How to make miniature square wrenches
Posted: Wed Jun 10, 2020 7:29 am
I recently bought a phase contrast condenser for my Orthoplan. There were no centering wrenches with it so I had to think how to resolve this problem in my workshop. As my solution might have wider interest, I present my results here.
The starting point is to find metal tube of appropriate diameter. The ideal inner diameter should be slightly smaller than the diameter of the centering screw head. In this case the diameter of the condenser phase plate centering screw is 1.5 mm. I found stainless steel tube from my storage which was good enough. It was originally the inlet tube of an old gas chromatograph which I dismantled years ago. If you don’t have a gas chromatograph or you don’t want to dismantle yours, you might find brass tube in a hobby craft shop. It should also work though is more soft.
Then you need a nail with square profile near the wanted diameter. Using a file, tune approximately 5 – 10mm length of the nail top to match the diameter of the centering screw head. Then cut the tube to get a piece of appropriate length and using a hammer tap the top of the nail into the tube. Then tap the tube with a hammer evenly from each side (the head with the nail inside) to mold the tube profile. Then take the nail off. Now the profile of the tube head should be square, more or less.
Finally, you attach thumbwheels to the opposite head of your wrench tube. I have plenty of thumbwheels of various shapes and sizes dismantled from old lab instruments and machines in my storage. I drilled a small hole through a thumbwheel and the tube inside and used a small nail as a rivet to fix the thumbwheel permanently to the wrench. The rivet is fixed by tapping using a hammer.
As you can see, these simple centering wrenches fit perfectly and there is no need for the complex and expensive construction of the original Leitz centering devices with cardan joints presented here http://www.microscopy-uk.org.uk/mag/img ... es7rev.pdf
The starting point is to find metal tube of appropriate diameter. The ideal inner diameter should be slightly smaller than the diameter of the centering screw head. In this case the diameter of the condenser phase plate centering screw is 1.5 mm. I found stainless steel tube from my storage which was good enough. It was originally the inlet tube of an old gas chromatograph which I dismantled years ago. If you don’t have a gas chromatograph or you don’t want to dismantle yours, you might find brass tube in a hobby craft shop. It should also work though is more soft.
Then you need a nail with square profile near the wanted diameter. Using a file, tune approximately 5 – 10mm length of the nail top to match the diameter of the centering screw head. Then cut the tube to get a piece of appropriate length and using a hammer tap the top of the nail into the tube. Then tap the tube with a hammer evenly from each side (the head with the nail inside) to mold the tube profile. Then take the nail off. Now the profile of the tube head should be square, more or less.
Finally, you attach thumbwheels to the opposite head of your wrench tube. I have plenty of thumbwheels of various shapes and sizes dismantled from old lab instruments and machines in my storage. I drilled a small hole through a thumbwheel and the tube inside and used a small nail as a rivet to fix the thumbwheel permanently to the wrench. The rivet is fixed by tapping using a hammer.
As you can see, these simple centering wrenches fit perfectly and there is no need for the complex and expensive construction of the original Leitz centering devices with cardan joints presented here http://www.microscopy-uk.org.uk/mag/img ... es7rev.pdf