More abrasive questions

[md21722]

I think I have the 4.5" angle grinders down with the cutoff wheels, flap discs, and grinding wheels. These typically run at 12,000 RPM at have a bunch of power, typically around 1HP. But what about the polishers and finishers which typically run at 4500, 6200, or 9000 RPM with about the same power. What are they really used for? I suppose they'd be used for sanding discs.... But why would you use a 5" sanding disc when you can use a DA sander?

They have large "eraser wheels" by 3M and others that you can use to get rid of pin striping and double sided trim adhesive tape off. The ones at Wal Mart (made by 3M) are often meant to be used in a drill at no more than 3,450 RPM. Would you try to buy a slow speed inline die grinder for something like this as a drill alternative?

And what about wire wheels? I see they go from 1" to past 4". The 4" ones are often rated at 15,000 RPM. Do you really want to run them at max speed? Or are they better used at a slower speed such as on a 9000 RPM sander/polisher tool?

 

[need-a-bow]

What are you looking to acomplish? Higher RPM give you more stock removal. At work we use only resin fiber discs and surface conditioning discs on grinders. Depending on the manufacturer, surface conditioning(scotch brite) can go too fast and melt, leaving streaks or smears.

A DA is a completely different animal.

Sent from my SM-G900V using Tapatalk

 

[md21722]

I mostly want to know the right things to do things.

I have 3" surface conditioning discs rated at 20,000-25,000 RPM but they almost look like they were melting (maybe they really were) at 20,000-25,000 RPM. Plus others I've asked said speed kills. It seems like anything you put on a 3" wheel should turn no faster than 12,000 RPM regardless.

What do they use these lower RPM tools for?

I get that carbide burrs typically run at high RPM's but also hear that people turn the pressure down to 60 psi...?

Put differently, what do people use a 4500, 6200, or 9000 RPM disc sander? How would its use differ than that of a DA?

 

[md21722]

Another speed question,

I was making setup bearings with a 1" flap disc rated at 30,000 RPM. On a 12,000 RPM angle die grinder, the flap disc never turned dark. Then I made another set on a 20,000 RPM angle die grinder and it started to turn color, a little black in spots. Does that mean I should use the 12,000 RPM angle grinder or is the discoloration acceptable? It didn't look like the abrasive was melting.

What's confusing me is why these abrasives are rated at such high speeds but yet others suggest much lower speeds.

 

[Hypoid]

I do not find these questions to be abrasive.

Are there price differences in the different speed-rated discs?

 

[md21722]

Not that I'm aware of.

The general rule of thumb is the larger the abrasive diameter the lower the speed. But then you have a 2" and a 3" Roloc wheel both rated at 25,000 MOS but the die grinder manufacturers themselves say 20,000 RPM is for 2" and 12,000 is for 3".

 

[Hypoid]

The general rule of thumb is the larger the abrasive diameter the lower the speed. But then you have a 2" and a 3" Roloc wheel both rated at 25,000 MOS

Soooooo, they won't fly apart below the rated speeds.

For every Hoon that graces our planet, there are three "Attorneys" looking over his/her shoulder.

DISCLAIMER: Yes, P.T. Barnum affirmed the concept, long before I was born.

 

[need-a-bow]

2" discs are generally rated for 25000RPM. 3" for 18000RPM. 4.5" discs for your angle grinder are right around 13000RPM. Scotch Brite should be run at slower RPMs than coated abrasives. Also, most tools are rated for 90 PSI. We run all our tools at 90PSI with 3/8" air lines to get enough airflow, with FLRs to keep our air lines clear and lubed. The main thing to keep in mind is the SFPM (surface feet per second). Bigger diameter, slower RPM.

Also, Ceramic and Zirc discs will last much longer grinding steel than cheaper A/O discs.

 

[cal]

Call Tom at Grind Tool Abrasives and ask him these questions. He will give you great answers and some of the best products you can buy.

http://www.grindtoolabrasives.com/