Just your basic piece of 1 1/2 inch schedule 40 PVC pipe.  Cut to 3 inches long. Square the bored end carefully (I used a lathe to true it).  Use a standard outer wheel bearing on the outer end of the spindle after you slide the PVC on. You really need to remove the backing plate for this test, but you can get a pretty good idea even with it attached as long as it's not damaged.

This is the bored end.  1.771 inches fits snugly on the base of the spindle if you chamfer the outer few thousandths to clear the small radius at the base of the spindle (the 1.785 clears the radius, but doesn't fit quite as snugly. Use a spare spindle (it can be bent) as you approach the diameter to be sure.  The counter bore is about 3/8 deep to clear the inner race platform at the base of the spindle.  The regular ID of the tubing will clear the sealing spacer and any bearing race that might be on there.

On the left, see a "nearly" straight looking spindle .. from this angle.  On the right, turned 90 degrees, it is quite obvious of the offset.  This is a VERY minor bend - using my right angle against the 'base plate' and eyeballing the match to the spindle, I was "PRETTY SURE" it was bent.  BTW - I use the spindle strengthening spacers on my car.  With the hit this one took (an FV front wheel at FULL BORE straight into the top of the wheel/tire from the side), it would have looked bent from a mile away without the spacer.

Another method is to eyeball the clearance between the inside race of the outer wheel bearing and the inside of the PVC pipe.  Again, it is obvious in this picture that it's offset... but not by much.

I have some spare spindles and was able to check them all for 'bent or not' in about 5 minutes and be confident of the test. I did find one bent about 1/2 as much as this one .. this one is being replaced!. 

If you decide to duplicate this tool for your own use, please send me $1000.  If you actually build one and use it on customer's spindles and they PAY you to fix them, please send me $5000 happy.

Steve at WedgeRacing dot com