Vacuum pump hose line

[Mike Cruz]

Does it matter what size hose you use? I mean, Do you get better or worse performance with large vs small? Is 3/16" hose too small? I ask because the vacuum gauge that I bought has a 3/16" fitting, so I got all 3/16" connectors and hose, hooked it up and I'm pulling 23" hg. But not sure how much cfm I'm pulling, or whether or not it matters. Figure it will be fine, but not sure. Thanks for your advice.

[Dan Hintz]

As long as you're pulling the level of vacuum you require, CFM doesn't much matter.

[Chris Burgess]

Your air flow will be restricted to your smallest fitting so if your pump has 1/4"NTP like mine than a 3/16 hose is all you need.

[Josh Bowman]

Mike,
Technically if you have a good seal, you can get by with a very small tube. Sometimes a small bug hole is in the form or a void opens and that's when some SCFM comes into play. The pump also has to be able to support the addional load. But to answer your question, I don't think under any of the above circumstances the differance between 1/4 and 3/16 would matter.

[Doug Wolf]

Mike, the CFM only matters if you have porus wood and/or a leak in your system. Then the pump will nead a higher CFM to remove the air leaking into the system.

You can pick up one of these filters at Wal-Mart for 2 or 3 dollars and mount it so you can see the debris through the clear plastic.

206294

[Mike Cruz]

Thanks for your responses, gentlemen. Glad to hear it doesn't make much of a difference. I must say, though, I heard today (from a guy in an "air supply place" in town), the difference it will make is in how fast the vacuum is created in the chuck. With a 3/16" hose, it may take a while to suck the air out of the chuck, whereas with a 3/8" line, it would create the "hold" much quicker.

For anyone using a 3/16" line, does it really take an inordinate amount of time to get...hold?

[James Combs]

Actually I suspect that it is a little counter intuitive, I don't have anything to prove it but it seems to me that the larger the hose the more air there is for the pump to remove so it may be a wash. With a small hose you have less air in the system but it leaves slower. With a large hose you have more air in the system but it leaves faster.

Just food for thought. In any case I don't think you would see a major improvement in speed of clamping by going to a larger hose.

[Dan Hintz]

I heard today (from a guy in an "air supply place" in town), the difference it will make is in how fast the vacuum is created in the chuck. With a 3/16" hose, it may take a while to suck the air out of the chuck, whereas with a 3/8" line, it would create the "hold" much quicker.
That is certainly true, but can you tell the difference if you have to drink 1 cup of liquid versus 1.1 cup? Unlikely. You're removing air from a pretty small chuck volume, so the difference may be a couple of seconds difference between the two sizes of tubing.

[Mike Peace]

I would not over think it. See Steve Schlumpf's tutorial http://www.sawmillcreek.org/showthread.php?84279-Vacuum-Chuck-System-%E2%80%93-How-I-Built-Mine
The vinyl hose he used works great and is very inexpensive at Lowes.

[Mike Cruz]

The thing is, I already bought the hose and fittings...at 3/16". So, I was wondering if I had made a mistake and needed to switch. From the responses, I think I'll stick with the 3/16" stuff...unless it poses a problem. I just didn't want to hook it all up, then realize I made a mistake and have to redo it all. Thanks for all the reassurance.

[Tony De Masi]

The thing is, I already bought the hose and fittings...at 3/16". So, I was wondering if I had made a mistake and needed to switch. From the responses, I think I'll stick with the 3/16" stuff...unless it poses a problem. I just didn't want to hook it all up, then realize I made a mistake and have to redo it all. Thanks for all the reassurance.

That would be a first...

[Mike Cruz]

Your infinite wisdom is as welcome as dandruff on a mangy flea bitten mutt. But your sense of humor is always appreciated... :)

[Dan Hintz]

I just didn't want to hook it all up, then realize I made a mistake and have to redo it all.


That would be a first...
This is why I spend twice as much as I need to right from the beginning :D Double the systems for twice the price... like government.

[John Giem]

Does it matter what size hose you use? I mean, Do you get better or worse performance with large vs small? Is 3/16" hose too small? I ask because the vacuum gauge that I bought has a 3/16" fitting, so I got all 3/16" connectors and hose, hooked it up and I'm pulling 23" hg. But not sure how much cfm I'm pulling, or whether or not it matters. Figure it will be fine, but not sure. Thanks for your advice.
The size of the hose used does matter and it can make a big diffence. If you system is leak free and your turning does not leak air through it then the airflow is small and vacuum drops from chuck to pump is not much of a concern. But if you have leaky wood in your turning then there will be air flow and the size of the hose and fittings cam make the difference in whether or not you can hold your turning. I have actually run tests that showed that a 3/8 inch hose and fittings, give much better performance than a 1/4 inch hose and fittings. Yes, the pump may have 1/4 inch NPT fittings but look at the hose barbs for 3/8 and 1/4 inch sizes there is a big difference and they both screw into the same sized port on the pump.
I have heard that 'I have a big vacuum pump and will overpower any leakage.' This is not always true. The amount of air moved from the vacuum chuck to the pump is more dependent upon the hardware between them than the capacity of the pump. I have measured the performance of some systems where the hardware between the chuck and pump limited the maximum flow to around 2 CFM whereas the pump capacity was 3.5 CFM.

[Mike Cruz]

Thanks, John. I've considered changing my lines...just might be doing it.

[Ken Hill]

I knew it, size matters:eek::p

[Andrew Kertesz]

I built mine folowing most of Steve's tutorial. No sense reinventing the wheel. Using his recommended hose sizes mine goes to 27 hg almost instantly.