TrigpointingUK

tommoir83 wrote: Wed Aug 05, 2026 7:10 pm Oh fantastic. These look really promising, thank you so much. I’ll send them over to my friend who has the 3d Printer and see how he thinks it will come out and then hopefully get one printed off. I’ll post a follow up here to show progress!

Do not print these yet!
I've had a set printed out, and there are several problems, mainly with the threads, that need sorting out before they're fit for purpose.

OK, a test batch of the updated design has just come back from the printers, and the threads are now much better. Feel free to try printing the updated stl files, and please let me know how you get on!

There are two versions available... Those with a _resin.stl suffix are based on the original OS design, with a 7/16 BSW 55 thread. With an accurate printer (and a bit of PTFE spray!) these work just great. However the clearances are tight, and a 55 degree overhang is pushing what fdm printers can achieve. So I've also created _fdm.stl variants, which have a much coarser, 45 degree thread, with greater clearances. These are less accurate to the original brass, but should be much more forgiving to print.

Fantastic, these look amazing. My brother-in-law had a go at printing one of the resin versions off last night for me (for info he reckons it was about £2.50 in filament material cost). Looks like it screws together well, but the finish isn't as smooth as your prints. Did you have to sand them, or maybe the printer/filament quality was better, or the settings different. He quoted it was an 8 hour print time for fine print.

This is nice! What did you use to make the STLs?

I printed plug_resin.stl and inner_plug_resin.stl on my FDM @ 0.4mm nozzle in PLA. (I think a part like this is better-suited to FDM than resin).

Both printed fine upside down with supports enabled for the thread:

Supports peel off without problem:

The plug does fit but it's still pretty tight! I had to use some steel bars to encourage it into place:

Not sure these would last long outdoors though!

One thing I would ask - anyone who prints & install either Ian's or my flat discs as replacement caps PLEASE make a note of it on either the TUK main site, the facebook page if you use it or here. Then we can keep an eye on how long they last before getting swiped, how the plastic is holding up long term etc.

Thanks for all the photos, especially the ones mid-production! Not having a printer myself, I've never seen this side of the process.

I'm so glad to see that everyone's managing to print these successfully, and aren't having to resort to the files with the simplified thread! I seemed to get a smoother finish from PETG than from PLA, but even using a commercial service, there's significant inconsistency both within and between batches.

Yes, the ones I got printed professionally are also quite stiff at first. I've not needed to sand anything down (beyond removing any roughness around overhangs), but I've definitely needed steel bars for the first few attempts, until any roughness wears down and they start running smoothly. The github repo contains STLs for a tool I designed to help do exactly this!
The STLs are actually generated by python scripts, which I vibe coded with Claude. We started off with the blender model that was used to create the flythrough video on the wiki homepage, then gradually added more and more detail with the help of calipers and thread gauges, using the plug from North Ockendon. Running those python scripts generates a STEP file, which is as close to the original as possible, plus multiple STL files for the various thread/logo variations. Visualisation of the results was done with FreeCAD.

For those without 3D printers, I have created an Etsy Shop, where I'm selling the prints I've had made. Believe it or not, my prices are close to cost, but are sadly more reflective of the 8hr print time than the £2.50 material cost. I'm more than happy if someone in the community is able to undercut me!

For anyone new to 3D printing who is thinking of dabbling in it I can recommend the Bambu Labs P1S series. (Currently about £330 direct from Bambu for the basic printer - considerably more if you use online resellers). They are easy to use & the software is reasonably intuitive once you get your head around it. Plenty of online video guides about how to set them up too. However there are dozens of other brands & models to choose from so do some research & make your choice.

You may see references to AMS units on the Bambu site (around £200) - there are the multi head add ons for printing objects in more than one colour. You DO NOT need an AMS units for our files - being one colour the basic printer is all you need.

A roll of basic PLA filament is about £10-15. You dont need to buy Bambu branded filament - any good quality generic filament is ok. I tend to use eSun or Sunlu brands from Amazon.

I mainly use PLA filament - you can also use PETG, although the colour range is more restricted for PETG. Traditionalists will want to buy grey filament to print their caps - thats the nearest to gunmetal bronze you will find.

So basic set up costs for someone starting from nothing - as Im familiar with the Bambu brand I'll use those - prices Sept 2026:

Printer £330
1 roll of filament £15 (varies a lot over time so shop around)