Dividing heads reviews & opinions?

[Senna]

Thank you all for your comments!

In reference to Ken's comment regarding the length of the thread, is it that dividing heads are not a very popular accessory for hobby machinists? In that case it might suggest that they'd be easier to find in "non-hobbyist" circles.

@Senna, you also said that you'd stay away from the oldest examples of the US units -- why? Is it just that they've seen the most wear & tear, or do newer units have different features? Are there any tells to help separate the older from the newer models?

With regard to the universal & semi-universal models -- I've seen some which pivot down from the horizontal perhaps 20 degrees and up about 80, thus making it impossible to mimic a rotab. Is there a common range of motion for the arc that the universals can traverse? It would seem to me to be enormously useful to be able to set the spindle into the vertical position.

@COMachinist, thank you for the images! How are the dividing plates used/mounted with your rotab? I've never seen dividing plates used with a rotab.

Would anyone have any guidance about what constitutes a "good" or a "reasonable" deal in a dividing head? Or are there too many factors to make any useful generalizations?

Hannes.

Hannes,

The primary reason I'd stay away from the oldest examples is the wear and tear you mentioned. Also the oldest ones have some REALLY esoteric parts and many of the accessories shipped with the DH when new have been scattered to the four winds over the decades.

The oldest examples are usually easy to spot because they look strange.
Here's an old B&S which also has the feed shaft for driving from the table feedbox.
http://www.ebay.com/itm/MACHINIST-T...0?pt=BI_Tool_Work_Holding&hash=item2c7b54bea4

I wouldn't touch this one.

Most Universal DH's I've seen will rotate slightly past straight up.

You will definitely be better served in the industrial marketplace than in the hobbyist marketplace. Just so much more choice.

On eBay I'd be looking for true auctions with no reserve rather than the BIN listings. I'd look to sellers such as STM Surplus and HGR Auctions. Both have true auctions with very low starting prices. Occasionally these will yield fantastic bargains.
I'd also look at the HGR website. Sometimes, usually actually, HGR has great pricing. They're easy to deal with and shipping isn't bad.
My salesman there is Marshal Michaels. If you need to pick a salesman you could do worse than Marshal.

 

[chuckorlando]

When I am looking I search "ending soonest" for auctions. Then once I get to 5hr or 8hr left in the listings I switch my search. I then look at "newly" listed and also switch to "buy it now" just in case a new one comes up for a deal. Gotta snatch it before anyone else see's it.

Yes roto tables can use dividing plates and tail stocks. Both tools have their pros. The table can use the chucks, plates, and tails stock just like a DH but dont do angles. Some do angles but they look rather flimsy to me so I dont pay much attention to those styles. But a RT can be layed down for rounding corners . A DH can lay down as well but they stick up so high they just aint the best tool for that. But as mentioned they can do all kinda angles and are built alot more solid in that department.
http://www.grizzly.com/products/6-Rotary-Table-w-Div-Plates/H7527
Heres a 6in grizzly table that comes with plates and all for reference. I am not endorsing it

 

[Stonebriar]

So let me ask a really stupid question. What is the difference between a dividing head and a super spacer?

Rick

 

[Marco Bernardini]

So let me ask a really stupid question. What is the difference between a dividing head and a super spacer?

Rick

Generally a dividing head has plate full of holes (it's not a disc brake!!!) to help you to divide a circle into a precise number of parts without to have to calculate the angle.
See these three videos:
https://www.youtube.com/watch?v=pIg8InzUu3U
https://www.youtube.com/watch?v=MXV7eV_WNEI
https://www.youtube.com/watch?v=AUMFXPqCJVs

If you place an hex socket wrench into a vise and a bolt through a scrap of plywood you'll have the cheapest 2, 3 and 6 side dividing table.
With a 12-point socket wrench you can even have more partitions: 2, 3, 4, 6, 12 sides.

 

[Senna]

When I am looking I search "ending soonest" for auctions. Then once I get to 5hr or 8hr left in the listings I switch my search. I then look at "newly" listed and also switch to "buy it now" just in case a new one comes up for a deal. Gotta snatch it before anyone else see's it.

That is the technique I use as well. The only thing I'll add is that sometimes the best auctions, from a buyer's POV anyway, are those that end in the middle of the night or very early in the morning.
Also you may have to cast a very wide net, checking all of Business and Industrial for instance to find the clueless seller who doesn't even know what he's selling.
Miscategorized items often yield great bargains.

