A Truss Mirror Grinding Stand

Years ago I built a mirror grinding stand from 2x4s and plywood designed to be so solid that it could be rigid when bolted together--no glue was necessary. It was very, very heavy, which was great for stability but a bother to keep around the basement when not in use.

The club has been talking about a mirror-making workshop, and although it doesn't seem like something that's going to take place any time soon I was motivated to build something better for my mirror work. After looking around the Internet for designs I settled on something like the Stellafane design. It's a simple sort of truss barrel.

What I didn't like about the Stellafane design was 24" diameter of the top--it's too big for my purposes--and the four-corner truss. I decided to try a three-corner truss instead. The four-corner truss is a standard for big Dobs and is used by Starmaster, Teeter's, Discovery, and Obsession. The thee-corner truss has proven itself on Orion and Meade Dobs, so perhaps it would work well for ATM work. It's a little lighter and less work to assemble, too.

Because I was using a three-corner truss it seemed logical to make the top and base hexagonal instead of the circles used by Stellafane. My hexagons are inscribed in a 20" diameter circle, which will be of adequate size to handle any mirror I can foresee working on up to 12" diameter.

Here's what it looks like after first assembly:

The stand is 37" from floor to top, just right for me.

What you can't see is that there are three rubber feet under the base to help it sit flat on the floor without rocking. At this point it's held together by wood screws. It seems rigid enough, but I won't know how really solid it is until it's in use. There may very well be some glue in its future.

Still to be done is the addition of adjustable cleats for standard mirror sizes: 6", 8", 10", and 12" should do it. The entire assembly will get sealed with polyurethane, with the top getting a nice sanding and a triple coat of poly to resist the water it's going to see.

A Mirror Grinding Stand

Among my many unfinished projects is a replacement mirror grinding stand for the one I'm using now. The current stand is very heavy despite being compact. The one nice thing about it is that it can be disassembled into a top, base, and legs. I'm making this new one to see if it might serve as a template for a mirror making workshop that the local club may hold sometime in the near future.

The new one should be much lighter. It will be built much like the Stellafane stand, but instead of a four sided truss design it will use a three sided pattern much like some truss-tube Dobs employ. I prefer the triangular design because it will save a little weight, will probably be just as solid, and makes it easier for the stand to sit on a flat floor without rocking. Also the fewer struts allow easier addition of my favorite ballast, 40# bags of water softener salt. The target height of the stand is 37" and it will double as a platform for mirror testing.

There are only 14 main pieces: Hexagonal top and base, six struts and six cleats.

Unassembled top and bottom of stand

This view shows the underside of the top and top of the base (if that makes any sense). The six cleats will be inset from the corners of the top and base so that the 2x1" struts sit flush with their sides. The top piece will be rotated 60° relative to the base so that the cleats alternate when seen in a top view.

The ends will be 3/4" plywood, which I hope will be stiff enough for the task. If not, I'll just add another sheet to the top. The hexagon is 20" across (vertex to vertex). and should be large enough to allow working on a mirror up to 14" across. I don't plan on ever working on one over 12", and probably won't go past 10" anyway.

The above needs some sanding before assembly; for that I'm going to wait for warmer weather so that I can use the garage and keep the sawdust out of my basement. In the meantime I'll begin working on my Canon DSLR portable power supply.