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 bubbles which result in 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, and the brush is the type with a floating tip, it is also possible that they are caused by a poor seal where the tip mates with the airbrush body. To check for this, rub a tiny bit of beeswax on this area and try again.  If you still see breaks or pulses, the needle bearing is probably bad.

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

I read on the web in a couple of places that replacing the bearing was no big deal.  So I visited my friends at Coast Airbrush 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 drove over to Coast and 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.


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