Dicing with Delrin - A Repair Job.

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Pete W.:
Hi there, Seadog,

Thank you for your post.

It looks from your pictures as though you had more room to take hold of your work-pieces than I have. You'll see that in the pictures in my next post.

Pete W.:
Well, I've made a bit more progress. I turned a couple of thick washers (aka clamp-plates) from aluminium alloy bar. Then I cut another piece of the 3/8" aluminium alloy plate and milled the edges clean & square - all routine stuff so no photos of that. Then I bored a hole to take the lower part of the spigot. I had to get a bit creative because the hole is quite close to the edge of the plate and I needed to avoid the boring tool hitting the chuck jaws. I stuck some small pieces of 1/16" Perspex to the jaws with double-sided tape to provide some clearance behind the plate. I cleaned the spigot and the plate and applied some Loctite before clamping the plate and the spigot together with one of the washers and a 1/4" BSF cap-head screw. Despite my cleaning the parts with IPA and leaving them clamped-up overnight, the Loctite didn't cure! Still, I was given that bottle of Loctite because its shelf-life had expired and that was about 20 years ago! :zap: :zap: :zap:

I've included a photo showing the facing of the rear of one of the dominos to remove the surplus thickness of the material where the optic will eventually seat.

The remaining photos (below) show the profiling process in progress. The captions on the photos are fairly self-explanatory so I won't write much here. I've achieved a good enough profile by taking a cut, then stopping the cutter with the counter-shaft clutch and winding the cross-slide to move the job away from the cutter. Then I slacken the securing cap-head screw, turning the blank through a small angle, taking the next cut and so on, 'rinse & repeat'. I tried smoothing the profile of the first piece with a fine file but I think I prefer the micro-faceted appearance of the second one.

Once I've profiled all five blanks, I'll need to remount each one in turn on the profiling fixture and drill & tap two M2 holes in each one to take an M2 grub-screw.

Right, photos:

awemawson:
Excellent work Pete - coming along nicely ... Why do they have the letter 'A' impressed into them :scratch:

seadog:
Nicely finished Pete.

Joules:
Just out of interest, Delrin has a melting point of 175 ℃ it would be feasible to make an alloy mould use a slug of delrin in a tube and a bottle jack (close fitting piston). Heat the mould and tube to 175 ℃, digital thermometer to keep an eye on temperature, then squeeze the delrin slug into the mould. Bit like the guys making Delrin nuts for lead screws, might not be worth the effort for a one off, but maybe worth gaining the knowledge especially if you are likely to have repeat work or multiple components.
I just offer this thought as I am in the process of making a mould to shoot some delrin components for a client :thumbup: Not using a bottle jack I might add :lol:

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