Spray Gun nozzle size ?

Finny · Post by **Finny** » Wed Sep 02, 2009 10:21 pm

I have a HVLP (High Volume Low Pressure) Gravity Feed spray gun, but I haven't used it up until now.
It has a 1.4mm nozzle, but my other gun has a 2.0mm nozzle.

Will this make any difference to what I can spray with it ?

I was looking to use it to paint the roof.
Initially in White and then in Silver.

Trev · Post by **Trev** » Thu Sep 03, 2009 3:42 am

I should leave this to the real experts but, I think the 1.4mm nozzle is too small for acrylic, I used a 2mm one, and I also have a HVLP 1.4mm nozzled gravity feed gun that I bought, used only once

, Trev

.

Devilrod · Post by **Devilrod** » Thu Sep 03, 2009 7:37 am

I'm only going on what my mate told me and he's a qualified painter. But his personal preference for acrylic is 1.8 for top coats and 2 or bigger for primer/putties. 2pak he uses 1.4

matchew · Post by **matchew** » Thu Sep 03, 2009 8:01 am

i and everyone i know has always used 1.8 for acrylic and i use a 2.5 for primer puttys.
you wont be able to use the 1.4 if your using acrylic

EK JAY · Post by **EK JAY** » Thu Sep 03, 2009 9:07 am

Hi Finny
i sprayed my sedan and wagon with a 1.4 tip in acrylic metalic
using a gravity fed gun

Finny · Post by **Finny** » Thu Sep 03, 2009 9:35 am

Just when it appeared to be clear, along comes EK Jay

I guess I'll try some testing first and see how well it works.

Where's Rosco when you need him

FB MAD · Post by **FB MAD** » Thu Sep 03, 2009 10:06 am

Rosco's still typing

Sorry Rosco, couldn't help myself, no offence intended

rosco · Post by **rosco** » Thu Sep 03, 2009 11:20 am

Hi Finny,
sorry have been on the caravan and Hilux forums for a few days.... got a lot of sorting out to do on both....... them sorting me - that is......

Ummm........ I have precious little experience with using the larger gravity guns - I have an Anest Iwatta suction gun with a 2.0 mm nozzle set that I use for full panel/body sprays.

I believe you must also understand that I have exactly zilch experience with spraying 2K - metals, pearls or COB.

I have used a large gravity gun to spray primer and it fell down very badly - the nozzle set was only 1.4 mm and I could just not get any body to spray - even pushing the pressure well beyond what was recommended...... it appeared that even when thinned down to stupid mixes (almost watery) - to permit the 1.4 mm pattern to "flow" - there was almost zip depth in the primer...... I cannot now even remember why I purchased that gun with the 1.4 mm set....... it is almost unused in probably 10 years...... read on about retailers..... may have fallen "victim" here.......

Using the smaller gravity guns - I feel very confident with the mid-sized guns using 1.5 mm nozzle sets (the best of these that I have is also an Anest Iwatta but marketed under the brand of "Air Gunsa".... made in Italy under license from Anest Iwatta) - but these affords only about a 4" fan.....and is probably at the very extreme of their ability.......

I know this may sound a paradox - ie - if acrylic can be sprayed through a small gun with a 1.5 mm set - it should be able to throw out the same viscosity with a larger gun.....
My feelings are that this is not entirely true - and you understand that I have absolutely know theoretical knowledge or expertise in this (along with just about every thing else I vomit up on your screens......!)
but my feelings are that although the nozzle set are similar in size - they are machined and designed to perform much different duties...... the "fan" air also comes into play here as does the volume the gun will pass prior to the nozzle set......

We have a number of professional spray painters on this forum and I would have liked to have seen some relevant opinion/knowledge from them...... come on fellas - throw up some lines......

My practical experience has been such that I use a crude suction gun with a very coarse 2.5 mm nozzle set for primer (I have not ever sprayed putty) and I note that I can lay some serious depth down with that - but higher pressure is also needed.....

When applying colour coats - to large panels I have always used the Iwatta suction - it is a wonderful instrument and is designed exactly for this purpose.

For very small panel repairs and touch ups - I use an 0.8mm touch up gun.... (in my early days - I actually sprayed using a little "Badger 200" airbrush - with a 3/4 oz bottle - my entire plenum intake grill is still covered in that paint...... yes - took all day... but I got there..... I did not have an air compressor - but had five spare tyres on wheels - the servo (1980ish) got a bit sick of me coming up and robbing his "air"....).

I probably have more confidence with these smaller guns than the larger - and I have found setup time to be almost down to a few very brief runs along the back of my workbench.......

The large Iwatta - one run just about blows away 50 ml of paint - it "consumes" 350 ml of paint and 340 litres of air per minute...... read on - there is mention of the "blue haze" a bit later.......

These are my working tools when spray painting and I believe you will find mention of these in that "War and Peace" I posted a couple of years back......

I would never use a "good" gun to spray primer, enamel or any mixed paint (POR 15 etc)..... I keep my "good" guns for acrylic colour coats.

Now the bit you were probably asking for without all the above, Finny.

My suggestion is to use a 2.0 nozzle set for acrylic, a 1.5mm for enamels and 1.2 mm (probably - I don't know, I have not sprayed it) for 2K.

I would also suggest that COB (and this may also apply to acrylic COB) would best be suited to a 1.4mm or 1.2mm - I do not know if COB is thinned or sprayed undiluted......? we need the pro's to steer you with this.......

