[Alex, Daniel]

I remade the bushing for the 1/4-100 screw, this time copying the F25USA1 from Thorlabs which we think is the currently used part. I used Nitronic 60, which is used in vacuum with (uncoated) stainless steel screws to prevent gauling/siezing up. I use the 1000.cam program to make the part in the Lathe with a spindle speed of 830 rpm. This went very well. I parted the piece with 0.016" left initially at 120 rpm and then 170 rpm as the diameter narrowed. I removed the nub and faced the back of the part at 1200 rpm.

I then used the 1002.nc program on the CNC mill to spot drill/countersink, drill, and tap the part. Unfortunately, something went wrong with the tapping (I used the tap from Newport) during the retraction, and the tap removed the threads on the top half of part. There might have been a chip that caused the part to be yanked up a bit. I was able to re-tap the piece so that the threads that exist are good, but the screw goes in around half way before engaging the threads. The issue in the mill ruined the tap.

I am not sure exactly went wrong, but I think I can peck tap next time with hopefully better results. As this was mostly a project while the lab was shut down due to flooding, I mostly want to move on and have Xometry, Hubs, or Thorlabs make the part. Newport was uninterested in making it, and Siskiyou doesn't have the right material bushing off the shelf either.

3 bushings will cost around $450 and take 3 weeks for Xometry and Hubs and 14 weeks for Thorlabs. I am enclined to have Hubs make the part as I have had good sucess with custom threads in the past (and I somewhat trust them more to actually make the part out of Nitronic 60).