Anybody notice this...is it normal?

[GregStith]

While troubleshooting on my airbrush (Olympos) I noticed as the needle starts to pull back, it's not centered. It actually rides on the bottom of the nozzle. As it completely retracts it's then centered. I can see this using a 60x Jewelers loupe. I switched my spare needle and also the head unit with the same result. I then checked my Iwata HP-CS. Same on it as well.

The reason I looked was I was getting tip dry mostly on the bottom side of needle if I do fine lines for long times, but tip dry is more uniform if I'm spraying heavier. Anyone else ever notice this?

 

[Vladimir]

I've noticed that long ago None of my iwatas have perfect centering including CM, MP-200 has the same as yours. I'd say even not perfect centering but as you say needle rides on the sides of the nozzle not only the bottom and every AB has its own needle position.

 

[AndreZA]

Not even my Micron stays center. It is impossible to make it run dead centre as there are some movement in the chucking guide where it is grabbed right at the back by the needle chuck nut and the only other thing that guides it is the packing seal infront of the trigger.

 

[GregStith]

Ok. Thanks guys. More info to put in the knowledge bank.

 

[RebelAir]

Mmmm I can't honestly say it wouldn't be an issue as it seems maybe thats how Iwatas are set up but I would assume if any of your needle edges are dragging that it would disrupt the venturi or at least off centre the venturi and create the build up issue your seeing. Mine doesn't appear to drag (Though am half blind, even with a loupe) and I would be inclined to think if it did it was a bent needle that would do such but hey maybe Iwata is different..But if you think how the airbrush works and how the venturi is created it seems to me a weird idea to off centre a needle to its hole deliberately as this has to affect its spray ability and pattern (maybe for the better?) but again just seems weird....

 

[basepaint]

You might have paint build up on the teflon seal pushing it down??

 

[GregStith]

You might have paint build up on the teflon seal pushing it down??

I just replaced the seal the same day. Both guns do this. One an Olympos the other Iwata. Two people here posting theirs is the same so I assume it's normal. Have you looked at yours?

 

[Nada]

All of my airbrushes are not perfectly centered. If you look at them under magnification.
Olympos Mp 200c
Iwata hp cs
Iwata hp bcs
Badger Krome
Sparmax .35
Harbour freight deluxe!

 

[GregStith]

I'd say that's pretty conclusive! Nobody has reported a centered one yet. Maybe if we all combine our finances and make an airbrush that has a needle that stays perfectly centered we'll have a winner!

 

[RebelAir]

Nah nothings ever conclusive...Most likely haven't reported a centred needle because most likely have a bent needle (99% of us probably do) LOL, but whether they are all like that aside, doesn't mean its right. Again can't comment on iwatas and perhaps all are indeed the same as it doesn't take much to off centre something at that size but if its dragging through the pull (Its that comment that brought me to comment, not the off centering), that isn't normal and its easy to imagine the negative effect it would have on spray pattern and angle and metal on metal wear and no-one can convince me otherwise LOL. Off centre is one thing and can imagine that off centreing is fine if there is indeed clearance around the whole needle, all that would do is change the angle of spray slightly, but the needle dragging the internal head nozzle is completely a different kettle of fish and could be damaging your airbrush..

 

[AndreZA]

If you look inside an airbrush, you will notice, like I've mentioned, that there is not much in the body that can hold the needle straight (red arrows). First problem is a needle that can bend. Second is that the needle chucking guide has a lot of play between it and the spring guide. And as soon as the needle retracts from the nozzle, there is nothing supporting it (green block) and it relies on the inside of the nozzle to guide it back to centre again. And that is way I call Iwata's Micron "Matched head" system BS.

 

[RebelAir]

perhaps in that design of Airbrush, if you look at other cutaway diagrams of other airbrushes you will note that some include a PTFE Needle Bearing much closer than shown above, you will also note that this is only a diagram, it does not actually indicate true size or dimension and I think you'll find the tolerances involves in some of the internal metal bores wouldn't be much bigger than the actual needle which in theory should not allow that amount of flex or drag in the needle only an inch further on. but the centring aspect isn't really the issue-Heres another diagram...



Pretty simplified idea but if indeed a needle is dragging you effectively stop all paint flow obviously on that side and will disrupt the pattern and throw globs of paint and all kinds of effects you don't want, again an off-centering isn't a huge issue but if you needle is dragging through the pull, it is..But hey when its all said and done..if it works...Who cares LOL

 

[AndreZA]

Here is the inside of a Badger. The closest can get the needle seal to the font is right at the back of where the cup ends. You can see there is still room if they did not step the tube. This will also make cleanup easier. If the cup moves closer to the front, that can also help.

