View Full Version : throttled coolant pump

09-01-2011, 02:49 PM
as an HSM'r i rarely use the coolant via the mill's pump.. either just
spray bottle or brush some oil.

when i do use it I have it throttled down to only a few drops a minute.

I just changed the hose (was getting ugly) and let the pump run to
clean the old fluid out. I didn't realize this thing put out so much coolant..
by eye, looks to be maybe a gallon a minute? feels like some decent

I've never worried about, but now i'm wondering if i could be doing
damage to the pump by having it throttled down so far.. and if it wouldn't
be better to put in sort of a "T" to send most of the fluid back to the


09-01-2011, 05:00 PM
I wouldnt have thought so its just the same as turning the tap down or off.
There might be a problem if the coolant was too low.

I use coolant all the time.

09-01-2011, 05:09 PM
I'm only drip on manually if I need lube, but I did dismantle an old coolant pump for a power hacksaw I had. It was like the old gas meters - two figure of eight lobes geared together.

If you throttle it you won't harm the pump, but you may be increasing the back pressure and thus the pressure on the glands at one end of the pump shafts.

It's all getting well lubed, whatever you do. The only friction is in the glands, and extra pressure should only harm them if the lube has grit in it which can be forced along the shafts. So if your settling tank is deep, there's enough lube to settle properly and you don't grind in the vicinity, it should be fine.

09-01-2011, 05:10 PM
I watched TV a program once

The secret life of a vacuum cleaner

it demonstrated that if you stop it sucking, the vac sped up and it used less power

wonder if the same happens in a pump with fluids

the coolant pumps are inpelar types ..aren't they ..same as a turbine in a vac

all the best.markj

09-01-2011, 06:03 PM
Impeller type pumps, as in vacuum cleaners and coolant pumps of the same design will run with less current when either inlet or outlet is blocked or restricted, the only thing you have to watch is overheating if blocked too much due to removing the cooling effect of the medium it is operating in.
IOW, you are removing the load from the pump.

09-01-2011, 06:06 PM
The reason a vacuum speeds up and uses less power is you are removing the load (And going to burn it out in a couple minutes)

A fluid pump may increase its load a but but you should be OK throttling it with a valve. I use the option valve for loc-line on my lathe.

09-01-2011, 06:36 PM
a wet and dry vac does not take cooling air for its motor from the suction hose..so will not overheat

all the best.markj

09-01-2011, 07:33 PM
If it worries you, you can always get the pump to pump through a slightly constricted loop and then hook a take off onto the pressurized side of the loop. Make sure it is the pressurized side otherwise the takeoff side will suck, literally.

It also provides for very fine level of flow control if you are cheapskate like me and don't have a needle valve to use in the flow line.

09-01-2011, 08:01 PM
I piped in a bypass on my saw, the pump that use to growl before when I throttled it down, now is whisper quiet. I'm not sure it was necessary, but it isn't going to do any harm.


09-02-2011, 09:54 AM
As a electrician I can say they burn up cause of lack of flow. Not enough coolant to cool pump housing. let the level get low and the flow be restricted and you'll see what I mean.

My coolmist unit rocks.. except for the times when the dead mouse floats in it long enough to make "soup"... nasty.. real nasty.. and I had a cloud of mist in the air breathing it..

09-02-2011, 12:08 PM
a wet and dry vac does not take cooling air for its motor from the suction hose..so will not overheat

all the best.markj

Every one I have used does.

09-02-2011, 03:06 PM
All our numatic ones do too. Sometimes our guys wegde the floating ball up to get a couple of extra gallons into the drum and end up blowing water out of the motor vents.

09-02-2011, 04:04 PM
Well, i would have thought that it would be trash, after that knocking your rcbs out, the lot ..or you have to dismantle them.. dry them out in a warm place for a couple of days

On the ones ive pulled apart ..that will be VAX cleaners, i know the the air for the cooling is taken in separately by its own little fan on these wet and dry vacs...infact sometimes the ping pong ball gets stuck ..it gets overfilled ..and water comes out of the vents ..but it never goes through the motor. ...if it did do, i would know about it ..by it tripping the power ..which it never has done ..


all the best.markj

09-02-2011, 04:32 PM
Guess that brand makes them different. I have heard many storied people trying to use shop vacs as vacuum pumps for things like vacuum forming and killing them from overheat.