Vacuum Pump Gloat

[James Combs]

I was in my small town a couple days ago and walked into our one and only pawn shop to ask directions to a small newspaper office and look what they had on the shelf.

A Robinair VacuumMaster 15500
185357 185356

It was tagged at $100 but I got it and a scroll saw (see http://www.sawmillcreek.org/showthread.php?161225-Equipment-Gloat&p=1653343#post1653343) for $200.

There is definitely a vacuum chuck in my future. I will also be using it in pen blank casting.

Has anyone used this particular brand and if so is it any good. I notice that its spec shows an ultimate vacuum of 35 microns. How does that relate to inches of Mercury? I tried to find a conversion online but no success yet.:(

Edit - Found it. 29.921 inches of Hg is 0 microns, so the smaller the micron rating the better. This one is apparently pretty good. I also found it new online for between $230 to $290.:D

[Bernie Weishapl]

Congrats on the pump. Sounds like you got a great deal James on the two of them.

[Steve Schlumpf]

Congrats on your new vacuum pump! I am not an engineer, but 35 microns doesn't seem like a lot of vacuum to me. Only way to know for sure is to give it a try. Good luck with it!

[Alan Zenreich]

Steve,

If I'm reading this chart (http://www.engineeringtoolbox.com/vacuum-converter-d_460.html)correctly, 35 microns should equate to 29.9 inches Hg, so he should be ok.

[Tim Thiebaut]

You made a nice score with this pump...never thought about visiting a pawn shop before...might have to check them out and see if there are any good things for turning up for sale.

[Steve Schlumpf]

Alan - looks like you are correct. I did a quick conversion from metric to inches... not the same thing! Should provide plenty of vacuum and at 5 cfm - should do it quickly!

[James Combs]

Steve,

If I'm reading this chart (http://www.engineeringtoolbox.com/vacuum-converter-d_460.html)correctly, 35 microns should equate to 29.9 inches Hg, so he should be ok.

Alan, that's the way I read it. I found a similar chart after the post in the power tool forum. At first I assumed larger micron numbers were better but didn't take long to understand the micron scale.


Alan - looks like you are correct. I did a quick conversion from metric to inches... not the same thing! Should provide plenty of vacuum and at 5 cfm - should do it quickly!

Thanks Steve, when I get it setup (it will be a while) I will be installing it with a bypass to reduce the amount of vacuum on the chuck and in my vacuum chamber. Both the vacuumed device and the bypass will be filtered to avoid contaminating the pump mechanics.