Machining a Headlight Lens From Plexiglass
Posted: Mon Sep 18, 2017 1:40 pm
I jump from project to project all of the time and here is another (very small) one. Except, it took an hour to do the machining but weeks, months and years to do all of the needed preliminary work.
I have needed to make a number of locomotive headlight lenses for some of the locomotives here; a project which has been laying around for decades.
I chose to make them out of plexiglass and of course made the classic mistake of a beginner for if you use this material, one needs to buy cast plexiglass rod not the more common extruded plexiglass rod. If one tries to machine extruded rod, then there is a chance that the plexiglass will crack or "craze" with time. Of course, cast plexiglass rod is much more expensive and difficult to obtain.
Then, I had to make the ball turning tools for my lathe to machine the curvature on the lens. And since there are two lathes here I decided to make any and all of the ball turning tools fit both lathes. Ended up with two different sizes of ball turning tools (for both small and large radii) and a number of different adaptors - which is a project in itself but that is another story.
Then, I decided to make a number of grooved concentric circles (6) on the curved lens surface to make it look more like a fresnel lens. Just set your lathe's compound at 90 degrees to the lathe's crosslide, zero out both slides when the lathe grooving tool just grazes the innermost ring circle, feed the compound forward (0.010" in my case) to produce a groove, retract the compound then more the crosslide to the position of the next groove (0.060" in my case) then move the compound forward again until the grooving tool just grazes the next ring, set the compound micrometer dial to "0" again and repeat the above until all six grooves have been machined.
To finish polish the plexiglass material and remove any burrs, I used a dead smooth file, followed by some fine steel wool dipped in any oil, followed by a paper towel dipped in Brasso. The result, a crystal clear lens.
"Easy peasy "as Jack Bodenmann says but if you don't have any of the above, then you have a work program.
I have needed to make a number of locomotive headlight lenses for some of the locomotives here; a project which has been laying around for decades.
I chose to make them out of plexiglass and of course made the classic mistake of a beginner for if you use this material, one needs to buy cast plexiglass rod not the more common extruded plexiglass rod. If one tries to machine extruded rod, then there is a chance that the plexiglass will crack or "craze" with time. Of course, cast plexiglass rod is much more expensive and difficult to obtain.
Then, I had to make the ball turning tools for my lathe to machine the curvature on the lens. And since there are two lathes here I decided to make any and all of the ball turning tools fit both lathes. Ended up with two different sizes of ball turning tools (for both small and large radii) and a number of different adaptors - which is a project in itself but that is another story.
Then, I decided to make a number of grooved concentric circles (6) on the curved lens surface to make it look more like a fresnel lens. Just set your lathe's compound at 90 degrees to the lathe's crosslide, zero out both slides when the lathe grooving tool just grazes the innermost ring circle, feed the compound forward (0.010" in my case) to produce a groove, retract the compound then more the crosslide to the position of the next groove (0.060" in my case) then move the compound forward again until the grooving tool just grazes the next ring, set the compound micrometer dial to "0" again and repeat the above until all six grooves have been machined.
To finish polish the plexiglass material and remove any burrs, I used a dead smooth file, followed by some fine steel wool dipped in any oil, followed by a paper towel dipped in Brasso. The result, a crystal clear lens.
"Easy peasy "as Jack Bodenmann says but if you don't have any of the above, then you have a work program.