# How to finish PA6 (alkamid, nylon)?



## stej (Jan 16, 2013)

Hi guys,

I tried to cut a slingshot from a sheet of PA6. It's great material and you can work with it the same way as with wood - rasp and file is your friend. Even sand paper can be used.

But I don't know how to finish it. I have a black sheet and after sanding (started at 60grit up to 1500 grit), the surface is still gray and not black. Also it feels like something with tiny invisible hairs.

On the other side when you cut it with knife or drill a hole, it's black and smooth, no hairs-like feeling. You can see the black holes from drill and next to the hole the parts treated with sand paper.

Any tips & tricks how to make it look black and smooth?


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## e~shot (Jun 3, 2010)

Check this Hrawk's video, I know it is different material but hope you can get an idea.


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## kobe23 (Jun 28, 2010)

direct fire exposure?


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## bigron (Nov 29, 2012)

:yeahthat:


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## stej (Jan 16, 2013)

Thanks guys, two good idea that might work. Will try. Also I came up with CA finish that turns gray to almost original black. So another option..


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## Viper010 (Apr 21, 2012)

Flame polish, or suspend by a metal wire and dip in a solvent bath. Acrylic handles on screwdrivers, for example, are often given a glossy finish by briefly dipping them in a bath of acetone.

Good luck, please post pics when finished.
Cheers, Remco


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## dannytsg (Jun 16, 2013)

Could always heat up an old flat head screwdriver over the stove and then smooth the edges.


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## Dr J (Apr 22, 2013)

Fablustre is one of the best polish along with white diamond. I also find that wetting the buffer helps a lot.


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## stej (Jan 16, 2013)

Viper010 said:


> Flame polish, or suspend by a metal wire and dip in a solvent bath. Acrylic handles on screwdrivers, for example, are often given a glossy finish by briefly dipping them in a bath of acetone.
> 
> Good luck, please post pics when finished.
> Cheers, Remco


Ok, the bath in acetone might be the most accessible I think. Will buy that asap and try it, I'm quite curious whether it will work.

Thank you.


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## stej (Jan 16, 2013)

dannytsg said:


> Could always heat up an old flat head screwdriver over the stove and then smooth the edges.


Currently I have nothing that is capable to heat the screwdrier up enough :/

Anyway, it looks like it could work. When possible I'll borrow some torch and I'll go for it.



Dr J said:


> Fablustre is one of the best polish along with white diamond. I also find that wetting the buffer helps a lot.


Dr J, could you please tell me, what Fablustre is? Also any link would be great. Google doesn't help me much.

Thank you.


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## Dr J (Apr 22, 2013)

Fabulustre is a polish which is used to put a quality finish on material like Black coral and plastics. I get mine from Rio Grande.

www.Rio Grande.com

Try it and let uus know how it woorks for you


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## Dayhiker (Mar 13, 2010)

I'm learning stuff here... love these threads. Please do come back and let us know what you do and how it comes out, stej?


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## Harpman (Feb 27, 2013)

Just go to any auto paint supply and get some rubbing compound. Get a buffing wheel, they even have them for your drill. Then buff it out. Depending on how shinny you want they make several different grits.


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## Dr J (Apr 22, 2013)

Great, I forgot about rubbing compoundi. In the early days we used rubbing compound and turtle wax to polish Black coral. Thanks for sharing!


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## stej (Jan 16, 2013)

Ok, ok, some great ideas. I bought aceton, but from what I have seen so far, it doesn't react visibly with PA6. I tried it with a scrap piece, not the slingshot itself yet.

Here is my offer: I have three slingshots with my design (you would probably find some similar already here as it's not easy to come up with something new). I wanted to share the result with nice finish, but changed my mind. If anybody from you thinks he is able to make a good nice finish, then select one of the slingshots on the pictures and post here. I'll send it to the first one.

I have the requirements:

1) you will share your findings. If you destroy that during your tests, I'm ok with it.

2) if you don't like the sape, just give it to somebody else so that it doesn't sit somewhere in a drawer 

I originally wanted to glue either leather or wood on the flat surface that's why I don't care about it right now. You can see white spots. It's because I had a paper pattern glued with CA onto the slingshot so that I see the shape. After that I sanded it a little bit away.

That's all.


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## stej (Jan 16, 2013)

I forgot one interesting finding - I tried sanding with paper wrapped around the file and used decent force and sanded in one direction. Then it appeared that the surface wasn't grey anymore and started to be nice and smooth and almost shiny. The sand paper was maybe about 240grit. Tried that later, but didn't work again.

Later when I experimented with ordinary paper wrapped around a steel bar, it gave similar results, but not as good as in the first case.


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## PorkChopSling (Jan 17, 2013)

Stej, I would love to give it go. I some compounds I can try on it.


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## Dr J (Apr 22, 2013)

As promised , I decided to give it a try.. I used started sanding with 240g and found that too aggressive so i move through the grits 389, 600 and eve that was cutting more than t wanted. The i found the cubby hole in my brain where this experience was stored and remembered what I did in the past, the disk was spinning too fast, on slowing it down,I was able to get a reasonable sanding job. Then I polished it with Tripoli, then a Rio Grande product called Sun sheen.


