[solved]Cox "Plastic" cleaning

Thanks for the quick reponse Ken.

I am very familiar with the chalky finish although not certain that it is entirely sunlight. I have quite a few of these parts which I would describe as faded (pinkish) which I think is sunlight but I put one of these in the dishwasher and it came out "chalky".

I did some research in delrin and it was originally used in "plumbing" systems but after a period of time broke down after exposure to hot water and particularly chlorinated water.

Delrin's resistance to fuel - especially glo and diesel fuel is remarkable but that seems to be the drawback in repairing or cleaning it. I have had qite a bit of success repairing the cracks using hot shim material to melt the two surfaces but you have to be very, very quick swiping the hot shim and squeezing the joint together. I have found one glue that works but it is white and can be seen afterwards - a plastic epoxy adhesive. Easy to trim of the outside but very difficult to remove from the threads inside - even using a tap. The glue is stringer than the delrin and the tap has a habit of ruining the delrin threads preferring to cut the delrin rather than the glue.

A friend of mine has had some sucess in polishing Cox plastic parts. Here what he send and before and after pictureThe process is as follows:
Start out with a grit of sandpaper that will sand the scratch out. Work gently with very light pressure on the sandpaper against the plastic. Always wet the plastic part or the sand paper first. I work with the wet-sandpapers usually and you can buy types of wet sandpaper that have a plastic film backing, but the paper backing types work better because it is more flexible which makes it a whole lot easier to sand smoothly around radius's, etc.
The goal is to just barely sand out the scratch or scratches, but no more. Now, change sandpaper to a higher grit count. I usually work my way up to the 600s to 800 grit or more. Remember to use water and very light pressure on the plastic part. When the last grit is used in this process, only the weight of the sandpaper itself, should be applied to the plastic.

Now, two other products come into play:
Meguiar's Mirror Glaze, and an old cotton tee-shirt. Apply the Mirror Glaze (shake bottle very well first) to a small area of the Tee-shirt with the Tee-shirt wrapped around your index finger or thumb kind of tightly. Using your index finger or thumb, rub the Mirror Glaze onto the plastic using back and forth linear motion. Small rapid but consistent motion is required along with even pressure applied to the plastic part. This motion will cause the plastic to heat up (I have burnt my index finger many times before trying to get out stubborn scratches). MAKE SURE THAT THE Tee-shirt STAYS WET WITH THE MIRROR GLAZE, or else the tee-shirt will scratch the plastic. You have to get the plastic to heat up. The heat combined with the Mirror Glaze, combines to form a new surface on the plastic.

Now, after this process, get a "real cloth" baby diaper. The are very soft and finely woven. Cut a piece of the diaper away and use it as a small rag. Again use the same technique as described above, and you will literally get a "mirrored finish". It really can be amazing depending on how much work you put into it.

All this said, it's very much practice make perfect on this process.

Jesere,

Thank you for the excellent response and before and after pictures. My order for Meguirs Mirror Glaze went off 2 minutes ago. Immediately after reading your response and seeing the pictures.

Have fun with it and keep us posted. If you would edit the title of your post to show it has been updated others who have read the post will see the additional info.
Joe

Ian How did this work out for you?
Joe

jsesere wrote:Ian How did this work out for you?
Joe

I found that the black delrin polished up nicely, just by using the Megulars that you recommended.



but the red is troublesome



The black staining goes deep and fine sanding starts to remove too much delrin. In places it works fine but for some reason the black oil has penetrated the delrin quite deeply. The powdery finish comes off swiftly with your recommendation and fine paper but the oil stains???????? Still working on that one!

i haven't tried it, but i wonder if you couldn't use Dawn or like product, antifreeze, sonic cleaner, etc. maybe get it hot, short of boiling to get as clean as possible and the re-dye red?

Mark Boesen wrote:i haven't tried it, but i wonder if you couldn't use Dawn or like product, antifreeze, sonic cleaner, etc. maybe get it hot, short of boiling to get as clean as possible and the re-dye red?

Dawn is a product I am not familiar with - but I have tried ultrasonic, soaking in alcohol, turpentine, "back to black", swarfega and detergents to no avail. Water and detergent to boiling (must use pure water as delrin reacts to chlorine). Chlorine and alkaline cleaners destroy the delrin and so does putting them in the dishwasher.
I keep experimenting with the cracked 051 carb holders I have.

Thanks for the suggestions though.

This is another example - I have got the shine back but the staining is still there. You can also see a black line where the two parts join - sanding would spoil the fit.

I fully understand the refurb of many unobtainable or expensive Cox Delrin parts but you keep showing the grief with medallion carb bodies...brand new they are way too inexpensive for me to screw with clean n polish labor.

Am I missing something?

This might work just as well with other plastic parts. Wings etc.

fredvon4 wrote:I fully understand the refurb of many unobtainable or expensive Cox Delrin parts but you keep showing the grief with medallion carb bodies...brand new they are way too inexpensive for me to screw with clean n polish labor.

Am I missing something?

They are my practise pieces - it doesn't matter if I spoil them.

I'll definitely try brasso - never thought of that one. I will have to look at oven cleaners - never used one (an oven) in anger! So I've never had to clean one!