View Full Version : schematic for a Jet 1236 p lathe
11-11-2009, 03:19 PM
Does anyone have a schematic for the head stock area of a jet 1236 lathe? somehow (I got it this way)( I know thats what they all say) the main shaft got bent on the one I have and I need to replace it or build a new one. I thought it might be nice to have some pictures to help me take it apart. can anyone help?:o
11-11-2009, 04:13 PM
Most of the chinese lathes are the same regardless of brand and paint color. The grizzly website has manuals for the 12x36.
I'm having a hard time imagining how a mainshaft could get bent. Not sure if it would be feasible to repair, I guess you could get a price and find out. I'd probably change the bearings while it was apart. That's getting into serious change and an HF 12x36 is $1800 or so.
What makes you think the shaft is bent ?
11-11-2009, 06:52 PM
I had a hard time getting things to line up properly, for instance I took a piece of round stock that I knew was straight chucked it up and it did not cut all the way around the piece. so, I placed a dial indicator on the chuck and turned it by hand and found that to be out of round by about 10 thousandths. I suppose that the 3 jaw chuck could be the problem but that seemed less likely than the shaft being bent.
I agree I do not know what would cause a shaft to bend but I remember when I got the lathe I asked if it "cut straight" and the answer was well I can make things straight with it. in hind sight I believe something was wrong with it when I got it.
all that said I still have a lathe that if i put a piece of stock in and cut it then turn it around I can not make the cuts line up.
do you think something else might be wrong, I am open to suggestions or coments? any help is appreciated.
11-11-2009, 07:07 PM
Without a chuck on it, try to verify whether the bore is running true. Maybe mount a taper arbor and take care to see how it fits, then whether it runs true or not. If it doesn't, you're probably in for an expensive fix as the bearings will probably be compromised as well, then the bearing seats in the headstock might be damaged-
If the spindle runs true, then remove the backplate from the chuck and see how true that runs. You'll find the answer.
11-11-2009, 07:18 PM
I should have mentioned that this is a mid 80's model lathe I have no idea if that matters or not from the CHINESE:mad: perspective. I will try to see if the bore is compromised and let you know
mid 80's means its probably not chinese, but taiwanese. which usually means higher quality.
And you should be able to get a manual from Jet.
Look on the website-
321336 was the old number for a 12x36, which they havent sold in years.
there might be something close on the website, but if not,
You should be able to call the Jet guys, and get them to fax or send you a correct one.
1.800.274.6846 - 7:00 a.m. to 5:00p.m.(CST, Monday - Friday)
Its extremely unlikely that the spindle is bent.
Do you have a dial indicator, to measure actual runout?
You need one. With a mag base.
Ebay, craigslist, enco- pick up a cheap one.
Take the chuck off, and measure the runout (roundness or lack thereof) of the inside of the spindle.
My guess is that your runout is in the chuck, and its mounting.
Could be as simple as crap in the threads, dirt, grease, etc.
Clean everything, remount.
When you are turning your test piece, are you using the tailstock?
Are you sure its lined up and dialed in?
I have never believed the "they are all the same machine with different paint jobs" theory.
but just in case, here is the link to the Grizzly 12x36 manual.
It looks to me like a completely different lathe than the old, 80's Jet-
For one thing, its gear head, instead of belt drive- but what they hey- it might help.
11-11-2009, 10:21 PM
I own a 1236P, and have the owner's manual. Here's a scan of the Headstock assembly. Direct link:
11-12-2009, 01:04 PM
Thank you everyone for all your help, I will check the run out first with out the chuck in place and hope for the best...
11-12-2009, 02:18 PM
Once again thank you for all your help, I checked the main shaft and their is zero run out on the inside and the out side, so now I know why we have senior members and, well those of us who have no clue. anyway you all saved me a big &$$ headach. I took apart the mounting plate for the chuck, cleaned it, cleaned the shaft and threads, placed it back on the lathe and found that it has .008 run out on the edge and @ .003 on the face.
so the obvious question what do I do now? by a new mount? a new chuck? or both. can I fix this at all?
11-12-2009, 10:13 PM
Well, now you mount ,remove, and remount that backplate a few times to see if it always comes back to the same runout. In other words, the same spot should show the same high or low with your indicator. Also it should fit well to the spindle without having any gaps where there shouldn't be. If so you can then re-machine it in place. If the chuck has to register on a part of it, you may have to turn that diameter a little smaller, then use a shim of something to bring the diameter back to what the chuck needs it to be. The aim is a snug re-mounting of the chuck onto the backplate.
A good examination of the chuck mounting surfaces is in order. There was probably a good crash at one point, bending something. Hope for the backplate to be that thing, then maybe consider just replacing it. You'll probably have to machine the backplate in place to fit the chuck, but there should be enough material on it that you can turn it to size and not have to use a shim.