I could have used one of these earlier this week. My eyes are not what they used to be and I had to layout and center punch a bunch of holes on the top and bottom plates of the Stirling engine I am building.
An optical punch helps you center punch more accurately. First you line up your scribe marks in the middle of the acrylic magnifying rod. Then, without moving the base, you replace the optical rod with the steel punch and give it a tap to mark your hole.
This homemade optical center punch looks like it can be made pretty easily and inexpensively. Don’t be intimidated by having to shape and polish the lens shape on the end of the optical rod. I suspect that a novice machinist might have a harder time getting the acrylic and steel rods to fit perfectly in the hole in the base, which is the key to making this tool accurate.
If you are in the U.S. you can get a 1/2-inch x 12-inch acrylic rod from SmallParts.com for $2.51 and a suitable 2-inch diameter chunk of 6061 aluminum is $3.54. By the way, Smallparts.com is great when you only need a short length of material and do not want to invest a lot of money on the three or six foot lengths most other metal suppliers sell.
If you would rather buy one already made, LittleMachineshop.com sells one for $74.95 (USD).
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