Withworth bolt for AR3a?

[KJ2005]

Hello,

Anyone who know whether the bolts used by AR for the AR3a speaker, is UNF" or Withworth"? - and the size ( approx 6 mm)?

The problem is that the front woodplate on my renewed AR3a speakers got a thickness of 34 mm ( I have added 12 mm), and that the original bolts for the midrange, can't reach the nuts on the backside of the frontplate. - need a lenght of approx. 25 - 30 mm

If any interest, please find the AR3a renoval speaker on:

www.diagrammer.hobbysider.dk and
www.ar3a.hobbysider.dk

Rgds.

Kim

 

[Buckapound]

I have never seen a Whitworth thread on any product sold in the US. At 6mm, my strong suspicion is that the screws on the A-R's are 1/4" screws, in all likelihood 1/4-20, The NF is 1/4-28, not much used on anything but machines like engines and other precision or high-torque applications. On a speaker, maybe, but it's easy enough to count'em up and see what you've got.

--Buckapound

 

[KJ2005]

Hello Buckapound

I have never seen a Whitworth thread on any product sold in the US. At 6mm, my strong suspicion is that the screws on the A-R's are 1/4" screws, in all likelihood 1/4-20, The NF is 1/4-28, not much used on anything but machines like engines and other precision or high-torque applications. On a speaker, maybe, but it's easy enough to count'em up and see what you've got.

--Buckapound

Thanks ,

I shall try to count - I have erlier build a car - MGB gt - from the bottom, and in UK they use UNF which has a shorter increase of the thread - or you may say "fine" thread. This thread on the AR's looks like Withworth - may be a rise of 55 degree - but I am not shure. I can't take the old nuts out of the speaker, because they have been glued to the porously woodplate. If I try - I may destroy the old dry woodplate. I will have to go finding a replacement bolt.

Thanks for your reply

Rgds

 

[Moondog55]

You could try retapping the existing T-nuts to suit whatever machine-screw you decide to go with.

Nice boxes BTW

Ted

 

[KJ2005]

Hi Ted

You could try retapping the existing T-nuts to suit whatever machine-screw you decide to go with.

Nice boxes BTW

Ted

Yes - have been thinking the same. The standard , metric, is 6 or 8mm, and if I messure the AR bolts - they are a tiny bit thicker than 6mm - I don't believe the old T-nuts stays in position if one makes an attempt with a 8mm tap. If I can't get the original bolt thread - what ever it is - I will try to find a 6,5mm or close, which is not standard size.

Thanks for trying to help.

Best rgds

Kim