merziac

More great advice, we're not getting any younger or healthier.

rccardr 

Beat me to it.

Next winter project is affixing the hose from an old shop vac to the large cardboard shroud I use around the buffer when wailing away with it indoors. It can be a very messing bunch of fiber flinging. Or flanging.

dddd

I think that you'll find that a three-speed switch has more than two wires going to the motor, exclusive of any ground wire. So the motor really has to be made for this sort of hookup.

That said, I have a big, waterproof AC motor that was destined for a wet-sander apparatus, and as I recall it can be wired for two different speeds, something like 3900 or 1850rpm.

So I suppose one might be able to create a switch setup that might allow on-the-fly speed changes.

I think that this is also related to the motor's optional (110/220v) voltage input, but it's been over 20 years since this motor was given to me when a sub-branch of a company I was working for closed operations and liquidated equipment post-haste to make space for other uses.

Notice how drill presses typically use a stack of different-size pulleys to allow speed adjustment, rather than altering the AC input power. This is because an inexpensive motor can make good torque efficiently when it is kept as a simple single-speed motor.

scarlson 

Yeah, a bench grinder is probably some sort of induction motor, which means it's brushless and it runs at a speed dependent on the frequency of the alternating current being fed into it, rather than the voltage as on brushed DC or AC/DC motors. Fan motors are often like this too, and the speed is changed by looping in different combinations of windings. Tesla cars and some machine tools use this type of motor, but they have either variable speed transmissions or variable-frequency electronic drivers, which take DC from batteries or AC from the wall and convert it to whatever waveform you want to drive the motor at a wide variety of speeds, using the magic of transistors. I bet you could make something simple to control the speed of an induction motor using some MOSFETs or thyristors and an Arduino, but it would probably be a pain and require extensive troubleshooting.

smontanaro 

Thanks for the introduction to AC motor properties. I guess I will just use it at 3600 RPM and be extra careful when starting out to avoid ruining whatever I'm polishing or myself.

big chainring 

Maybe a diamond tread tire. Clement made a tire long time ago with a diamond tread. I think that would bridge the gap between gravel grinder and road buffer.

bazil4696

Polish it up like chrome! Keep the cloth wheel wrapped in a baggie to prevent dust contamination between sessions. Rake the wheel often to keep the buffing compound fresh. I just used the tang on and old file. I never got really good at polishing aluminum, but black and white compound seemed to work.

OTS 

Coming from the dental field we had an expression in school, "if it shines, it flies"
I have a Baldor Polishing Lathe that runs at 1725 RPM in low and 3450 RPM in high.
My bench grinder runs at 3450RPM.
So if your using your bench grinder you are just running on high.
A few polishing tips:
Keep your rag wheels separated, don't use your green compound rag wheel for your red compound polishing.
Each compound gets their own separate wheel.

Tapered Chuck

Splash Hood

You can sometimes find a used splash hood/splash tray on ebay for cheap, it helps confine the mess.
Splash Hood
A Lathe tapered Spindle Chuck makes changing rag wheels quick and easy.
LATHE TAPERED SPINDLE CHUCK

gugie 

Here's my setup.



See the mess. the little vacuum and plastic thingie are pretty much useless. I plan on building a 2X4 "booth" around it with a large fan and filter.

Chr0m0ly 

Fixed it for yeah! 😉

USAZorro

Let me know what wheels you find that will fit. I got a grinder with the same size wheels as your for this very purpose, but I bought 6" polishing wheels thinking there would be clearance... um, no.

Olefeller77 

One thing I don't recall being mentioned is- Do not try to push your work hard into the buffing wheel. Let the compound do the work. Harbor Freight has the polishing compound bars. A full bar should last you a couple lifetimes. lol

