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8" Mirror Grinding
8" F6 Project

Throughout this site click on any image for a larger picture.

Locating a tube became the 1st task. I wanted to find something local an I did not want to break the bank in purchasing one over the Internet. A 9" tube is what I wanted but I had to settle on a 10". I eventually located a nice solid 10" sono tube from a local concrete supply company here in Akron Ohio. I believe this tube was made for astronomy. Notice in the image to the right (Star Paper).

What I purchased was a 12 foot long (shortest they had) 10" diameter tube for about $18.00. First challenge after acquiring the tube was to remove the wax coating on the inside of it. I found nothing on the Internet on how to remove wax so I came up with my own ideas.

I ended up using two methods sanding and fire. I was not about to sand a 4 foot tube by hand so I created the sand-o-matic. The picture on the right is what I came up with. It is a 1/2 aluminum bar salvaged from a old lawn chair with a paddle board bolted to it. I used some scrap pieces of paneling thumb tacked to a 1/2" piece of plywood to create the paddle. I used cutout pieces from a milk jug as support backing for strips of sandpaper (80 grit an 120 grit was used) that was sandwiched between the panel piece an plywood.

This assembly was then inserted into my hand drill. I had to help balance the paddle board assembly when using it, as it was not balanced an the spin action from the drill wanted to make the device flop around inside the tube. But surprisingly this worked quite well. The sanding action of the 80 grit did remove the wax but did it in a scratch like fashion. A finer grit may of been better than the 80 grit. Instead this is where fire comes into play. After a session or two (session=15 minutes) I would use my leaf blower to clean out the wax dust then wet the inside of the tube with a rubbing alcohol and water solution then light it. The alcohol and water would ignite an melt the remaining wax into a solid surface again, but would not get hot enough as to burn the tube :-) (This was done outside just incase).

The image to the right shows how the sanding would leave the kinda rough wax like surface. The rubbing alcohol treatment smoothed this out, then the sanding process would continue. It took about a hour or so of this back an forth process to completely remove all the wax form the tube.

Below is pictures of before an after the de-waxing. Before I started the sanding process on the tube I covered/protected the edges with a epoxy glue. This was also done on any holes drilled in the tube (focuser, an bolt holes) for added support.


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October 17, 2009