Solved With A Strip Of Brass
I think I finally resolved a problem that has been an issue since the building of the original prototype stand. From the beginning, the operation of the lock pin was sometimes a little more difficult than it should be. Janey has mentioned having some trouble with it. Sometimes it would work easily, sometimes not. While I built the second workstand a while ago, I have waited to drill the hole for the lock pin in the new base until after solving this.
The problem turns out to be a result of using hardware store parts that were close, but not perfect in their fit with one another. The 5/16" bolts are exactly that, .3125 inch. But the pipe that fits over it, curiously is called 1/4" pipe. In fact, it actually has an outside measurement of .55 inches, with an inside diameter of .364 inches. Quarter inch? Go figure.
I believe I have solved the problem with a tiny strip of brass.
(Brass Strip Insert)
[ATTACH=CONFIG]555301[/ATTACH]
(Placement of Brass Collar)
[ATTACH=CONFIG]555302[/ATTACH]
The pivot shafts of the swing frame are made from pieces of pipe, with a bolt running through them. These bolts also go through the holes in the uprights of the swing frame and form the two perpendicular shafts for the frame to pivot on, rotating in the base of the workstand. The bolt is exactly centered. It is the slight mismatch in measurement that creates the problem. The inside diameter of the pipe is slightly larger than the bolt going through it. This allowed the pipe to be slightly off-center, which varied the tracking of the holes in the lock disc with the lock pin. It made the lock disc slightly eccentric in its rotation.
The small strip of brass, formed into a circle, is slipped in between the bolt and the pipe during assembly, keeping the pipe centered on the bolt while the bolt is tightened. This is only necessary on one end of one pipe, where the lock disc and pivot shaft pipe meet.
(Brass Collar Fills Gap)
[ATTACH=CONFIG]555303[/ATTACH]
This adds just slightly to the process of assembling only one of the pivot shafts, but its fairly easy to do and the results are well worth it. All the holes in the lock disc will now work equally well with the lock pin. And, now I can drill the hole for the lock pin in exactly the right place.
More soon,
John