I am making a mirror cell to support a telescope mirror. The cell is a triangular frame made with 1 inch x 1.5 inch rectangular aluminium tube with 1/8 inch wall thickness. In mm this is 25.4 mm x 38.1 mm, wall thickness 3.175 mm.

Inside the tubes there will be 3 spherical bearings, 10 mm ID, 20 mm OD and width of 15 mm

I am following a design from an American astronomy website. In this the spherical bearings are place in housings made of Nylon which fit in to the aluminium tube.

I worked out that I need to cut Nylon bar in 3 pieces to around 34.93 mm x 22.23 mm and length of maybe 50 mm each. So I probably need a length of nylon bar of around 200 mm to allow for mistakes cutting the bar.

Direct Plastics sell Nylon 6 sheet 40 mm thick x 250 mm x 250 mm for £57.64. I wouldn't mind getting this quantity which is more than I need in case it might come in handy in future. But I don't want to pay this much.

Does anybody know where I can get Nylon cheaper or is there a cheaper material I can use? Nylon seems to working fine for the telescope cell in the U.S.A. so a similar material would be good.

The bearings will have some quite heavy duty springs keeping them under pressure, and supporting the telescope mirror, they are for collimationg the telescope mirror, which is quite heavy.

I don't know how much it weighs but it is 508 mm in circumference and 40 mm thick glass so it is quite heavy. I can carry it but it is rather hard work!

David

Of course I meant the diameter of the mirror is 508 mm (20 inches)!

Thanks for the information, Ebay is quite a bit cheaper. I will have a look at delrin. I am planning on adding a fan to the cell.

How easy is it to machine what I need out of round bar? I have a mini milling machine. I assumed milling a sheet would be a lot easier but maybe I am wrong? I also have an Aldi portable band saw. I only use the milling machine occasionally, but it comes in very useful sometimes.

Regards

David