Thread: DANGER!!! I have an idea

Seeing that my little lathe is almost a hundrid years old and parts are almost impossible to find has me wondering about making a few parts to get her in good shape.The little clutch gear seems to be a short lived idea that doesn't seem to show up after the 20's.The gear doesn't seem to be something that couldn't be fixed quite easily,hence my idea! why can't the gear teeth be machined off and have a ring cut that could be sweat or pinned or tac welded back onto the gear body.The gear has 31 teeth and is about 3" in diameter.Without this gear I can't run any of my feed functions.

What do ya think?

What exactly is wrong with the gear? teeth too short to engage the worm? Are you sure its not the worm that is worn? If I had a choice, I would remake the worm...

allan

If you look at the first pic,the bottom of the gear shows a flat spot where the teeth are worn away. The worm looks OK but does show some wear in the two center teeth.

if it functions then just lube it up and re-assemble- it only runs the feeds so it`s no biggie if it`s worn.
now if it doesn`t function, then that`s different... your idea would work fine, but the real difficulty is that it is not a straight cut spur gear, obtaining the gear will be the hard part($$$$) and it is not easily made for the average home guy like a straight cut spur gear is.

ps- i can`t tell from the pic, so my reply may be way off base

I guess it doesn't function enough to keep me from being frustrated and it is not something that I can do,that is why I posted it.The machinists that I used to work with did this type of repair often on some of our old paper machine parts and being much larger were probably more suited for this type of repair.

I have been searching for parts for a few months now and my apron just doesn't come up so I feel that if I want to be able to use this machine I am going to have to get some things fabbed.as long as it doesn't cost me the price of a new lathe then I think it will be worth the effort.

Ok- so some of the teeth on the gear are sheared off. Will it drive ok until it gets around to that spot? If so, I would consider brazing a little lump where each tooth was, and milling them back into shape. It would not be a perfect worm wheel, but the depth is pretty shallow, so you could plunge cut with a form tool in a flycutter.

If you are not setup to do that yourself, then you had best be sitting down when you get a quote to have that thing made...

allan

OK, I'm gonna throw out an idea and you guys can howl with laughter if you want:

When I first got my 9" Jr. lathe way back in 1974, it did not have a threading dial. I moaned and groaned about that until my dad suggested that we ought to be able to make one. I was with the program except for the part about cutting the worm gear that has to run with the lead screw. What we did was to first duplicate a section of the lead screw thread on a piece of drill rod steel. It took some doing but we finally got the tool bit ground right and we were able to cut a duplicate of the lead screw. We hardened the duplicate screw section and ground away portions of it to make an 8 flute gear cutter.

Then, since South Bend had seen fit to make the threading dial worm gear on his 9" workshop lathe out of brass or bronze, not sure which, we reasoned that we could make one out of brass and it should work for quite a while. We also reasoned that if we were to mount the gear blank with the spin axis vertical on top of the tool rest on the compound, we might be able to get the the gear cutter we'd made out of drill rod to cut the worm gear and also rotate the gear as we cut it. So, with the gear cutter being rotated by the lathe, we just advanced the cross feed on the carriage to start the cutting process and advanced it until we had the tooth depth we thought we needed on the gear.

It turns out that this technique will work for a gear of that size IF you get the diameter of the blank just right. I think it took about 3 tries before we got the process to give us a gear of the right diameter with the correct number of teeth on it. The point is that it did work and that threading dial still works today some 35 odd years later. (The body of the threading dial was made on the lathe in pieces and the pieces welded together to position the threading dial in the correct location on the carriage.)

Depending on how serious and/or desperate you are, I suspect you could make yourself a duplicate of the worm, turn the duplicate into a fluted gear cutter, and cut yourself a matching worm gear in brass or bronze....or maybe in plain old aluminum if you don't work the feeds too hard. It might be worth a try if your lathe can still cut a thread even though the power feeds don't work.

Vandis,Yankee ingenuity at its best!! Trouble is I don't have any threading gears or a milling machine so I am really needing to get creative.

where are you located?

What Vandis said will work. I rebuilt a speedo drive dear for a Triumph 650. Yours will be a lot easier than that. I had a friend tig weld the bad area of the drive gear and leave the very ends of the teeth original for reference. I roughed the teeth in with a dremel and files, made a hob out of drill rod and hardened it. I chucked the drive gear in the old unmentionable lathe, walked the bench drill press up to it with the hob(probably unmentionable but made in USA). I clamped the press in place, put the belt in slowest position to make the motor drag act as a brake and ran the lathe till it smoothed out.

This was long before I found the internet. 1986 or 7. But I sold that bike in 1995 to a friend and just recently met the man that bought it from him. Neither has had to change the speedo drive.

Ben

There's a lot of info on making hobs and cutting worm gears in this thread:

Thread Dial Kits, any interest?

Seems all of my pics are dead links from a previous ISP. I should upload new ones...

nmaineron,

We're about 220 miles south of you in the Portland area

City folk eh!Love Portland,my daughter lives there.