Classic cars forum & vehicle restoration.

Penguin45 · Joined: 28 Jul 2014 Posts: 381 Location: Padiham

Wolseley 4/44 gear knob by Penguin 45, on Flickr

That's a picture of the remains of a Wolseley 4/44 gear knob. As you can see, it's got a threaded hole in the centre casting. And that's where the fun starts.

The hole is 0.2555" or 6.49mm. As far as I can work out, the thread is 20 TPI.

5/16" UNC 18 will engage, but not advance.
1/4" UNC 20 is a drop fit - no engagement at all
5/16" W 18 is too big.*
M7 x 1 will fit and advance 3 1/2 turns before binding.

So, what's the thread? Any ideas appreciated.

Chris.

* My only Whitworth tap since a burglary...
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'67 Wolseley MkI 18/85, '70 Austin MkII 1800 The Landcrab Forum.

Penguin45 · Joined: 28 Jul 2014 Posts: 381 Location: Padiham

Further to... I found a 1/4" W 20 die, so spun up a bit of bar stock. It's a drop fit, so no go. Logically, it must be 5/16". 5/16" 20 turns out to be a British Standard Cycle thread. Gosh.

Could anyone confirm this thinking before I go spending on taps and dies?

Chris.
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'67 Wolseley MkI 18/85, '70 Austin MkII 1800 The Landcrab Forum.

Ray White · Joined: 02 Dec 2014 Posts: 6319 Location: Derby

It can't be cycle. 5/16" BSC is 26 TPI.

3/8" BSF is 20 TPI.

5/16" BSF is 22 TPI

If that helps?

ukdave2002 · Joined: 23 Nov 2007 Posts: 4105 Location: South Cheshire

Cycle threads can be either 20 or 26 tpi. There are cycle threads on pre war Morrises, the track rod being one.

Dave

Ray White · Joined: 02 Dec 2014 Posts: 6319 Location: Derby

Kenham · Joined: 12 Mar 2012 Posts: 209 Location: Kent

In cases of trying to find what a thread is ,it is best to dismiss the task of giving it a name. If the thread you are measuring is 5/16th 20tpi then that is what the thread is. Whit, BSF, UNF, BA, cycle thread, whatever , the thread you appear to want is still 5/16 20tpi. I have some very strange taps , all made for some specific purpose no doubt and you will never find them in a thread chart. If you have someone who can cut a thread on a lathe you can try it to make sure before you buy a tap perhaps.

Ray White · Joined: 02 Dec 2014 Posts: 6319 Location: Derby

The Wolseley gear knob looks rather fragile and very discoloured with age. Understandably, you refer to the "remains".

I wouldn't like to say how long it might last in service before breaking up so perhaps a good replacement would be your best hope. I believe it should be imitation ivory with a chrome bezel at the end.

Good replacements are probably rare.

Best of luck.

bjacko · Posted: Sat Nov 04, 2023 5:50 am Post subject: Wolseley Gear change knob

On the 4-50 and 6-90 the knob comes with the shaft to which it attaches. Are you sure it is not a tapered thread?
I imagine most of the BMC cars would have similar installations and use the same threads which at the time may have been unified.
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1938 Morris 8 Ser II Coupe Utility (Pickup)
1985 Rover SD1 VDP

ukdave2002 · Joined: 23 Nov 2007 Posts: 4105 Location: South Cheshire

I recently had to figure out what an obscure internal thread was. I sprayed a light lubricant into the thread and filled the thread with glue from a glue gun, before it set I stuck a screwdriver in, 5 mins later when the glue is set simply unscrew, it?s far easier to identify what the male thread is.

Dave

Penguin45 · Joined: 28 Jul 2014 Posts: 381 Location: Padiham

Penguin45 · Joined: 28 Jul 2014 Posts: 381 Location: Padiham

Penguin45 · Joined: 28 Jul 2014 Posts: 381 Location: Padiham

Returns...

Wolseley 4/44 gear knob by Penguin 45, on Flickr

Brilliant - all is revealed. 11 turns over 1/2", so 22tpi and tapered. Therefore, it must be a 5/16" 22 BSF tapered thread.

Tracy Tools have the taps. I can't recall ever having cut a tapered thread, so if there's any special techniques involved I'd be grateful for the information.

Dave, you're a genius.

Chris.
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'67 Wolseley MkI 18/85, '70 Austin MkII 1800 The Landcrab Forum.

petelang · Joined: 21 May 2009 Posts: 444 Location: Nottingham

Shame there isn't a "Like" button as I reckon that from Dave was well worthy of one. Stuck that in the memory bank for future reference.
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Daimler Fifteen 1934
Armstrong Siddeley 15 Long 1933
Daimler V8 250 1969

peter scott · Joined: 18 Dec 2007 Posts: 7119 Location: Edinburgh

Ray White · Joined: 02 Dec 2014 Posts: 6319 Location: Derby

William Morris bought the Hotchkiss plant in 1923 and renamed it Morris Engines. A legacy of this was the use of obsolete threads. M8 x 1 is one such thread and is what MG used for the gear knob on my TC.

Unlike the 5/16"BSF thread on your Wolseley gear knob it is not tapered.

Well done Dave. You have cleverly shown that necessity is the Mother of invention.