Graham-ophones

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ARTY GB (1) copy Zwarteschijf

Various Parts

Ken Priestley

Leather cloth

F R Ratchford J Hewitt

Diaphragms

Meadows and Passmore

PLEASE NOTE:

I DO NOT SUPPLY

ANY PARTS

I'M MERELY

A COLLECTOR.

This design was based on an idea I received from gramophone collector Barry from Peterborough who very kindly shared the design of his turntable mat jig with me.  To Barry's basic idea I've added my own thoughts and here therefore are the details of the Turntable Jig........Mk II?

 

Not so much for the person with just 1 gramophone but great for the collector/restorer

Turntable Mat Jig

Materials:

 

The Base - 13" square 18mm MDF fitted with 4 x rubber feet to assist with stability and prevent movement in cutting, and covered in felt to give the workpiece a purchase while cutting.

The Pivot - Min 30mm long M8 bolt the top 1/2 of which is reduced down to the diameter of a gramophone spindle. NB fitted centrally to base board with an inset hole on base surface to accommodate the nut.

The Clamp Disc - an lp of 12" dia cut for blade and drilled to take lugs of clamp

The Cutter - 1 piece 2" x 1"  grooved to take no 10 Swan Morton Scalpel Blade and small 1/2" No 4 c/s screw and washer to fix.

The Hole Cutter - 7mm brass tube ground on inside edge to form a blade.

The Workpiece - 2 x 13" square pieces of felt glued together with spray carpet adhesive to give adequate thickness and stiffness.

The Template -  It is essential that the blade position and holes for the lugs in the cutter and the holes for the same lugs in the clamping disc are in the same place.  This is best done by using a template marked out with the lug and blade positions.

The Workpiece - I cut the felt down to 13" squares and bond two together to increase thickness and stiffness.

The Pivot. - Essentially this is an M8 bolt of which I modified the top half to match the spindle of a gramophone and cut to 30mm long.

The Base - underside showing the rubber feet to assist stability and centrally located pivot.

The Base - top view.  NB the nut for the pivot has been set into a recessed hole so as not to affect the work surface which has been covered with felt.

The Cutter - This was marked out using the template for positioning the cuts on the Clamp.  The locating pegs are 2 x No. 4 brass screws which have then had their heads removed and filed to a depth determined by the lp thickness

The Clamp - I used an LP which I marked out using a drawn template for locating peg position and a slot for the cutting blade.  The cut is set at a rad of 119mm for an HMV 10" table

This picture shows the Cutter Assembly in position on the Clamp Disc

The Hole Cutter - I used a 7mm dia brass tube available from model shops to punch out the hole.  The tube was "sharpened" on the inside diameter  to form a blade.

The Workpiece having been trimmed to 13" square and had the hole for the spindle punched out using the hole cutter is now in placed on the base board. (Ignore the fact the felt is cut in the photo...that was just me back tracking for the purpose of the instructional photos)

Cutting is just a matter of locating the cutter in its location holes and with downward pressure of one hand in the central area of the disc, moving the cutter around the workpiece a couple of times.

Once cutting is complete simply remove the Clamping Disc, Cutter and excess felt revealing a perfect mat.

The finished mat with a perfect hole and pefect cut edge.

The Template - The positions of the lugs and the blade position need a template to ensure accurate positioning.  The long centre line was used to construct the position of the cutter tangentially at the cutting point. (The "crumpling" is because I nearly threw mine away after I'd made the jig.

A selection of mats.

Click thumbnails for a larger image

Click thumbnails for a larger image