 

[Stonebriar]

Generally a dividing head has plate full of holes (it's not a disc brake!!!) to help you to divide a circle into a precise number of parts without to have to calculate the angle.
See these three videos:
https://www.youtube.com/watch?v=pIg8InzUu3U
https://www.youtube.com/watch?v=MXV7eV_WNEI
https://www.youtube.com/watch?v=AUMFXPqCJVs

If you place an hex socket wrench into a vise and a bolt through a scrap of plywood you'll have the cheapest 2, 3 and 6 side dividing table.
With a 12-point socket wrench you can even have more partitions: 2, 3, 4, 6, 12 sides.

So I have seen both with the plates which means they can both index. What else makes them different?

 

[Senna]

So I have seen both with the plates which means they can both index. What else makes them different?

My understanding is that a dividing head and a super spacer are one and the same. Merely different nomenclature.

 

[chuckorlando]

I could be wrong here... My understanding is a super spacer runs off plates with notches in it. It is faster to use a SS spacer as a 6 notch plate will do 1 of 6 every turn. An 8 notch does 1 of 8 etc etc. So no counting or anything. But is limited in the number of divisions on the plate. A dividing plate set covers bout any divsion you could want and on the rare instances it does not, you can use a hole intended for 2x as many divisions or 3x or what ever. So for example if you needed 12 holes a 24 hole set up would work by simply skipping every other hole.

 

[COMachinist]

Thank you all for your comments!

@COMachinist, thank you for the images! How are the dividing plates used/mounted with your rotab? I've never seen dividing plates used with a rotab.
Hannes.

Hi
They have 4 flat head screws that mount them to the hub flange. Then the spring plunger bolts to the worm shaft.
One other thing you should think about. The older DH weigh about 40-65 lbs and some of the real old ones can get up to 100 plus. I'm 65 years old and to lift them up on to my machines, well I would need some help, crane or over head chain hoist or two men and a boy. You need to keep in mind what it is your doing. For me this is just a hobby. I do not do production runs, or job shop stuff. There is no need for a DH/Rotary table that has more cast iron in it than small bock Chevy. :roflmao:
CH

 

[Argonavis]

They have 4 flat head screws that mount them to the hub flange. Then the spring plunger bolts to the worm shaft.

I confess this comes as a revelation to me -- I didn't realize the degree to which an RT & DH had overlapping functionality. I really appreciate the fact that you mentioned this!

While I am clear on some of the distinctions between a DH and an RT fitted with index plates, I'm quite sure I don't understand all the nuances. I'll take a stab at making a quick-and-dirty list below. Corrections and clarifications would be very welcome.

An RT appears to have the following features:

• Pros
  • An RT is intended to be rotated during a milling process.
  • A higher ratio (often 90:1) will improve the accuracy and reduce the influence of sloppy index-hole location.
  • My sense is that RTs appear to gain mass rather quickly as the radius (table-to-CL) increases. This would tend to increase rigidity, even while decreasing "portability".
  • Since the RT has both a tapered spindle and a table with T-slots, work-holding is very flexible.
• Cons
  • Since their form factor is defined by the diameter of the table, they can get quite wide/high.
  • Similarly, the larger tables can get quite heavy.
  • The higher ratio requires more cranking, thus makes operations slower.
  • Most RTs appear to be either horizontal or H/V, but cannot pivot throughout a range of angles like a universal or semi-universal DH.
  • RTs don't typically have provisions to be synchronized with the table motion.
  • Due to the geometry of the RT handle, especially with index plates, the handle often must extend off the edge of the mill table which places some limits on the positioning of the RT.

DH features:

• Pros
  • Lower ratio (often 40:1) decreases the number of turns, thus increasing speed of operations.
  • Tend to be lighter than RTs of roughly equal capacity.
  • Tend to be more compact in form.
  • Universal & semi-universal models can pivot through a fairly wide range (> 90 degrees), thus making a variety of angled cuts fairly easy.
  • Some DHs have input shafts which allow the DH to be synchronized with the mill table motion.
  • The entire DH, with handle, sits high enough on the mill table that positioning is not as much of an issue as with an RT.
• Cons
  • Is not typically intended to be in motion during the milling process.
  • Work-holding options are more limited by not having a integral table with T-slots.
  • When used in the "horizontal mode" (vertical spindle axis) the overall height of the DH plus the chuck or work-holding fixture can make it difficult to use effectively. Rigidity can also suffer in this orientation.
  • The lower ratio, especially with some 4:1 DHs, can make accurate placement of index plate holes much more critical.

If this synopsis is reasonably accurate, it seems as though the RT is a slightly more flexible device, generally, even while being somewhat more cumbersome in some ways. Would that be a fair statement?

Hannes.