Two POTD today! One intentional, the other not so much . . .
First the unintentional. Was working on the intentional project on my Clausing lathe when I heard a “thump, thump” noise under the head stock cover. Lathe was shut down and the chuck moved back/forth, nothing looked out of kilter. Stepped to the side and jogged the lathe on, what’s this, looks like one of the drive belts is fragmenting! Shut the lathe off and retrieved the remnants; not used to seeing Gates belts with fur on them . . . Sorry to report, the mouse who made a nest in the head stock of my lathe didn’t make it. Next hour was spent pulling out about 2 softball sized wads of fiberglass insulation and a couple of pinkies. Lessons learned, might want to put some Decon in the base of the lathe.
On to the intentional project. I flipped the quill lock on my Jet mill to let it return to the up position, and as luck would have it, the plastic handle hit the arm on the DRO and snapped in two. After gluing it together for the third time, figured it was time for a new knob. I did the work on my Clausing lathe instead of my Grizzly G0709 for a number of reasons. First, this project was being made from aluminum and would require flipping the part to work both ends. Both lathes have collets, but the Clausing is generally set up with a 5C collet chuck while a 3-jaw is left on the Grizzly. The collets won’t mark up the work. Second, the project was going to require threading an internal blind hole. The Clausing goes down to 28 RPM while the Grizzly’s slowest speed is 70 RPM. Sure like the increased reaction time for internal threading. Third, both lathes can thread 12 tpi, but on the Grizzly I’d have to pull the end cover and rearrange the quadrant gears. No such problem on the Clausing.
OD of the lever is 0.490”, cool, probably ½” x 13. Nope, ½” x 12 tpi. Don’t have a tap for that so it’ll have to be single-point threaded. Started with a 1” aluminum round. Measured the major diameter of the thread (0.490”) and the distance from the major diameter to the opposite side minor diameter in a number of places. The difference doubled and subtracted from the major diameter should get me close to the tap drill size (used a 25/64”).
Faced and tap drilled the center hole. Original knob was threaded 1” deep, but I went 1 3/8” deep with the tap drill for some clearance at the end of threading. Used a 2” travel dial indicator to give me my Z-axis position while boring a generous relief shoulder at the bottom of the hole. Should have needed about 0.050” per side to clear the thread, but went an extra 0.040” in case the boring bar was flexing.
Ground the threading tool from 3/8” HSS. I bottomed out the boring bar into the hole and marked the position on the tool. Should have room for 16 threads (1 3/8” deep at 12 tpi), but only went 14 threads deep. I probably sounded like an idiot counting out loud “1, 2, 3, 4, etc.” as the chuck rotated during each pass, but the pucker factor is at a max for me when threading an internal blind hole. Checked the fit with the quill lever off the mill and stopped when it fit well.
Turned a taper on the base of the knob per the original and turned down the body but left a raised ring. This was knurled with my Rockwin hand Knurlmaster. Parted and flipped the knob for facing and chamfering the back side. Finished product works and looks great!
Services were held for the unintentional project after the intentional one was finished.
Bruce
