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Hi everybody.
Got a funny problem trying to attach something to a car I'm restoring.
The manufacturer of the item claims the thread on the bolt to attach it to the car is M6.
So I bought some stainless M6 nylock nuts.
The M6 are too small. So I bought some M7 ones instead. The M7s are too big.
I'm guessing the problem is I'm looking at an imperial thread.
So what is a commonly used imperial thread size between M6 and M7?
Hopefully third time lucky?
Thanks.
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pptom
Part of things
Posts: 475 
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1/4"
Might be fine or coarse though. unF or unC
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pptom
Part of things
Posts: 475
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If you can see the threads and compare them to an M6 then UNF will have more threads (closer together) and UNC will have less (further apart)
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So they could be M6 but with a fine thread?
What is 'standard' - i.e. if you order boggo M6 nuts as I did?
Should I be looking for "M6 UNF"
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UNF is an imperial thread designation.
M6 is normally 1mm pitch and fine is 0.75mm
A standard pitch M6 will usually go about half a turn into a fine nut in my experience which can be a clue. If not then you may well be looking for a 1/4" bolt of some variety.
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Proton Jumbuck-deceased :-(
2005 Kia Sorento the parts hauling heap
V8 Humber Hawk
1948 Standard12 pickup SOLD
1953 Pop build (wifey's BIVA build).
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LowStandards
Club Retro Rides Member
Club Retro Rides Member 231
Posts: 2,716
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Send the M6 and walk away
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Depending on the age and origin of the car it could be BSF, BSW or even BA thread.
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Last Edit: Feb 7, 2024 9:52:02 GMT by colnerov
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UNF is an imperial thread designation. M6 is normally 1mm pitch and fine is 0.75mm A standard pitch M6 will usually go about half a turn into a fine nut in my experience which can be a clue. If not then you may well be looking for a 1/4" bolt of some variety. This is about what I was seeing actually. |
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jimi
Club Retro Rides Member
Posts: 2,220
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Metric Coarse  Metric Fine  |
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Black is not a colour ! .... Its the absence of colour
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Get some callipers out and measure..
Outside diameter of the thread should be 6mm pretty exact. 6,3mm would indicate 1/4".
Then measure the pitch. hold the callipers parallel to the thread. You should start at the top of one 'ridge' and the other end would then have to end exactly on the tenth 'ridge', and the distance you measure divided by ten will give you the pitch.
Hope this is clear..
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Stop guessing, and measure what you have.
That takes the cheapest digital caliper, and a £5 thread guage.
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Stop guessing, and measure what you have. That takes the cheapest digital caliper, and a £5 thread guage. I'm not against the idea of having a surplus of stainless nylock nuts on the shelf. The joy that comes over me when I find a jar full of exactly the right fastener / cable clip / washer / etc is worth the pain of a very minor / temporary disappointment trying to figure out what is required. |
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I'd double check both the nuts you've bought and the thread they're not quite fitting on.
It's not uncommon for an older thread to be damaged or for new threads to have not been manufactured properly.
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Will be 1/4” UNF I reckon. They are similar enough that you can fit a 1/4” UNF nut on an M6 bolt (bit slack) but not the other way around.
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1967 Triumph Vitesse convertible (old friend)
1996 Audi A6 2.5 TDI Avant (still durability testing)
1972 GT6 Mk3 (Restored after loong rest & getting the hang of being a car again)
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Feb 10, 2024 12:05:56 GMT
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The official nuts from the original manufacturer were pennies so I ordered a handful. I am not convinced they are going to fit but I'm open to the possibility and it hasn't cost much to give it a go. The listing for the part says the threads are M6 and they clearly aren't so I wonder whether the supplier has provided M6. They've arrived so will find out today.
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No one seems to have asked what the car is :-)
What is the car?
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