I may also point out - if you haven't used the gravity gun yet for "finish" coats..... be absolutely sure you don't ever get "tempted" to pull that trigger with either the air missing, valve closed, hose disconnected (anywhere) or fan wound right in....... I did this once and had to wait a few days to block it back - you will get a STREAM of paint run out and onto your work.........

If you need more (and I would understand if you do not finish reading my thoughts.... they usually "run" a bit) I will give anything you ask some more thought.....

But for now - I'm hoping the forum "pro's" will climb all over me and point you in the right direction........

ps - just decided to edit this (usual practice on re-read).....
It also depends on how much volume air you have - the compressor - it is probably futile trying to get a large gun with a large nozzle set to spray top coats if you just do not have the "volume" to support it..... I hope this makes sense.....?

Also - when i went researching my colour coat gun - I was fortunate enough to find a retailer who did not simply try to sell me the gun he was making the largest profit on - the information I received then related exactly to what I purchased with the Iwatta...... solid colour acrylic - with ample air this was the W -77 with the 2.0 nozzle set..... frightfully expensive - but at the end of the day - it gave me results I could not have hoped better for....... at my entry level of spray painting.

If my air supply volume were to be less - we were going to drop down to a 1.8mm set, still a W-77 - but a different model number and with a much reduced air consumption - because I had the air to support it, it has proved to be capable of a very even and consistent pattern with very good width and volume of paint delivery......

I suppose the short of these last two paragraphs is ...... what is the output (cu ft per min if you can please) of your compressor - if it's under 14 cfm.... my gun will not suit - it will "starve" for air......

HVLP guns use a very much reduced volume of air hence ... high volume/low pressure - and I am led to believe they produce less "overspray" and "clouding" of the environment........

I remember when using the Iwatta - after two minutes - the entire room (double garage with very high ceilings) was a turquoise "fog"..... I could barely see the vehicle....... through the "mist".....

The HVLP gun I have has four fan holes in the "wings" (for pattern) and five holes each side of the needle orifice (for atomisation) I note that the pic of yours does not seem to show that many.......

frats,
Rosco

I was going to throw up a bit more - but I believe this is probably enough to confuse you with for now.........

NoMAD · Post by **NoMAD** » Thu Sep 03, 2009 11:33 am

I wouldn't use that gun regardless as it looks like it's from Super Crap Autos!

Cheers
NoMAD

Finny · Post by **Finny** » Thu Sep 03, 2009 1:24 pm

Thanks Rosco.

Yes I'll be doing an acrylic COB.

I bought a new compressor last year, 3hp twin with 17cfm, so pressure should be Good.

It may well have been a cheaper gun, not sure.
Can probably take the 2.0mm nozzle off the other gun to use on the gravity one. Could try that also.

I'm back to giving it a try.

That's probably the best answer anyhow

rosco · Post by **rosco** » Thu Sep 03, 2009 1:57 pm

Hi again Finny,
on other machine - this one is a bit slow to type on..... not that you'll notice..

Umm..... when you come to changing nozzles - I was told that the nozzle set and needle are all a "job lot".....

17 cfm...... that's much more than I have (14 cfm) - mine "just" keeps up with the big gun...... your's should "romp it in".......

Still waiting for others to join in this - please.......

Can't help you with COB - I have sprayed it, but only to "seal" some other products......... and using touch up gun.....

guess we'll both have to wait for the "pro's" to come into this......

frats,
Rosco

Finny · Post by **Finny** » Thu Sep 03, 2009 8:00 pm

Used the 1.4mm today with a White Acrylic.
1 paint to 1.5 thinners.

Seemed to work OK.

Adjustments on the gun were very easy.

Much easier than the suction gun.

Anyhow, it just seemed to lack a bit of "power" ?

Paint flow was good and had more issues to getting along from front to back of the car in one run, than with the actual gun.

Not sure if it would perform once it had some pearl or metallic in it ?
I think it would need a larger nozzle.

I just thought for the roof it would be better as the cup is on the top and not underneath, like on the Siphon gun.
That way I could get closer to the roof without hitting it with the paint cup.

I will still try it with the silver on the roof, but will go back to the other gun if I find any issues.

The nozzles are different widths, so not interchangable on different brands/suppliers.

blue ute · Post by **blue ute** » Thu Sep 03, 2009 9:57 pm

Finny wrote:I just thought for the roof it would be better as the cup is on the top and not underneath, like on the Siphon gun.
That way I could get closer to the roof without hitting it with the paint cup

May I suggest Finny if your pot is hitting the roof you're way way to close to spray.

Finny · Post by **Finny** » Thu Sep 03, 2009 10:27 pm

No so much hitting as hit.

Poor technique and lack of control.
Just one slip and bang a mark on the fresh paint.

Did it twice when using the primer.

Was trying to avoid a hit.
Especially when getting towards the middle of the roof.

I know, Practice, Practice Practice.

Smooth customs · Post by **Smooth customs** » Thu Sep 03, 2009 10:32 pm

the first thing that must be done when doing something you have not attempted before, or using a material for the first time. Is to spend a little time and read the manufacturers instructions.

paint companies produce tec data sheets that outline the contents of the material supplied and the safety requirements when using their material.
it should also contain the recomended thinning, or hardener ratios. under different conditions.
it will also list the best gun set up, and recomended pressure at the gun.

but in 30 odd years in the industry, most home builders or painters either ignore these data sheets or put them on the work bench to stop spills from the paint can.

Trust me, it can make a big difference. As setups can differ greatly from one manufacturer to another.