Air cut off tool problem

[drjim]

Chaps

Tried my new cut off tool today for the first time, it ran for about 30 secs until the compressor emptied out (little wolf 25l jobbie), but then wouldn't do anything else. Air just hisssed out from the back end. The same happened with a very cheap air wrench I got off eBay.

Now I vaguely wonder if my titchy compressor is too powerful and I should have turned the regulator right down or something, or is it just not providing enough air? Have I ******** my brand new cutter - admittedly it was cheap off eBay but made by Rolson so better quality than the other.

Or am I just doing something wrong, do I need to use my 10mm hose rather than the little one that came with the comp?

Anyone have any advice?

Jim

 

[Justme]

Do you have an oiler in the line?

Justme

 

[Hitch]

It shouldnt have caused it harm in 30secs...does the tool turn easily by hand?

I doubt a 25l compressor delivers enough air to run it for long. If yours isnt pushing enough air to turn the shaft, it will come out the xhaust of the tool.


Although a lot of tools say max pressure is 100psi or whatever, they normally work fine well above that.

 

[Justme]

The thin pipe wont help either. Is it one of those hard plastic coiled things?

Justme

 

[drjim]

No oiler, I just stick a bit of oil in the end of the hose as I connect it up. Seemed to be spinning freely throughout.

My impact wrench runs slower and noticeably less powerfully when using the small diameter hose, so I wonder if it is just flow rather than pressure. I'll try using the bigger hose next time.

I'm feeling more reassured that I haven't broken it, but will be keeping my fingers crossed!

Thanks for the opinions.

Jim

 

[drjim]

The thin pipe wont help either. Is it one of those hard plastic coiled things?

Justme

It's the PVC one that came with the comp. I have a 30M wide bore rubber hose that I got to connect tools in my hand in the back yard to the compressor in the cellar of my house (pre-workshop), but it's a PITA to coil it up all the time. I need to get some hooks/a reel on the wall to make it easier.

Ta for further advice!

Jim

 

[Hitch]

Compessors have two main err, thinggys...

Max pressure, which is fairly standard.

The other, is Free air delivery, which is often measured in cfm, cubic feet/minuite.
Your 25litre tank will deliver the entie tankfull in under a minuite, thats less than 1cfm, add the actuall compressor output to that, say 1fm (if motor runs about 1m to fill the tank from empty). Thats 2CFM. If your cut off tool is rated at 4CFM, it will run for about 30 secs, then the pressure will drop substantially.

 

[shenion]

Water can be a killer too. I found white ooze coming out of my grinder. Was frozen the next day; did free up and work fine after some persuasion.

I now have a good water trap and an oiler.

 

[drjim]

I think my comp is rated at 6.3 cfm, but it is a wolf one!

Will see if making sure the comp is full and using the bigger hose makes a difference. Might justify buying a bigger compressor to play with!

 

[Justme]

Compessors have two main err, thinggys...

Max pressure, which is fairly standard.

The other, is Free air delivery, which is often measured in cfm, cubic feet/minuite.
Your 25litre tank will deliver the entie tankfull in under a minuite, thats less than 1cfm, add the actuall compressor output to that, say 1fm (if motor runs about 1m to fill the tank from empty). Thats 2CFM. If your cut off tool is rated at 4CFM, it will run for about 30 secs, then the pressure will drop substantially.

Er not quite. That 25L is under presure so contains more than 1cf. If the tank is at 120-140psi it will contain more like 250L which is just under 9cf. Depending on pipe size you could get all of that out in a min but most will be at too low a presure to operate the tool anyway.
Whats the min presure for the tool to work? Say 80psi? so you only have 60 psi to play with so a cf of 4 or 5 ish.

How long that lasts will be down to the cfm needs of the tool.


2 cfm 2 min
4 cfm 1 min
8 cfm 30 seconds
16 cfm 15 seconds



Justme

 

[Hitch]

I should have said, 'at the same pressures' there somewhere shouldn't i

 

[drjim]

I'm going to have to go down there tomorrow and figure this out!

 

[shenion]

My old compressor was 5.6CFM @ 90 PSI with a 11 gallon tank..

Would run my die grinder at about 60% duty cycle. That is compressor runs continuously and you need to stop and let compressor catch up.

My "newer" compressor is 9.6CFM@90PSI 20gal tank. Will run my die grinder all day long with compressor running at about 40% of the time.

Both are 125PSI. I woudl estimate the die grinder needs 8 CFM to work well.

There is a noticeable difference in torque when I use a 1/4" hose and a 3/8" hose. I had several 25' and 50' hoses. I got a 10' 3/8" hose and it made a big difference.

Still dreaming of a 60-80 gal tank, 175 PSI, and 13+ CFM

 

[Luke]

Something like a cut-off tool/air wrench is going to use 25L in seconds, and the compressor will never keep up once the 25L has gone.

Simple as.

 

[drivewasher]

I looked into this closley last year. The manufactures con you as most use the displacement or intake cubic feet per min figures, the ACF (actuall cubic feet) delivery is lower than the displacement
Off memory my compressor is 19cfm which is 14 acfm.
The tools used need the ACFM

 

[Wozzaaah]

Yes DW, displacement figures are nearly always quoted instead of free air delivery figures but as all compressor manufacturers do the same I suppose it levels the playing field somewhat although like you say, air tools specify the FAD requirement. On a similar vein, I've noticed a lot of newer hobby welders are using 150 in the model number when they are in fact only 130A, now that is just plain misleading! Most air tools are very air-hungry, my little 50l jobbie won't run much for any length of time, using a windy gun, the tank empties in no time.