I bought myself a Harley Davidson. When I started to tweak it a bit, I noticed that all the screws follow American standards. The hex heads on the bolts fit inch sockets and not mm.
The hex screws are according to SAE standard.
I wanted to replace these screws with black ones. I had some at home, so I thought I'd just swap them out when I got them out. But then it turned out that it's not just the heads that are different, but also the threads. They are coarser threaded than our standard screws.
Does anyone know what their threads are called? I was thinking of googling them to see where I can order new ones. But I need to know what the screws with these threads are called. Do you know?
The hex screws are according to SAE standard.
I wanted to replace these screws with black ones. I had some at home, so I thought I'd just swap them out when I got them out. But then it turned out that it's not just the heads that are different, but also the threads. They are coarser threaded than our standard screws.
Does anyone know what their threads are called? I was thinking of googling them to see where I can order new ones. But I need to know what the screws with these threads are called. Do you know?
Probably UNC or UNF, unified threads "coarse" or "fine".
So if they have coarser threads, or at least fewer threads than our standard, is it UNC?Fotografen said:
Yes.
Strictly speaking, the metric system is also the main standard in the USA, although progress is slow. So the right thing to do is to drill all the holes and re-thread them. 
A thread gauge is a good tool if you're working on older technology beyond just your bike. They aren't very expensive and can handle identifying most common threads.
A thread gauge is a good tool if you're working on older technology beyond just your bike. They aren't very expensive and can handle identifying most common threads.
"We're converting to metric, inch by inch..."Z z_bumbi said:
Just need to clarify that he's joking about re-threading; the only thing worse than having a strange threading standard is having multiple threading standards on the same machine... regards a Polaris owner 🤬Z z_bumbi said:So the right thing to do is to drill up all the holes and re-thread.
(The threading gauge tip is very good though
)
It wasn't as easy to order UNC screws as I thought. Need to order black screws equivalent to M8x35 and M6X40. But it wasn't just about searching for M8x35 UNC. They don't have exact M8X35 dimensions.
What should I search for to find the right screws?
What should I search for to find the right screws?
Know-It-All
· Västra götaland
· 10 919 posts
Well, m6 should correspond to 1/4 and the closest m8 is probably 5/16 ...
Do you know any old gearheads? They might have basements full of fasteners with imperial threads.T Tovin said:
You should be glad you don't have an old English motorcycle. I do. Four different threads. English inch, and Whitworth and British cycle thread. There you go!
I remember when a rocket (one of the Ariadne rockets, if I remember correctly) crashed because the American subcontractor forgot to convert their input data to inch, as they were calculating in inches...Z z_bumbi said:Carefully considered, metric is also the main standard in the USA, although it is progressing slowly. So the right thing to do is to drill up all the holes and re-thread them.
A thread gauge is a useful tool if you're working with older technology more than just the bicycle. They are not very expensive and can identify most common threads.
You will probably need to search for inch measurements, like M12 being closest to half an inch, etc. Black 1/2 inch will probably yield something, the rest there should be some list you can google.
M8
Black 5/16 screw
Black 5/16 screw