Rotary tools

[vilts]

I have another tool in my wishlist. High-speed rotary, probably NSK Presto. But I'm little concerned about its air requirements.

Specs say it needs 1.4CFM of air at 35PSI (to me it is 40 l/min at 2 bar). So, when I have a compressor with 0.74 CF tank (21l) at 115 PSI (8 bar), does it mean it drains this tank with 2 minutes or even less? If of course 0.75CF @ 115PSI is the same amount of air as 2.46CF @ 35PSI. This would be an enormous amount of air...

Could someone who uses NSK, GRS or other high-speed rotary chime in and tell me I'm wrong on this? Some real-world examples would also be nice - how big tank and how often it needs refilling.

I'd love to buy air rotary, but if my compressor isn't good enough, then probably must go uMotor way.

 

[KCSteve]

Don't have a rotary yet (other than my Dremel) but my GraverMach SC has the air outlet on the right that you can hook one up to so if your compressor can handle your Graver logic says it should be able to handle the rotary.

Of course when you run the rotary you'll be running it for longer 'bursts' than when you're graving so your small compressor will have to run more. I've got a small compressor as well so when I do get a rotary that'll be a concern for me as well.

I'll have to watch this thread and see what the people who know what they're talking about say.

 

[leschowe]

Hi Vilts,
I have a GraverMax SC like Steve, above, and I use the air outlet to run a cheap
Russian High Speed Rotary tool. (I plan to purchase the GRS unit this spring). I would
guess that my Russian unit uses the same air as the GRS unit -- don't know for sure
because I can not read the specification on the Russian too.

The tool is powered from a 6 gallon, 150 PSI Porter Cable compressor that I purchased
from Home Depot. The compressor specification is: 2.6 CFM @ 90 PSI. This set up
runs the tool quite easily although the compressor runs at about a 40% duty cycle while
I am using the tool.

Hope this helps somewhat,
Les Schowe

 

[Robert Morales]

In my limited experience with my GRS 850, it will empty my 20 gal tank in a hurry. I usually fill the tank up to 60 psi and it's good for hours with the Monarch. The 850 will show signs of low pressure in maybe 15-20 min. I turn it off because it's in the basement and don't like to hear it cycle in the middle of the night.

 

[tldcowboygear]

Howdy Folks,

Quick question, would a rotary tool that works with the Gravermax be a better option than a Foredom or other brand flexshaft?

D.C.

 

[fegarex]

The AUX air outlet on a Gravermax/Gravermach is just that and is limited to the compressor attached to it.
Because it is there doesn't mean you can run a rotary tool unless your compressor can handle it.
I know the rotary tools eat a lot of air.

 

[Powderhorn]

Tldcowboygear; The main difference is that the Foredom is electric powered, and turns at 14000 RPM, the GRS 850 is air powered, and turns between 300,000 and 400,000 RPM. Now as to the fine points, with the Foredom, you have a stiff flex shaft that you have to overcome for movement, and angles to the work piece. The GRS 850 has just a small very flexible air tube, that does not drag on you, and it is more like using a pencil to work with, and a big plus is that it can eat metal in a big hurry.

 

[tldcowboygear]

Powderhorn,

Thanks, I have been considering a foredom or like tool. I think that I will check further into the GRS850.

D.C.

 

[thefox]

rotary tool

Hi everyone!
I have just noticed the compressor discussion. I have the GRS rotary, and it really uses the air. I think that the major portion of air that's used is the way the throttle is designed. It constantly bleeds quite a large volume of air when the foot throttle is not engaged. When the foot throttle is all the way down, there seems to be no air escaping except what goes through the turbine. I really can't see the need for the variable foot throttle, because I always run mine full throttle anyway. It appears to me that a simple on-off foot valve would be better, hence less air use, and a small comressor.

Bryan Clary

 

[Powderhorn]

Thefox; If you are having a large air bleed when you are not using the 850, check your foot valve for leaks, there should be no air bleed there. The other question, is are you running it off of the graver foot pedal, if so that would explain the bleed.

 

[jimzim75]

Hi Vilts,
I just got a NSK E-Max(DC electric motor). What a sweet machine. I know your asking about
the air powered model. I passed on it for a couple of reasons.

No.1
air powered hand pieces have no guts (Low torque). Unless your cutting
wax they slow down from 45000 to 35000 under load.

No.2 I don't have to
buy special burs. I can keep on using my 3/32" burs.

No.3 it has a gear reduction that I can put in to do metal work. (High torque).
I can take it off quickly to have the full speed for light duty stuff.(Low torque).

No.4 That air driven models really, really sounds like your at the dentist.
That's not really a good reason but ya know how it is. I have to go to dentist
on Friday, Oh boy........ I'm so excited................. So not having something around
that reminds me of a place I'd rather not go. Well?

Good luck, I hope you get a nice new toy, soon.
Jim

ps: I forgot to mention the E-max has a brake. Which actually kinda cool.
One more thing, the hand piece has absolute 0 run out (The burs run true, without wobble.) and a sweet quick change.

