Tell me about this 14-1/2 x 6’

[rwdenney]

This post concerns the repair of broken idler cam. At the start of this thread, I knew the lathe’s power-feed shifter was broken off. The shaft was broken right at its base, where it joined the cam itself.

The cam serves two functions. One is that it shifts the idler gear (which always engages the output pinion of the power-feed clutch) between 1.) floating in air (the middle neutral position), 2.) also engaging the cross-feed drive gear (which always engages the pinion in the cross-feed screw), or 3.) engaging a gear on the carriage drive shaft (which also engages the handwheel and the rack in the bed).

The other purpose is preventing both the power feed and the half nuts from being engaged at the same time. The notch in the cam permits the lockout lever from disengaging the detent on the bottom half nut. When not in the notch, that detent is engaged preventing the half nut from moving into the lead screw.

The second purpose is why it broke. The lockout pin was frozen solid in the apron casting from hardened lubricant, and I’m sure someone tried to loosen it by hammering on the handle. Uncle’s son remembers that handle being broken at least 20 years ago, but he didn’t know the story.

The handle shaft is therefore loaded in shear but not in bending. The idler gear is trapped by the cross-feed drive gear, which keeps it from racking on the handle shaft. But it does carry some power-feed drive forces.

Before doing anything else, I drew it up in case I ever need to make another one.

The handle shaft fracture surface fit the fracture surface on the cam tightly, suggesting brittle fracture. That’s good, because that surface interlocks in shear if the two parts can be held together strongly.

So, I clamped it together and drilled a 1/8” pilot hole through the middle of the shaft. I enlarged the hole in the cam plate to the pilot hole size for a 3/8” stud. Of course, I thread it crooked, because I’m a hack. So, the stud wasn’t straight. I enlarged the pilot hole into a clearance hole in the shaft large enough to accommodate the crooked stud, and the countersunk it deeply enough to provide a well for epoxy.

I mixed up some 3M DP420 industrial epoxy and filled the clearance hole, plus applying it to the fracture surface and the threaded hole in the cam.

Here’s the backside of the cam where the stud is screwed in flush to get full thread depth. It’s too close to the stub shaft for the idler gear to allow a fastener inserted from the back.

I then sank the handle shaft over the stud, installed a washer and a nut while the epoxy was workable, wiped off the excess, checked it for alignment, and the let the epoxy cure.

At this point, the stud is mechanically threaded into the cam plate and embedded in a solid mass of epoxy. After curing, the nut isn’t really needed, but I had no reason to remove it.

And then I drilled a hole across the stud so I could ream it for the taper pin that secures the handle. I only broke two drills drilling through the hard stud. I finished it up by hand using a taper reamer, while holding the part in a V-block in the vise. This didn’t go well. I ended up finish reaming it with the handle in place, enlarging it slightly for a #4 taper pin.

Here’s the finished repair:

You can see the epoxy interface in the fracture plane.

It’s back in the apron, which required complete apron disassembly—next post.

Rick “thinking that part could be turned from bar stock without too much drama”Denney

 

[rwdenney]

Rebuilding the apron was a voyage of discovery. I followed along the Ilion Press rebuild book and used their felt kit. I also benefitted greatly from George Bell’s Youtube video made when he restored his SB13.

I reported earlier that my apron didn’t match what Ilion showed, and someone suggested it might be an ex-factory modification. I’m persuaded there were many of those. The handwheel shaft, the shaft holding cross-feed gear, and the idler gear were sleeved or bushed in bronze, which I don’t think is original.

And the bushings for the worm gear were bronze. They were also press-fit, and they simply had to be perfect to work. I suspect they were line-bored or honed after installation. I simply could not them installed so that the worm wouldn’t bind. Every time I pounded them in and out to try a different alignment I had to scrape off the burr raised by the pounding, even using a wood drift.

I noticed that George Bell inserted the (iron) bushings easily without all that drama, and I realized that they were doweled to prevent rotation and didn’t need an interference fit. I sanded them down with emery cloth until they fit with only light tapping—a slight slip fit. That relieved the alignment issue and the worm sleeve turned easily after that. It also allowed me to position the felt channels so that the felts could be routed safely.

(The apron had only a few remains of felts, and I also extracted a nut—the edible kind at least at some point—from the apron sump. That told me where the felts went. It also told me the apron was dry at least at some time since the last time it was rebuilt.)

Some prior rebuilder installed a ball oiler in the casting around the handwheel shaft, and did so decades before Ilion’s book. It kept me from having to add the recommended oiler. The felt for the handwheel shaft really added some drag to the handwheel, but I’m sure that felt will break in.

I really worked the sliding surfaces so the interlock for the half nut would work smoothly and reliably.

I then throughly cleaned the rack and the lead screw. The keyway in the lead screw makes cleaning in place difficult, but I reinstalled the end bearing and cleaned it while the lathe turned it under power. All strategies effectively covered me in grime, but only some really worked. In the end, I used carb cleaner and then ran the edge of a rag in the thread root all the way along the length of the screw as it turned.

The apron is in place, full of oil (SB Type C—Mobil Heavy-Medium ISO 68), and working as it should. It’s clean and has all new felts, but I did not strip the staining or repaint it. As I said in the OP, I’m not a restorer. I just want it to work reliably.

