Custom nut (Round slotted knurled thumb nut

[Philip LeeParticipant @philiplee66080]

sorry i didn't know I can get a 3.2mm drill bit and 3.2mm is the hole for that tap set.

https://www.toolstation.com/cobalt-drill-bit/p73476?store=DH&utm_source=googleshopping&utm_medium=feed&utm_campaign=googleshoppingfeed&mkwid=_dc&pcrid=&pkw=&pmt=&gclid=CjwKCAjw1MajBhAcEiwAagW9MRAPEz2Zgd-gaA39qUFPohcJLn-5f0vhwdHezpMRpi5jPCWm883RERoCfjMQAvD_BwE&gclsrc=aw.ds

Your idea is interesting and could work.

I am searching for a thicker knurled nut

[Philip LeeParticipant @philiplee66080]

come to think of it. Bill's method would work.

How do you dome the top of the nut to make it round?? Can you please elaborate?

[Howard LewisParticipant @howardlewis46836]

The tapping size for 5/32 BSW is 3.3 mm

At 3.2mm, unless your drill cuts oversize, you risk a broken tap

Looking back, since the fan was made in Birmingham, (Assumed UK rather than USA ) the thread is almost cetrainly 5/32 BSW

Make a properly dimensioned drawing of what you need, and someone might be willing to make one for you

See your PM

Howard

Edited By Howard Lewis on 27/05/2023 15:09:10

[Michael GilliganParticipant @michaelgilligan61133]

In case everyone has forgotten … 5/32” Whitworth was the size for Meccano screws

so one of those would make an ideal reference for checking the thread size.

MichaelG.

[Bill PhinnParticipant @billphinn90025]

Posted by Howard Lewis on 27/05/2023 15:08:29:

The tapping size for 5/32 BSW is 3.3 mm

There's no unanimity on that, Howard; quite the reverse, in fact:

3.2mm here, and here: 3.2mm and here: 3.2mm…even 3.1mm.

Philip, in the image, a thumb nut is set up for doming. The technique is very simple. Hold the drill in a vice or Workmate: spin the chuck and hold a cutting tool (e.g. a file) or an abrasive material at the right angle to create a slight dome.

[JohnFParticipant @johnf59703]

Philip — see your messages — Flashing box on the menu bar LHS

John

[Nicholas FarrParticipant @nicholasfarr14254]

Hi, the tapping drill size for 5/32" does range from 3.1 to about 3.3mm depending on the % of engagement required. If those stainless steel thumb nuts are used, it would probably be prudent for someone who has done little or no tapping before, to drill a 3.3 hole. 3.3mm will give a 60% engagement and should be strong enough, and this is the size that Tubal Cain suggests in his tapping table in the Model Engineers Handbook, although he does say in his material list that stainless steel should have 50% engagement, but if it is free cutting it can be 60% engagement.

Regards Nick.

Edited By Nicholas Farr on 28/05/2023 07:45:36

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