08/22/00
Today I made the crown wheel arbor, the crown wheel pinion which has nine "trundles" (pins) and the the crown wheel collet. The arbor assembly is complete. The arbor was made from 3/32" drill rod. The upper pivot was made first, the rod being held in a 3/32" collet in the old Mosely lathe. The pivot was cut by hand, using a graver.
Next I made a blank to make the unitized pinion and collet (unitized to save space.) It was made from a piece of 3/8" brass. First, a "spigot" 3/16" in diameter was cut on the 3/8" brass so that it could be held in a 3/16" collet on the old Mosely lathe, where most of the work will be done. Then, a through hole was drilled in the blank a little undersized, and the hole was reamed with a reamer which is .0015 undersized. The collet was then trued, and a slit was made in it. This slit will eventually be deepened to cut off a slice which will form the lower shroud (plate) of the lantern pinion. For now, the slit serves to allow some chips to fall through when the lantern pinion holes are drilled.
Drilling both shrouds simultaneously, with both shrouds separated only by a little slit ensures that the holes will be accurate -- the pins will be exactly concentric to and parallel with the arbor. Lantern pinions are excellent gears when properly made.
The lantern pinion drilling rig consist of a block of aluminum which is mounted on a homemade compound rest (not the best). It has two 3/16" router bearings mounted in it, through which can be inserted various tools. The tools are driven by a little wooden pulley which is driven from a countershaft on the lathe.
The first tool inserted through the router bearings is a rod with a point on one end, used to zero out the assembly --there is a dial indicator attached to the crossfeed which is set to zero. Then the crossfeed on the lathe compound is then screwed out to where the dial indicator indicate the correct radius for the pinion, which is 0.1125" in this case.
The next tool which is inserted is a center drill mounted in a 3/16" brass arbor. This is used to make nine dimples in the end of the pinion blank (there is an index plate mounted to the back of the lathe to permit indexing.) This permits accurate centering of the tiny drill when the pinion is drilled.
Next, a .032" drill which is mounted in a 3/16" brass arbor is slipped into the bearings in the aluminum block, and the pinion holes are drilled. They are not drilled through the front shroud, but form blind holes, since the fron shroud also acts as the crown wheel collet.
Then the back shroud is parted off through the slit already cut, leaving the front shroud in the lathe.
The front shroud is then press fit onto the crown wheel arbor. Should the shrouds fit a bit loosely (as they were in this case) the arbor can be expanded with a knurling tool, so there's a tight fit. You can also use Loctite.
Then the arbor (with front shroud/collet now mounted) is inserted into the 3/32" collet on the old Mosely lathe, and a spigot turned to the correct size to fit snuggly in the hole in the crown wheel itself. Then the arbor is held by the top, and the back pivot is turned, using a steady rest for support and truth. At this point, both pivots are hardened and tempered to blue.
Then the back shroud is staked onto the arbor and the pins are put in the holes. I often make a "reamer" from the pin material (carbon steel "music wire") to ream the holes to the exact size of the pin. The reamer is simply a piece of pin material with a pyramid ground on the end, as mentioned in the last installment. If the pins are snug, no adhesive is needed.
The wheel is held onto the collet by four small "dimples" from a round-ended punch, and is now finished.
Today's links:
Collet/pinion blank, showing slit.
Finding the center of the blank.
Zeroing out the dial on center.
Center drill, making nine centers.
Drilling the nine holes.
Knurling (expanding) the arbor.
Cutting the arbor bottom pivot.
Crown staked on arbor.
Crown finished.
Ain't it pretty?