Rick “state of good repair is the target” Denney

 

[gard]

I am about ready to line the saddle V ways with turcite which is a bearing material made to be glued in place. This will be my first experience with it, It almost looks like bronse, its a high tec plastic. Any chance that is what is on yours? I am currently working on a SB 10L but also have a 14 1/2

 

[SLK001]

The apron is in place, full of oil (SB Type C—Mobil Heavy-Medium ISO 68), and working as it should.

If you're talking about the apron reservoir, it should be filled with SB Type A oil (ie, Velocite Oil No. 10 ISOVG 22 - aka Spindle Oil).

I've attached the Lubrication Chart for your lathe.

 

[rwdenney]

If you're talking about the apron reservoir, it should be filled with SB Type A oil (ie, Velocite Oil No. 10 ISOVG 22 - aka Spindle Oil).

I've attached the Lubrication Chart for your lathe.

That chart makes no sense to me, to be honest. All oil drainage from the upper two oilers ends up in the reservoir, resulting in a mix of A and C. And the Ilion book suggested that C oil be used for everything in the Apron.

My chart is in the shop. I wonder if they agree—I’ll check later.

Rick “doesn’t like mixing oils” Denney

 

[SLK001]

Most of the other oil in the carriage is "flow thru" and excess will usually drip into the tray below. The reservoir is a source for wicking oilers and the lighter oils wick the best.

And the Ilion book suggested that C oil be used for everything in the Apron.

The book uses Type C oil as an assemble oil and saturates all wicks with it. My book says nothing about filling the reservoir with Type C oil. In fact, it doesn't mention filling it at all.

 

[rwdenney]

But, sure enough, the chart agrees with the other chart. Like I said, I’m a hack.

I drained the apron and filled it with Velocite #10.

Rick “that’s why I describe stuff—so I can be corrected” Denney

 

[rwdenney]

I am about ready to line the saddle V ways with turcite which is a bearing material made to be glued in place. This will be my first experience with it, It almost looks like bronse, its a high tec plastic. Any chance that is what is on yours? I am currently working on a SB 10L but also have a 14 1/2

It’s definitely metallic bronze and not Turcite. As with all bronze, there is a touch of stiction from a stop but it moves smoothly and does not rock. Near as I can measure at present, the cross slide is at the correct right angle to the spindle, but I won’t be really sure of that until I attempt to face something large enough to check flatness on my surface plate. I indicated the surface of the 7-1/2” fixture plate as I moved the slide, but I have no confidence in that. The fixture plate itself has a runout of 5-6 thousandths, but it has lived a hard life.

The tailstock has also been shimmed (between the v-way casting and the tailstock body) to adjust its height; presumably it was ground to remove wear and then shimmed to compensate and align it to the shimmed saddle. By scribing a point on the end of a ground dowel pin it’s within a couple of thou. But that dowel, though mounted in a 4C collet, showed TIR of about 12 tenths, so I don’t know if it’s the center or the spindle that’s not quite perfect.

I don’t have the Morse taper insert for the spindle, and for turning between centers, my expedient will be installing a straight-shank center in a collet. The 4C collet closer installs in the spindle in front of the face plate, with a bit of overhang so that the faceplate will serve to eject it. But I don’t have the straight-shank center yet.

With my watchmaker lathe, one proves the tailstock by trapping a razor blade between centers, but that may be more precision than I need (or will get) from this big South Bend.

Anyway, I’ve confirmed that its alignment is at least basically okay. Improving the measurement regime from thousandths to tenths will be a lot more work, and the next step for me is some test turnings.

Rick “measurements are more fun than cleaning off grime” Denney

 

[rwdenney]

Here it is after basic leveling and after rebuilding the headstock bearings and the apron. The damage from the moving accident has been corrected and the lathe is fully operational. I’ve taken off a lot of grime but the paint is what it is.

The tool box is a provisional—I’m trying this out. It’s a biggish box (a cheap and cheerful Park from a few decades ago) and it holds tools, the quick-change tool holders (for when I get the tool post mounted), a drawer full of HSS bits, a couple of Armstrong holders, 4C collets, sleeve collets (everything but the chuck), centers, center drills, and so on. Metrology is in a different box, as are general drills, mills, and reamers.

The bar in the collet chuck above was part of getting some baseline measurements. TIR of that collet chuck is a thou or two. It was easy to bump in the bar at the tip, but I would need the steady for machining. (The steady rest and the 4-jaw chuck are still rusty and they are over on the bench.) TIR at the spindle is a tenth or two. I chucked up a 3” bar in the 3-jaw and made some facing cuts. After some experimentation with tool position, sharpening and honing, and feeds and speeds, facing was flat according to a straightedge but I have not measured any more precisely than that.

The live center is an old Do-All, made by Royal. It works but I’ll rebuild it eventually. It came with a slip-on bull nose for pipe.

I picked up a plastic 3D-printed indicator holder and it works really well.

I guess it looks cleaner than in the OP. It’s certainly cleaner on the inside.

Tool post is next. I found a plate that is a close fit to the compound slot that just needs to be drilled and threaded for the 18x1.5 mounting stud for the Shars CXA toolpost I bought. I don’t have a tap that size but one is on the way along with a big enough Greenfield tap wrench.

Then, I can make the dovetail insert for the milling attachment.

Rick “hatching a design for a new connecting bar, too” Denney

 

[SLK001]

Do yourself a favor and clean the paint off your gearbox plate. It will be easier to see and make changing gears quicker.