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MG TD TF 1500 - Fan blades screws

Hello,
The DPO fitted 4 different screws to fix the fan blades to the water pump pulley !

What are the original screws ?

Laurent.

LC Laurent31

The bolt thread is 5mm X 0.75mm, total length is 43 mm threaded length is 18 mm, 1/8" Whitworth Hex head.

John
J Scragg

The most common replacement screws that are used is a 6 X 1 mm - with a metric head of course. Cheers - Dave
DW DuBois

The original 5 x 0.75 mm bolts were to the previous Systeme Internationale (S.I.) system. I used four bolts 5 x 0.8 mm, which is 5mm coarse in the current ISO system.
R A WILSON

I think you're wrong. The SI system for a 5 mm diameter was a 0.9mm pitch.
The 0.75 mm pitch was affected to the 4 mm diameter.
LC Laurent31

I agree, the 5 x 0.75mm thread was to an old 'French Standard Thread' system - see attachment - which I thought was the same as the SI system. There is also another old 'French Metric Thread' system which does have 0.9mm pitch for 5mm diameter. However, my SI chart shows for 5mm dia, the fine pitch was 0.5mm, and the coarse pitch was 0.8mm - it does also show the 0.9mm pitch in a column headed JIS.
Sorry for any confusion.

R A WILSON

I have tried to attach the chart I have mentioned, but the system tells me that the file is too large - I rescanned half the chart, but it was still too large. I do not know what JIS means.
R A WILSON

5MM X 0.8 metric is easily available in almost any bolt form (with fully or partial threading) and thread length you need.

WHTroyer

Also, as most know, 5mm x 0.75 metric taps and dies are still available if needed.

WHTroyer

Order fan blade bolts from Moss and they will send you 6mm.
D mckellar

Hmmm...
P Hehir

JIS - Japanese Industry Standard. So not original specn.
Dave H
Dave Hill

Still trying to attach my chart, but the system keeps telling me the file is too large. However, for sizes below 10 mm diameter, the SI and ISO fine and coarse pitches are the same.
R A WILSON

If you'd copy the file in an email to me I think I may be able to shrink it and send the smaller version back to you. My email is shown above this posting. Bud
Bud Krueger

ISO coarse pitch is the same as JIS standard pitch. For 5mm that is 0.80.

WHTroyer

Thats odd, I finally managed to attach my chart, and it shows JIS data which is different. Your JIS data appears in my DIN Standard column, and as I mentioned before, LC Laurent's 5 x 0.9mm is in the JIS column.
I wonder where that gets us.
For LC Laurent, I do hope you manage to secure your fan blades to your water pump.

R A WILSON

It is confusing and your chart is as correct as mine. Part of the confusion with JIS is based on the age of the car or motorcycle (looking at just transportation).

According to my bolt charts/records, the JIS standard prior to 1967 for most companies was 5mm with 0.90 pitch as you say. After 1967 companies adopted 0.80 pitch to be consistent with the ISO standard. This changeover affected several bolt sizes and you will find conflicting JIS charts depending on the age of the source. More than a few bolts have been stripped over the years.

WHTroyer

Oh well, my MG TD has it's full complement of nuts and bolts to the original spec related to position on the car, and I have a reasonable quantity of spares to last me out. I suspect my every-day car has nuts and bolts in it - I will ask my local dealer next time it goes in for a service.
I do appreciate your replies.
(PS, thanks, Bud, for the offer, but my next attempt seemed to work).
R A WILSON

Just a thought, but I bet that Morris Engines Division, when they moved into the Hotchkiss works in Coventry in 1923, were less than impressed when they found their metric threads were to one of two old French standards that they had probably never heard of. I expect they were anticipating the SI system, which was supposed to have been adopted internationally since 1898, and particularly Europe and the UK (GB in those days).
R A WILSON

So much for Metric being a worldwide "standard". <grin>
Lew3

OK thanks guys,
Even Moss don't offer the correct replacement screws(I was about to order). So I will drill and tap for a 6 x 100 metric screw.

Laurent.
LC Laurent31

Be careful. I had ordered some new screws (forget from who) and they snapped at a very low torque.
Mike
Mike Hart

I measured the shank on my original screws and it turned out to be 5.2mm.
That is why I make the sleeves for the MGB fans at 5.3mm ID.
Regards
Declan
Declan Burns

I don't know what bolts Moss is supplying now but in March 2015 I bought from Moss part 320-120 and got 5mm x 0.75 x 43mm. The hex head is too big for a 1/8ww wrench but a 10mm fits perfectly.

B Mooney

If anyone has two of the original bolts you won't be using I would be interested in buying them.

Bill
B Mooney

what are they about $ 8.00 ea. ?
Plus shipping.
M Grogan

They run from $6.24 at AS to $6.99 at Moss.
Any body have two originals they are willing to sell?
B Mooney

This thread was discussed between 12/11/2016 and 19/11/2016

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