Dividing head advice

I had assumed that the photo showing the spindle height was with the knee fully down which would rather put paid to any chance of cutting if the gear blank could not be got down far enough even if doing a vertical cut let alone a horizontal one unless it's a large dia bevel gear.

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That’s right Jason

Steve, those items in you photo are really indexers as they will just give a small range of numbers which will divide into the 48notched plate eg 2. 3, 4, 6, 8, 12 & 24.

If you could do away with the chuck and mount the gear blank to a short arbor fitted to the taper you may just be able to get it low enough to be able to cut a 45deg bevel, nor sure if there is a way to retain the tapered arbor in the socket.

I notice you also have a Dore, why can't you use that and just angle the dividing head on the mill table? That's how I do bevels on my vertical mill.

Steve, I have a Tom Senior dividing head, which is as compact as any I guess.

Chris Gunn

You are right about the Burke head, I found some more pictures of it, which showed numerous indexing plates, simply with different numbers of notches around the outside. So that one isn’t much use.

I could certainly use the Dore Westbury, however having now bought and refurbished the Burke horizontal mill, if I am to buy a dividing head I would like one if possible that does fit it. It came with a number of involute cutters, and has clearly been used for that purpose in the past, and gear cutting is a natural operation for a horizontal mill.

I took another look at the grinder I want to fix, looks like it’s a 5 1/4” gear with 144 helical teeth.

Perhaps I will start with a couple of change gears for the lathe!

Steve

Edited By Steve355 on 29/12/2021 12:16:55

Well you could always just use the existing gear to index 144T on the new one or just make a section to fit into the gap and save yourself the cost of a dividing head.

If it is a helical gear then one ideally needs a universal dividing head (where the dividing head can be driven by the table leadscrew) and a universal mill (where the table swivels). Like this:

To cut the tooth spaces on a helix:

However, if the gear is narrow, and the helix angle small, then one might be able to get away with a straight cut at the helix angle. A picture of the gear in question would be useful.

Andrew

..there're a few bits and pieces that might be of interest here, not that easy to hit results from a search, but if you pick your way through the various indices..

Vintagemachinery.org - Photo Index - Jefferson Machine..

..if nothing else, you might find some further 'names' to do further searches on, small dividing heads & indexers were also made for lathes & shapers..

here’s a couple of pics Andrew. The small gear is clearly helical, but the large one (the one I want to remake) may just be diagonal cuts. I would say that if a universal table and head is needed, that’s well beyond the scope of me and my little mill. I’ve just had this grinding wheel for ages, it has a broken gear, and I thought it might be a decent little project to learn the process. But perhaps not… there are probably much easier ways to fix it - a welder and a file come to mind.

Steve

Don't worry, you don't need the rotating bed for that, just move the vice or whatever over at an angle. And you don't need a dividing head to make the repair piece. After silver soldering in a repair piece (remember to heat all the gear not just locally to avoid stress) you can mount the gear and with a detent in its one of its own teeth to align the cutter with an existing tooth. Then index off the teeth.

In the good old days, a skilled fitter would file a dovetail for a plug of cast iron to fit in, then hand file the teeth.

Neil

The thing is, the pic shows the worst area but there are several other damaged teeth, perhaps 5 or 6 damaged areas altogether. One other damaged tooth can be seen in the pic of the gear out of the casing. Hence why I was considering making a new gear originally.

The purpose was to learn how to do it rather than necessarily fix this 110 yr old grinder. But fixing it is on my list of things to do so I thought perhaps I could combine the two.

Anyway, assuming I am going to do the repair on the mill and not with a file, I would still need a chuck or arbor holding device to keep it steady and concentric. If so, I may as well get a dividing head or similar.

Steve

Edited By Steve355 on 29/12/2021 22:30:52

144T and 5.25" dia gives 27.8 DP, so 28DP, for a 5.21" OD?

Since it is an old machine, a guess says 14.5 P A?

Relatively easy, if it were a spur gear. The inclined teeth make it more difficult, but not impossible, if the teeth are straight rather than genuine helical.

So the D H will need to be set at an angle across the table of a horizontal mill or inclined on a vertical mill.

It will be interesting to know how you proceed.

Howard

Edited By Howard Lewis on 29/12/2021 22:46:57

The equation for OD, number of teeth and DP for a spur gear does not work for a helical gear. The helix angle also needs to be taken into account. A helical gear has two DP values, normal and transverse. Normal DP is most common, ie, the DP at right angles to the helix. If I get time I'll look at the numbers in more detail later.

My gut feel is that straight cut teeth would probably work, although it would depend upon the precise application and how fast the gear runs. I'm not sure what grinder means; the gear shown looks similar to that on my defunct power hacksaw, used to give a substantial speed reduction.

Andrew

Large dia wet wheel grinder maybe, my Tormek stone runs very slowly.

Tooth count on the pinion would be helpful for those wanting to crunch the numbers as that can be used to get the two helix angles.

It’s a simple hand crank bench chisel grinder. The type your grandad had in his garage. Quite old, made in 1910.

Ah so the big one is the pinion

You can use an online calculator to work out angles and the DP. I did it for 12T & 144T but just change the tooth count to suit your machine

You couldn't expect a sliding safety or the spring bayonet of course

Very nice collection there. Never tried one myself - do you shoot any of them? Top and middle ones look as if they're made for a realistic dispersal pattern of shot. Fourth one down looks especially exaggerated, presumably for visual effect.

I guess it'd be hard to find a use for that many divvy heads...

That’s the first time I’ve had a thread hijacked by an actual highwayman