I have my G0781 back up a running. I wanted to summarize my experience for others.
The first question to address is whether it is worth it to fix the transmission or as suggested above, install a direct drive. I ordered my gears from Walmart before I really thought about that. I can see going either way. The mill is running and working well, but it is still noisy. I learned a lot about my equipment and I would not hesitate now to take on some serious modifications. Frankly, I'm to much of a newbie to give advice except to suggest that you think about a direct drive.
Now to the install. I went by the Youtube videos and that is really all you need. I want to emphasize a couple of things.
1. Photograph the everything before you take it apart. The Grizzly parts list is great, but the real part may not look exactly like the drawing.
2. Beware the potential to loose the detent spring and/or ball when removing the 'downfeed handle and hub' and the 'range shifter'.
3. Here is the most important advice that I could give. The four hex head bolts holding the headstock casting to the headstock mount were unbelievable tight. My recommendation is to use only a high quality Allen wrench and with a straight end (no ball end). I had to use a 12" cheater on all four bolts and I could hardly believe that I didn't snap the wrench or round hex bolt. I soaked the bolt heads in WD-40.
4. I didn't have much trouble getting the lower bearing to come out. Maybe I was lucky.
5. The gear set that I used was CJ0618 metal gear set which is commonly used in miniLathes and miniMills.
6. I had to de-burr the gears and clean out the keyways with a file. For sure, I had to use some emory cloth on the inside of the large gear. It was pretty rough and wouldn't go on the shaft without smoothing the bore. One YouTuber smoothed the large gear bore by taking a skim pass on a lathe. A minute of hand work with emory cloth is all that I needed.
7. The fine adjustment (Z axis) on my mill head has always been very tight. When reassembling the pinion shaft, which raises and lowers the head, I saw that the gear casing was binding on the worm gear when the bolts were snugged down. For the short term, I fixed this with shims. I'm thinking that this is a design flaw.
8. I left one plastic gear in the drive train - the 38 tooth transfer gear (part number P0781105). The shaft key had twisted about 10 degrees in the plastic. I cleaned that up but had to cut another keyway. I believe there is a metal gear available on AliExpress for about $20 plus shipping. It appears to be a Module 1.25, 38 tooth gear with a 12mm diameter shaft hole. That is the only metal gear that I can find that looks close to the original.
Smarter Shopping, Better Living! Aliexpress.com
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Best to all,
Spajo