 

[RebelAir]

prob not the best cutaway as it doesn't really show the other bit and that indeed would and could show centered (Or close too) alignment, again a simple diagram but another model and only a mere diagram

and I'm sure we can go back and forward with cutaways showing different designs all night with seals in different spots, my point is that the Needle bearing should allow for central alignment if the needle is straight in the nozzle (or as close as possible). There is no reason the airbrush needle would flex enough to drag the nozzle especially if its only about 1 inch or so away, it doesn't have to support an elephant, just a straighten the needle which is why they are often elongated, but another important "seal" if you want to call it that is also created at the front end of the nozzle, this will also assist slightly supporting the needle because that paint flow should in effect lift the needle if it can get around it on all sides and its not being "mechanically denied", not doubting what your saying andre and soz if it comes across argumentative as thats not the intention but yes when a needle is bent, it won't centre right but it shouldnt flex enough to ride the edge as you describe (Unless somethings wrong) and I challenge anyone to check there needle on a glass surface and tell me theirs isn't bent, some will call me a liar but many will nod and say..yup-bent LOL, but we can still paint well with a slightly off centered/bent needle we all do and its extremely hard to keep the buggers straight, even through the manufacturing process so some bending is likely but over that inch if its actually riding the nozzle then it doesn't sound good and that's all I was trying to pass on..and if all iwatas do that, Id be concerned about metal fatigue in the tip of the nozzle as constantly dragging it would I'm sure create micro cracks in that area reasonably quickly, seeing your needle ride isn't a good thing imho..... But will shut up know, its just because I've been away for a bit, brain is bursting with airbrush chat I haven't got out in awhile so probably overthinking it LOLOL

 

[GregStith]

First off thanks for you guys in-depth responses. I didn't realize that I put in the original post that it's riding on the nozzle because it isn't. Once the needle starts to retract it is off-centered to the bottom but not touching. @RebelAir I'm not saying it's conclusive that this is optimum. I agree it "should" be centered. I'm saying that if 100% of responses are "off-centered" covering various makes then it must be "normal" or typical.

I have a brand new needle and seal in mine. I even loosened the needle, rotated, tightened then tried again and it was still off-centered to the bottom so no bent needle. Changed head unit, still off-centered to the bottom. There is indeed tolerance in the spring guide. Maybe if the back of the needle could be slightly lowered it would raise the tip of the needle on mine. I like to modify things so I'll at least try to study it this weekend.

 

[AndreZA]

I just checked my Micron and I wish I could record through the magnifier. As soon as I pull the trigger back the needle starts dropping. It never touches the side. But how far it drops is very unpredictable. One pull it is the width of the tip the next is it almost completely. An like it said, it is all to do with hoe loosely the needle guide sits inside the spring guide. It wiggles there with the packing seal as the pivot point.

 

[Don Wheeler]

Believe or not, air flow is more critical than paint flow. As paint exits the nozzle it clings to the needle due to something called the Coanda effect. When doing fine lines, it doesn't break free of the needle until the very tip. It doesn't matter how it gets there. But, if the nozzle is not pretty well centered in the spray regulator ( air passage ), you will get a distorted pattern. As the needle is retracted the spray breaks free further back, and the opening around the needle becomes a larger arc until paint exits around the entire circumference. As Andre pointed out, the needle is only supported at two points. And, the closest one to the nozzle tip is as much as 25mm back and is essentially a piece of plastic. That makes it pretty difficult to hit a target that is a fraction of a mm in diameter. That's why even in expensive airbrushes you will often see some offset as you retract the needle.

Unless the offset is so much that the needle actually scrapes and binds ( I have actually seen that ), I don't think you will see any ill effects.

Don

 

[RebelAir]

Hahaha, call that one solved, no riding after all so all good, enjoy your off centered airbrushes LOL, I'm happy using my nearly centered one, but it is important when describing trouble shooting issues to describe them correctly as there is a big difference in dragging or not dragging, otherwise we all discuss un-related ideas LOL, but hey that's some of the fun of it Either way glad its sorted Greg, looks like your got nothing to worry about as all iwatas do it...Mmmm wonder why the charge so much for matched heads when the don't actually sound matched to the needle at all..But shouldn't bash the ol'iwata, even in jest,as they are a good gun and can in the right hands do amazing work....

 

[GregStith]

I adjusted the tightness of the needle seal and it actually caused fluctuation in the needle location slightly. Too many factors for something with such minute tolerances I guess. I'm sure someday somebody will come up with a design that allows for perfectly centered needles. I'm sure that'll be cheap!

 

[Don Wheeler]

They could design a nozzle that supports and aligns the needle while still allowing a path for paint. But, it would be more complex, harder to keep clean, and wouldn't buy you anything functionally.

Don