• Please review our updated Terms and Rules here

Thumb Nuts for the PET

Hugo Holden

Veteran Member
Joined
Dec 23, 2015
Messages
4,647
Location
Australia
I liked the way in the SOL-20 computer that they had two large thumb nuts to remove the top cover.

In the PET there are two screws at the front to release the top. But it means having to remove them with a screwdriver to get into the unit. It would be better if they were thumb nuts.

I looked around to find something suitable. They would have to be a fairly long thumb nut because they are recessed somewhat.

Could have machined my own from scratch, but that wouldn't help anyone else. So I started to look around at what readily available part could be used or perhaps "re-tasked".

The screw thread is 10-32 UNF, or 3/16 inch diameter 32 TPI. Interestingly this is very close to the UK type of screw known as 2BA.

RS components sell some nickel plated brass 2BA terminals:


I have attached some photos. All that is required is to cut down the long side of the threaded rod, so it projects about 1/4 inch. Then screw the thumb nut onto that with some epoxy resin (JB weld or similar). With these terminals the central part has been pressed on to the rod.See photos.

Then it makes a tall thumb nut for the PET.
 

Attachments

  • Thumbnuts.jpg
    Thumbnuts.jpg
    207.6 KB · Views: 10
  • thumbnuts2.jpg
    thumbnuts2.jpg
    323.3 KB · Views: 10
Hugo, I realize that you're in the UK, so getting 10-32 UNF hardware is a problem. Is there enough slop in the fitting to work in an M5 thumbscrew instead?
 
Whatever--neither of you lives in non-metric land here. How else would we have inherited PCs with a mad mixture of 6-32, 8-32 and M3 hardware? You guys still have to live with ICs and connectors on 0.10 inch spacing!
:) I confess that I'll often get a bit of hardware missing screws. I'll first try 10-32, then M5 if the UNF screw seems to be a bit loose.
Three barleycorns, dry and round, you know! Party like it's 1300.
 
The original thread appears to be 10-32 UNF, which is 0.1875" or 4.7625mm and 32 turns per inch.

Unfortunately the 5mm metric thread is a little too large and won't screw into the hole.

It just turns out that the British 2BA thread is 0.1850" or 4.699mm diameter and 31.4 turns per inch and it screws in very well to a 10-32 UNF threaded hole even over more than a 1/2" length. This is the thread on the RS Binding posts.

There are thumb nuts out there, but they generally don't have a particularly tall profile and due to the recessed nature of the arrangement in the PET would need a spacer added to work.

RS Components have outlets worldwide, in the USA the company is called Allied. The binding posts I cited which are easily converted into the Thumb Nuts are available inside the USA:


(One interesting thing, certain hardware can be difficult to acquire inside the USA, Nickel plated Brass for example, but it is common in the UK, Europe & Japan. Also other types of threads like BA, BSW, metric etc are uncommon in the USA where UNC and UNF abound, but luckily in this case, the part I selected to make the Thumb Nuts, is available "everywhere")
 
Back
Top