Badger Needle Bearing
Can you change your own Teflon needle bearing in a Badger airbrush?
Yes, you can, but it probably doesn't make sense. Badger has the nice policy that they will do it free as long as you own the brush, and I've read that the turn-around time is very short. Besides, you will have to pay about $4 for a teeny tiny part that's easy to lose or mess up. Never the less, I've done it. When I was experimenting with making fine lines, I convinced myself that the needle bearing needed replacement.
Symptoms Actually, the main symptoms of a worn needle bearing are either pulsing or leaking and very little drag when the needle is removed or installed. Normally you should feel some resistance. In a siphon airbrush, the vacuum in the paint chamber in the body of the brush can suck air through a worn bearing and cause a pulsing in the spray. To check for this, spray plain water and move the trigger slowly through its entire range. There should be a continuous spray with no breaks. But, if you see breaks, it could also be caused by a very small fracture in the tip, or a leaking head or tip seal. To eliminate this possibility, turn the brush upside down, fill the paint chamber with water, press the trigger but don't pull back, and hold the trigger for one minute. If you don't see any bubbles in the paint inlet during this time, the needle bearing is probably bad. (This tip was given to me by Herman Robisch at Badger.)
With a gravity fed brush, you may see paint leakage into the rear portion of the body.
Some airbrushes have an adjustment on the needle bearing. If your's does, that may be all that is required.
First Try
Note : Before you try doing what I did, watch this video. It looks like this guy really knows what he's talking about. I hadn't seen it before I did my experimenting. Apparently, the bearing should come out the front on some models and the rear on others.
I read on the web in a couple of places that replacing the bearing was no big deal. So I stopped by Coast and picked one up. They are reeaaly tiny, the bearing, not Coast.
To remove the old bearing, I dismantled the brush except for the air valve assembly. Then I ground the end of a bicycle spoke nice and smooth and flat and used it to push the bearing out the front of the brush body.
To install the new one, I sanded the end of a round toothpick so that it would fit in the hole in the bearing. I threaded the bearing on the toothpick and pushed it in from the front until it was flush with the back of the paint cavity.
When I re-assembled the brush and tried to install the needle I discovered the rub. The needle didn't want to go through the bearing. It was real tight. It turns out that Teflon, being plastic can be deformed. I had slid the bearing on the needle when it was loose and it felt really nice. But the hole in the brush body is a tight fit, and pushing the bearing from the end caused it to squish a little and become too small for the needle.
So I e-mailed Badger and begged for help, and a nice man there e-mailed back with the words "Use a number 55 drill bit". A number 55 bit has a nominal diameter of 0.052 inches and the 155 needle measures about 0.050 inches. It turns out I have a number 55 bit, so I chucked it in a pin vise and carefully reamed out the bearing. The first try it was still a little too tight, so I worked it again. Then, HORRORS, it was too loose. However, luckily I found that by pushing on the end of the bearing again I was able to tighten it up and now the needle feels and works great.
The moral of this story? Well, you decide. But if you decide to try it, you might end up sending your brush to Badger anyway.
Postscript
Because I can't leave well enough alone, I eventually managed to damage the new bearing. It will only take so much reaming and pushing. So I bought another one. This time I came up with a better way to install it. It occurred to me that reaming might be causing internal scratches that could lead to leaks. So I made the tool shown below.
I installed the #55 drill bit backwards in the pin vice. Then I put a tiny bevel on the exposed end by rubbing it against a diamond stone. I wanted to eliminate any burrs. The Teflon tubing is just slightly larger than the needle bearing, so it acts as a stop when the bearing is fully in place. The bearing was a snug fit on the bit. My theory was that the drill bit being just slightly larger than the needle, would prevent the bearing from collapsing during installation.
Well, it worked pretty well. The needle was still a bit tight, but usable. However, I discovered that Teflon apparently has some memory. The next day, the needle was too tight. So I removed the needle and pushed the smooth end of the bit through the bearing as I twisted it. After a few strokes like this, the needle felt about right when I re-installed it. It's been a while now, and it still feels and works OK. But, if this doesn't do it, I swear I'm sending the brush to Badger to get fixed right.
Conclusion
As far as I know, Badger is the only airbrush manufacturer that uses a press-in needle seal/bearing. Most airbrushes seem to have a ring seal backed up by a threaded adjustment nut. Tightening the nut compresses the seal and makes it fit tighter around the needle. The Badger seal has both good points and bad points.
No user adjustment
This is fine, if it's not needed. But, due to close tolerances and variation between needles, you may find that a replacement needle doesn't feel like the old one did. I ran into this when I bought a fine needle for the 155. If it's too tight, you can buff the needle with some very fine wet or dry paper and loosen it. Or, you can expand the bearing with the proper size drill bit. If it's too loose, you have a problem. You can tighten the bearing by pressing on both ends and squeezing it, but Badger doesn't document this.
Not user replaceable
Well, it is if you know how. But, Badger discourages this and they don't sell or publish details of the tools required. They will replace it free forever, but you need to send the brush back to the factory for this. But, the bearing really shouldn't wear out with care, and turn-around time is reported to be very fast.
Badger uses both types of needle seals. They use the adjustable type in the Renegade Velocity and Spirit, and some of the Thayer & Chandler brushes, but the press-in bearing in the rest of their models, including the expensive Sotar line.