I recently bought an SL-5310 and noticed that one of the noses that go into the hinges had broken off the cover. An extensive search on the interwebs revealed that the same cover is shared beetween quite a number of Technics SL- models (no warranty list: 220, 221, 230, 231, B3, D2, D3, 5100, 5110, 5200, 5210, 5300, 5310, 3200, 3210, 3300, 3310, Q2, Q3, Q33), but there no NOS covers, and well preserved covers are extremely hard to come by. So I decided to repair my original cover.
The idea of making anything from metal was quickly dumped due to the complexity of the part and my lack of filing skills.
So I fired up Sketchup to design a 3D printed part from scratch that would replace the whole nose. The part eventually should conceal any damage done to the back of the cover, be stiff enough to handle the weight of the cover, keep the cover in its original position/geometry on the turntable and should look as much as possible as an original Technics part would look like. I'm not an engineer at all, so this took quite some time. One thing that turned up in the process was that the nose and the back of the cover do _not_ form a right angle.
I sent my first design to a 3D printing service, received two prints, re-designed the part, had more prints made, re-designed again and finally received prints that fitted my needs. I ordered a few sets of different nuts and bolts to try and eventually had a repair kit that looks like so:
And here is a description how my first repair was done. You need some masking tape, a 4mm and a 4.5mm drill, a Philips screwdriver and a 7mm spanner.
This is the cover's sad state as bought with the turntable:
First use the old Dremel to completely remove the rest of the broken nose and make a notch in the size of the shallower lower part if the nose. It might be wise to use some masking tape to mark the working area and protect its surroundings. You have to create an even surface.
Use sanding paper to remove any remaining protrusions. Dents don't do much harm as long as they keep within the masked working area. I removed my masking tape too soon and had to do some polishing work after this stage.
Check if the repair part fits. It has to be flush with the lower edge of the cover. You may want to check on the turntable if everything aligns properly.
Hold or fixate the repair part excactly in place and very carefully drill two 4mm holes through the cover. Take the repair part off and enlarge the holes to 4.5mm. Remove any edges form the bores.
Attach the repair part with two screws and nuts. This is how it should look like now from the inside of the cover:
And this is how the finished repair looks like.
If anyone is interested, I have some spare kits here (complete with nuts and bolts), and I can send them anywhere.