The definitive guide to metal finishing

[neksmerj]

I'm thinking of writing a guide to metal finishing, drawing on resources from Forum members, and from what I've learned.

I have machine restoration in mind, from treating badly rusted components, through to newly polished, painted, or blackened parts.

Hopefully it will become a "sticky" for all our newcomers to easily access.

Do you want to contribute? If yes, probably better to send me your contribution via a PM, if that's ok. Else via the Forum.

I'm thinking of approaching James Groom, for his approach. I'll take him him a very rusty part, and watch how an expert goes about it. He will get something out as will the Forum. These posts finish up on Google.

What do you reckon?

Ken

[malb]

Glad that Jamie is still there and that you found him helpfull. He has probably 45 years of hands on experience, and absorbed about as much again from his father when he was learning. (He probably still is learning the odd new trick.)

We always found him very helpfull when it came to informal teaching and problem solving, but he was doing our contract polishing and getting us up to speed helped take some of the load off him. I could try and put a few bits together for your guide, but you would be better getting it directly from Jamie than getting it third/forth hand from me.

[neksmerj]

We all have different approaches to polishing machine parts.

What we are looking for is minimum effort for maximum effect. I can't be bothered going through various grades of emery paper, or what ever.

Dings I attempt to file out, then linish or a lick with emery paper.

If the part is rusty, I attack it with a Scotchbrite rough finishing wheel mounted on a tapered mandrel in the grinder. On the other end is a fine Scotchbrite finishing wheel.

The rough wheel produces a course satin finish, and will remove metal, so don't press too hard. The finer wheel produces a nice satin finish. These processes are done dry.

Off with those wheels and on with a stitched sisal wheel one end, and a soft sisal or calico wheel the other. Using the stitched sisal wheel and some black "Fast-cut" compound will produce a nice shine that almost looks good enough.

The satisfaction comes from using the calico wheel and some Green compound. This quickly produces a bright chrome like finish. That's it, simple.

The pictures show the handle part polished with rust, the other fully polished.

Do you have any tips you would like to share?


Ken

[Master Splinter]

Another tip or two would be on safety when using buffs - such as making sure the piece will fly off in a non-harmful direction if it grabs, and workholding - making sure there are no sharp edges or other points which could cut you if the piece is whipped out of your hands.

(Not that I'm speaking from experience here....cough cough cough....)

[neksmerj]

MS,

You raise a good point. Safety is vital. I've had many bits ripped out of my fingers, and for that reason, I always wear gloves of a light cotton nature, and glasses.

The gloves also serve to wipe off the bloom, and save the fingers from hot metal.

Ken

[Dave J]

And always polish away from sharp edges as shown below and turn the part around to do the other edge, or the part will be gone before you can say "crap".

http://www.woodworkforums.com/attachment.php?attachmentid=166865&stc=1&d=1302441550

It took me weeks to get the aluminium tray and other things polished on our 4wd show truck. Now a repolish takes about 5-6 days, but I still look like a coal miner every day after it.
I don't mind polishing small things, but doing big jobs are a pain. I have had a few guys come up to me that want their prime mover bull bars polished, and have offered $1,000 + but I refuse them because of the work involved.
Also stainless steel is a lot to polish from raw than aluminium.
It's not a job I would pick to do every day, my hat goes off to the fellow mentioned above.

Dave

[neksmerj]

Spot on Dave.

I do a lot of design work for boat fittings made in aluminum 6061. Unfortunately, these get made in China. They send the parts back mirror finished on all surfaces.

I do not know how they do it, the finish is perfect. A $200 dollar part here, costs $20 over there.

Sad but true.

Ken

[method m]

If you want an even better finish than a calico mop, try using a swans down mop to remove any "fog" left on your parts.

neksmerj, for that machine handle you posted, I would have used a lea wheel or grit wheel instead of a scotchbrite wheel. Just a different way to achieve the same result.

[neksmerj]

Pray tell MM.

What is a lea wheel or grit wheel? We all want to know.

Please expand on your reply.

