ARTY GB (1) copy Zwarteschijf

Various Parts

Ken Priestley

Leather cloth

F R Ratchford J Hewitt


Meadows and Passmore






HMV No 21 Insulator

Anyone with an HMV No.21 soundbox or the Columbia equivalent the No.15 can't fail to notice the insulator that lies between the two parts of the soundbox's back plate.    Few will have tried to remove it but curiosity always gets the better of me and prompted by a fellow collector I removed mine.  For those who haven't seen one there is a photo below.  Now all my insulators haven't been too bad.  They are still pliable although showing natural signs of perishing on the edges.  However what happens if one does need replacing?  I tried and tried to manufacture a replacement without success and then came up with some useful stuff called "Sugru" (click to link)


Note: The red washer was made in exactly the same way as the No.4 gaskets See "HMV No. 4 Gaskets" (click to link)


IMPORTANT:  As the original screws are not used the alignment of the spigot with the needlebar position and the pressing of the backplates together to obtain a uniform thickness that matches the original are points that you will need to take care over.


I have used black Sugru so you can distinguish just what has been done but red makes more sense.  Note also that the Sugru will fill the holes where the screws once went.  This excess Sugru is simply levelled off at these points.  On the video you can see how from the rear the Sugru is apparent where there were once screw heads showing.  A minor price to pay for a working insulator.


The video show the insulator on a 15a soundbox (Columbia equivalent to the HMV No. 21) working. Click the video link to You Tube to view larger


Here's how I did it. (Click thumbnails for a larger picture and information)