07-03-2012, 06:31 PM
How to make a Wartime Civilian Receiver repro radio back panel using a router jig:
A short while ago I posted a thread on how to make a custom router jig for making replica radio backs. In that case, it was for a pre-war Little Maestro. I posted it inform, encourage and perhaps inspire others to have a go - not because I wished to attract requests or orders for back panels – I simply don’t have the time, and even at the minimum wage it would be hopelessly uneconomic! To make a router jig, all that is required are basic woodworking skills and a cheap light duty DIY router with a 6.4mm (¼”) router bit. Routers that would be up to the task can be bought for under £30, and better, more powerful ones for under £40, such as this 1000 Watt one:
http://www.screwfix.com/p/direct-power-p...ter%20230V
Most commonplace radio backs seem to have slots which are ¼” wide, about 1” long, in rows spaced ½” apart. They seem mostly to have been made of millboard, which is rather like layers of compressed paper. Over time – particularly on radios such as DAC90As with droppers, the backs become brittle and pieces drop off exposing dangerous parts in the rear of the set. That is what happened in the 'Little Maestro' for which I recently made a jig and new replica back. If you are lucky, as I was with the Little Maestro, the remnants of the back will enable a pattern to be drawn by using the old back as a template, or if you can get your hands on one, an undamaged back could be used.
To make a back panel - whatever it’s shape when finished - the blank from which it is made must start off as a rectangle. In the case of the Little Maestro and the Wartime Civilian Receiver they're rectangular anyway, which makes life a bit easier. Something like a DAC90A is of course rounded at the top and corners, so you’d start off with a rectangle and when the slots have been routed, remove the blank from the jig and finish shaping it either on a bandsaw, with a jigsaw, a scrollsaw or whatever tools are to hand.
The basic requirement of a router jig are that the movement of the router must be restricted vertically to the length of the slot that is to be cut, and must have no sideways play. The blank in which the slots are to be cut must be held in the jig in such a way that it can slide sideways one step at a time to enable a row of slots to be cut, then the router guide can be moved down and repositioned on the jig to cut the next row of slots. The simplest way to hold the blank in place while each slot is cut and to accurately reposition for the next slot it is to have two panels – one either side of the blank, which can be move sideways and repositioned on dowels as each new slot has been cut.
When I posted my thread about the Little Maestro jig, although I said I wasn’t able to meet requests for that or other backs, Mark (‘The Mender’) asked if I’d make him a back for a Wartime Civilian Receiver. Given the hassle that Mark’s had this last year, particularly when the forum was de-railed, and getting this premier forum back on a firm footing with the rest of the team, 24/7 I was only too pleased to offer to have a go.
I’d previously considered what might be the best material to use – the original backs tend to be from 3mm – 5mm thick. MDF in 3mm and 5mm is available, and is possibly preferable to normal hardboard, but having looked into the options, oil tempered hardboard seemed to me to be the favoured material. Normal hardboard is too soft and fluffy, but oil tempered hardboard is far superior, and has proved to be so in use.
I’ve attached a few pictures of the jig that I made for the WCR replica back, which might help make a bit more sense of these waffly notes. The jig consists of a 22mm chipboard base onto which two lengths of hardboard to act as guides are screwed to enable the blank to be held in position while sliding freely from right to left. Then there is a router guide with a hole cut in it the width of the sole-plate of the router, which will allow the router to move down in that guide for the length of the slot – in this case, about an inch. When one row of slots has been cut, the router guide is moved down to the position in which it is desired to cut the next row, and so on. In the case of the WCR, the distance from the top of one row to the top of the next is 1½” and there are four rows. In the pictures of the jig, the pairs screw holes for the other positions of the router guide can be seen.
