WD Motorcycle forum

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Comment

Dec 8, 2021 - 5:25PM

Re: Need thread size and pitch - 1941 G3L

Good show, but what was the size???

So 1-13/16" just measured one, never use decimal inches on brit bikes, confuses the hell out of everyone.

Lex

Alun Mills

Dec 9, 2021 - 12:56AM

Re: Need thread size and pitch - 1941 G3L

Lex Schmidt

Good show, but what was the size???

So 1-13/16" just measured one, never use decimal inches on brit bikes, confuses the hell out of everyone.

Lex

Lex

No idea. As I said, he just used the steel slider extension as a Tap to re-cut the thread in the slider.

90% of the thread in the slider was good. Just needed the part where he welded in a missing bit to be threaded.

Al

Ron Pier

Dec 9, 2021 - 7:20AM

Re: Need thread size and pitch - 1941 G3L

1 13/16" is 1.8125". As you say Lex your old imperial measurement is probably more accurate.

While we're discussing measuring....Metric measurements for engineers are in mm! cm are for dressmakers.

Ron

email (option): ronpier@talk21.com

Ian Wright

Dec 9, 2021 - 10:44AM

Re: Need thread size and pitch - 1941 G3L

Based on the 'inch' system they are all Imperial measurements whether expressed as a fractional or decimal dimension (the latter originates from the word 'deccem' which is Roman for 10)...How something is dimensioned has some thinking behind it...'Standard' manufacturing practice would be that if a dimension is expressed as a fraction..eg. 1 1/4"..then the 'standard' tolerance applied would be + or - .015".(1/64").

When the same dimension is expressed as a decimal (1.250") the standard tolerance applied would be + or -.005"...So the finished part would be within the range of 1.245"- 1.255"...

These are general standard tolerances for manufacturing...If the same dimension needed to be more accurately produced for a particular application a 'closer' tolerance would be specified...eg. 1.250" +.002" -.000"...So the finished part would be within the range 1.250"- 1.252"

These tolerances have now become 'dated' with the introduction of CNC machines but in the home workshop or a non CNC environment they are still relevant...In those cases, if more than one component is being produced, a tolerance is always employed as it is impossible to manufacture consistently to exact dimensions manually...To achieve a very close tolerances a component may well have been initially machined on a lathe, for example, and then 'finish ground' to size on a grinding machine, a more accurate process...

The importance of considering tolerances when remaking parts and trying to correctly identify them is illustrated by the following...A spacer that fits over a 3/4" diameter wheel spindle may well have a .010" clearance and at that would function perfectly well...The same clearance between a 3/4" gearbox shaft and the bush that fits over it would probably be three or four times too large for correct function.....Ian

email (option): ian@wright52.plus.com

Lex Schmidt

Dec 10, 2021 - 5:20PM

Re: Need thread size and pitch - 1941 G3L

Thanks Ian, for the explanation, but where did you and others went wrong here? I saw it immediatly, as a fork slider of that small size would be only fit for a moped or a fairground attraction bike.

Ron, what dresses are you making now?? sometimes you worry me!

Lex

Ian Wright

Dec 10, 2021 - 7:29PM

Re: Need thread size and pitch - 1941 G3L

I don't know anything about the sizes of anything on a WD Matchless and I didn't even think about the sizes quoted...
My post was only to help (I hope) clear up the apparent confusion about how to express the measurements and to point out the thinking behind and purpose of tolerances ....Ian

email (option): ian@wright52.plus.com

Ron Pier

Dec 10, 2021 - 7:46PM

Re: Need thread size and pitch - 1941 G3L

What small size are you referring to Lex? The original poster quoted 1.8" which is nearly the same as the 1 13/16" you stated. Ron

email (option): ronpier@talk21.com

Alun Mills

Dec 11, 2021 - 1:43AM

Re: Need thread size and pitch - 1941 G3L

Just confirming please.

The bolts that screw into the sliders to secure the mudguard stays, part number 41-G3L-M38 (010795) are 5/16 bsf at 22tpi?

Cheers

Al

Ron Pier

Dec 11, 2021 - 7:42AM

Re: Need thread size and pitch - 1941 G3L

Mine are 5/16 Whitworth 18tpi. (Course thread for ally). Ron

email (option): ronpier@talk21.com

Lex Schmidt

Dec 11, 2021 - 6:27PM

Re: Need thread size and pitch - 1941 G3L

I just checked that, and they are in fact BSF! the bottom and top ones, 4 per slider.

Will get back on the other thing later tonight.

Cheers,

Lex

Ron Pier

Dec 11, 2021 - 7:39PM

Re: Need thread size and pitch - 1941 G3L

I haven't checked all mine. The one I took out is Whitworth so maybe a PO has modified the threads? Ron

email (option): ronpier@talk21.com

Lex Schmidt

Dec 11, 2021 - 7:50PM

Re: Need thread size and pitch - 1941 G3L

Checked 2 sliders, one NOS, and both have BSF.

So more like a POS changed yours!

Lex

Dec 11, 2021 - 7:56PM

Re: Need thread size and pitch - 1941 G3L

I think you will find these bolts are all available from Steve Surbey at AMC Classic Spares. JT

Jan

Dec 11, 2021 - 8:43PM

Re: Need thread size and pitch - 1941 G3L

Ron Pier

The metric system has been in use since 1792, and is trusted by 15/16th of the world population... :smile:

Jan

email (option): wd.register@gmail.com

Ian Wright

Dec 11, 2021 - 9:15PM

Re: Need thread size and pitch - 1941 G3L

:laughing: :laughing:I see what you did there Jan ...The Metric system is efficient but dull...Whereas the wonderful Imperial measuring system (developed from the Winchester System of 1588), whether weights, volumes or measurements is so much more entertaining...Ian

email (option): ian@wright52.plus.com

Alun Mills

Dec 12, 2021 - 7:38AM

Re: Need thread size and pitch - 1941 G3L

Lex

Thanks, I just need to order a 5/16 22tpi tap now before my machinist does something silly and use an M8 tap.

Al

Alun Mills

Dec 16, 2021 - 3:38AM

Re: Need thread size and pitch - 1941 G3L

This worked a treat at re-cutting the thread section that was welded over.