Author Topic: A small dividing head  (Read 2137 times)

Offline steamer

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Re: A small dividing head
« Reply #30 on: June 22, 2021, 01:19:22 AM »
You"re going to be a very very busy man!

Coming along nicely...
"Mister M'Andrew, don't you think steam spoils romance at sea?"
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Offline RReid

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Re: A small dividing head
« Reply #31 on: June 24, 2021, 01:17:06 AM »
Thanks Steamer! Busy is OK, helps ward off brain stagnation.

Using the DH in rotary table mode worked out pretty well to finish off those old truck mirror clamps.


With that out of the way I've gotten back to finishing the rest of the components needed to use it in the intended dividing head mode. That starts with getting the division plate I made earlier mounted. I turned off most off the boss for the existing 3/4-16 mounting hub, and bored it to 3/4” ID, removing the threads in the process. I then tapped in a brass plug. It's a nasty old thing, with an offset hole through it.  Doesn't matter though, it's only temporary and I could work around the hole.


I center drilled it, the took to whole shebang, still in the chuck, over to the mill to drill a ¼ hole using an end mill. Since the hole I want and the hole already there overlapped a bit, a drill bit wouldn't have run true, but an end mill will. I can now slip the division plate over the worm shaft where the crank arm also attaches. With the worm shaft and the division plate concentric, I tap drilled through the plate and into the side plate of the frame for 3 6-32 screws. Then the holes in the frame get tapped and the plate gets clearance drilled. Got two of the three done today, one left for tomorrow.


Last step will be to knock the brass plug out. Then move on to making a nicer crank arm with a sprung stop pin, etc.
Regards,
Ron

Offline RReid

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Re: A small dividing head
« Reply #32 on: June 25, 2021, 10:24:21 PM »
To finish off the DH, I made a brass stop pin and set it up with a spring cut down from a ball point pen for engagement, and a 5-40 threaded shank with finger nut so I can retract and lock it for “cranking”. Since I've only made the one hole circle at this point, I didn't worry about making the pin adjustable for radius. Ditto for making a pair of sector arms, those these can be pretty easily added as the need or desire arises.



So at this point I consider this small dividing head to be “finished”. Here are few pictures of some of the set-up options it offers.

Horizontal, with 4J chuck. The chuck jaws are reversed and set for a 3” diameter, and there is still plenty of clearance over the table.


Horizontal, between centers with standard Taig tailstock. The dovetail plate is the same one Taig uses to mount the headstock on the milling machines.


Vertical, using the lathe's milling attachment.


Vertical, using a bit of extruded aluminum angle.


Mounted to the lathe cross slide.


Overall I have to say I'm pleased with the compactness and versatility of this design. It remains to be seen what shortcomings show up as I get to using it more!
Regards,
Ron

Online Kim

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Re: A small dividing head
« Reply #33 on: June 25, 2021, 10:27:47 PM »
That is really nice, Ron!

And you've got a lot of good 'use modes' covered with that design.

Well done!
Kim

Online crueby

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Re: A small dividing head
« Reply #34 on: June 25, 2021, 10:51:17 PM »
Sector arms? What are they/what do they do?
 :popcorn:

Offline steamer

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Re: A small dividing head
« Reply #35 on: June 26, 2021, 12:38:59 AM »
Yes   Make ye some sector arms!....Saves a lot of counting and head scratching in use.

Dave
"Mister M'Andrew, don't you think steam spoils romance at sea?"
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Offline steamer

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Re: A small dividing head
« Reply #36 on: June 26, 2021, 12:42:50 AM »
This is part two of his lecture on dividing heads...but he gets into the sector arms explaination, and how to use them   


Look at part 1 too...


Dave
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Offline steamer

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Re: A small dividing head
« Reply #37 on: June 26, 2021, 12:45:59 AM »
Also ...consider a spindle lock.    With a spindle lock, you avoid the work vibrating due to the back lash of the gearing...it makes for a very rigid setup, and better accuracy.

Dave
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Offline RReid

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Re: A small dividing head
« Reply #38 on: June 26, 2021, 01:01:08 AM »
Quote
Sector arms? What are they/what do they do?

Sector arms are an aid to keeping track of the " turns plus holes" on the division wheel. They consist of two arms that can rotate independently on the worm crank axis, be locked to rotate as a pair, or be locked in place.

In use, one arm would be set at the "starting hole", which is also the hole you must return to to get one full revolution of the crank. The other arm is set at whatever number of holes beyond the starting hole is required for the job in play, let's say as an example 5 holes beyond. They are then locked together as a pair, so they can later be rotated together without loosing their angular separation.

The first cut is made with the pin in the starting hole, then the crank is rotated the required number of full turns (marked by the 1st arm, plus the 5 holes (marked by the 2nd arm), the pin is inserted there, and the second cut is made. Next, the arms are rotated together to bring the 1st arm to the current pin position, and the cutting process is repeated.

This image of a Brown & Sharp version should help.

Regards,
Ron

Online crueby

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Re: A small dividing head
« Reply #39 on: June 26, 2021, 01:03:24 AM »
Thanks for the explanations guys! Great videos too!

Offline steamer

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Re: A small dividing head
« Reply #40 on: June 26, 2021, 01:04:28 AM »
Quote
Sector arms? What are they/what do they do?

Sector arms are an aid to keeping track of the " turns plus holes" on the division wheel. They consist of two arms that can rotate independently on the worm crank axis, be locked to rotate as a pair, or be locked in place.

In use, one arm would be set at the "starting hole", which is also the hole you must return to to get one full revolution of the crank. The other arm is set at whatever number of holes beyond the starting hole is required for the job in play, let's say as an example 5 holes beyond. They are then locked together as a pair, so they can later be rotated together without loosing their angular separation.

The first cut is made with the pin in the starting hole, then the crank is rotated the required number of full turns (marked by the 1st arm, plus the 5 holes (marked by the 2nd arm), the pin is inserted there, and the second cut is made. Next, the arms are rotated together to bring the 1st arm to the current pin position, and the cutting process is repeated.

This image of a Brown & Sharp version should help.



 :ThumbsUp: 8)
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Offline RReid

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Re: A small dividing head
« Reply #41 on: June 26, 2021, 01:19:02 AM »
Quote
Also ...consider a spindle lock.
Quote
Thanks for the input and the videos, Dave!

I do have a spindle lock, consisting of a nut at the back end of the spindle that can be tightened against the bushing. That is effective, but I can see where it may prove awkward if it requires two wrenches and two hands to tighten it without rotating the spindle. If that's the case I'll install a more traditional clamp style brake. That was the original intention anyway, so there is room for it.
Regards,
Ron

Offline steamer

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Re: A small dividing head
« Reply #42 on: June 26, 2021, 01:21:47 AM »
Quote
Also ...consider a spindle lock.
Quote
Thanks for the input and the videos, Dave!

I do have a spindle lock, consisting of a nut at the back end of the spindle that can be tightened against the bushing. That is effective, but I can see where it may prove awkward if it requires two wrenches and two hands to tighten it without rotating the spindle. If that's the case I'll install a more traditional clamp style brake. That was the original intention anyway, so there is room for it.

 :ThumbsUp: :ThumbsUp: :ThumbsUp:
"Mister M'Andrew, don't you think steam spoils romance at sea?"
Damned ijjit!