Making a backing plate on the lathe?

I'm currently tearing down and rebuilding my new to me 9" Southbend
lathe. It had a lot of gunk in it, and a few missing or damaged parts.
The only show stopper is the backing plate the HF chuck was mounted on.
It was aluminum and apparently was either crooked as all hell to start
with or got bent in the move. A good 1/8" runout.
Since I have a pretty good supply of 5/8" thick steel available I'd
like to make a back plate from it. The 4-jaw chuck is still usable
despite the broken screws, so I'll use it to hold the plate and make the
center hole. Then screw the plate on and finish it.
But I've never done any internal threading before. What do I need,
and how do I measure it?
I could just cut the plate flat and then swipe the threaded bit from
the back of the 4-jaw and screw the two together. But I'd rather have a
one-piece plate. Actually, either way I go I suppose I'd have to have
two pieces since my raw plate is 5/8 thick and I'd need a hub of some
sort where it threads onto the spindle.
Anneal the steel plate? It's the intermediate plate out of a 15.5"
clutch, so the surfaces are probably work hardened to some degree. Plus
having pieces of ceramic worked into the surface.
Also, the step pulley around the spindle is gummy. How to clean it
out? If I have to take it apart, how do I get it apart? Getting it
apart would be handy anyway because then I'd have the option of putting
an automotive belt on in place of what came with it. The current belt
slips a lot at high speed and tends to jump out when the splice meets
the slipping pulley.
Reply to
B.B.
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Sometimes I think people don't look at the excellent metalwebnews site. Try:
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Grant Erwin
B.B. wrote:
Reply to
Grant Erwin
Unless the flat belt is stretched on one side, it sounds like your pulleys aren't parallel.
If you've never done any threading, I'd recommend getting a partially finished chuck backing plate from one of the suppliers, at least the threads are finished and all you have to do is turn the thing so the face is perpendicular to the spindle and it's flat and turn the diameter to fit the chuck. I've made them from 1" hot rolled, you start by making a male replica of the spindle nose for a testing gauge. I had a number of disks that were flame cut, scrap from a large crane maker. One of these was drilled, tapped and secured to a faceplate. Getting the edge cut down was a lot of fun because of the HAZ from the cutting operation. I had a boring bar setup for doing the initial boring, this takes awhile. The threading tool fit the boring bar, I ground one out of Tantung because I didn't want to have to keep stopping and resharpening. You DO need a threading gauge for both grinding the tool and setting it up. It probably took a couple of hours to thread it to depth on the gauge, you do also have to turn the register once it's threaded. The first one I made was the first really coarse internal thread I'd ever cut. Chewing off the extra thickness to cut the weight down took a number of extra hours. Lots of chips left on the floor after that job!
Once you get the threads cut, you can remove it from the faceplate, mount it on the spindle and true up the mating face to the chuck. This would be the starting point for the partly finished back plate. If the threads don't fit the spindle at this point but fit the gauge, you've got a problem. I've picked up threads before and recut, this is NOT a job for a tyro, though.
I wouldn't use anything but hot-rolled or cast iron for a back plate, cast iron would be my preference because of its mechanical properties. Anything else is liable to have stresses in it. It IS the basis for whatever precision you get with the chuck, after all.
If you've got no faceplate and still want to do it, swipe the back plate from your dud chuck, check for trueness and attach your slab to that. Just don't run the boring bar into the spindle bore!
You can locate the holes for mounting the back plate by chalking up the chuck recess, putting the new back plate in place and giving it a rap with a rawhide mallet. Shadows of the holes will show up and you can use those to centerpunch and drill.
Some of the old machinist's manuals give a better description of how to fit a back plate.
Is the pulley's surface gummy or is it the bearings? If it's the surface, it's probably somebody's belt dressing and you'll have to use some solvent to clean it off. I've never had my spindle out, but there's a split threaded collar on the outboard end that you can remove, I'm not sure if the spindle just slips out at that point or whether there's something else that has to be removed. Don't have an exploded view handy.
