I'm currently looking around for a good used vacuum pump to start vacuum infusion.From what i learned so far there are several type's of vacuum pumps ,Rotary vane, Diaphragm ,piston type ,and others.
I know rotary vane is used the most and diaphragm pumps don't pull as much vacuum .I want to make small to medium parts  as a hobby and maybe also sell some parts if they work out well.
I also like the pump to be quiet and last long enough.I rather buy a used one from a known brand then a new chinese one.
I'm  currently watching a few used pumps  :

One is a dual diaphragm pump from Vacuubrand  ,this is the MZ2 pump which has a flow rate of around 2 - 3 m³/h and pulls about 7mbar vacuum.This pump allready has a vacuum regulator and vacuum gauge .

The other is a rotary vane pump from Shimadzu GDH60 which has a flow rate of 50l/min and pulls 10-² pa vacuum.This pump looks brand new ,but doesn't have a vacuum gauge and i'm not too sure if this brand is something reliable.
It is made in japan and does use a Mitsubishi motor  so my guess is this is a good quality pump.

Both of these pumps are for sale cheap  both buyers don't really know what they are selling .
Then yesterday i found a brand new DVP LB.3 rotary vane pump for sale .This is the same pump as the one from Easy composites ,except the easy composites one is the LB.4 which has a flow rate of 4m³/h and the LB.3 has a flow rate of 3m³/h .This pump isn't that cheap but the seller asks a lot less then the retail price.
Anyone have any suggestions?

Normally I'd suggest getting a rotary vane pump, but that Vacuubrand pump looks like it pulls really good vacuum (or plenty for most things) and the regulator and oil-free nature makes it very versatile.  If it pulls 7 mbar that will be good enough to work fine.  Most vacuum bags never get that good!  And it you get into it you can pick up a good oiled-rotary vane pump with a oil filter later on for larger or really high-vac uses.

I wrote a post about vacuum pumps that may be helpful: https://explorecomposites.com/articles/tools-and-equipment/buying-a-vacuum-pump/

And going to have to see if I can learn more about those Vacubrand pumps and their diaphragm + good vacuum.  I saw some at an auction and they looked nice - and went for $$ - so I haven't got one!

Thanks i have read your article before!
I found some other ones
- Thomas (Rietschle) picolino VTE3  a dry rotary vane pump .
This has a 3.5m³/h flowrate and  150Mbar absolute .From a spec sheet it said it draws 85% vacuum.
It also makes low noise only 55DBA.

- A Vacuubrand ME4C
3.6m³/h  and 80mbar dual diaphragm pump

Most of these pumps are listed under the name of the driving motor  and not the brand of the pump.
Maybe that's why they all are listed cheap...

Why are there some pumps rated at 800Mbar  and other at only 7mbar ? Isn't closer to 0 ultimate vacuum? or is it the other way around?

Yeh, you definitely want closer to 0. I wouldn't bother with anything that can't pull less than 10 millibar. As Chris said, you will probably find your vac bags won't get that good and you'll be around 15-20mbar for most applications, but you certainly don't want to be limited by your vacuum pump. If you were just doing wet-lay vac bagging then fine, but for infusion you need very high vacuum. 150 or even 80mbar is not good enough.

Keep in mind that diaphragms won't last forever and have to be replaced quite often. And they are very expensive. This is why most people use oiled rotary vane pumps. They are very cheap, very reliable, reach good vacuum and need close to zero maintaining. Even of the ultra cheap eBay pumps only one failed at my workshop, and I was even able to repair it. In comparison only 1 of 5 of the diaphragm pumps at the university institute reached enough vacuum for infusion, because they all had leaking membranes and it was to expensive to repair them all.

some companies give out the under pressure instead of the absolute pressure. So the 800mbar pump will likely reach 200mbar absolute pressure. 800mbar absolute vacuum would be worse than some vacuum cleaners.

Thanks guys ,this helps.
I found these charts which makes it easier for me to understand how much vacuum is what.

So i bought a brand new D.V.P LB.3 vacuum pump which is almost the same model as the ones from Easy composites.
Only difference is this one has a slighty lower pump capacity .
The seller selling this bought it in a lot and was selling it again,so i got it cheap-er for 150euro including shipping which is a great deal.
It only needs a electrical power cable,on/off switch and some rubber feet which i allready have laying around here.