Cleaning Up Jet 1024P's Apron

Saturday, February 16, 2013
Jet 1024P apron covered in old grease and oil
You won't believe it, but there is an apron under all this gunk.

When I purchased my Jet 1024P lathe a few weeks ago I pretty much knew that I will spend hours and hours bringing it back to a serviceable condition. Although the important parts of the lathe appeared to be in good condition, there was something loose in the apron. Engaging one of the power feeds made horrible grinding noise. It didn't feel like a broken gear or a missing tooth, so my guess was a loose key or something similar. Before spending time on anything else, I decided to dig into the apron. Taking it off the lathe didn't take much effort: after removing the lead screw, I had to loosen two hex screws on the top and the apron readily disconnected from the rest of the carriage assembly.

The half nut is filled with old grease.

Like the rest of the lathe, the apron was covered in old grease, chips and some sort of abrasive grit. All that was covered by liberal (and somewhat random) smears of fresh graphite grease; the bottom of the casting was under as much as an inch of gunk, barely clearing the gears. The biggest challenge when taking the apron apart was cleaning enough of it to see how it was held together. At the end I ended up soaking the whole thing in 2 gallons of WD-40 overnight, and most of the gunk simply washed out.

 
There is clearly a par missing,
so the pinion gear 's teet barely catch the worm gear

My initial guess turned out to be wrong: there were no keys in the apron. The gears are held in place with pins, but unlike my newer 920 lathe, these aren't the cotter pins. Instead, Jet uses slightly tapered solid pins pressed into the holes with similar taper. Once I figured out what was going on, the apron came apart in mere minutes. After some more soaking in WD-40 and scrubbing the gears looked like new. Although most of the gears are made of some sort of cheap cast iron variant, the teeth showed almost no wear. Moreover, it looks like the power feed worm gear has been replaced with a nicely made steel one. The gear driven by the worm is made of brass or bronze, and judging by the quality of the cut was custom made as well.

With the brass spacer the gear should mesh correct now

The two new gears appeared to be well made but the installation was clearly botched. After a close look at the mesh between the two gears I discovered that only the edge of the pinion gear was contacting the worm gear, so it looked like there was a part missing. I wasn't able to find a drawing or a photograph, so I simply cut a bronze washer, thick enough to align the center of the brass gear with the axis of the lead screw. Once that was in place, I tried dry-fitting the power feed gears and discovered the source of the rattling noise – the shaft is held in place by a washed with a set screw. When I was taking the apron apart I noticed that the set screw wasn't wasn't tightened (or came loose over time). Once properly secured, the washer held the whole assembly more or less in place, but here was still a small gap (about 2 hundredths of an inch). Since the gears appeared to be grinding directly on the apron casting, I decided to kill two birds with one stone... I had a small piece of Turcite* sheet laying around that was exactly 0.006” thick, so I cut four washer and installed two pairs on each side of the power feed shaft. Once that was done, the power feed has become silky smooth, and the rattles were gone.

*Turcite has self-lubricating properties similar to PTFE (Teflon), but doesn't compress. I was able to find some on eBay years ago, but similar product is sold by McMaster Carr under brand name “Rulon”.

The apron looks much better after thorough scrubbing with WD-40 and brake cleaner.
Surprisingly there was almost no rust. All that discoloration turned out to be old, gummed-up oil and grease.

Cleaning up the apron turned out to be much easier than I expected. The brown discoloration was gummed-up lubricant, not rust, as I initially thought. Once soaked in liberal amounts in WD-40 it washed off with no effort. Getting the chips out of the bottom of the casting was a bit more messy, but at the end I persevered.

Overall my impression of the apron construction and condition is pretty positive. The gears are made of a passable alloy and should hold up well to my use, especially the worm gear and the pinion it drives. Naturally I wish Jet made the gears out of some better alloy and installed some bushings or bearings, but that would be clearly way out of the price point. Eventually (if I get sufficiently bored at some point) I will recut the gears out of proper steel and install bushings on the power feed spindle. For now, though, I will keep cleaning the machine and posting my progress.

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