Horizontal slot mortiser (update)...

So I just created a 2-part video of the Jessem Mortise Mill mounted on my rolling cart. The two-part video for this can be seen at: https://www.youtube.com/WoodskillsCourses . Tech in wood joinery meets handcrafted design + build. Top is the mortising unit mounted horizontally, below the micro-adjust system. The original story follows as this is an update to an earlier post. The Jessem Mortise Mill unit was purchased a few years back and I created a few loose tenon slots successfully with it. The original mortiser design was to mount it vertically and use a power drill from the top down. Although this worked, I found the drill pressure would push the board down no matter how much clamping pressure I used. So I put the Mortise Mill aside for a few years until recently. During a shop reorg, I found the unit gathering dust and decided to re-incorporate it in my shop. I had always wanted a horizontal slot mortise and thought why not set this up to create slots horizontally instead of vertically. Original instructions were to install it vertically with boards placement underneath. So I decided  instead to mount it so slots were created horizontally as a horizontal slot mortiser. 

Next step was to find a suitable platform, i.e. workbench surface to mount it. A rolling cart in my workshop was ideal since I could wheel the unit away when not in use and the footprint of the Mortise Mill was not large. The rolling cart has large locking casters which do a good job of keeping the cart immobile. Installed it so the surface of the base plate was even with the surface of the cart, this took some time. I used large enough 1/4-20 bolts to maintain rigidity and keep it from shifting. The Jessem mortise Mill requires that a shop-vac be attached to the dust port otherwise the unit begins to clog up with sawdust, this can also be seen in the videos.

Have been using it since and am pleased with the system. The addition of the L-shaped wood bracket to support stiles while being mortised works well. The ends of rails to be mortised are easily supported by the wood surface of the rolling cart. I like the fact that I can permanently leave the Mortise Mill bolted to the rolling cart.

The only small issue was the vertical adjustment of the slots on a board. Since the Mortise Mill was installed horizontally, the adjustment was not as smooth as I would like due to the weight of the sliding carriage of the unit. Notice the etchings on the Mill are upside down. So, using scrap walnut and maple, in comes the micro-adjust setup to solve the problem. It is all wood construction with a 1/2 inch lead screw and wood handle. The end of the lead screw has a custom cradle contoured to fit the bottom edge of the sliding part of the Mortise Mill. I can precisely dial-in slot placements for either offset or different thickness boards now! 

Since the micro-adjust system is cantilevered off the rolling cart, I beefed up the supports, it's probably over-engineered now. Things to watch are the exact placement of the tip of the lead screw over the center of the edge of the Mortise Mill for smooth operation. A large paddle switch for the built-in Mortise Mill dust collection was installed for convenient access.

The two-part video for this can be seen at: https://www.youtube.com/WoodskillsCourses

Completed, tested and have been using for a few months now. Works great!