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Well Built, But Very Hard To Use
on March 28, 2012
The machine is built with high grade aluminum and brass knobs. The Jessum loose tenons are made from hardwood and they are exacting. They fit the mortise very closely.
The downsides are numerous. Set up is difficult. It literally takes me an hour to set up the machine. Because the slots need to be exact the jig needs a micro adjustment rather than loosen the knob and push it one way and then another. If one side is a little off the measurement to correct it is one-half the difference, and that makes it tough. More than once I have ended up moving the carriage setting back and forth numerous times and making test cuts to get the mortise where it needed to be. This is frustrating and time consuming.
But the big problem is clamping. If you watch the videos demonstrations you will note that no one is shown clamping the stock to the unit. If you use a C clamp the motion of clamping will turn the stock, and if you use a quick clamp system it will not hold the stock in position while it is being milled. The problem is the jig is slick - that is - well machined. The areas that the stock butts up against need to be rough. I tried attaching sandpaper but that did not work well. It changes the measurements and makes centering the stock harder. I finally attached sandpaper to the quick clamp and that helped. The clamp area is small, and the area where the stock must the clamped is below eye level causing me to do deep knee bends every time I changed the stock. The stock must be held very tightly or it will move while the cut is being made and destroy your work.
Setting the machine for side to side and end to end cuts for the mortise is not easy. It takes a lot of test cuts. The depth is simple to set. Once set correctly, IF your stock does not move during the cut, the results are excellent. The jig is made for cutting the mortise at the end of stock. Cutting a mortise down the stock, such as the middle of a leg, is much harder because it does not have a way to hold the stock at the same location every time (the stop block can't go more than about 2 inches from the top or bottom of the stock). This leaves the user with an eyeball job trying to line up the stock with the machine. If any of the mortises are off it may show because the stock will not go together square.
The cutting is slow, especially in hardwood. My battery powered drills will NOT cut the mortise. I use a corded drill for this work, but even with a one-half inch DeWalt drill the work is fairly slow.
It is also important, very important, that the stock be absolutely square and straight before it is inserted into the jig. The clamps do not pull the wood into square (nor should it be expected to do so).
I am impressed with the strength of the loose mortise. It also allows you to put your project together in units.
The machine comes with a three-eights drill. Jessum also sells one quarter and one half inch drill and bearing sets for the unit. The Zip Slot has a vacuum attachment. That is a 2 1/2 opening. My old Sears vacuum easily slips into the jig, but the suction holes to the stock are small causing the vacuum to work a lot harder than it should. The vacuum heated up during a long session of mortise cutting so I had to shut it off while changing stock. The time between stock changes is long.
Jessum advertises that the jig can be used for doweling. It does work but the drill (3/8 anyway) that came with the Zip Slot is a little too big for the dowels. I changed to a drill one step down ( 1/64) and it worked well. The "slop" in the bearing was so small with my regular drill it did not matter.
Compared to other kinds of joining systems, such as the Kreg Pocket Hole, this system is slow in the extreme. I will assume these joints are stronger but I have not ran a test. The Kreg system works well if you clamp down the work before inserting the pocket screw and the results seem strong enough for most applications. The key difference, besides strength, is the mortise is a hidden joint allowing its use in finer furniture projects or other uses were an exposed joint is not desirable.