Fixing up the ol' dividing head

[Deanofid]

Some rebuild work to share, for those interested in that kind of stuff.
I have this little dividing head that I made a some years ago for the Taig lathe.

It's done me a good job, and has helped me in making a small gob of gears...

including these, for a Craftsman 109 lathe,

and these clock wheels and escapement, plus, probably about 60-70 other gears.

It's been a good tool, but is somewhat limited because of the builder. At the time, I had just sold my
Sherline milling macihne, and had planned on a Taig mill in the near future to replace it. Things didn't
work out exactly to plan, but a Taig mill did eventually end up in my shop.

For a while, between a couple of different shop set ups, (about two years time, I think), the only
machine I had was the Taig lathe, and whatever tooling I could make on it. When I realized it would be
some time before I got another new milling machine, I started making tools to be able to do all the
milling projects I needed, using the little lathe. The dividing head was one of the earlier ones, and I
made it with a small 3/8"-24 spindle so I could use it with a good drill chuck. It was fine for using on
the lathe, and was really the only sensible choice, since I didn't have a way to cut larger threads, like
3/4"-16 for the Taig chucks. Larger threads are just not something that can be done with good
accuracy when using a die if you don't have a good way to hold them.

Things change, and I do want to be able to mount a Taig chuck to the dividing head. It will make
accurate setups for things like gears much easier. In the past, I put an arbor in the drill chuck on the
dividing head, and fooled with it, repositioning the arbor in the drill chuck until I got rid of the runout.

I started by taking the little dividing head to bits, putting the spindle block in the mill, and getting the
spindle bore dialed in.

Then bored it out to .625" with the boring head. That's about the largest it can go and still have
enough meat to be sturdy. It's quite a bit larger than the original bore and spindle, which were .470".

Now a piece of 1" stock is chucked up in the "big" lathe, (the 6" Atlas), and a spigot is turned down to
about .600" on one end. This spigot is for work holding at the moment, but will be turned down to
.250" after the bulk of the material has been removed for the spindle running surface. Behind that
diameter, a length is turned just short of the depth of the bore in the spindle block, and to .6245" dia.

Then the spindle block is tried for fit. Got lucky and hit it right on the first try. The fit is nice and close,
and it almost wants to squeak as it goes on.
This part of the spindle is slightly shorter than the block that it runs in, so the spindle can be adjusted
some for end play.

Once all the hard turning is done in the middle of the shaft, the spigot is turned down to .250, which is
the bore of the worm gear. You can see in this picture that it isn't very substantial once it's been turned
down, and that's the reason for leaving it big while taking the heavier cuts in the middle of the shaft.

I used a threading tool to get in close to the live center, and canted it sideways a bit so it could cut to
the corner, and then back it out with the cross slide to face off. What is needed here is a half-dead
center, but all my centers for this machine are either live, or all the way dead.

Now the three jaw is replaced with the four, and the piece is dialed in nice and close for work on the
other end.

The end is faced off to bring the unfinished bit to length, then center drilled for the live center.

It's not very long at this point, but still, I use a live or dead center whenever I can. There's nothing like
having both ends supported if it will fit in with your plans.

More to come after my supper. Just an hour or two.

Dean

 

[ksouers]

Looking good so far, Dean.

What grade steel are you using?

 

[Deanofid]

Hi Kevin. It's 12L14. I bought a few three ft. lengths a while back, in various sizes. I used to get it in
the form of drops from a screw machine shop, but you're lucky to get pieces more than 5" long.
Whatever gets kicked out of the self chuckers.

Here's the second and final part of the project.

After facing, a skim cut is taken off the length to clean up the factory bumpy parts, then a length is
turned to mimic the length and diameter of a Taig lathe spindle nose, since I will be using Taig chucks.

Getting set up for threading.
Compound set at 29 degrees, tool tip set to 90 deg with the work. The tool tip is then run up close to
the work and the cross slide set to zero. This is home base, and lets you run the cross slide in and out
when running the tool tip back and forth with the carriage, so you don't have to mess with the compound
except to dial in another cut.
Set the cross to zero, and you won't loose your place.
An old machinist beat that into my head. Someone else probably beat it into his head sometime before
WWII. His name was Jack Cuddy, and he was a patient guy, and a nice man to have for a friend. I
wish I remembered everything he tried to teach me. I wish he was still around to ask..

Cutting the threads.
The above shot is a number of cutting passes into the job. The first cut I take when cutting threads is
always a very fine scratch on the blued shaft. Then it is checked with a thread gage to make sure I've
got the correct gearing set on the lathe. This way, if I goof with the gearing, I haven't ruined the work.
After that, get serious and dial in a real cut. About .005" for the first cut on this 3/4-16 thread, and
progressively less as the thread gets deeper. Always dialing in the thread with the compound slide.

How deep to take your cuts depends on lathe size, how far the piece sticks out of the chuck, whether
it's supported on the end or not, the diameter of the work piece, and the coarseness (or fineness) of
the thread. It's a judgment call, for sure. When in doubt, take finer cuts, or run a test piece to see how
the equipment will act for the given situation.

Threading oil is usually dripping off my threads when cutting them. I had just run a brush over these to
clean off the chips for the picture. Normally, I use the kind of of cutting oil that is made for pipe
threads. The kind of stuff that smells sort of like sulfur. It has sulfur in it, so that would probably
explain it.
Sometimes I use Tap Magic, which works pretty well, too.

