4cfm, and i DIDNT notice it was ONLY 20 microns. i usually pull 25-30 on my venturi. kinda upset i put some $ into a robin air to then get the wrong one.
I’ve heard 4cfm is enough to do small parts like sportbike parts. Maybe it won’t be enough to do a full car hood or roof though? I think you’ll be better than ok with it. I was going to buy a 4cfm robinair too, but ended up with a 6cfm because it was the only one i could get with a full warranty on ebay.
Edited: Hey I looked it up my 6cfm robinair pulls just 20 microns also. It’s way plenty to infusion or vacuum bagging. I believe it will pull like 29hg.
Are you having a hard time finding plumbing fittings to fit the polyethelen vacuum line to it? I have searched high and low for fittings and even bought a small assortment. Nothing fits the threads on my Robinair pump.:o
Help me find fittings!! Please 
It’s not pipe threaded either.
microns is different than in/hg. also, cfm really doesn’t matter.
I’ve got the 5CFM Robinair. Pulls full vacuum just fine. I also use a venturi on the air compressor as well. I’ll be infusing some small parts first, hatch cover, etc. so I don’t expect to run into any problems. Now, when I get to the hull of the boat, 31’x10’ I’ll probably need a way to pull down the bag fairly quickly but I’m counting on the Robinair to keep it down till the resin kicks.
I got most of the fittings I needed at Lowes & Home Depot. The thread on the outlet from the Robinair is an ACME thread and the 1/4" NPT threads are different. What I did was sacrafice a 1/4" T by jamming it onto the ACME thread with plenty of thread goop. I know this probably ruined either the ACME fitting or the T fitting but I also couldn’t find an ACME to NPT adapter. I was going to machine a piece of Delrin but ran out of luck finding an ACME 1/4" tap.
I was going to machine an adapter out of brass, but the lathe guy at work is so slow, it will take him a month or longer to get to it.
I don’t think from this definition that those are ACME threads on the Robinair pump.
http://en.wikipedia.org/wiki/Acme_thread_form
I’m wondering if a refridgerator repair shop would have the fitting.
The fitting is called o-ring boss
get an o-ring boss to female npt. then male npt to hose barb
4CFM will work just fine for smaller parts, but if you are looking to make large parts, or to daisy chain several moulds together, you are probably going to have problems.
Personally if I was thinking of trying the RTM process, I would make a vacuum tank out of an old propane cylinder, and draw vacuum with a triple stage venturi pump, operated by my shop compressor.
Already have a new PIAC triple stage pump (Ebay £20), and with the addition of a few fittings, taps, pipe, and a vacuum gauge, would have a very capable vacuum source for less than £100.
I’m just going by what the manual said (Acme thread) that came with the pump. I also have ACME leadscrews on my CnC router and the threads look the same.
You might try an automotive shop that sells air conditioning equipment or a refrigeration supply shop.
edit:
Ok the fitting that comes mounted on the Robinair is a JIC which is either a 37 or 45 degree flare fitting. http://www.kurthydraulics.com/threads.php
Is it possible to get a female JIC fitting that on the male end of the same fitting is O-ring boss type?
They say O-ring boss is the same as JIC but without the flare.
I’d like to just adapt off of the Robinair JIC T fitting.
I thinkI have this figured out now with your guys’ help.
The threads on the vacuum pump are JIC 37degree flare or SAE 45 degree flare. The large port is 3/4 inch thread.
Here is where to buy/find the adapter to make the JIC and adapt it to NPT pipe thread.
http://www.discounthydraulichose.com/product_p/6501.htm
An alternative place to buy this fitting is at a Hydraulic Supply store.
From there you can pick up a pipe thread adapter with ferrel and nut from the hardware store. I’ll include a photo of the NPT to 3/8 polyethelene line adapter.