[fcastro]

Hi guys, I am in the process of polishing a set of aluminum wheels and have been reading about what the ideal speed to use us (3600-7000rpm) and what size wheel to use etc and now I need to make a decision as to what tool to get the job done. A polishing or bench grinder is out of my budget range. Aside from that I think it would be hard to use an 8inch wheel in a lot of the sections.

So with that said, I have found 2 mini-die grinder that say they have adjustable speeds on them. But the problem is they never say what the slowest speed would be once adjusted. The max speed is 25,000 which is way too fast for polishing. I was thinking 4"inch wheels and adjusting the die-grinder to 7000 rpm (not sure if that is possible)

Campbell Hausfeld PL1520 Pro 1/4" Mini Die Grinder:
http://www.amazon.com/Campbell-Hausf.../dp/B000Q5VHWO

Chicago Pneumatic CP876 Air Mini Air Die Grinder:
http://www.amazon.com/Chicago-Pneuma...4217277&sr=1-2

Anyone have any experience here as to speed and or which one is best? Or if this is even possible?

thanks in advance!

[oldred]

Any air grinder is adjustable by simply controlling the air flow however power drops with the speed. If you are going to use a die grinder to polish then you will need to use a small wheel at a relatively high speed. One problem with air die grinders, at least the ones that make any usable power, is they they require a LOT of air so you will need a fairly large compressor if you need to run the die grinder any length of time such as for polishing. Polishing with a small air grinder like that is extremely inefficient requiring several HP to run a compressor large enough to operate a tool that is only fractional HP.

[fcastro]

thanks for the reply oldred,

Wow I never even thought about that aspect of it. I have a craftsman compressor. I have never used an air grinder but basically from all the research of I have done. If I use a 4" wheel and can get the die grinder down to 6000-7000 rpm I am golden. But it sounds like you are telling me I can get the speed down but I may not have enough power because of air? (Sorry still trying to learn things)

Craftsman Compressor Specs:
150 PSI Max
6HP-2HP 33 Gallon
8.6 scfm @40 PSI
6.4 scfm @90 PSI

The Campbell Hausfeld Professional 1/4" Mini Die Grinder specs:
8.1 CFM
90 PSI

while the Chicago Pneumatic CP876 specs:
6 CFM
24 CFM (@LOAD)

Thats as detailed specs I can get from both grinders. What do you think?

[techron]

i agree with oldred, die grinders are air gobblers and will bog down you apply pressure. try useing a good adjustable speed 3/8 drill with a button to lock the trigger down, it wont spin as fast but you can apply a LOT more pressure. it will work good with your 4" buffing wheels and black compound.

i do a lot of polishing and i use
1 pedastal mounted buffer motor with long spindles and 10" wheels
2 drill press set to fastest speed and 4" wheels
3 3/8 drill with 4" wheels
all work fine, which one i use depends on the size and shape of the part.

[oldred]

The really bad news is that compressor is not nearly big enough to run a die grinder, not for more than a few seconds at a time anyway. In order to run a die grinder enough to do any kind of real polishing you would need at least 15 CFM and you would spend some time waiting even then, 20 CFM or more to run continuously. I know it hardly seems possible for a tool that small to use that much air but if you take one apart it becomes apparent that they are almost a free flow through the thing.

[Brian_B]

I am not familair with these die grinders, but I do know the air tools eat air. I have 5 HP with a 60 gallon tank and have to wait on it with some of my tools (and painting).

[fcastro]

Wow I am glad I decided to ask on this forum. Ok so its looking like the air die grinder is not an option now

High speed drill - I have looked into this and it seems I would need to find a drill that can do at least 3500RPM. I have yet to find a drill at places like sears that can do that speed. Online I found a few but they are expensive. Anyone have any pointers here?

I also own a DeWalt DW849 7"/9" Electronic Variable Speed Polisher. This can do 3000RPM but from looking at my 7" velcro wheels diameter and putting it on my wheels surface, most of the wheels surface (side grooves etc) it will not make good contact. Thats why I figured I need 4" buff wheels.

Also own a RotoZip (its like a big dremel for cutting things) but the lowest speed setting for it is 15,000RPM twice as fast as I need it to be.

This is a picture of the wheels I will be working on. I figure the dewalt can hit the flat areas but I don't foresee much success with the side grooves.


Its a shame a dremel can't hold 1/4" rods because I know they can spin at 3000RPM.

[oldred]

This was on sale a week ago for 39.95 and probably will be again shortly. Coupled with one of the Harbor Freight router speed controllers this would work a heck of a lot better than that air die grinder and no compressor needed!


http://www.harborfreight.com/cpi/cta...emnumber=44141

[Youngster]

Thanks for the tip on the HF die grinder. Even at 50 buks, it would be worth it. I've polished quite a few Intake manifolds. I use 180 grit DA sticky discs on a cut down rubber sanding block to rough them in. For tight areas, I use an eraser. Then some 220 grit. Next is my secret weapon. A 110 motor out of an old refrigerator with a flex shaft and 4", 3", 2" and mushroom buffs. Sounds like a lot of work,huh? The results are worth it. Your wheels would be much easier that the rough castings I start with. The point is the motor was given to me and I think I paid 20 - 25 buks for the flex shaft. For working alum., you only need 1700 -1800 rpm. For steel 3400 -3600 works fine. You are not going to get that out of an air die grinder. Electric is the way to go. The one other thing you need is patients, and lots of it.

Hope this helps, Youngster

[fcastro]

Hey guys thanks for the feedback!

oldred thanks for the tip. An elelectric die grinder with a router sounds like a good idea. However how do you guys feel about me just getting an electric drill instead? My thoughts are based on the fact that I will probably have use for a drill down the road.

I'm looking at this: Dewalt217 (0-4000 RPM)
http://www.toolbarn.com/product/dewalt/DW217/

I have had some serious issues trying to find a high speed drill. I figure at 4000RPM I can slap a 4" buff wheels (polishing numbers work out SPFM 0.25 x 4" x 4000RPM). All the other drills I have found run at 3000 or 3500 kind of odd I thought.

Anyone have any feedback about the drill idea?

[techron]

Originally Posted by oldred

This was on sale a week ago for 39.95 and probably will be again shortly. Coupled with one of the Harbor Freight router speed controllers this would work a heck of a lot better than that air die grinder and no compressor needed!


http://www.harborfreight.com/cpi/cta...emnumber=44141

oldred, because of the write up of that HF tool a few days ago i decided to get one. got a flyer in the mail and it was on sale for $29.95 and the flyer had a 10% off entire purchase coupon. the trip to HF was necessary because my mig quit feeding, upon further invistagation i found the wire spool was empty!! i picked up some wire and a few other goodies on sale and got 10% off those as well.

[oldred]

Originally Posted by techron

because my mig quit feeding, upon further invistagation i found the wire spool was empty!! i .

The leading cause of MIG welder failure!

[fcastro]

Hey just curious how do you get coupons via mail from Harbor Frieght? Thats a great deal!

[oldred]

Yep, get E-mail coupons about twice a week and just got some paper ones in the mail.