Slowing down a pneumatic die grinder

[carbon]

Hey, I'm not even sure what to search for, but here's what I was wondering about. I noticed that some air tools have a built in regulator, so you can slow it down. Like this Jet die grinder (look at the end, the twisty thing). The reason I ask is it looks like I should be grinding steel and bronze with my 1/2" carbide bit at about 8000rpm, whereas most die grinders run at 12000-30000rmp range.

Are there little devices that fit on the hose near the tool to accomplish this? That way any die grinder would have this ability.

I notice the bronze sort of 'burns' with the setup I use. And I searched for 'regulators' on the forum, but it seems that term means multiple things with regards to compressors.

 

[jakeb]

HF sells some little regulators that will go on the end of any air tool. I have one on my die grinder, helps a lot to be able to slow it down.

Not sure if I got the one I have from HF or not, but they are $5 there and probally about the same at other places.

http://www.harborfreight.com/brass-air-inline-regulator-32905.html

 

[alex71]

those little regulators (including ones that are built in to some tools) will slow the tool down, but at the expense of power. If you want a slower grinder, buy a slower grinder... unless the power loss doesn't matter to you.

 

[carbon]

Alex71, do you know of any that are ~8000rpm? I've seen RA die grinders at 3-4k rpm and 12k rpm, but nothing in the middle. Heck, maybe that chart that I linked to is phooey.

those little regulators (including ones that are built in to some tools) will slow the tool down, but at the expense of power. If you want a slower grinder, buy a slower grinder... unless the power loss doesn't matter to you.

 

[nate379]

How about don't hold the throttle on it wide open?

 

[alex71]

Alex71, do you know of any that are ~8000rpm? I've seen RA die grinders at 3-4k rpm and 12k rpm, but nothing in the middle. Heck, maybe that chart that I linked to is phooey.

I don't know of any offhand, but someone probably does. Now that you mention it, that chart does look a bit odd. I've never worked bronze with a carbide bur, but I can tell you that carbide burs are typically good for anywhere from 30K to 100K rpm, depending on size...

 

[carbon]

How about don't hold the throttle on it wide open?

Ya, it's tuff to do that when you're pushing the grinder around for an extended time. Easy to have the tool get away from you. I've got a ton of flashing from the foundry that I have to remove

 

[billw9]

Buy yourself a pneumatic flow control valve. These are commonly used in industry to slow air cylinder speed and should work for a die grinder.

 

[DanCo]

I have 1 from Matco pn# AR335. I forgot what I paid for it.

Air Regulator
*Increase or Decrease air pressure as required
*Eliminates line pressure drop at tool
*1/4 male x 1/4 female NPT