Slot Mortiser

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Project by geekwoodworker posted 05-28-2014 09:22 PM 6079 views 34 times favorited 13 comments Add to Favorites Watch

Saw this on and had to make one. I built this one quickley with the intent of making a better one later. It has worked so well I haven’t had a reason to make another nicer looking one.

I have made some modifications on it such as:

1. I used 16mm shafts with brass bushings at first but then upgraded to 16mm linear bearings. Definately a better way of going.
2. Built a maple top with T-slots on top surface and on front edge so I could add different fences and hold downs.
3. Put the handle on the right side as I like to stand behind the machine when using it and not beside it like Mathias does.
4. I used t-slots for positive stops left, right, front and back. At first I had them at front near table but they filled up with wood chips so I moved them to the back and haven’t had any problems since.

I love this machine and use it all the time. Used it to make the base it is sitting on. I use loose tenons as I find that easier. I also use regular carbide bits. Some people may use up spiral bits as it pulls wood chips out of the hole. I find that the chips are blown out by the bit anyway. Since regular bits are cheaper and I build these tools to save money then I am way ahead of the game.

I don’t think I will make another one any time soon.

Here is a short video.


13 comments so far

View woodchuckerNJ's profile


1140 posts in 1057 days

#1 posted 05-28-2014 11:07 PM

good job… Would love to build one myself. Think it would be handy.

-- Jeff NJ

View AnonymousRequest's profile


861 posts in 972 days

#2 posted 05-29-2014 02:49 AM

Great job! Love it.

View TheFridge's profile


5682 posts in 909 days

#3 posted 05-29-2014 03:00 AM

Nice job on it. One day I’ll try to put one together.
Matthias wandel has some great stuff. I’ve followed him for years and wait impatiently ever week for new articles.

-- Shooting down the walls of heartache. Bang bang. I am. The warrior.

View exelectrician's profile


2327 posts in 1851 days

#4 posted 05-29-2014 03:52 AM

Your build looks top notch especially noting the fact that you went with linear bearings, they are so smooth.

I have a slot mortiser and I use it a lot. It is great for doing loose tenons and slats between two rails.

-- Love thy neighbour as thyself

View Underdog's profile


879 posts in 1459 days

#5 posted 05-29-2014 12:29 PM

That’s a heck of a build! And linear bearings? Isn’t that kinda pricey?

How does it work on end grain?

-- "woodworker with an asterisk"

View geekwoodworker's profile


350 posts in 884 days

#6 posted 05-29-2014 12:54 PM

Yes the bearings were fairly pricey as I had to buy 8 of them. Got them for $10 ea but it was worth every penney. The bushings worked well but would bind up slightly making the whole cabinet move if wheels weren’t locked. The whole build costed about $200 with price of router (got router used off kijiji). Used scrap wood as always. Compared to price of buying a mortiser this thing is cheap and way more versitile. Works flawlessly on end grain and long grain.

I used to have a mortising machine to cut the square holes and after a while my arm would get sore. And couldn’t cut end grain on it as it was vertical.


View Underdog's profile


879 posts in 1459 days

#7 posted 05-29-2014 04:16 PM

Reason I ask is because I had a Ritter miter mortiser, and the darn thing would wallow out the holes when it hit the end of the slot. Didn’t make for a very good mortise and tenon joint. I assume it was just because the 1” spindle just hung out too far to be rigid enough. I finally sold the darn thing.

-- "woodworker with an asterisk"

View geekwoodworker's profile


350 posts in 884 days

#8 posted 05-29-2014 04:30 PM

This thing makes the mortise nice and smooth all the way to the bottom (and even). Knots don’t make any difference either as it plows right through them and stays straight. In the first picture I am mortising 2” deep (3/4” bit) into spruce and the Loose tennon was tight all the way down. During dry fit I couldn’t get it back out and had to use pliers to pull it out.

View majuvla's profile


8739 posts in 2291 days

#9 posted 05-29-2014 06:20 PM

Always impressed by those wooden machines.

-- Ivan, Croatia, Wooddicted

View Woodwrecker's profile


3914 posts in 2999 days

#10 posted 05-29-2014 09:18 PM

Very nicely done !
That would see a lot of use in my shop.

And welcome to Lumberjocks.

-- Eric, central Florida

View DocSavage45's profile


7656 posts in 2266 days

#11 posted 11-25-2014 07:24 PM


Saw your reference to this machine. Mathias would be smiling!

-- Cau Haus Designs, Thomas J. Tieffenbacher

View Gregg M.'s profile

Gregg M.

162 posts in 1105 days

#12 posted 12-17-2015 08:17 PM

I watched the video. That is awesome. Thanks for sharing.

-- Marvel Woodworking, West Chester, PA -

View  woodshaver (Tony)  's profile (online now)

woodshaver (Tony)

3940 posts in 2776 days

#13 posted 04-01-2016 01:35 PM

I was just looking at the Slot Mortise machine that Majuvla built and saw a link to your machine.
Nice build as well! I really like all the added modifications you made to compliment your build.
I also made one back in 2012. You can see it here.
Oh! And nice job on the video as well!

-- Tony C UAW, St Augustine FL, My high school shop teacher said "You can do it"... Now I can't stop!

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