Author Topic: Harold Hall's basic dividing head (Read 14741 times)

xo18thfa · « **on:** May 15, 2011, 09:24:06 PM »

Got started on a Harold Hall “Basic” dividing head project. This dividing head appears in the Workshop Practice Series #37 on Dividing by Mr Hall. It uses a “direct” method of indexing, namely change gears for a lathe. The change gears are from an Atlas 6”.

Mr Hall leaves the design somewhat open ended to suit your existing tooling. My dividing head will have a #2 Morse taper in the spindle for standard collets. If I ever need to mount a chuck, Sherline is the way to go I think. Sherline spindles are 3/4" x 16TPI. #2 Morse taper to 3/4" x 16TPI shanks are available.

I am following Mr Hall’s plan with only one deviation. Instead of locking the spindle with clamping splits sawed into the body, I plan to use the capture nut technique from George Thomas’ Universal Pillar Tool. My milling machine is not very rigid and probably won’t make those substantial cuts in the dividing head body. So, we will see how capture nut will work.

Here’s Mr Hall’s basic dividing head.

Here’s what’s been done so far.

Here’s the roughed out spindle. This week I’ll take it to a friend’s shop and have the #2 Morse reamed in.

The thrust collar on the spindle is pressed on. Mr Hall specifies carving the whole thing from solid. I did not want to waste all that material. The hole in the spindle is step bored to match the #2 Morse. Read somewhere that helps ensure the ream goes in straight.

Everything is coming along well so far.

sbwhart · « **Reply #1 on:** May 16, 2011, 01:24:44 AM »

Nice bit of machining

that will be a handy bit of kit

Stew

John Rudd · « **Reply #2 on:** May 16, 2011, 04:55:02 AM »

This was one of the first jobs I tackled when I got my first milling machine....

" My milling machine is not very rigid and probably won’t make those substantial cuts in the dividing head body" Didnt have a problem using a 4 in slit saw to cut the slots on my mini mill...

I used En1a for the shaft/block and cast iron for the bearings, basically built as per the instructions by Mr.Hall...

Must say, it has worked great for me using the gears from my 9*20 lathe as indexing wheels.....

Good luck with the project..

Bernd · « **Reply #3 on:** May 16, 2011, 09:26:45 AM »

Bob,

I was so impressed with your grinder table build and how nice it looked it inspired me to order the book. I also ordered the Lathe version of the series.

Thanks for showing what you've built out of that book. Sure inspired me.

Bernd

Sorekiwi · « **Reply #4 on:** May 16, 2011, 08:19:53 PM »

That unit is on my "round tuit" list (and has been for a couple of years!!)

I have a small rotary table, but the dividing head looks like it would be a lot more conveniant.

There's another pic of one in this thread: http://madmodder.net/index.php?topic=3506.0

Great work so far!

xo18thfa · « **Reply #5 on:** May 16, 2011, 08:48:57 PM »

Thanks men. "putzed" on it a bit more today. Boring out the headstock and taper ream the spindle are the 2 big jobs to do.

Kenneth: The spindle is 1018 cold roll. The headstock is 12L14 free machining. Maybe not the best choice, but trying to you up some leftovers.

John: I looked at using the change gears from the 9 x 19, but the Atlas had a wider variety.

Bernd: You can get most of Harold Hall's books thru Amazon, for a reasonable price.

Thanks again, Bob

Bernd · « **Reply #6 on:** May 17, 2011, 08:31:02 AM »

Quote from: xo18thfa on May 16, 2011, 08:48:57 PM

Bernd: You can get most of Harold Hall's books thru Amazon, for a reasonable price.

Thanks again, Bob

That's were I found them and ordered from. Thanks again.

Bernd

xo18thfa · « **Reply #7 on:** May 18, 2011, 09:03:45 PM »

More progress on the dividing head. The spindle nose got reamed to #2 Morse taper. Turned out perfect. Looks like it was ground in. The retaining ring and detent thing is done too.

