Jet 1236P

All discussion about lathes including but not limited to: South Bend, Hardinge, Logan, Monarch, Clausing and other HSM lathes, including imports

Moderators: Harold_V, GlennW

spro
Posts: 6754
Joined: Mon Feb 20, 2006 11:04 pm
Location: mid atlantic

Re: Jet 1236P

Postby spro » Mon Jul 10, 2017 7:58 pm

Thanks Rex. That is a keeper as are You btw!

jcarmon
Posts: 25
Joined: Thu Jul 06, 2017 3:40 pm

Re: Jet 1236P

Postby jcarmon » Mon Jul 10, 2017 8:45 pm

Well, I found something bewildering. The chuck wont screw on. Ive completely disassembled the chuck, cleaned, re-oiled it, and it just wont screw back on. The still rusted face plate and drive plate screwed on, and cleaned right up. But the one piece I expected to have the least problems with , just throw me for a loop. Yesterday It fit like a glove, today I must have been holding my mouth wrong. Chuck itself works like a charm. Scroll, pinions, and jaws turn with one finger, just as smooth as a new ball bearing. But I must have done something wrong when I remounted it. Oh well, thirds time seems to be the charm.

spro
Posts: 6754
Joined: Mon Feb 20, 2006 11:04 pm
Location: mid atlantic

Re: Jet 1236P

Postby spro » Tue Jul 11, 2017 4:58 am

Well for starters, a section of 2X6 with plywood atop to center the chuck to the spindle. It makes it easier and believe me, untold thousands do that. We are all pretty strong but those chucks are heavy that you can't get the "feel" of the thread engagement. The other thing with mine; the spindle end and thread are slightly tapered, so it is easy for it to start wrong. I was frankly appalled, at the loose fit of those threads but as it cinches up closer, gets much better. The main thing is the register of two parts. The "neck" past the threads is pretty dead on and the back plate is total flush against the thrust surface. I never removed that back plate from that chuck for it could not be any better than it is.
Our dear Harold often advises avoiding threaded spindles, for that and other reasons (like rapid reverse) but we are stuck with what we got at a particular time.

jcarmon
Posts: 25
Joined: Thu Jul 06, 2017 3:40 pm

Re: Jet 1236P

Postby jcarmon » Wed Jul 12, 2017 7:44 pm

It seems its easier to thread the plate on first, and then bolt the chuck to it. Once I did that, it went on and off with ease. Guess I just had to play with it for a while. Ive about decided the designers of this lathe did everything they could to confuses new users. One full turn of the saddle hand wheel is .580". Makes measuring a pain. Three turns should be 1.5 inches, not 1.74 inches. Never thought I'd say this, but I miss metric. And whoever decided not to put some form of chuck stop on this thing is an idiot. Sucker spun itself off threading today. Even my little Harbor Freight tool didn't do that.

User avatar
Rex
Posts: 677
Joined: Wed Apr 28, 2010 6:29 am
Location: DFW Texas

Re: Jet 1236P

Postby Rex » Wed Jul 12, 2017 8:20 pm

The G9249 had a simple chuck lock. The collar of the backing plate was drilled for two clamps that hooked the plate to the spindle. Probably could be retrofit pretty easily if there is room in there.

spro
Posts: 6754
Joined: Mon Feb 20, 2006 11:04 pm
Location: mid atlantic

Re: Jet 1236P

Postby spro » Thu Jul 13, 2017 3:35 am

I was trying to put together how this would happen but I see now. Our Encos were capable of metric as well as inch by the included gears but only one thread dial. Unlike inch, I found that only one spot of the dial could reliably enter the thread. This leads to reversing motor because it is more dependable that way but yeah not with a 20lb.+ chuck.

jcarmon
Posts: 25
Joined: Thu Jul 06, 2017 3:40 pm

Re: Jet 1236P

Postby jcarmon » Thu Jul 13, 2017 10:46 am

My HF 5980 3n1 had a set screw in the cluck plate collar that you could just tighten the crap out of and held the chuck to the spindle when in reverse. Ive got a set of metric taps, so I guess I could drill and tap this one too. How big a set screw would you think I should use? Couple of 8mm should do it I'd think.

User avatar
SteveHGraham
Posts: 6533
Joined: Sat Jan 17, 2009 7:55 pm
Location: Florida

Re: Jet 1236P

Postby SteveHGraham » Thu Jul 13, 2017 11:07 am

This sounds pretty cheesy. I would be concerned about accuracy issues if I had to reattach a chuck to a mounting plate all the time.
Don't trigger me, bro!

spro
Posts: 6754
Joined: Mon Feb 20, 2006 11:04 pm
Location: mid atlantic

Re: Jet 1236P

Postby spro » Thu Jul 13, 2017 2:06 pm

If you use 3 screws spaced 120* apart, you can further adjust the accuracy while locking it.

ccfl
Posts: 118
Joined: Wed Jun 01, 2016 9:14 am

Re: Jet 1236P

Postby ccfl » Thu Jul 13, 2017 5:08 pm

Spindle nose threads are supposed to be loose, right? They should only provide clamping force and let the register behind the threads handle alignment. Otherwise the threads will be influencing things and making threads accurate enough for that task is not easy to do.
"Never trust a man who puts a witty quote in his sig line." -Mark Twain

spro
Posts: 6754
Joined: Mon Feb 20, 2006 11:04 pm
Location: mid atlantic

Re: Jet 1236P

Postby spro » Thu Jul 13, 2017 6:51 pm

Exactly ! I cannot say how far a spindle is threaded from here nor what aftermarket back plate- but- there is a tiny bit of give in the neck register/radial clearance. Now the problem is; driving bolts atop precise threads and what damage that can do. Mine has a fair amount of unthreaded neck register, so 8mm could be set in but that still disturbs the original surface. (sure brass or plastic insert)
I would investigate Rex's earlier information about the clamps.

User avatar
Rex
Posts: 677
Joined: Wed Apr 28, 2010 6:29 am
Location: DFW Texas

Re: Jet 1236P

Postby Rex » Thu Jul 13, 2017 10:59 pm

The clamp deal depends on a groove cut in the OD of the register. I looked at the Logan and. South Bend today and neither had enough material to do this.

But honestly, I cannot recall the last time I needed a lathe to run in reverse. I do remember once I hit reverse by accident and got hurt. I no longer make my lathes reversible unless they come to me that way. Drum switches mostly go to eBay. YMMV


Return to “Lathes”

Who is online

Users browsing this forum: No registered users and 7 guests