Two lateral guide panels are needed, which are advance towards the left to enable the next slot in a row to be cut. In the case of the WCR, the slots are ½” apart, and to accurately position the two lateral guide panels, two rows of holes were drilled in each guide, half an inch apart. Dowels were positioned and glued into the baseboard to enable each lateral guide panel to move sideways half an inch at a time for the next slot to be cut. In the case of the WCR, there are three rows of 21 slots, then for some inexplicable reason that eludes me, 20 slots in the fourth row, and a pair of holes. Hence, the two lateral guide panels need two rows of 21 holes each, to position them over the dowels. To allow for any minor differences that would inevitable arise if these two guide panels were drilled separately, they should be taped together when drilling the holes.
It sounds like a lot of rigmarole I’m sure, but it isn't as daunting as it may sound.
It takes perhaps 2 -3 hours to make the jig, but once made, depending on how many slots need cutting and whether the blank needs any additional shaping, it should take no more than 45 minutes to cut all the slots. In the case of the WCR, there are 83 slots. Of course, it would be possible to make a back by other means using say a drill and fretsaw or chisel, but that would be very tedious and if you needed another, you’d have to go through the same palaver as before, whereas once a jig is made, it would take perhaps an hour from start to finish, taking about 30 seconds to cut each slot. It simply involves setting the depth gauge on the router to cut through the board, plunging the router in at the top of the slot, then pulling it towards you until the slot is cut, then switching off and repositioning the board laterally to cut the next slot.
To paint the backboard I used Homebase ‘Home of Colour’ ‘Double Espresso’ matt emulsion, which was the nearest match I could find to the original colour. It comes in 75 ml tester posts, presently on offer ‘two for three’ which works out at £1.00 each. Each pot will do several boards and covers well. I’m indebted to Tony Thompson (‘Aerodyne’) for having provided the excellent artwork (via Joe) for the 'instruction notice' to fit on the back. I aged some paper by soaking it in strong coffee, then ironing it dry between two sheets of kitchen roll. It’s a little darker than it may appear in the pic.
It will be on its way to Mark the guv’nor in tomorrow’s post.
Hope that’s of interest.
Rear cover pattern can be found here:
http://www.thevalvepage.com/radios/warti...#RearCover
A short while ago I posted a thread on how to make a custom router jig for making replica radio backs. In that case, it was for a pre-war Little Maestro. I posted it inform, encourage and perhaps inspire others to have a go - not because I wished to attract requests or orders for back panels – I simply don’t have the time, and even at the minimum wage it would be hopelessly uneconomic! To make a router jig, all that is required are basic woodworking skills and a cheap light duty DIY router with a 6.4mm (¼”) router bit. Routers that would be up to the task can be bought for under £30, and better, more powerful ones for under £40, such as this 1000 Watt one:
http://www.screwfix.com/p/direct-power-p...ter%20230V
Most commonplace radio backs seem to have slots which are ¼” wide, about 1” long, in rows spaced ½” apart. They seem mostly to have been made of millboard, which is rather like layers of compressed paper. Over time – particularly on radios such as DAC90As with droppers, the backs become brittle and pieces drop off exposing dangerous parts in the rear of the set. That is what happened in the 'Little Maestro' for which I recently made a jig and new replica back. If you are lucky, as I was with the Little Maestro, the remnants of the back will enable a pattern to be drawn by using the old back as a template, or if you can get your hands on one, an undamaged back could be used.
To make a back panel - whatever it’s shape when finished - the blank from which it is made must start off as a rectangle. In the case of the Little Maestro and the Wartime Civilian Receiver they're rectangular anyway, which makes life a bit easier. Something like a DAC90A is of course rounded at the top and corners, so you’d start off with a rectangle and when the slots have been routed, remove the blank from the jig and finish shaping it either on a bandsaw, with a jigsaw, a scrollsaw or whatever tools are to hand.
The basic requirement of a router jig are that the movement of the router must be restricted vertically to the length of the slot that is to be cut, and must have no sideways play. The blank in which the slots are to be cut must be held in the jig in such a way that it can slide sideways one step at a time to enable a row of slots to be cut, then the router guide can be moved down and repositioned on the jig to cut the next row of slots. The simplest way to hold the blank in place while each slot is cut and to accurately reposition for the next slot it is to have two panels – one either side of the blank, which can be move sideways and repositioned on dowels as each new slot has been cut.
