I need a favor please. Would the owners of the 766 who have a means to measure readily available please post the outside diameter of the spindle threads where the faceplate or chuck mounts. I know the nominal size is 1-1/4-8 but I need to know the actual outside diameter to a thousandth. Thank You, Hu
Hu, I just measured mine, and it is exactly 1.25" and that was with my higher quality calipers that measure in inches and thousandth's. My cheaper one that is digital has the battery dead in it at present time, so the necessity of the inch measurement. The needle was exactly on the 1-1/4" line and I measured about 3 times to make sure I had it correctly lined up and not off to one side.....this is the thread portion.
Roger, I appreciate the help! Hoping to get a larger sample but it looks like a sizing die has been ran over my spindle nose to clean up the threads. That might not be an issue in itself but I am concerned about other work on the spindle. Some noises from the headstock and I hope to have time to disassemble it tomorrow to know more. I do have authorization from Grizzly for the disassembly and some parts coming. May need more when I get things stripped down. Should be interesting regardless. I'll know my 766 when I am done! Hu
I had to replace one bearing in my g0766 ,it had a rattle in it. No problem from griz they sent 2 bearings. Ran nice and quite for around 10 hrs. Then it developed a different noise , it ended up being the two set screws 8mm x 1.25 pitch in the spindle pulley . I know I tightened them but set them again, and in a few more running hours the noise came back. I used two more set screws and used them as a jam nut. No further issues, I went this route vs. a thread locker for disassembly ease in the future. As a whole this is a great machine , can not wait to get the new tool rest base.
Glad you caught the problems early, David. Did you have difficulty pulling the spindle? I've noticed that a tell-tale sign of a slightly-loose set screw (or screws) in a spindle pulley is a "tick tick tick tick" directly related to rpm. Reversing the spindle rotation can cause the sound to go away for a short while, as the set screw re-registers slightly against the key in the key way. The pulley can appear to be quite tight on the spindle, yet still have a loose enough set screw to cause the tick. As the screw gets looser, the tick can become more of a knock and mimic a bad bearing. Worse, the harder steel of the spindle can cause the bore of the softer spindle pulley to egg out, requiring replacement (this, coincidentally pointed out to me a couple of years ago by a Grizzly tech). So it's important to catch it early, especially in these bigger lathes with very high torque. (cont)
I've found that medium (blue) threadlocker on the set screws is very good insurance, and doesn't hinder removal when necessary. Using a second set screw on top of the first is an interesting solution. My only worry would be that whoever adjusts or removes the pulley in the future might not know to look for the lower screw and end up galling the spindle by cranking down hard on the puller. On the G0766 and the G0733, there are two set screws on the spindle pulley, and, if I'm remembering correctly, I think only one key and keyway, so the second screw tightens directly onto the spindle, rather than a key.
that spindle was quite the pain to get out the first time, I think it was basically put in dry. I vacuumed quite a bit of casting sand out of the headstock also. I used red grease everywhere there were mating surfaces and reassembly was still tighter that I think it needed to be. Oh the tach. sensor support plate does not need to be removed ,but the gap is .053 inches if you want to check it afterwards. You should tap the bearing in past the outer casting edge on the pulley end to make sure that the keyway has enough clearance to be placed back in. And I did not see in the exploded view the is a spacer washer that goes between the bearing and the pulley it is also directional so look at it ,you will see the way it goes in. If I can help further send me a question.
David Privett, Thanks for your offer of help! My machine is back together now. I am going to reply here to keep the whole group in the loop. I remembered somebody else had already dealt with a bad bearing and was going to check who. My phone was closer than the computer since I was in my shop/barn so I just called Grizzly instead. Described the piece of black mystery metal that was on the spindle, roughly 3/8" thick, boss on one side roughly the size of the inner ring on the bearing, boss on the other side roughly the size of the outer ring on the bearing. The tech I talked to was absolutely sure it didn't belong in there and we decided it must have been part of an assembly tool that was left behind. My headstock is sans that spacer now. Maybe lightening it up some is where that extra 20RPM came from! Unless I have an issue I'm not taking the headstock down again so things will have to rock and roll like they are. Hu
Hu's and David's comments about the "mystery metal" spacer found on their G0766 spindles stunned me because I went through the same experience in early 2013 with my G0733 as I was developing a vacuum adapter and handwheel system for that lathe. Looks like the G0766 has the same issue. Yet Grizzly tech reps are evidently still unaware that the mystery spacer even exists (and it is still not depicted in the respective parts diagrams and parts lists), despite now having been reported over two years ago in the G0733, and by Hu most recently in the G0766. I think this is important for several reasons, foremost being that the spacer is held in place only by thick assembly grease, thus can come loose at any time and produce sounds that mimic a bad spindle bearing in these lathes. I wrote about this in my tutorial a couple of years ago on the handwheel/vacuum adapter system for the G0733. I'll start a separate thread in this group and paste the relevant excerpt from that tutorial.
This is in response to Hu's original posting requesting measurements of the spindle. If I measure the actual threads on my G0766, they are 1.230". I was sent a replacement headstock and the diameter was 1.230 when measured with the burrs and roughness in place (I estimate that if they were cleaned up, that it might mieasure a couple thou less. At the back of the spindle after the set screw area (where there are no threads), the diameter is 1.260. That is 0.010 over nominal. One of the faceplates that I bought from another supplier wouldn't fit as there was 0.010 of interference. This has been reported by others with some otherwise good chucks. I have studied the Machinist's Hardbook and this seems to be a mistake on the part of the manufacturer. I carefully used a file to remove the interference plus a little more. I removed 0.015 total diameter or 0.0075 on the radius. It took me perhaps 10 minutes.