Stan
Reply to
stans4
Go to Ebay and get a copy of "how to run a lathe", the Southbend version. It'll answer many of your current questions. I'd agree with another poster who suggested that you buy a threaded backplate from someplace like Enco, etc. Later on you can make spindle stuff.
Pete Stanaitis -----------------------
B.B. wrote:
Reply to
spaco
You are correct. I've bookmarked it. Thanks!
Reply to
B.B.
I haven't bought any of these backplates from this supplier, but the plates are threaded for some common spindle threads. Look near the bottom of the Lathe tooling page, Machine Tool Toolings, Lathe Tooling
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They have 4" to 8" semi-finished threaded plates for plain back chucks from $29 to $49. Threads available from 1"/10tpi to 2-1/4"/8tpi
You might find that making a steel plate and threaded hub will end up being quite a big job, and might not provide optimal performance. If I were fabricating this type of part for myself, I would probably approach the hub portion as a section long enough to be tightly press-fit into a bored hole through the plate, and welded together. Anything less might not provide a safe or secure mounting method.
WB metalworking projects
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Reply to
Wild Bill
If you've got $30, here's a semi-finished one:
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Certainly worth that to avoid having to try to do internal threading.
Stan
Reply to
stans4
So I put the lathe together and found that the gear change box is too badly worn to work properly. I can't run the left lever in the 'A' or 'E' positions. In A the gears bind up after a revolution, and the lever simply will not go into E at all. The other lever is just hard to move, but still works. This means I can't possibly cut the threads to make a back plate without fixing the levers. It all comes down to the bore in the end of the lever is so badly egg-shaped that it cannot stay in place. Other than a few scars the shaft is fine. The gear teeth all look like crap, but don't appear to be the source of the problem. Alright, I plan to put the lever on the 4-jaw chuck and bore it out for some brass bushings. I intend to loc-tite the bushings in place. Do you think loc-tite is acceptable? Can anyone tell me what the correct distance between the idler shaft and the hole I'm cutting is? I don't have a good one to take a measurement from. I could probably get away with just eyeballing it since the gears themselves are in bad shape, but I'd like to have the distance right in case I get (or eventually make) new gears. Recommended way to finish the bore? I figure I'll leave it rough for the glue's sake. How snug a fit between the bushing and shaft? Someone mentioned that the factory wiring should be able to reverse the motor. (single phase) the motor I have is not original and the wiring has been changed, but the switch seems to be OEM. How does one go about wiring a single-phase motor to reverse? Also, anyone know how to get the spindle apart? I still need to clean the tar out of the inside of the step pulley. It looks like I'll have to pull the gear off the tail of the spindle, but I don't want to go forcing anything before I know for sure. I tried uploading some photos to the dropbox under "BBlathe".
Reply to
B.B.
Yes, absolutely!
The way it is, is OK. :-)
A gap of 0.1mm is ideal. You can make it a bit smaller if the bushing would mis-align. But Loctite is quite good in centering light parts.
HTH, Nick
Reply to
Nick Mueller
In it's simplest form, a motor (assuming 110v here) has 3 wires, a hot, a neutral and a "starter" wire. When the starter wire is connected with the hot, the motor runs on direction, when connected with the neutral, motor runs the other direction. With multi-speed motors, more wires are present and the connections become murkier. Search for any wiring diagrams on the motor, look into any coverplates, try to find a wiring diagram and study it. It may be apparent how its done. Some motors cannot be reversed because the starter wire is integral with the winding and not available for change. If you can find wiring that's not clear to you, maybe post of closeup picture of it so we can see it.
The reversing switch you mentioned changes the connection of the starter wire from hot to neutral.
Reply to
Gary Brady
What lathe was this? I may have a spare gear box
Gunner
Political Correctness
A doctrine fostered by a delusional, illogical liberal minority and rabidly promoted by an unscrupulous mainstream media, which holds forth the proposition that it is entirely possible to pick up a turd by the clean end.
Reply to
Gunner

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