elcraft

Well, I was going to chime in about RPM and the existence of the tapered screw spindle, but you beat me to it. My experience is based on the Jewelry trade; a step sibling to the Dental trade. I would make only a couple of additional comments, though.
The Baldor polishing lathe you have pictured, has, tapered shafts to allow for quicker spindle changes. The grinder motors will usually have threaded, straight shafts ( left hand threads on the left side) and are no where near the quality of a Baldor or Redwing Dental lathe.
Tapered screw spindles, for use with grinder motors, are available through jewelry suppliers. They should be ordered to match the spindle shaft diameter ( usually 1/2" , 5/8", or very occasionally 3/4"). They are specific to which side of the motor they will be turning on, i.e. Right or left hand threading on the tapering screw thread to keep the buff in place. They are usually secured to the grinder shaft with set screws or grub screws. The buffs for these tapered screws are often reinforced with shellac, leather, plastic, or lead. The standard buff you might get from Harbor Freight or Sears is usually designed to go over the 1/2" diameter shaft- the hole is a tad too large, and will try to run up on the widest part the taper screw. That may move the buff too close to the motor housing to allow for adequate maneuvering of the part being polished.
The grinder's speed should be 3450 or 3600 rpm. If the grinder is only the 1725 rpm, super high polish finish is difficult to obtain.
In Jewelry Polishing, there are usually two Steps or compound changes; "cutting/buffing" and "coloring/polishing". Cutting compounds are Tripoli, Bobbing, Emery, etc.. They remove sanding marks or rubber compound wheels finishes. Polishing compounds put the final high gloss finish on. Polishing compounds are red rouge ( for gold colored metals) and white or green rouges for white or silver colored metals. As described , the buffs should be used only with one compound. Obtaining a high luster is difficult if one skips the initial cutting/buffing stage. There are specific cutting compounds designed for stainless steels and non ferrous metals and precious metals, as well as aluminum.
In my set up, I actually use a grinder motor that has been stripped of grinder wheel guards. I tend to use bobbing compound to cut with ( less heat build up than Tripoli or emery) and Green rouges (usually crocus based compounds) for aluminum or steel high polish.
I have used Jewelry specific terminology here and in no way mean to "correct" or dispute your terminology. I do contend that using Jewelry suppliers rather than Dental Lab Suppliers, will probably be more economical and adaptable for BF members, though.
Good luck!

speedevil 

Sorry I'm a little late to this party. So you've expanded the bench grinder's repertoire by using accountrements?

rccardr 

HEY, hey hey! Enough of that dirty talk here!

Hudson308 

Reminds me of when I was chatting up Jimmy Shine at a car show. He once had a Hudson Super Wasp that was previously owned by Steve McQueen.
When I mentioned the provenance he said "the what?"
I said "the provenance".
He said "the what?"
I said "the uh... history".

And just when you think I'm going waaaaaaay off topic... we were discussing some aluminum I had polished with a converted grinder.

Polished cast aluminum intake and cylinder head

smontanaro 

I ordered these:

https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1

They haven't arrived yet.

WRT the tapered screw spindle, I wasn't able to easily find one which would mate up with the existing 1/2" spindle. For the time being I will just suffer with slow changes. In any case, I think the buffing wheels would sit outboard of the existing small shroud on my grinder.

elcraft

These should work for 1/2" shafts:

https://www.amazon.com/Spindle-Adapt...45&s=hi&sr=1-2

I highly recommend Loc-title or similar to secure the set screws. Vibration from polishing being more than you expect. WRT those cloth buffs, there is a process of dressing them down to run smoothly. One should scratch them up with a file tang
(evenly across the buff) while spinning at speed and then some careful scissor trimming (like a beard) to remove hanging strands that leave lines in the high polish finish. A piece of coarse sandpaper (60 grit) held against a rigid board or plate will smooth the last bit out. Depending on the manufacturer, the buffs may run more smoothly if mounted in a particular orientation. Once they are dressed and running smoothly, Mark the direction of rotation with a Sharpie- you will thank me later....

crank_addict

Fortunately have access to all levels of high end finish grinding to buffers but its way overkill for bike components. Machine buffing bike parts is useful for only 1% of the time.

One can take out some heavy gouging and scratches by hand and incremental grit sand paper. Get to the 1000 grit and then final hand rub with Mothers aluminum polish. Really doesn't take much effort, pretty clean procedure, far lower cost and you have better control vs holding at spinning wheel.

Often seen by novice buffers is a ruined or overdone part.

seypat

I've heard, or maybe read somewhere, that if you go to your local peeler/pole swinging joint, you can get a bump/grind and something buffed all at the same time.

madpogue 

Same warnings apply - don't get your buffers/compounds mixed up, and watch those RPMs.....