When I posted my thread about the Little Maestro jig, although I said I wasn’t able to meet requests for that or other backs, Mark (‘The Mender’) asked if I’d make him a back for a Wartime Civilian Receiver. Given the hassle that Mark’s had this last year, particularly when the forum was de-railed, and getting this premier forum back on a firm footing with the rest of the team, 24/7 I was only too pleased to offer to have a go.
I’d previously considered what might be the best material to use – the original backs tend to be from 3mm – 5mm thick. MDF in 3mm and 5mm is available, and is possibly preferable to normal hardboard, but having looked into the options, oil tempered hardboard seemed to me to be the favoured material. Normal hardboard is too soft and fluffy, but oil tempered hardboard is far superior, and has proved to be so in use.
I’ve attached a few pictures of the jig that I made for the WCR replica back, which might help make a bit more sense of these waffly notes. The jig consists of a 22mm chipboard base onto which two lengths of hardboard to act as guides are screwed to enable the blank to be held in position while sliding freely from right to left. Then there is a router guide with a hole cut in it the width of the sole-plate of the router, which will allow the router to move down in that guide for the length of the slot – in this case, about an inch. When one row of slots has been cut, the router guide is moved down to the position in which it is desired to cut the next row, and so on. In the case of the WCR, the distance from the top of one row to the top of the next is 1½” and there are four rows. In the pictures of the jig, the pairs screw holes for the other positions of the router guide can be seen.
Two lateral guide panels are needed, which are advance towards the left to enable the next slot in a row to be cut. In the case of the WCR, the slots are ½” apart, and to accurately position the two lateral guide panels, two rows of holes were drilled in each guide, half an inch apart. Dowels were positioned and glued into the baseboard to enable each lateral guide panel to move sideways half an inch at a time for the next slot to be cut. In the case of the WCR, there are three rows of 21 slots, then for some inexplicable reason that eludes me, 20 slots in the fourth row, and a pair of holes. Hence, the two lateral guide panels need two rows of 21 holes each, to position them over the dowels. To allow for any minor differences that would inevitable arise if these two guide panels were drilled separately, they should be taped together when drilling the holes.
It sounds like a lot of rigmarole I’m sure, but it isn't as daunting as it may sound.
It takes perhaps 2 -3 hours to make the jig, but once made, depending on how many slots need cutting and whether the blank needs any additional shaping, it should take no more than 45 minutes to cut all the slots. In the case of the WCR, there are 83 slots. Of course, it would be possible to make a back by other means using say a drill and fretsaw or chisel, but that would be very tedious and if you needed another, you’d have to go through the same palaver as before, whereas once a jig is made, it would take perhaps an hour from start to finish, taking about 30 seconds to cut each slot. It simply involves setting the depth gauge on the router to cut through the board, plunging the router in at the top of the slot, then pulling it towards you until the slot is cut, then switching off and repositioning the board laterally to cut the next slot.
To paint the backboard I used Homebase ‘Home of Colour’ ‘Double Espresso’ matt emulsion, which was the nearest match I could find to the original colour. It comes in 75 ml tester posts, presently on offer ‘two for three’ which works out at £1.00 each. Each pot will do several boards and covers well. I’m indebted to Tony Thompson (‘Aerodyne’) for having provided the excellent artwork (via Joe) for the 'instruction notice' to fit on the back. I aged some paper by soaking it in strong coffee, then ironing it dry between two sheets of kitchen roll. It’s a little darker than it may appear in the pic.
It will be on its way to Mark the guv’nor in tomorrow’s post.
Hope that’s of interest.
Rear cover pattern can be found here:
http://www.thevalvepage.com/radios/warti...#RearCover
Regards, David.
BVWS Member.
G-QRP Club Member 1339.
'I'm in my own little world, but I'm happy, and they know me here'
BVWS Member.
G-QRP Club Member 1339.
'I'm in my own little world, but I'm happy, and they know me here'
