Curse of using a machine to upgrade another.

[swatson144]

A while back I bought a Jet 9x20 and quickly started not liking it's lack of features (for me it's a good machine but I am spoiled). More recently I was blessed with a 12x36 Jet. I had already done some mods to the 9x20, tumbler reverse, 4 bolt clamp, and a few others.

When the 12x36 was installed the 9x20 became a trainer lathe and didn't see much use. A year or so went by the 12x36 got a collet set and some other niceties. It had proven itself to work well. So I decided it was time to start dealing with a few more of the 9x20 problems. With no power cross feed it was bad enough but it felt like twiddling an etcher sketch knob.

The picture shows that the "bearing" surface is cam shaped (feft of the flange and bench block.
View attachment 41398
As I crank around on the tiny little wheel I kept expecting do do de do de doo doo de do POP goes the weasel! So I decided I'd do a Steve Bedair kind of mod and go with a longer mount
View attachment 41399
and a 7/16 x 20TPI lead screw. The bearing was a nice press fit 16x8x4mm and all was going so well. There I was with a piece of A-2 hanging out of the collet on the 12x36 just trying to find a method to get a good finish and on the second wimpy little pass with the second tool the curse set in! I had checked to make sure the tool left me with clearance to the end of travel (I'd even had to adjust the compound) with a full 1/4" I went with the RL-5 and at the end of a not quite optimal cut I found the feed lever felt as if it was welded solid. A quick glance down to make sure I was moving the right lever the right way and then a grab for the clutch just at the time of the crash.



I've put the 9x20 back together So I have something to make the gear blank with and I'll be repairing the 12x36. It looks like the gear had been brazed before .

More to come over the next few days.

Steve who says craptastic things happen to me such as loosing the inline pictures.

 

[8ntsane]

Sorry to hear your being cursed Steve. :nuts:
Some days certainly feel that way, been there, done that,,

Hopefully nothing else was damaged, and the repair goes smoothly. Sounds like you have a gear to cut now.

Hope it goes well.

 

[swatson144]

Thanks for the good wishes Paul.

I got the little lathe back together, Took the 4jaw off the rotab and mounted it on the 9x20. Turned the blank. remounted the chuck and blank on the rotab sitting on the mill.

I don't have a 1.75 mod involute cutter but I have something very close and it should get me back running if I fudge 2 degrees on a second pass. If it runs too loud I'll buy a #6 1.75 mod and do it again.

Hopefully I'll be to busy making money tomorrow but if not I'll be cutting, drilling and broaching.

I did call Jet and they found the part but it was "obsolete to them" Oh well the tooling (cutter and broach) I need would be about 100$ to my door but I think I can pull it off with stuff in hand (for my use). I figure they weren't exactly precision gears 30 yrs ago when they were made and haven't improved with age.

Steve

 

[DMS]

Curse of using one machine to upgrade another... I don't get it. That's normal, right?

 

[swatson144]

It's like the one you are using to do the work gets jealous of the one getting the upgrade. That supposedly starts the curse.

Even though there was no sign of pending trouble I had been wanting to go through the apron on the 12x36 but put it off until the 9x20 was a little more pleasant to use. I haven't liked the way the half nuts engage

Steve

 

[swatson144]

Well the Jet 12x36PS is repaired. Finally.

After spending time scrounging up stuff the should work to replace the 16 tooth, 1.75 modulus, 16mm ID. I ended up using a lot of what I had on hand or my friend had. I did not find a 1.75 modulus cutter but I have a bunch of involute cutters to work with.

I set up a 1 /14" chunk of brass on the 4 jaw on the 9x20 and turned it to OD of 2.239. Then the 4jaw and work piece came off the 9x20 lathe. After removing the back plate the chuck was mounted on the rotab with dividing plates. (I had previously trued the bore in the chuck so it just drops onto a bushing for this kind of work) The rotab was mounted on the mill drill and aligned for work.

After hitting the bottom of the involute cutter to the point that the gear teeth were sharp I was still no where near meshing with the driving gear. At this point they were pretty nice looking.



The roots of the teeth were too wide (or the valleys were too narrow) so I selected another involute cutter to hopefully get a little closer. At this point I started trial and error, getting closer to something that should work but getting uglier all the time. I'd put the driving gear against the blank to check it. By the time it got to where it seemed (measured as best possible) like it would at least fit into the machine, it was ugly indeed!



So nothing to do from there but take the chuck and work over to the functioning lathe and bore it to 16mm bore and test fit.

Sorry but the inline pictures is screwing up on me again I can see the pictures in the preview but can't see them in the message panel, so I can't type around them.

The picture below the meshed gears is the spare gear I made at the same time as I made the repair gear. The lathe is assembled and working quieter than it has ever run and working fine. This was all caused by the ball detent on the feed lever and that has been replaced while I went through the apron for potential problems.

The worst part of the dis/re assembly of this machine is removing the confounded switch. It has to be removed to get at the feed selector shaft. The wires are too short to get the switch out of the box while it is in it's position, but you can't move it until you get the 2 SHCS screws out from behind the switch. So when I got it all back together again the lathe wouldn't run. "DANG!" says I. After once again removing the switch box and the wire stays so I could get the switch out for a look. I could see that a starter winding wire had pulled loose while wiggling the switch to get at the screws. If I ever have to mess with that switch again I am making a new box that will be easier to R&R.

Steve

 

[PurpLev]

nice repair job. and good thing you had a backup