08/21/00
Today I made the pallet arbor and the collet on it which holds the pallets. The collet was made with a tiny 0-80 setscrew, so that the pallets can be adjusted later on the arbor.
The arbor is made from 5/64 drill rod. The pivots are cut on the end of the arbor by hand, using a graver with the arbor mounted in a 20-size collet in the old Mosedly Jeweler's lathe. The length is slightly less than the 2 1/2" span of the frames. The interior width of the arbor (between the pivots) is a bit less than the 2" internal span of the frames. This allows the Allen screw "end stones" room to adust the end-shake of the arbor.
The collet was made from a short piece of 1/4" brass mounted in a 1/4" collet in the old Mosely lathe. The shape was turned by hand, using a graver. A boss is cut on one end which is a close fit through a hole in the pallet body itself.
A through hole was drilled at less than the 5/64" finshed size and then reamed with a homemade hobby-lobby reamer which works well -- simply a piece of 5/64" rod which has four facets ground on the end to form a pyramid. Doesn't have to be hardened or even made very well to work quite well. These "reamers" make the hole just right. Use oil, or they can get stuck. Don't expect them to remove more than about .005" of material, or to cut steel.
Before reducing the length of the collet to final form, I removed it from the lathe and drilled the hole for the 0-80 set screw. I made a dimple made with a center punch, then held the piece in my fingers in a machinist's V-block while drilling.
The piece is drilled in long form to make it easier to hold in the V-block, then returned to the lathe to cut off, using a cut-off tool. (The one I use is made from a hand-held Xacto blade and holder -- just one of many tricks learned from JM Huckabee.) Then the hole is tapped for the gnat-like 0-80 set screw.
Normally, I would rivet (expand) the boss on the collet to lock on the pallet body, but for now the pallets are mounted on the collet using Loctite 690. This will permit them to be removed from the collet to be finshed and hardened when the time is right for that.
The pallet arbor can be adjusted to a perfectly smooth, zero-clearance endshake between the frames, using the setscrew "end stones" in the end pieces. A good plan, I think.
Today's links:
Reaming collet hole to size.
Drilling set screw hole in collet.
Tapping collet.
Collet with tiny set screw.
Pallets and arbor.