I use an air operated 2 3/4 (70mm) disc sander, it is the best thing I have used to pre
polish.
I only use 120-400-600 discs ( I don't know if these grits are internation) that velcro on
and use it all the time for ally staino and steel on flat & tube, I fuckin love it!

 

Best to let them do it if you want a quality job.

 

my plater charges extra if you polish it first. he says takes longer to correct my errors than for him to do it right the first time.

 

X2. Make sure there's no big gouges in it and they do the rest. The process is critical and they want to do it their way or no warranty.

 

Unless you are getting a "deal" from a plater you know, they probably won't discount it any, and may charge more as stated. Call the plater and ask. I am sure they will tell you how they want it!

 

i have always metal finished my parts before chrome. I start with files and 36 or 60 grit rolocs, finish with 180 on a DA. i am not trying to polish the parts really, but to make sure there are no pits, bumps, dents, casting marks, etc, that they might miss at the chromer. Always had great results, but it also depends on how you use these items. IT's mostly for my peace of mind since i sent hours and hours making whatever i am about to get plated, but i have no complaints so far...
Body shops don't do free bodywork before they paint your car or bike, so why would a chrome shop polish your stuff for free...but what's done beforehand sure affects the outcome.

 

I agree it's your responsibility to get the piece in shape for the polisher/platers, even if you point out a flaw and give the owner specific instructions to fix it, by the time he tells his lead guy who tells is polisher who tells his grunt sander, it gets lost in translation and they just plate over that weld.
and then they smile like candy chewing retards when they hand you a box containing 75% of the parts you brought in.

 

usually i let the chromer do it. i usually bring them nicely finished parts,but not polished. my friend just had a frame done at a new place ,it came out just as nice as our usual spot,and was cheaper. if the parts are polished its cheaper still.there's a couple places around here that do that for certain projects. i need that. 3700.00 was the last quote i got for one small triumph from the place i've been using for years.

 

It's kinda like guys that do there own "body work" thinking they are going to get a break on there paint job when they take it into a shop. When a painter or plater is going to put there name on a finshed product, they want to make sure it has a solid foundation first. They don't want to risk there reputation by painting/plating over who knows what.

Those guys do that stuff all day everyday, and have all the right tools and materials to prep it the way THEY want. Nothing wrong with sanding down the rough areas and welds, but thats as far as I would go as far as "prep."

Sixball

 

On sissybar stuff, it easier and probably cheaper to buy polished stock to start with. If I can't get it, I'll rough polish the stock before I start bending it up. I hope it helps a little.
Larry T

 

actually they're not plating over who knows what. they did'nt make or weld the parts,and you can tell by looking at something in bare metal if its a pos. if the polishing is done right it's not uncommon for a shop to do a plate only or do touch ups where needed and adjust the cost accordingly.and actually,unless your're polishing the parts yourself,chrome shops don't generally like you to grind the welds in my experience. mike raised the point about warranty,and that concerns me more than anything else about the platers on this thread. i don't do bodywork,but i also don't use bondo everyday. i do however make things out of metal everyday. can we hear more about tools,grits and processes ? tips,tricks and techniques? i remember patina turner saying he cut his discs a certain way...

 

...i do however make things out of metal everyday. can we hear more about tools,grits and processes ? tips,tricks and techniques? i remember patina turner saying he cut his discs a certain way...

I've been a silversmith for 30 years, a steel fabricator for longer than that, and I just started making knives a couple of years ago. No matter what metal or what the final finish will be - bare metal, paint, plated - there are a few things that I've found to be universal.

1) BE PATIENT. nuff said.

2) Change your media like it was free. Belts, pads, sheets, whatever, it's never worth trying to make them last. When the media quits cutting, not only are you wasting elbow grease, but you're creating gouges and grooves with an uneven cut.
2a) Cheap media is a lot more expensive than the good stuff.

3) Increase grit value x2 each step. In very high grits you might go up in smaller steps, but you never want to go more than double the last grit. Again, it costs you time to try to skip steps.

4) If you can, sand/grind/file across the grain of the previous grit. It makes it much easier to see the scratches left from the last step.

5) Sand those scratches out! It will NOT blend in, and the paint probably won't cover it up... Nothing worse than getting to 600g and realizing that that 240g scratch is getting uglier and uglier.

6) It's awfully easy to go too far, and damned difficult to put the metal back. Files, the proper sanding blocks and mandrels, and a good straight-edge are your friends.

7) An old bladesmith gave me this tidbit and it completely changed the way I approach finishing and sanding:

You never remove a scratch or gouge. You're removing everything that ISN'T that scratch.

When you look at things from that perspective, the whole process makes a lot more sense.

Doc

 

If you have a plater in mind that you are going to use, I'd check with them as far as what they will accept. That was kind of pointed out earlier, that different platers have different attitudes when it comes to what condition they want the part when brought to them.

And as stated earlier, you may be wasting your time and money on materials prepping the part if the shop has to go over it again to do it "there way" and in turn costing more, instead of saving money. Especially on several parts of different shapes and sizes.

My "bodywork" analogy was simply an example trying to demonstrate that some shops want to do the whole process, versus trying to "jump in" and start where the owner left off, and hope for the best. Sometimes the little things you can't see because you haven't worked the part the whole way through can bite you in the ass, and shops don't want that.

Bottom line, all shops are different, so the best thing to do is ask the shop of your choice what there expectations are from you when bringing in the parts, and at that time, they can tell you what sort of grit they want the part(s) worked up to, or if they are going to charge you the same ammount regardless of the prep.

Sixball

 

^^ VERY helpfull info, Thanks!