Polishing Lap Channel Cutter
I found it very hard to cut channels into a polishing lap with a knife. After a search on the Internet I found this channel cutter method http://www.atm-workshop.com/pitch-lap.html and decided to make one. The cutter was made from 0.5 mm thick copper sheet and a 65 mm long piece of 9 mm square brass. It is really worth the effort to make one. After you have used it you would never want to struggle with a knife again.
Here is a few photos of the channel cutter:
 |
 |
 |
 |
| The sheet is bolted to the square piece of brass. | The portion that fits into the soldering iron was turned round in the lathe. | The angle of the cutter is about 60 degrees. | The cutter fits in the place of the soldering point of the soldering iron. |
A flat cutter was also made. It is handy to cut away high points and to fill in low ones. Here is a few photos of it:
 |
 |
 |
Cutting technique
It is important that one moves the cutter at the right speed. If one moves it to fast then the pitch does not have enough time to melt and pieces might break out. If one moves to slow the pitch melts too much. The correct speed is when one feels a certain amount of resistance against the motion of the cutter and it cuts evenly.