Ross Sackett's amateur telescope making
Mirror grinding stand
Grinding mirrors requires a steady support. This grinding stand is a modified
version of one built by veteran ATM Dick Parker. Dick's design is
inspirational; I've changed it a little to simplify the joinery and to better fit the
way I work. Most of my design is built of 3/4" plywood and 3/4 X 2" pine. The
height of my bench places the work surface 36" above the floor, but you may
want a different height. Pile some books on the edge of a table and mimic
the action of grinding on them to see what height works best for you.
The top is 20" diameter 3/4" plywood.
The top support is a 17 X 17" square of 3/4" plywood, with the corners
clipped off to make an octagon.
The truss consists of eight 3/4 X 2" pine slats approximately 34-1/2" long.
Vary the length to change the height of the work surface above the floor.
The base is a 17 X 17" square of 3/4" plywood.
Three of the feet are 3-1/2 X 3-1/2 X 1-1/2 pine; the fourth adjustable foot is
4X4X3/4" plywood with a 1/4-20 stud levelling knob run into a tee-nut.
To build the stand start by jigging the top support and base on your
workbench. They should be square to one another, separated by a distance
equal to the desired height minus 3-3/4". Cut your eight truss slats several
inches oversize. Using glue and screws attach the pair of poles on each
face to the center of the sides of the top support and the corners of the
square base making a triangulated eight-pole truss (just like a telescope). If
your slats had square ends then you will need to cut off the overhanging
"ears" using a handsaw. (This is much easier than trying to miter them to the
exact length.) Screw the top to the top support so that you can remove it if
you need to replace it. Glue and screw the four feet to the base
overhanging so that the truss slats register against the feet for added
Give the whole thing a couple of coats of polyurethane or spar varnish to
waterproof it. Two 16X16" concrete pavers provide plenty of ballast. To
move the stand you could remove the pavers to lighten it, but is easier to just
pick the whole thing up using a trash can cart.
OR, you could attach some cheap lawnmower wheels and make it
self-propelled (well, sort of...). I did this mod so that I could move it around
inside the house during the chilly winter season when I can't use my shop.
Vertically, the stand still rests on the four pads but the wheels contact as
soon as it is tilted more than 20 degrees or so. It is nicely balanced so that it
feels pretty light. It stores in the corner of my office out of the way until I want
to do some polishing.
My telescopes and ATM Projects