06:05 PM

Friggen sweet.

View Dan'um Style's profile

Dan'um Style

14193 posts in 5445 days

#15 posted 07-26-2009 06:20 PM

I’ve got to get one of these some day !

-- keeping myself entertained ... Humor and fun lubricate the brain

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