Imperial threads

[cliff366]

Hi chaps hope your all good I've got a thread I need to re tap after powder coating and assuming its imperial
as a m10 fits the hole but need a pitch of 1.75 but seems metric in m10 only goes to 1.5
But I'm lost when I look at charts on size can you help me please
Cheers

 

[Pete.]

25.4/1.75=14.5, so it seems you need a 14tpi thread, but that's unlikely so it's probably either a 3/8 BSW with a 16tpi pitch or a 7/16BSW with a 14tpi pitch.

 

[MattH]

You can get M10x1.75 but it seems it's favoured by the Americans.

 

[mike 109444]

25.4/1.75=14.5, so it seems you need a 14tpi thread, but that's unlikely so it's probably either a 3/8 BSW with a 16tpi pitch or a 7/16BSW with a 14tpi pitch.

Or 3/8 unc (which is much the same bar the thread angle)

 

[cliff366]

Cheers this is on a original vw roof rack aprox 1960s
I had found one 1.75 m10 but like you say was in USA and £40 !!! But worse case if couldn't get one to fit that's the route I'd have to go

 

[MattH]

Hi chaps hope your all good I've got a thread I need to re tap after powder coating and assuming its imperial
as a m10 fits the hole but need a pitch of 1.75 but seems metric in m10 only goes to 1.5
But I'm lost when I look at charts on size can you help me please
Cheers

If it's just for cleaning out powder coat then a tool could easily be turned on a lathe.

 

[Pete.]

You can get M10x1.75 but it seems it's favoured by the Americans.

It's so unlikely it's not likely at all. I never yet saw or even heard of any instance of it's use.

 

[MattH]

It's so unlikely it's not likely at all. I never yet saw or even heard of any instance of it's use.

Well live and learn:

http://www.mscdirect.com/product/details/09037185

 

[Pete.]

I'm wasn't saying the pitch doesn't exist, just that it wasn't in common (or even un-common) use. If the roof rack is in fact m10x1.75 that'll be the first time I heard of it. Such a coarse thread on a M10 bolt would reduce the root diameter to 8.25mm, so why would you bother putting in a m10 bolt which has the tensile strength of a 8mm one? Perhaps it would work well screwed into plastic.

 

[tinman123]

like pete id be shocked if it was a 1.75, its more like a 3/8 bsw id say.
m10 x 1.75 is classed as a special tap, i dont think in all my time ive came across it in anything.
it id be a rare one to see it in a tapping chart if at all.

 

[Pete.]

Even Tracy tools don't list that pitch - and they will sell you a M15 or M17 tap

http://www.tracytools.com/taps-and-dies/metric-taps-dies?page=2

 

[rikrobson]

If its imperial its not going to be 1.75mm pitch. you'll need to work out the threads per inch 14tpi is near (1.75 ~= 14.5tpi) that so i suspect it could be a 7/16-14 UNC or 7/16-14 Whitworth the main difference here is the angle of the thread form 60 for the UNC and 55 for the W

Don't you just love the way that there are so many threads

 

[mcostello]

If all You need to make Your day is a 7/16" X 14 tpi tap just Let Me know, I am in Colonial Imperial land.

 

[Rudi McAnichal]

Cheers this is on a original vw roof rack aprox 1960s

Is it likely that VW would have used Imperial threads? And if so, why?

Maryland Metrics website has lots of data tables for obscure screw threads:
https://mdmetric.com/fastindx/inxtst.htm

 

[Richard.]

Rather than guessing based on the likelihood that thread comes about I would suggest it's measured properly and confirmed. Have you got a thread gage?
A 14TPI gage won't fit properly over a 1.75 pitch and vice verca even though they are close.
The thread angle will be different as well.
As Matt said if your wanting to just clean a bit of powder coating and you have a lathe you could turn it out of bog standard steel and put a couple slots down it like a tap for the removal to escape.

 

[Windy Miller]

Do you have the bolt that screws into it? You could always various nuts as per the thread suggestions posted here.

I would just file a couple of grooves from the tip of the bolt along the length for a short way, and gently work it in and out. That ought to be enough to clear a bit of paint I would think.

 

[cliff366]

Cheers guys it was a 7/16 14p so thank you for the help
I don't have a lath to be able to turn a tool

 

[Richard.]

Shouldn't need to. That's a common tap size.

 

[rikrobson]

is it UNC or BSW? the UNC is american and 60° and the whitworth 55°?

 

[cliff366]

If its imperial its not going to be 1.75mm pitch. you'll need to work out the threads per inch 14tpi is near (1.75 ~= 14.5tpi) that so i suspect it could be a 7/16-14 UNC or 7/16-14 Whitworth the main difference here is the angle of the thread form 60 for the UNC and 55 for the W

Don't you just love the way that there are so many threads

Yep my knowledge of threads is if it don't go on the threads not right lol