The BSA A7-A10 Forum

Technical (Descriptive Topic Titles - Stay on Topic) => Frame => Topic started by: dsj666 on 26.09. 2018 19:02

Title: Plunger Columns
Post by: dsj666 on 26.09. 2018 19:02

Anybody know what is the thread size and type is in the end of a plunger column please?
The one where those aluminium caps on the top screw in.

Cheers

Title: Re: Plunger Columns
Post by: Rex on 26.09. 2018 21:50

I can measure the TPI and major diameter tomorrow if you wish. Best send me a PM tomorrow afternoon as a reminder though... ;)

Title: Re: Plunger Columns
Post by: Rex on 28.09. 2018 10:09

It comes out at 0.875" dia and 20 TPI. HTH.

Title: Re: Plunger Columns
Post by: duTch on 28.09. 2018 11:07

 I bought new SS ones from Lightning Spares and always figured they are BSC whatever size

Title: Re: Plunger Columns
Post by: dsj666 on 28.09. 2018 11:16

Quote from: Rex on 28.09. 2018 10:09

It comes out at 0.875" dia and 20 TPI. HTH.

Thanks Rex...it would appear that's a 7/8 x 20 TPI  BSC thread then, and taps seem to be available..!!

I was contemplating cleaning up the threads so they don't damage my new end plugs..!!

Title: Re: Plunger Columns
Post by: Rex on 28.09. 2018 13:11

I recently bought two new stainless end caps and I had to spend ages lapping them in to fit the plunger column threads, just like I did with the stainless fork seal holders and stanchion top nuts too.
Close, but not close enough to fit perfectly.

Title: Re: Plunger Columns
Post by: duTch on 28.09. 2018 17:56

 I should add that I had a mate fabricate new columns from Chrome bar which entailed machining threads in to match, so probably also needed to tidy the plug threads.