Power Feed Randomly Skips a Beat

[David2011]

The binding I’m noticing is pretty severe at times, even locking up the works at times when I’m turning the spindle by hand. It seems to happen more frequently when I’m manually turning it in reverse.

The original/first owner made a hand crank from an MT4 sleeve, some 1/2” threaded rod and a shop built aluminum handle. When I’m chasing the threads on valuable/irreplaceable parts from the battleship’s guns I often use the hand crank instead of the motor to prevent destroying anything or at least until I’m certain that the tool is perfectly aligned. I’ve had to repair the threads on some big bronze bushing/nuts that locate the hinge shafts for 5” gun breech blocks. With a good, sharp HSS bit it’s surprisingly easy to cut threads with the crank.

Break’s over. Back to the shop for now. I’m making new screws for an assembly for the 5” gun sights. They’re 1.125” x 7 tpi left hand x 18” long. They’re being made from all thread since my lathe won’t cut 7 tpi or left hand threads. I’ll post that over in member projects when they’re finished.

 

[David2011]

Look at your parts breakdown for the apron, part number 403 and 404. The key wears out and so does the keyset in the worm gear. Been there, done that.

The aforementioned parts #403 and #404 have finally both arrived. The key arrived in January. The worm gear arrived last Thursday, June 6, after a ridiculous time on backorder. It showed to be in stock when I ordered it in January. I was sitting at my computer and saw UPS drop off the delivery so I immediately took it to the shop to fix the lathe.

Since the lathe was still “sort of“ working I had been reluctant to disassemble the apron before the parts arrived for fear that it was so marginal that it might not work if reassembled without replacing the needed parts. The original worm gear and key both showed some wear but not enough to have been the source of the problem. I’m glad I had the new ones just the same because I wouldn’t be happy putting the old ones back in.

As disassembly continued multiple other problems were uncovered. A screw that held one of the gears on its shaft was very loose, almost to the point of falling out. The screw that was supposed to be holding the gear driven by the worm gear was missing completely. The key between that gear and its shaft was sufficiently beaten up that it was keeping the gear on the shaft. Wiping the old grease away revealed the core problem of some missing teeth. Working with the gear to remove it I saw that the gear was wobbling and binding. Eureka!

Since I bought the lathe 2 years ago I thought that the leadscrew had a slight bend in it, most noticeable when engaging the threading dial. The problem was actually a bent shaft, the one on which the gear with the broken teeth rode. I made a list of the parts needed and got on the phone with Grizzly that same afternoon. Those parts arrived today, June 12 and they’re already installed. The lathe runs better than than when I bought it. The leadscrew has always had the wobble and it started having power feed skipping a full year ago: one of those things that just got worse with time.

At least I don’t have to worry about it messing up while demonstrating it to potential buyers. No way would I want to sell it without fixing it right.