A GUIDE TO CHOOSING THE BEST GRINDER FOR METAL POLISHING
We often get asked by customers what is the best grinder for metal polishing? While this can heavily depend on your skill level, there are some clear favorites that can be the difference between your aluminum and stainless looking like a mirror, or your metal looking worse than what you started with.
The first question i would ask in determining what grinder is right for you - what is your skill level? For beginners I would strictly recommend a 3,500 RPM variable speed grinder. Variable speed polishing machines are great for adjusting your speed between the different stages of polishing. As an example, you will want to do your cut & color stage using a 9" orange airway and tripoli bar (cut stage) as well as 9" yellow airway with a Tripoli bar (coloring stage) at the full 3,500 rpm speed. With your final step of a 9" domet flannel airway and purple polishing bar, you will want to slow down the speed of your grinder to about 1,800 RPM, which is where this variable speed option is fantastic. In essence, you want a grinder that allows you the flexibility to control the speed and thus the ability to focus on getting a better finish. On your final show shine finish stage, slowing down the speed of the polisher allows better control and less opportunity to burn or haze the aluminum due to over production of heat from a faster RPM. For this we highly recommend the Makita 9237c or the Makita GA7021 which are both fantastic machines depending on whatever has the best deal at the time.
Once you are able to master the art of polishing (if thats even possible) with good pressure, the proper angles and the proper products, it's then time to step up to what the professional polishers use. Almost all of the professional polishers we know and work with use the Makita ga7021. This is a fixed speed 8,000 rpm buffer. Once a buffing wheel is loaded onto this buffer you will get an industry standard 6,000 rpm's. Most professional polishers run their cut stage (Orange wheel/tripoli bar) AND their color stage (Yellow Airway / Green Rouge) using this fixed speed of 6,000 RPM's. It is important to note that professional metal polishers will always go to a 3,500 RPM polisherwhen doing running a flannel or cotton buff so they can dial down the RPM's.
Below is a table showing the maximum safe operating speed for each size of buffing wheel:
It is important to note that we ALWAYS recommend using safety flanges when polishing whether you are using insertable flanges in place of center plates or exterior flanges that go on the outside of the buffing wheels.
All of the machines we discussed above have a 5/8" arbor shaft which is compatible with all of the 5/8" arbor hole airway buffing wheels we manufacture here at Renegade Products.
TOO LONG, DIDN'T READ ALUMINUM POLISHING MACHINE GUIDE:
Best grinder for professionals: Makita GA7021
Best grinder for beginner polishers: Makita 9237C
Absolute necessity safety flanges: Flanges
Best polishing kit with sanding supplies: Big Rig Restoration Kit
Best aluminum polishing kit for beginners: Aluminum Polishing Mini Kit