| Author |
 Topic  |
|
|
DDMDSN
New Zealand
329 Posts |
 Posted - 20/03/2016 : 21:58:41
|
With some of the bakelite parts becoming quite rare particularly fuse boxes and accessories, repairing is becoming an important consideration.
The following is offered on how to repair damaged and broken bakelite parts. Materials required are shown below. The P Type spare plug holder is a repro that has been colour matched and bakelite appearance finished. See items for sale. I have repaired brown bakelite using this method, items now either on my car or sold such as a CJR2 fusebox and cover. Small repairs when done correctly are very hard to spot, and the repair at least as strong as the original material.
Best wishes.
Donald McLeod
PB0759
1. Clean item thoroughly in soapy water using a soft cloth
2. Mask off area to within about 5mm of area to be repaired
2. Prepare damaged surfaces with precision grinder, V channel for a crack (like preparing for a tooth filling)
3. Feather sand 5mm either side of damaged area with P800 grit SiC abrasive (wet and dry).
4. Clean area to be repaired with wax and grease remover
5. Hold piece square for joining (clamp/brace)
6. Make mould around area to me filled with masking tape and/or blue tak or similar
7. Mix 24 hour araldite, precolour with a drop of enamel paint
8. Carefully fill in area to be repaired. Difficult joins may need several applications to complete. Avoid overfilling or dripping.
9. Block back cured repair with P800 W&D.
10.Remove masking tape.
11.Paint repaired area and overlap on to unrepaired area about 3 mm with colour matched cellulose dope. To match MG bakelite brown will need red, blue, clear, black and yellow dope, and talcum powder for the semi gloss effect. To gain a slight cloudiness effect, can be achieved by increasing humidity during application and drying.
12. Cellulose dope application best done in low humidity, warm environment about 22 degrees.
13. Cellulose dope application does not require sanding between coats, the dope dissolves in to itself. When applying, ensure dope has not dried too far, and go over each area only once per coat using with a good brush.
14. Allow to dry, can be recoated quite soon between coats depending on how good you are at painting with dope.
15. Mask off area repaired. Buff paint down with P800, then P1000 and then P1200 W&D until seam almost invisible.
16. Clean whole unit, and lightly polish.
The dope finish is resistant to chipping, and has a texture and appearance very close to that of bakelite.
|
|
|
Bruce Sutherland
United Kingdom
1545 Posts |
|
|
LewPalmer
USA
3209 Posts |
Posted - 21/03/2016 : 23:41:43
|
Superglue can be used for repair.
It is possible to repair broken bakelite in a way that is very hard to detect. The first thing is to make solid joints and if you are lucky, you can piece the bits together and glue them in place with superglue (cyanoacrylate). Doing this slowly and carefully is the main secret; it may take quite a bit of 'dry runs' to get the three-dimensional jig-saw to go together properly. Plasticine will help keep the pieces together while the glue cures. For pieces under mechanical stress, superglue will probably not work; in this case you will need to use a modeller's drill to make holes for inserting short pieces of wire to pin the joint in several places. A traditional slow-setting epoxy glue such as Araldite is used to make the joints and this can be built up behind the joint out of sight to give added strength. When nearly set, surplus Araldite can be trimmed away with a sharp blade. An alternative method which also has a lot to commend it is the use of glass-fibre cloth and resin (bonding paste), as used for patching car bodies. The materials are used on the inside of the case to be mended and the trick is to use a file or grinding tool to thoroughly roughen the surface. Using a putty knife or wooden spatula, the roughened area is then covered with a thin layer of resin (about 1/16th inch thick). A piece of glass-fibre cloth is then pressed on, smoothed out and left to cure. Once fully set another thin layer of the bonding paste is spread over the cloth for extra strength. This can be sanded for a smoother finish if desired when cured. Yet another possibility is Loktite BlackMAX adhesive, which is a cyanoacrylate that has rubber dust loaded into it. This helps the impact resistance and also gives a black colour. Some hairline cracks will remain and these can be filled with the self-curing black resin body-filler paste available at auto accessory shops. Once cured you can use very fine wet-and-dry paper (as used for car body work) to smooth the joints until they can no longer be seen or felt. Finally polish with Paste Polishing No. 5 (Baykobrite). For brown bakelite you could mix artist's powder paint with clear epoxy glue but be sure to mix in the powder extremely thoroughly.
Lew Palmer
PA1169, PB0560 |
 |
|
|
DDMDSN
New Zealand
329 Posts |
Posted - 22/03/2016 : 09:28:02
|
Good information, the seems to cover the subject well.
I guess it is what works, and care in preparation and application is important in all cases.
There is also a move away from the original materials such as phenolic based resins, as these are highly toxic.
The main problem I have found with superglue is it is also extremely good at gluing your fingers together.
It would be great to see some examples posted of the results of the handywork.
Footnote, it is easy to find that bakelite used fillers to give it strength and the various heat and insulating properties. By itself it is quite brittle. Dare we ask what filler was used in MG bakelite. Might also pay to take care and use safety equipment if sanding or grinding it as a precaution.
Donald
PB0759 |
|
|
| |
Topic |
|
|
|
Forum Locked
Topic Locked
