ATM Teflon PFA for Dobsonian bearings

[mdholm@telerama.com]

The other day I mentioned the current S&T article on Dobsonian bearing 
materials.  Someone pointed out that Teflon PFA is relatively hard to find and 
rather expensive.

The S&T article, which is by Martin Lewis, addresses both problems.  I will 
quote a snippet.

"PFA is a specialty plastic, and it may be difficult to find a vendor prepared 
to sell the small amount typically used in telescope construction.   One source 
that will do so id Boedeker Plastics (800-444-3485, www.boedeker.com).  This 
company can supply PFFA sheet in 1/8, 3/16 and 1/4 inch thicknesses.  Ask for 
grade 350 sheet, and expect to pay approximately $10 to $15 for 6 square 
inches."

Well that is a pretty high price by the square inch, but isn't really a lot to 
get a superior bearing material for a telescope.

The S&T article is very thorough.  Very much worth reading.  It is in the 
October 2003 issue.

Martin discusses various bearing materials, including a couple of add on 
lubricants.  He actually did careful friction measurements, so it isn't just a 
bunch of speculation, or a rehash of old ideas.

Mark Holm
mdholm@telerama.com