M8 x1.5mm bolt needed... #$@&%*!

[RichA]

I can't seem to find a M8 1.5mm countersunk bolt needed to fit my front door knob.

Story so far:
The door knob came with a bolt, but at 70mm it is too short.

So I ordered a 100mm bolt off ebay; which was the wrong diameter ! (I ordered M6 when I now think I need M8).

So I ordered an M8, but this has the wrong pitch!! (I ordered a 1.25mm when i now think the I need a 1.5mm)

However, all the M8s I can find have a 1.25mm pitch. Am I mssing something? Any suggestions on where to go for an M8 1.5mm countersunk bolt? (or a threaded bar & dope nut)

Thanks.

 

[rsgaz]

where to go for an M8 1.5mm countersunk bolt

It doesn't exist. M8 coarse is 1.25mm pitch. The only other choices in M8 are fine(1.0mm) or extra fine(0.75mm).

Could be a 5/16 UNC thread. That has 18tpi, which works out as 1.411mm pitch.

 

[Burnerman]

.......or 5/16” BSW
John

 

[RichA]

Thanks, that is really helpful. I reckon it is more likely to be 1.4.

Is UNC the same as BSW?

Any suggestions where do I get a 100mm/4 inch countersunk 5/16 bolt?

 

[rsgaz]

Is UNC the same as BSW?

No, despite them both being 18TPI for 5/16 https://anemo.eu/what-difference-between-bsfbsw-and-unfunc
They may appear to thread together OK, with some force.

where do I get a 100mm/4 inch countersunk 5/16 bolt?

https://www.accu.co.uk/en/imperial-socket-countersunk-screws/30611-SSK-5-16-18-4-A2

 

[RichA]

Thanks again. On a new product, which is more likely UNC or BSW?

 

[rsgaz]

If it's made in England, I'd be guessing!
If it's made in China, probably UNC.

Might be cheaper in the long run to just buy a 5/16 UNC nut first to try out on the bolt that came with it, instead of guessing and having to buy even more incompatible bolts!

 

[scbk]

Have you not got a local bolt shop? Take in the existing bolt/knob.

 

[Stivino]

Why not buy a thread gauge for about £6, or ask in your local engineering workshop if they would gauge it for you.

 

[foxhole]

I can't seem to find a M8 1.5mm countersunk bolt needed to fit my front door knob.

Story so far:
The door knob came with a bolt, but at 70mm it is too short.

So I ordered a 100mm bolt off ebay; which was the wrong diameter ! (I ordered M6 when I now think I need M8).

So I ordered an M8, but this has the wrong pitch!! (I ordered a 1.25mm when i now think the I need a 1.5mm)

However, all the M8s I can find have a 1.25mm pitch. Am I mssing something? Any suggestions on where to go for an M8 1.5mm countersunk bolt? (or a threaded bar & dope nut)

Thanks.

What is the bolt for exactly? Pic?

 

[Ian H]

I got a door knob with a bolt but didn’t use it, I could post a pic of it next to a tape measure. Your welcome to that if it would help?

Mine fitted like this but I had to drill 8 holes in it.

 

[RichA]

This is a pic of the bolt. The bolt goes through the front door from rear to secure a large door knob on the front. (Similar in look to Ian's, but with a different fixing). There is a decorative cap that covers the head.

 

[Burnerman]

Ach zo! Ze Whitworth thread has rounded crests whereas the Unified thread has flattened crests......anyone's guess!
John

 

[RichA]

Thanks. The manufacturer has confirmed it is a BSW 516.

So I now need to track down a 4" BSW 516 Countersunk bolt...

[Of course I ordered an UNC dome nut yesterday.... which I can add to be unwanted list with the M6 bolt and the M8 bolt]

 

[Ian H]

Who is the manufacturer?