Tomorrow get started boring out the head stock for the spindle.

xo18thfa · « **Reply #8 on:** May 21, 2011, 08:37:06 PM »

More progress. A machinist buddy suggested a method to turn the cotter nut while boring out the headstock for the spindle. Worked like a champ. Turn the hole for the cotter nut first, then bolt in a length of stock. Two parts in one setup.

Harold Hall’s plan calls for cast iron bearings in the headstock. I had some nice bronze bearings on hand, so I used them instead. They are a very light press fit into the headstock.

Spindle fits in just right and turn very smooth.

All the hard work is done. Should get this project wrapped up this week.

Sorekiwi · « **Reply #9 on:** May 21, 2011, 10:21:26 PM »

Nice! That trick with the cotter nut is pretty slick too - saves time and guaranteed to fit perfectly!

xo18thfa · « **Reply #10 on:** May 23, 2011, 08:42:11 PM »

Got the last of the small parts done and the dividing head is operational. Here’s the single gear set up.

The cotter nut locking scheme for the spindle works great. It does not take much turn on the handle to fully clamp down the spindle. I went with the split nut rather then solid.

Here is the multi gear set up.

There is a design fault in Mr Hall’s plan for the multi gear arrangement. The plan calls for a key slot only part way along the spindle. The key slot needs to go all the way to the shoulder in order to secure the inner gear. Rather then try to mill the slot longer, I inserted a half-inch spacer between the detent arms.

That should solve the problem. If you build one of these, be sure to mill the slot all the way to the main shoulder on the spindle.

I ordered a set of #2 Morse taper collets. Just need to make a little draw bar to fit.

Next is the paint shop and a nice storage box.

Bernd · « **Reply #11 on:** May 23, 2011, 10:25:10 PM »

Nice work Bob.

Received my book today. I see that I'm going to be busy with some new tooling projects. Thanks for motivating me with your fine work to buy the book. Now all I need to do is find time to get round-tuit.

Bernd

xo18thfa · « **Reply #12 on:** May 24, 2011, 11:40:10 AM »

Quote from: Da_Kengineer_Meister on May 24, 2011, 01:23:17 AM

This did indeed come along very quickly. The work looks great! Have you had a chance measure the amount of slop / backlash under force when it is locked up with the 2'nd gear engaged?

No, have not measured it, but it's there. Have to use the time tested backlash remover, tension by hand when tightening. The total run out on the spindle nose is 0.0004". Sometimes it's better to be lucky then good.

xo18thfa · « **Reply #13 on:** May 27, 2011, 11:35:56 PM »

The dividing head is all done. Just so happens a set of 2MT collets came in the mail today.

And the multi gear set up.

And a handy storage box.

It looks like 2011 is the year of shop upgrades. Next up, a boring head.

andyf · « **Reply #14 on:** May 28, 2011, 03:53:08 AM »

You've done a great job there, Bob

I'm curious: is the detent spring loaded, or does it screw down?

Andy

saw · « **Reply #15 on:** May 28, 2011, 05:49:12 AM »

Fantastic nice build

xo18thfa · « **Reply #16 on:** May 28, 2011, 12:15:42 PM »

Andy: Yes, spring loaded

Benni: Nice vertical seam engine build on your website. Turned out beautiful.

Thanks. Bob

Sorekiwi · « **Reply #17 on:** May 28, 2011, 07:55:17 PM »

Very very Nice!

Whats the (black) finish that you used?

xo18thfa · « **Reply #18 on:** May 29, 2011, 01:49:48 PM »

Quote from: Sorekiwi on May 28, 2011, 07:55:17 PM

Very very Nice!

Whats the (black) finish that you used?

Hi Mike: It's just regular spray paint. Dark gray. The camera is not too good.

vr Bob

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Author Topic: Harold Hall's basic dividing head (Read 14741 times)