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Old 19th January 2019, 09:58   #1
Daveluck
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Default M30 diameter

Morning,

Not car related...

So I know an m30 bolt is 30mm diameter to the outer edge of the threads....but does 29.6mm qualify as an m30?

I'm changing the trv heads on my rads.
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Old 19th January 2019, 10:11   #2
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The M30 designation is only the nominal diameter, there will always be a tolerance, 29.6 is near enough, do not worry, the top of the thread is always slightly rounded to ensure clearance when fitted..
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Old 19th January 2019, 13:51   #3
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Are metric threads used on plumbing parts? I always thought they were BSP, but maybe it's changed?


TC
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Old 19th January 2019, 15:17   #4
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29.6mm (How/with what are you measuring it?) is closer to 30mm than either 3/4" BSP or 1"BSP
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Old 19th January 2019, 16:26   #5
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Just looked up Metric thread tolerancing and depending on the grade the minimum O/D could be 29,522mm, max O/D 29.947mm, so 29.6mm could well be a nominal 30mm
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Old 19th January 2019, 17:31   #6
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If you're changing the TRV's and wondering what size thread they are then as far as I know they're std, so you can't go wrong.
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Old 19th January 2019, 17:52   #7
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Quote:
Originally Posted by T-Cut View Post
Are metric threads used on plumbing parts? I always thought they were BSP, but maybe it's changed?


TC
I think you may be correct, BSP is still used on iron and brass pipe fittings as I've used them recently when changing gas meters.
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Old 19th January 2019, 18:00   #8
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Quote:
Originally Posted by RoverP480 View Post
Just looked up Metric thread tolerancing and depending on the grade the minimum O/D could be 29,522mm, max O/D 29.947mm, so 29.6mm could well be a nominal 30mm
Get a set of Zeus charts and you can check the pitch just to be sure, they've proved very useful for when I've been checking screws and bolts.
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Old 19th January 2019, 18:06   #9
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Quote:
Originally Posted by kelvo View Post
Get a set of Zeus charts and you can check the pitch just to be sure, they've proved very useful for when I've been checking screws and bolts.
Zues been over 30 years since I last heard that when I was an apprentice
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Old 19th January 2019, 21:01   #10
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Quote:
Originally Posted by T-Cut View Post
Are metric threads used on plumbing parts? I always thought they were BSP, but maybe it's changed?


TC
They certainly are on trv heads

Quote:
Originally Posted by Avulon View Post
29.6mm (How/with what are you measuring it?) is closer to 30mm than either 3/4" BSP or 1"BSP
With a cheapy Chinese digital caliper

Quote:
Originally Posted by RoverP480 View Post
Just looked up Metric thread tolerancing and depending on the grade the minimum O/D could be 29,522mm, max O/D 29.947mm, so 29.6mm could well be a nominal 30mm
Good enough for me!

Quote:
Originally Posted by Heddy View Post
If you're changing the TRV's and wondering what size thread they are then as far as I know they're std, so you can't go wrong.
As far as I can tell there are at least 3 different sizes depending on age and manufacturer!
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