Note in the shot above, a bevel has been cut on the end of the shaft. It was done before beginning the
threading job. Makes for a nicer thread start, and helps that first thread find its way into the first thread
of the chuck, or fastener, or whatever you're going to put on that thread.

When the threads started looking close, I tried one of my chucks after each shallow pass until it went
on without any tight spots. Running the DI on the outside of the chuck shows runout of a bit less than
a thou.

There are thread depth gages made for checking critical threading jobs. Some are built into a
micrometer. Some are a type that uses precision ground thread wires, which fit into the threads and
are then measured with a mic. I was taught how to use the latter method by the same fellow who
showed me a lot of things, but I've forgotten through lack of practice. Shameful. The threads I cut are
all "cut-and-fit", which is probably all that's required in most home shops. If you have to cut threads for
a job to a print with a thread spec though, it requires proper measurements.

This is the original spindle, along side the new one. Much more hefty duty-ish.

Going to the worm gear, now. It had been mounted on the other spindle with a screw through a thin
collar that came on the gear. It needs something more substantial, and, it needs a means of getting rid
of end play in the spindle, so, it has to be able to move back and forth on the spindle a little.

I cut a couple of collars from brass stock. One to act as a thrust washer for the end play situation, and
one that will be the new mounting collar for the gear.

Here, the original collar can be seen, and it's about to be cut off.
To set up the gear in the three jaw without having the face of it wobble, it's put on a temporary arbor
and held in the drill chuck. Then the lathe chuck jaws are snugged down gently. Not tight enough to
smush the gear teeth, but enough to hold it for cutting.

Once the old collar is gone, the new one is lined up with the gear using an bit of round stock, and the
tap holes are drilled through both pieces. Then the holes in the collar are opened up for clearance on
the 4-40 screws that will be used.

It would be nice to counterbore the holes for the screws, but when I put my counter bore pilot in one of
the holes to check, it looked like there would just not be enough meat in the collar. The C'bore would
come through the side. That's called lack of foresight. I should have made the collar a little larger in
diameter.

This shot shows the back end of the assembly buttoned up. Thrust washer on the inside, then gear,
and lock collar.

That's it. My old friend is ready to get back to work. Almost like having a new tool.

Thanks for looking,

Dean

 

[Powder keg]

Looks like you made a good job of it Dean. Nice job on the threading!!! Thanks for sharing.

 

[gmac]

Dean
You've read my mind . After we were talking to Joe D about his dividing head I started gathering the materials for a build - with the thought in mind of changing the spindle to mount the Taig chuck as you've just done. Now I have a cookbook - thank you!
Like Joe I'll have to have someone else cut the 3/4" thread.
Are there any other changes you'd recommend to the general design having spent some time using it?

:bow: Keep reading my mind will you....

Garry

 

[hobby]

Nice job on your divideing head,
I also like the gears you made in the previous post, they look professionaly done,

Looking at all the work you did on this project, it would take me probably a couple of shop sessions to get all that done, (I mean, just to get that spindle done so nicely, would have been a major accomplishment for one evening).

I admire how you were able to keep with this, from start to finish, all in the same evening.

Keep up the good work..

 

[joe d]

Dean

That came out well, and in record time too! I'm glad to see that I'm not the only one to remind oneself of direction of rotation with a nicely placed magic marker arrow! :big:

Garry: Make sure that your spindle lock screw is long enough to clear the Taig chuck... that way you won't have 2 different sized ones in the box you keep the finished tool in like somebody here.....:wall: (oh well, I guess I needed the practice)

Joe

 

[Maryak]

Dean,

And fix it you did - very nice. :bow:

Best Regards
Bob

 

[Deanofid]

Thanks everyone, for the comments, and for checking out the thread.

I didn't mean to imply that I did all this in one evening. It took about eight hours. Some yesterday, and the rest this afternoon. I'm not fast!

Dean
Now I have a cookbook - thank you!
Are there any other changes you'd recommend to the general design having spent some time using it?
Garry

Maybe just a few thoughts, Garry. The writeup tells about making a thick thrust washer to adjust spindle end play. To adjust it, the gear collar lock nut is just loosened and the slack taken out.

If you can work in a way to make adjustments for worm and gear backlash, you'll be doing well. On this one, that is adjusted by shimming he spindle block up a little, where it meets the uprights for the base.

It needs some kind of spindle break. I didn't show how that will be done with the new spindle. (You could see it on the old one). Just some kind of pinch block run down snug against the large bare part of the spindle that sticks out the front of the divider will work. You want something you can set with one hand, like a simple cap screw going through an 'L' shaped piece of aluminum bracket.

Pick a worm and gear ratio that is easy for you to work with.

If you do one like this, you might think of giving it a thicker base piece. Mine now has to set up on a 1-2-3 block so I can use the chuck.

If I think of something else, I'll put it in this post.

Thanks again, all.

Dean

 

[arnoldb]

Good going Dean; a very neat piece of work :bow:
Regards, Arnold

 

[cfellows]

That's a nice dividing head. That gear looks familiar. I've got several 64 pitch, 100 tooth gears that look just like that, including the funky collar. Picked them up on Ebay a year or so ago.

Chuck

 

[ksouers]

Very nice fixup, Dean. I'm going to have to do something similar for my Sherline chuck and the spindexer.