Airtool... how can I decrease RPM without decreasing torque?

[Dadnatron]

I have a project in which I need a 'die grinder' type device for power, but I don't want the RPM of a typical die grinder.

I am looking for something to power a cutter which I am designing, but need the RPM to be drastically lower. Tho RPM on the tools I have seen are in the range of 13-20K and I am looking for something in the 500-1000 or even less range. (At least at this time.) However, I still need to keep the torque of the machine to run the cutter. I am afraid, although I don't know for sure, that the high RPM will cause too much heat in the foam I am cutting. (memory foam type material)

I am not familiar with airtool workings. I have and use several, but that is it... I use them. The most I do to them is oil them.

I suspect there is a way to decrease the RPM via orifice reduction etc. But I also suspect that would drastically decrease the effective torque. Otherwise, I suspect I would need to change the internal 'gearing' in some manner, which I am willing to do, if it is reasonably accomplished by a 'novice'. I am pretty handy, and not afraid to take on a task, and I am willing to 'sacrifice' a few HF tools in order to give it a try. But, I don't know where I'd begin.

If you know of a die grinder/cut off tool with either a variable speed or MUCH lower RPM, that might work for me without necessitating all the hassle. I also don't know whether simply turning down the air pressure would decrease speed without torque, although I would think both would be affected.

Straight cutters, saws, hot wires, etc will not work.

I need to be able to slow down a cutoff wheel machine or something along those lines. Something similar to or along the lines of the pic below.

 

[4570Man]

Maybe use an air drill that already turns slower? I don’t know of any way to slow an air grinder without loosing toque short of an external gear box.

 

[bcp]

700 RPM, $26

1/2" Reversible Air Drill

Bruce

 

[Industrial Toys]

I have a large variable speed dremel. But, even variable speed (110V) electic tools lack power when you slow them down as there is not a feedback circuit.

 

[RNeumann]

700 RPM, $26

1/2" Reversible Air Drill

Bruce

I have a simple inline valve that allows for fine air flow adjustment. But it doesn’t really work well to adjust RPM- it seems to either spin or not spin as opposed to being variable speed.

My thought was exactly what is posted here- find a tool with the correct RPM.

FYI- I thought most foams were cut with an electric knife......like the old school knives you used to cut the turkey with.

 

[Dadnatron]

The drill might work... but my issue is the handle angle will get in the way of my cutter. If I rotate it out of the way, then my control on the cutter requires 2 hands which takes away usefulness. Otherwise, I could just use a cordless drill. But I wonder whether I could scavenge the guts of the drill and move the important parts to a die grinder or cut off. perhaps just the gearing etc.

I was reading and it appears there might be the possibility that a flow valve will decrease the RPM while maintaining torque. But I'm not sure. Any recommendations on good types of flow valves which maintain constant pressure?

Air Motor Selection and Sizing | Hydraulics & Pneumatics

• Air motor speed can be regulated through simple flow-control valves instead of expensive and complicated electronic speed controls.
• Air motor torque can be varied simply by regulating pressure.

 

[4570Man]

I doubt the drill has gearing except for the right angle gears. I imagine it’s a similar concept to a hydraulic motor where you use a bigger displacement motor in relation to the flow to go slower.

 

[bcp]

There are in-line air drills.

Here's the first I found. It costs a little more than the HF drill.

https://www.intlairtool.com/dotco-inline-drill-15lf085-40-0-4-hp-3-8-24-e-drill-diameter-capacity/

More:
In-Line Air Drills - Grainger Industrial Supply

Bruce

 

[aczlan]

The drill might work... but my issue is the handle angle will get in the way of my cutter. If I rotate it out of the way, then my control on the cutter requires 2 hands which takes away usefulness. Otherwise, I could just use a cordless drill. But I wonder whether I could scavenge the guts of the drill and move the important parts to a die grinder or cut off. perhaps just the gearing etc.

I was reading and it appears there might be the possibility that a flow valve will decrease the RPM while maintaining torque. But I'm not sure. Any recommendations on good types of flow valves which maintain constant pressure?

Air Motor Selection and Sizing | Hydraulics & Pneumatics

• Air motor speed can be regulated through simple flow-control valves instead of expensive and complicated electronic speed controls.
• Air motor torque can be varied simply by regulating pressure.

No load speed will be higher than loaded speed, but a simple valve inline will reduce loaded speed without reducing loaded torque.

Aaron Z

 

[BLSXJ]

in theory... you want a flow control valve... it limits the volume of air flowing without a pressure drop. I use them to control the speed of a pneumatic cylinder, without reducing force.