Next up - gear cutting/ gear cutters!

[Chris152]

We have a B&S dividing head, which we bought a while ago. We want to learn to use it, but don't actually need to cut any gears so I'm reluctant to buy specific cutters til we do. They're not cheap, especially if we buy individually. Cheap sets go for about £70, no idea if they are any good - so far, most of our kit has been old, good quality and relatively cheap.
I'm wondering about mounting a steel disc in the chuck and just marking it with a milling cutter at the edge in the correct positions, just to get the idea of locating the cuts. I've watched a few videos on how to make the rotations, and we have three discs to select them.
Does that make sense as a method for learning the tool? Or would we be missing a whole other dimension of gear cutting? (Speed/ feed/ depth, of course.)

I'd appreciate any advice.
Thanks, Chris

 

[ChaiLatte]

I'm wondering about mounting a steel disc in the chuck and just marking it with a milling cutter

Glue a piece of paper to the steel disk and use a sharpie held in the machine's spindle to mark it. If you end up with a 'gear' having 29 1/2 teeth, you know something has gone wrong. Change the paper and try again.

When confident, substitute paper for plywood or MDF and sharpie for something more sharpier.

 

[Chris152]

...substitute paper for plywood or MDF and sharpie for something more sharpier.

Great idea. Thanks.

 

[J-G]

but don't actually need to cut any gears

Dividing heads are not just used to make gears. They can be used to create 'flats' at specific angles to each other, specifically squares and hexagons, but actually and polygon you happen to need.

Gear cutting often requires an odd number of 'turns' plus 'holes' depending upon the number of teeth and which index hole ring you select. To learn the basics I would recommend that you set it up to mill a hexagon. If your head is a 'normal' 40:1 ratio then having cut one side, you'll need to turn the 'handle' 3 and 1/3rd turns - so if you use a plate with 30 holes that becomes an easy 3 turns plus 10 holes, if you have a 60 hole plate then it's 3T + 20H - - - - and so on.

 

[Chris152]

We'll definitely have a go at a small hexagon, J-G. Ours is indeed 40:1.

Didn't have a Sharpie as such, ChaiLatte, but we have some whiteboard markers which wipe from the steel, even easier to start with. This was just direct indexing to get the idea. I'm genuinely excited that it works - our first go!

Which oil is best for these - ISO 68 or 32?

 

[ChaiLatte]

...if you use a plate with 30 holes that becomes an easy 3 turns plus 10 holes, if you have a 60 hole plate then it's 3T + 20H

In principle, you are correct, In practice, it would be most unusual for a dividing head (especially one with a 40:1 ratio) to be supplied with either a 30 hole or 60 hole plate as they add no useful prime numbers to the dividing range.

The foundation below what you saying is that the hole circle must be exactly divisible by three.

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To the OP: have a look on the Internet Archive. There are two books called 'Treatise on milling'. One is by Brown and Sharpe, the other by Cincinnati. There is not a lot relating to dividing heads that they do not cover.