Ken

[bollie7]

or the part will be gone before you can say "crap"
and anyone who has ever used a buff knows that "crap" is a lot faster than "ooh S**T"
:U
Has anyone else noticed that when this happens with a small part, it always seems to end up in the area that is hardest to reach under the work bench, even if the bench is at the opposite end of the workshop to the buff/grinder? Why is that?:~

bollie7

[method m]

and anyone who has ever used a buff knows that "crap" is a lot faster than "ooh S**T"
:U
Has anyone else noticed that when this happens with a small part, it always seems to end up in the area that is hardest to reach under the work bench, even if the bench is at the opposite end of the workshop to the buff/grinder? Why is that?:~

bollie7

It's the same physics as when you drop a buttered piece of bread, always lands face down.

What's worse is when you are just finishing a part and then it goes flying, putting more scratches or dents in it.

neksmerj, I will post up a couple of pics when I get home tonight.

[Gavin Newman]

It's the same physics as when you drop a buttered piece of bread, always lands face down.

But if you drop a cat it always lands feet first. So what happens if you spread the back of a cat with butter and then drop it?

[Dave J]

and anyone who has ever used a buff knows that "crap" is a lot faster than "ooh S**T"
:U
Has anyone else noticed that when this happens with a small part, it always seems to end up in the area that is hardest to reach under the work bench, even if the bench is at the opposite end of the workshop to the buff/grinder? Why is that?:~

bollie7

I left out the word I would have use to keep it clean for the forum.lol

I have the shed wall behind my buff, but when a part shoots out it always seems to hide somewhere.

For bigger stuff, I Have a thick steel plate that I bolt the grinder to outside. This keeps the crap out of the shed and lets me maneuver longer things like the side boards of the tray. If it's a cool day it also helps keep the grinder cooler after working for hours.


Dave

[method m]

What is a lea wheel or grit wheel? We all want to know.

Please expand on your reply.

Ken

Basicly, A lea wheel or grit wheel are soft sisal wheels that have had a coating of abrasive applied to them. They work well on cast parts or parts with different contours as they can flex and shape to that part to give a uniform finish.

So you can use any wheel that suits your application, thin, thick, large diameter etc..etc!

The picture below shows a "bar" of lea compound that you apply to your wheel and the sisal wheel in the picture had been coated with "grit". Basicly abrasive available in many grades that you glue onto your wheel to give the desired finish you are after.

http://img15.imageshack.us/img15/3719/photo0233xx.jpg (http://img15.imageshack.us/i/photo0233xx.jpg/)

The downside to using these wheels is that they take a bit of time to prepare for use, especially the grit ones where you must glue the abrasive onto the wheels and wait for it to set which is why some people don't recommend using these type of wheels.

here is a pic of a cast aluminium part we did using a grit wheel to smooth the casting.
http://img16.imageshack.us/img16/1729/photo0192c.jpg (http://img16.imageshack.us/i/photo0192c.jpg/)

In progress

http://img607.imageshack.us/img607/9537/photo0194e.jpg (http://img607.imageshack.us/i/photo0194e.jpg/)

And after sisal stage done, now that's a lot better.

http://img709.imageshack.us/img709/6136/photo0199lu.jpg (http://img709.imageshack.us/i/photo0199lu.jpg/)


Hope that helps

(http://img339.imageshack.us/i/photo0202o.jpg/)

[Com_VC]

What sort of buffer is needed? Do you want one with lots of HP? Also what RPM is best suited and would variable be an advantage? I wouldn't mind setting up a propper buffer, at the moment I have something similar to a washing machine motor with a tapered arbour I bought from H & F

Thanks

[method m]

Obviously, the bigger the hp of the machine, the quicker you will be able to polish and the larger diameter wheels you would be able to run.

Ideal polishing speed is around 2800-3000rpm so a variable speed machine would be good for adjustment of speed when using smaller or larger wheels but not essential.

When you are constantly stalling the motor or slowing it down by putting pressure on a wheel, then you know that you probably need a more powerful machine.

You will get the job done using a small machine, but it will take longer and will probably vibrate the whole workshop down if you try to run any decent sized wheel on it.



Lot's of good information here.

Introduction To Buffing and Polishing - Caswell Inc. (http://www.caswellplating.com/buffs/buffman.htm)

[eskimo]

But if you drop a cat it always lands feet first. So what happens if you spread the back of a cat with butter and then drop it?


haha...bloody hell.......I know the answer to that one..it hovers/oscillates between upside down or feet down:D

you know the same idiots I do