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## ash (Apr 23, 2013)

If I was going to abrasive-polish it, I would go about it more or less the same way Dr J has described. My usual sequence:


Sanding with 120, 180, 240, 320, 400, 600 grit dry sandpaper. 
Wet sand with 1200 grit sandpaper in water.
Polish with a cotton buffing wheel and Menzerna Fine compound, Tripoli or similar
Glaze with Star Polymer, 3M Imperial hand glaze or similar

Nylon isn't the ideal material for polishing, though. You may never get it as glossy as Dr J's PVC one above. It's pretty much impervious to solvents like acetone. You'd need something pretty dangerous to glaze the surface.


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## stej (Jan 16, 2013)

PorkChopSling said:


> Stej, I would love to give it go. I some compounds I can try on it.


Sent a PM.


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## TimR (May 22, 2011)

I just found a white cutting board, half inch thick, in a thrift shop. I don't know what that would be made of.

I cut a couple of different PFS's and a Ferret Hunter. It is easier to shape than wood, I think.

Experimenting on some scrap I found a heat gun would soften the surface up enough to let it smear. Maybe something like a heat gun on a stand and a butter knife might get a good surface.

Also I tried my wife's potato peeler. That seemed to give a shaving leaving a clean surface but I didn't dare use it long for fear of ruining it. Can you resharpen those?


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## ash (Apr 23, 2013)

White cutting board is probably either nylon or HDPE, depending on manufacturer and quality level.

I reckon the usual potato peelers are not easily resharpened, but then potatoes don't really put up as much of a fight as cutting boards do :lol:


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## stej (Jan 16, 2013)

Today I again found a while to experiment. As I still don't have anything to heat it up, also acetone didn't work, I continued with dirty tools. Sand paper again, from 60 to 1000 grit and then I tried a buffing wheel like this










I couldn't press too hard because the drill started vibrating. Maybe some bigger (more loose) wheel would work better. I used some green past as the polishing stuff for the wheel. After some time it started shining. Still a little bit dull, but I would consider this parts as finished.





















I also buffed (by accident) part of the slingshot where I tried CA glue and I was surprised how shiny it was. So it is definitelly a way - sand maybe to 400grit, then CA glue and buffing wheel. Will try that maybe next time.


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## Dr J (Apr 22, 2013)

Great , why not try the following sequence. Sand then buff with cotton buffing wheel using rubbing compound used by car body workers followed with green turtle wax and see how that turns out. Before all the fancy polishing compounds, we used this system to polish Black coral to a super shine although I have not tried this method on the material you are trying to polish, I am certain it would work and it is cheap. If you are using a Dremel with adjustable speed control try slowing it down. Sometimes very fast speeds create so much friction that the item does not polish as it gets too hot 
I am off island at this time, but when I get home I will give it a try.


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## PorkChopSling (Jan 17, 2013)

Thank you Stej for letting me give this a try. PA6 is a very unforgiving material in some ways, I started with a fine sanding drum on my dermal, and I found that at high speeds the material did not react well, it peeled/melted or created dents. It was better at slower speeds, and made it a dull shinny. On the sanded parts I tried some buffing compound a redish brown one that came with my dermal which says it is for metal and plastic buffing and a gray one I use to use on buffing up old pocket watches (old hobby). The redish one left a copper tone on the PA6 epically on what looked like tiny little scratches left by the sanding that was not apparent until the red/brown compound was used on it. Not bad, but not shiny. The gray one was a little better, but once again I can see tiny little scratches one the surface. I believe I need to fine sand it some more and even wet sand it. Pictures to follow, I just wanted to report on my attempts so far, more to follow.


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## stej (Jan 16, 2013)

PorkChopSling said:


> Thank you Stej for letting me give this a try. PA6 is a very unforgiving material in some ways, I started with a fine sanding drum on my dermal, and I found that at high speeds the material did not react well, it peeled/melted or created dents. It was better at slower speeds, and made it a dull shinny. On the sanded parts I tried some buffing compound a redish brown one that came with my dermal which says it is for metal and plastic buffing and a gray one I use to use on buffing up old pocket watches (old hobby). The redish one left a copper tone on the PA6 epically on what looked like tiny little scratches left by the sanding that was not apparent until the red/brown compound was used on it. Not bad, but not shiny. The gray one was a little better, but once again I can see tiny little scratches one the surface. I believe I need to fine sand it some more and even wet sand it. Pictures to follow, I just wanted to report on my attempts so far, more to follow.


I don't know how rough the fine sanding drum on Dremel is, but I use Ferm and there is only one sanding drum which is quite useful when used after rasp and file. But I also noticed that PA6 starts melting when I press to much or sand one part for a long time.

What grit is your sanding drum? Also could you post pictures of the buffing wheels you used?