 

[leschowe]

That's correct Rex. When I run the Rotary tool from the AUX output of the
GraverMax SC, I turn the SPM control on the SC to zero, then adjust the pressure
setting on the SC up to the amount need by the rotary tool. The tool can then be
turned on and off by opening and closing the AUX control on the SC.

You also must be sure that the compressor regulator (on the compressor) is set
to a high enough pressure to run the tool but lower than the maximum that the
GraverMax SC can tolerate.

Les Schowe

 

[thefox]

Hi, Powderhorn,
I am running it off the foot pedal that I bought just for the turbine from GRS when I bought the set-up. I am new at this, but after using the turbine I find it hard to justify trying to run it at any speed other than full throttle. I would like to hear the results others have had.
Bryan Clary

 

[Peter E]

I have the GRS 850 and it is connected to the Auxiliary Air input on my Gravermax. It has a knob right above the hose that is turned counter-clockwise to open the input to the 850. The foot pedal is not used at all. It does use a LOT of air and causes my Sil-Air compressor (bought from GRS) to work MUCH harder than the engraving handpieces. The compressor was supplied with a cooling fan and most times I don't even need to turn the fan on when engraving. If I don't turn the fan on with the 850, the compressor gets hot fast! Once I realized that, I always use the fan with the 850. I had heard the 850 will cause the Sil-Air to overheat and shut down if used for too long but have not experienced that. When I notice the compressor getting too warm, I turn off the 850 for a while.

That being said, I have a Dremel (old style) a Foredom Model H hanging flexible shaft (1/4 hp 22,000 rpm) and a Foredom high speed bench grinder (14,400 rpm) with a flexible shaft. The GRS 850 made by NSK is in a completely different category (300,000 - 400,000 rpm). For some uses (backround removal) it is far superior to the others, and as mentioned is not inhibited by the bulk as in the Dremel or the stiffness of the shaft in the Foredom.

For tasks like using cutoff disks, sanding, or where slow speed higher torque is needed, the others are more effective than the 850.

Hope this helps,
Peter

 

[Ron Smith]

I have both a foredom and a high speed rotary. the differences primarily is the torque. I find the foredom frustrating sometimes due to the tool wanting to walk off of the metal doing small pieces. On the other hand, the high speed will remove metal quickly, but you have to kind of paint with it as it pulls down easily, so there are advantages and disadvantages. The torque is handy for stone setting and such, the high speed seems handy for better control in small areas. Maybe this will help to decide based on your purpose, but what the heck, you will probably end up with both types in the end if you are a craftsman as well as an engraver.................Ron S

 

[vilts]

Actually the reason I'm worried about the air consumption, is that my 'main' workplace is in apartment with neighbors next door and if the compressor will kick in after every 5 min it will be a problem. Now, if it'd take only 20 minutes it'd be no brainer.

I have used the GRS 850 handpiece and absolutely loved it. No comparison at all to 20k rpm dremels. But if the 50000 rpm micromotor tool is about the same in usability as the high speed for removing engraving background then I think it'd be safer to buy that.

Peter E, what do you think how often the SilAir works? In every 2 minutes or so? Maybe I'll need to buy bigger tank for my compressor and it'd be allright...
Ron, can you tell what's the rpm of the foredom tool? In web I found that they're at about 15-18k rpm? Then theoretically 50k rpm would be much-much better?

My main usage at first will be just to remove engraving backgrounds. Later when I feel like it I'd like to give a go at carving (that means micro motor tool, I think).

 

[vilts]

Jim. I looked up the E-Max and it seems to have max speed of 35k rpm. How is it's usability in removing backgrounds?

I have used the lower speed dremels and they are not that controllable, kind of drag away. But maybe that extra 10k rpm makes the difference.

Please enlighten me

 

[KCSteve]

Didn't FL Flinter post about how to add a secondary tank to your compressor setup to reduce the amount of time it spends cycling? I've been thinking about doing that with my little compressor but for just engraving it's not a priority.

 

[jimzim75]

Hi Vilts,
Quite good. It's robust without the gear reducer, so at high speed you can shave
small layers. With the reducer in the speed of course goes down but the
power it better than a Fordom by double. The hand piece is absolutely true.
I could do high quality dentistry with it.

So as long as your using a sharp bur. You can get great cuts.
I think it's twice a expensive as an air driven model. But then it out classes
it, the same amount. In my mind, it is the preferred rotary tool.

Don't try one, because you'll always be sadly comparing it to its weaker
brothers. Unless your going to buy it.

 

[Peter E]

Vilts,
The Sil-Air comes on frequently when using the 850 handpiece. I haven't ever timed it but I would say it may be as often as just a couple of minutes. Using the control knob, I found after about 180 degrees there is no benefit from opening the air input any further, and that allows the compressor to keep up better than fully open. It definitely taxes my Sil-Air. When using the Monarch or 900 handpieces, once tank pressure is established, it can be perhaps 10 to 15 minutes before the compressor needs to come on. Then it is only for a short time.

If you need to use the 850 for long periods of time (say more than 30 minutes non-stop) you probably would want a higher output compressor than the Sil-Air.

Peter