Astronomical Society of South Australia Whyalla Group - - Mirror O Matic Page 6

Whyalla Group Mirror O Matic Page

I usually have lots of trouble faceting the lap. Using a Machine requires evenly sized facets and I can't do that by hand. After visiting John D.Uptons site ATM Workshop and seeing his method of using a vee shaped shim heated to cut a path through the pitch, I decided to try this. Not being steady of hand though, I needed something to support the lap while it was being cut. I came up with something similiar to a Guillotine. Using a piece of chipboard (the blade) I will attach the lap to this and slowly lower it down until it melts its way through the pitch. The shim has a runoff trough shaped into it to steer the melted pitch away from the lap. This will drop into a can below. I have also made the angle of the arms adjustable to help position the cutter. By altering the position of where the soldering iron is clamped, I should be able to have nice evenly spaced facets. After doing the channels in one direction, turn the lap ninety degrees, cut those channels and Voila! (hopefully) a nicely faceted lap. As can be seen from the last 4 photos, the cutter worked quite well. I need to get some copper shim or a more powerful soldering iron though. It took an hour and a half to do this. Still, the results are worthwhile I think.

This is an overall view of the cutter from the left hand side. This is a trial fit of all the bits and pieces.

This view shows the cutter positioned ready for work. All that's needed is the can for the melted pitch and the lap itself.

This is an overall view of the cutter from the right hand side. This is a trial fit of all the bits and pieces. As can be seen, the angle of the arms is adjustable to allow the depth of the cut to be varied to suit.

Another view from the near front.in particular, note the high tech soldering iron positioning device!

This shows the pivot point to good advantage. The 1 inch block fits into the 1 inch hole drilled in the back of the lap. When all the channels in one direction are cut, I spin the lap 90 degrees and start again.

A closeup view from the right side of the shim attached to the soldering Iron.

An overhead view of the shim showing the shape that will channelled into the lap.

This is the first channel being made. Near the bottom of the cut you can see that the width of the channel changes. I realised after starting the channel that it was slightly too deep and needed to be made slightly shallower.

After the first row of channels were cut, I rotated the lap 90 degrees and prepared to start again. The edge of the lap has not been bevelled yet.

This is the completed lap after finishing the channelling. At this stage the edge bevelling hasn't been done.

Tah dah!!! The completed lap, very nice looking I reckon.

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