Dipper/horn switch thread specs?

[AgentX]

Hi--

Anyone happen to know the thread specs on the screws/holes that hold a Norton dipper/horn switch direct to the handlebar?

I am guessing I will do well to switch to the smallest metric or SAE equivalent which will work, as I don't own tiny taps of any British thread patterns...anyone else done that?

This is the type of switch:

 

[Bernhard]

No idea what yours are some engineer with thread pitch gauges and a mike will be able to tell you.

I just drilled & tapped my handlebars if I remember it rightly, 2 BA.

 

[Bodger]

Hi--

Anyone happen to know the thread specs on the screws/holes that hold a Norton dipper/horn switch direct to the handlebar?

I am guessing I will do well to switch to the smallest metric or SAE equivalent which will work, as I don't own tiny taps of any British thread patterns...anyone else done that?

This is the type of switch:

I have done this several times. You are overthinking this. Just drill and tap to something convenient that fits, metric, BA, UNF or whatever. The hard part is drilling the holes on a radius to the center of the bar. I don't think any concours judge is going to take the screws out, measure the threads and deduct points. FWIW I've had the Emgo version of this switch short out when switching between low and high. Might just have been a bad example or damage caused by the handlebar grip pressing against the switch lever. Depending upon where you place the switch and the type of grip you may have to trim off a bit of the grip "cuff" to allow the switch toggle to clear.

 

[NoLongerHere]

I seem to remember mine being 4BA but it wouldn't have broke my heart if it was even metric.

 

[Bernhard]

I have done this several times. You are overthinking this. Just drill and tap to something convenient that fits, metric, BA, UNF or whatever. The hard part is drilling the holes on a radius to the center of the bar. I don't think any concours judge is going to take the screws out, measure the threads and deduct points. FWIW I've had the Emgo version of this switch short out when switching between low and high. Might just have been a bad example or damage caused by the handlebar grip pressing against the switch lever. Depending upon where you place the switch and the type of grip you may have to trim off a bit of the grip "cuff" to allow the switch toggle to clear.

Agreed with most of this, however as you only have a thin bar dia of metal, I consider it more practical to use a FINE thread as this is going to get more threads in the metal. prior to drilling bar, put a piece of masking tape over where hole is to be drilled, and if you can centre punch and start of with a v. shallow hole done with a centre drill, it has to be done carefully if you use a hand powered drill, but grease screws before inserting or they will rust!

 

[AgentX]

Thx, all. Believe me, I'm not trying to be a purist. Frankly I don't know why I asked...will just be buying whatever screws match my smallest fine-threaded tap and enlarging the holes in the switch a bit if need be. Definitely will be taping and center-punching the bars before drilling.