Building the base for the sander.
Base Design Requirements
Because I want to be able to do quick belt changes, the belt carriage has to be mounted on one side so I want the base to be rock solid. The motor mount needs to be adjustable to allow the belt to be loosened if necessary without too much trouble and the base should protect the motor from dust. The table/rest should provide a solid platform for sanding both vertically and horizontally but needs to move out of the way for belt changes. It should also provide a port for dust collection. Here is the Sketchup drawing of the base and motor mount with the table/rest pivoted out of the way.
The carriage is bolted to the vertical board that sticks above case and will have about 1/2” clearance underneath. I probably could have made the base out of 1/2” PW but I didn’t want there to be any flex in the belt carriage mounting.
The motor mount is attached on one side with 2 hinges to allow it to pivot for belt tension adjustments and I am using 7.5” hose clamps to hold the motor to the mount. I actually made the bottom out of an old table leaf, instead of plywood, that a neighbor gave me that turned out to be particle board with hardwood veneers but it was free.
I cut rabbets and groves in the bottom and sides for the back, sides and carriage mounting to provide more rigidity and this made everything go together nice and square as well. I first just clamped everything together just to test that everything fit together well. It turns out that the motor mount itself actually helps make the carriage mount very rigid even without the clamps I had to make the curved motor mounts about 1/2” shorter to give me more room to pivot the motor. I also changed the design so the the top on the base will be 1/2” plywood instead of the 3/4” I used everywhere else to give me more room. It’ll be tight but it should work. Just in case, I will make it easy to remove the top to give me better access.
I decided that I had better not glue everything together in case I need to make adjustments later so everything is simply screwed together. With the rabbets and groves, it is very solid. Here it is with everything but the top and doors screwed on.
Unfortunately, I didn’t think about being able to remove the belt without taking the motor off. If this proves to be a problem, I may have to cut an access hole in the back. I probably needed another 1/2” to be able to slide the belt over the end of the motor shaft.
The carriage is attached with 6 crown bolts and t-nuts. It is very solid and doesn’t flex at all. I could probably sit on the carriage without it flexing. I didn’t think through in advance where to run the power cord out of the box. The switches (there are 2 toggle switches because it is a 3 speed motor) will come out of the right side but this would be the top when sanding vertically so would not be good to have the cord sticking out of the top. I may have to put a hole in one of the doors to accommodate the power cord—still TBD.
Next, I will make the pivoting table/rest, paint it, get the wiring hooked up and complete assembly.
-- Nathan, TX -- Hire the lazy man. He may not do as much work but that's because he will find a better way.