Thanks for your experiments


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## stej (Jan 16, 2013)

Ok, I have to say that it's quite hard to get a decent finish with a sanding paper. It's because when using the sand paper, tiny hairs arise and they hide the scratches that have to be sanded. But suddenly they are not there. So without proper powertools it's quite boring and repeating process - sandpaper p80 - p600, try to polish. Oh, there are scratches, so again - P120 - p600, try to polish. Oh man, scrathes again etc. Also P600 is too rough, I guess P1500 is enough to get nice and shiny surface. But I'm quite fedup with this black PA6. The white one is probably much better as the scratches are not so visible there.


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## ash (Apr 23, 2013)

When I'm polishing I go to P1200 before polishing. Everything has to be perfect for that to work. I still don't think a thermoplastic would become properly glossy even then.

You could try sanding it to P320 and spraying it with gloss lacquer suitable for plastics.


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## stej (Jan 16, 2013)

ash said:


> When I'm polishing I go to P1200 before polishing. Everything has to be perfect for that to work. I still don't think a thermoplastic would become properly glossy even then.
> 
> You could try sanding it to P320 and spraying it with gloss lacquer suitable for plastics.


Yes.. I tried to polish earlier to see the scratches. Otherwise the scratches started appearing with P1000 and I had to take quite rough sand paper and start again. And this is what I don't like about it :/

CA glue works well also, but doesn't hide the scratches.

In case you would like to give it a try, I might send you a piece of PA6 and report then


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## Dr J (Apr 22, 2013)

Many years ago, when I owned a jewelry manufacturing and repair facility, we were often asked to replace or polish scratched watch crystals. We tried many products, but the one which consistently gave us the most satisfactory results was a product from Germany displayed below. I have not tried it on HDPE as yet, but I cannot think of any reason why it should not work. I think the key is that it was not machine buffed, it was rubbed on and then rubbed of with a soft cotton rag. A t-shirt should work admirably. I still have a tube fater all these years, I will give it a try with before and after photos. Then we will all know!


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## reset (Apr 13, 2013)

Used to polish the aluminum on by semi's with Simichrome and the mags on my pickups. Havnt seen that stuff in years. Had forgotten all about that stuff. It got so you couldnt get it anymore. Real good stuff.


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## Dr J (Apr 22, 2013)

Decided to do a quick test as promised. If it turned out well I would keep it, so I cut out a Bill Hays free template using a band saw. Used a rotary rasp then some sand paper 60grit up to 400 then simchrome polish. A bit of unpolished pipe is shown for comparison


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## Dr J (Apr 22, 2013)

For those who are interested the pipe is 12.5mm thick or about 1/2". It was cut from a 10" PVC water pipe. I also have 12" in white and yesterday I got a bit of 10" blue. I am promised black and grey.


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## stej (Jan 16, 2013)

Dr J, I think PA6 is different beast. PVC and HDPE feel somehow more soft for me so I think you can't compare them to PA6.. Anyway, thanks for the tip, I'll keep my eyes open


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## Dr J (Apr 22, 2013)

Ok, have you tried Color Restore? By hand, not on a buffing wheel. Earlier you said that the holes left by the drill was acceptable, have you tried a rotary rasp? They come in different sizes and are available from RioGrande.com.


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## TimR (May 22, 2011)

reset said:


> Used to polish the aluminum on by semi's with Simichrome and the mags on my pickups. Havnt seen that stuff in years. Had forgotten all about that stuff. It got so you couldnt get it anymore. Real good stufI


It's still around. We use it to polish the handbells at church.


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## trobbie66 (May 13, 2012)

Ive been watching this thread for a while and decided to try polishing diff plastics. Like on other finishes it seems a few coats of wax (on a smooth and dull) bring out the lustre. A little less dangerous than chemical solvents and fire. Give it a try !


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## stej (Jan 16, 2013)

One more try how to finish PA6 is here. I think it's nothing new, but might help for somebody's decision. After I saw my Bosch grinder, I noticed that the body is made from PA6 and probably sandblasted. So I checked what company around my city is able to do that and gave it a try. Here are the results:

They tried plastics, corundum and steel balls (probably 0.45mm).

Plastics didn't work, because it was softer than PA6.

Corundum could work after the steel balls. Corundum alone looks like this:









Steel balls:









And all three together:









(2 steel balls, 1 corundum)

I also noticed that the surface can be scratched easily just by my nail, anybody could explain this?

I tried to wipe also the surface just with a paper and the paper got gray color. I thought it was because of dirty steel balls, so I tried to wash out the mess under the water - that's the right slingshot (the handle, it's more pale).

As a result - it is interesting finish, maybe a good start for shiny one. And we are at the scratch again


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## Bajaja (May 13, 2011)

Wow, looks realy smooth. And what about firs steel sand and then corundum?

Možná bude to poškrábání nehtem dáno tím lehce "chlupatým" povrchem. Ty minichloupky se prostě zmáčknou. Věřím, že koumák jako ty vyzkouší očistit to lihem a vzít na to ještě smirek nebo něco... Každopádně vzhled je úplně suprový :headbang:

:cookie:

David


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## stej (Jan 16, 2013)

Reznik Krkovicka said:


> Wow, looks realy smooth. And what about firs steel sand and then corundum?


That was exactly what I have in my mind. Next time I'll go there, I'll check that out for sure


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