I bought a Us General Vacuum pump but I have a question about it.
It states that the ultimate vacuum is a measly 1 pascals or .00295 inches of mercury. The pump I use at school regularly pulls 20 inches of mercury.
Am I just reading the specifications wrong or is this pump really that weak?
It’s model 98076
Missplaced decimal? I can inhale more than that.
It can pull down to that level of vacuum remaining. So full vacuum at whatever ambient pressure happens to be, minus 1 pascal!
Man…
I need one of your pumps. I wish I could afford these things. Even used they’re over 200 dollars.
I think there may be a misunderstanding here. These are the specs for the 98076-2V vacuum pump from Harbor Freight:
[i]1/4" SAE intake fitting with dual ports for R134A and R12/R22 systems
75 micron/10 Pascal maximum vacuum
Includes 8 oz. pump oil bottle and 5 foot 9" grounded power cord
115 volts, 60 Hz, 1/6 HP, 1720 RPM; 1/4" inlet port; Oil capacity: 200 ml; Overall dimensions: 10-3/4" L x 4-3/4" W x 8-7/8" H
Weight: 15.28 lbs.[/i]
Huh,
Ten pascals? That’s still pretty weak. Atmospheric is 101 kpa. I’m debating filling it up with oil and just seeing how strong it is. Hopefully if it’s weak they’ll take it back
Maybe you’re not understanding the measurements.
Full vacuum is 0 kPa. No vacuum, or atmospheric pressure, is 101.4 kPa. A low number indicates that there is little air pressure remaining, therefore a high level of vacuum!
But all that aside, it’s still from Harbor Freight. In other words, it will go up in smoke at the worse possible time!
Well I tried it out and you’re dead on. I infused a small 2 by 6 inch part. The pump pulled 65 cm of mercury (25.5905512 inches|1 atm = 29.9246899 inches).
Normally I use this large blue belt drive GE pump at school but I wasn’t able to take it home. Luckily this small thing chugged along for an hour with little problem. The only complaint I have is the oil mist. It fogged up my garage which is kinda annoying.
On that note. Do any of you have suggestions for a reliable pump that doesn’t spray oil?
Did you do a leak test? If the bag isn’t holding vacuum and the pump has air flowing through it, it will be a smoke machine.
exactly. HVAC pumps aren’t meant to pull air. If you can connect your vacuum cleaner to the airline to suck most of the air out, and THEN turn on the pump, it won’t mist. There are mist-proof mufflers out there…or a glued on tube with lots of airweave/towels 
Wow dead on. I realized there was a leak in my resin trap somewhere and I’m gonna find it later today. Ruined that infusion but it was cheap fiberglass anyway
The initial mist isn’t too bad but the leak is drawing air through which Tet and you have both identified as the problem.
Thanks for the tip a ton. I appreciate the advice
75 microns is a pretty serious vac to pull, plenty for bagging stuff (i.e. if you hook up a digital micron meter, you’ll never see it get that low on a bag). HVAC pumps will pull down on a 1 metre square bag with no problem at all, and they don’t muck around getting there either.
has anyone used one of the hf pumps for any length of time?i was kinda wondering how long one might last?im running a venturie pump.i think it works well.im not sure how it compares to one of the high dollar pumps?anyone know how much of a difference there would be in vacuum between the two?
So far for me I haven’t had any problems. I took it out of the box, dumped in the oil and it’s worked like a charm. If any problems come up in the future I’ll post in this thread though.
thanks canyon,i see you bought the smaller of the two they sell.i was thinking about trying the bigger one.on your bag how hard is it pulling down?with my vacuum generator i can hardly pull a pleat from the part.just wondering if these pumps will pull down harder?
The small harbor freight pumped pulled 23.4 inches of mercury on an area slightly bigger than one square foot pretty fast, I would say less than 10 seconds. With that pressure I was able to easily infuse two parts.
As for the pump itself it’s pretty nice. Small and light and feels well built. So far it turns on and off reliably and chugs along quite well. I had it running for 14 hours once and so far I’ve had no problems.
thanks for the info.i think i might give it a try.i have my vacuume generator for a backup so i wont be stuck if it quits in the middle of a cure.
i just bought one of the hf 3 cfm pumps.i think it works pretty good.i have used it for 2 curing cycles.its very quite and runs nice and smooth.its a 2 stage pump.witch i dont fully understand.it sounds like it switches modes after its been running awhile.it pulls a harder vacuum over the vacuum generator i was using before.i removed the t fitting it came with and installed a male 1/4 pipe to male 1/4 hose barb in its place.the cost was 149$and i got the 1 year warranty for another 20$
Its a bit late of a reply, but I’ve been using a harbor freight 2.5cfm pump for about 2-3 years now for smaller parts and it works just fine. I’ve probably bagged nearly 100 parts off it, and usually can get around 27-28 inches of mercury on it at the bag. I’ve never tested the vacuum of the pump itself directly with a gauge though.