Powder coating..

General cycling advice ( NOT technical ! )
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V4281051
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Joined: 5 Jan 2007, 8:21pm

Powder coating..

Post by V4281051 »

I am shortly going to have my old Trek touring bike powder coated..should I leave bolts in the cantilever bosses and in the bottle cages and mudguard/ carrier bosses..?
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simonineaston
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Re: Powder coating..

Post by simonineaston »

No.
S
(on the look out for Armageddon, on board a Brompton nano & ever-changing Moultons)
V4281051
Posts: 158
Joined: 5 Jan 2007, 8:21pm

Re: Powder coating..

Post by V4281051 »

What is to stop the powder melting into the cantilever bosses and threads of the braze ons?..And even the bottom bracket threads?
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gazza_d
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Re: Powder coating..

Post by gazza_d »

The powder coater will mask off the threads and bosses for you
They are probably used to bikes and motorbikes, certainly the ones I've used have been.
If in doubt then mention it when you visit.
Pneumant
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Joined: 7 Oct 2010, 8:25pm

Re: Powder coating..

Post by Pneumant »

Hi, Yes you need to cover the threaded parts to keep clear of powdercoat. Use masking tape and tape over all the bare metal part of the bosses. Same applies to the forks. Leave loose sacrificial bolts in mudguard eyes, brake & bottle bosses etc. Use old traditional BB cups in the BB. I would leave slightly loose and mask off the right cup facing edge and axle holes. Job done!
robc02
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Re: Powder coating..

Post by robc02 »

Ask your powder coater. The one I have used specifies that you must mask off any areas that you don't want coating.

I put bolts in all internal threads and mask or block plain surfaces that I want leaving clean. For instance I use a piece of threaded rod with nuts and large washers on either end to stop powder getting into the head tube. Also don't forget that blasting grit will get into the smallest of gaps and will be very difficult to completely remove.

If you don't do this and the coater doesn't do it for you, expect to spend several happy hours using taps, dies, reamers, files etc. while pondering how long this is taking compared to a bit of masking.

An ounce of prevention is worth a pound of remediation... or something like that.
Campag
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Joined: 2 Dec 2018, 8:04pm

Re: Powder coating..

Post by Campag »

I've used a local powder coating firm a few times to restore old frames. Worked very well maybe because I :

- explained which parts needed masking off (bottom bracket, threaded bosses etc) when handing them over to the receptionist
- also marked these with insulation tape / cardboard tube in the bottom bracket as a reminder

Excellent results - I have some 40+ year old frames that are looking as good as new and didn't require any cleaning of the threads because they had followed the above requirements.
PH
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Re: Powder coating..

Post by PH »

robc02 wrote: 7 May 2021, 7:59pm Ask your powder coater.
Is the correct answer!
It may depend on their stripping and preparation methods, they may use silicon bungs to protect threads which come out cleaner than a fitted screw. Also depends who you use, not all powder coaters are the same and it's not always reflected in the price. I prefer to use companies with a lot of cycle experience, I don't mind paying a bit more for that.
WrightsW5
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Re: Powder coating..

Post by WrightsW5 »

Yes, it depends, some will coat whatever you hand over as it is, so if you don't mask it , it will coated. And I have heard of those with no experience of bicycles, sandblasting through a frame tube when getting the old paint off.
borisface
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Re: Powder coating..

Post by borisface »

I had a frame powder coated a few years ago. The threads were fine as was the overall finish and it still is. However, the powder had been applied quite thickly. I didn't think this would be a problem until I tried to fit the wheels. The diameter of the front and rear dropouts had been reduced so much that the axles wouldn't fit. So the first thing I had to do was get a file take away some of the paint on the inside of the dropouts.
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horizon
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Re: Powder coating..

Post by horizon »

Personally I think it also worth asking whether the powder coat will be applied directly to the bare frame or there will be a primer coat.

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scottg
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Re: Powder coating..

Post by scottg »

borisface wrote: 10 May 2021, 10:08ams[snip] So the first thing I had to do was get a file take away some of the paint on the inside of the dropouts.
And if you are using horizontal drops, mask off the outside where the q/r contacts,
I had a slipping wheel till I got down to bare metal.

So much simpler in the days of dip tanks...... :)
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