Myford Bull Wheel Indexing

My toolpost mill is very convenient to mount and I have been considering a similarly quick and convenient way to do simple indexing rather than mount my GHT HDA. This solution is based on Harold Hall's design **LINK** except I have made the base a permanent feature, that still allows the headstock cover to shut on to the buffers. The indexer slides onto a T slot and is secured by half a turn of the locking lever.

The detent spring is pretty strong, hence the big knob. The traditional coloured dots are for 4, 6 and 10 divisions.

Rod

That's cute, neat and well executed.
Nice job!

Lucky, you myford users. The bull wheel on my lathe has (useful?) factors of only 5 and 13, I think!

Neat, you could have won the MEW reader's Tips with that

Neil

Someone will now suggest you make an expanding arbour to stick in the back end to mount any of your change wheels or plates from div head and an indexing pin.

Edited By JasonB on 17/09/2019 18:58:45

Now theres an idea

Martin P

Edited By martin perman on 17/09/2019 19:22:44

Something like this:

Came with the lathe when I got it. As did this indexing arm:

The pivot slips rather tidily onto the reversible thread/fine feed stud. Of course, if you have a gearbox it is unlikely that you will have many change wheels! (Mine did since it was a conversion, the gearbox was a later addition). I don't think the idea was ever completed, it needs a spring or something similar to keep the detent engaged. It's quite a neat idea though.

Rod

If a gear tooth shape is machined/filed in the centre of the detent when rotated 90 deg you can get 1 tooth rotation as well.

Emgee

This is my version of using the bull ring indexing method on the Myford S7 which has a 60T wheel. Red painted markers are used to indicate the 0,90,180 and 270 positions (diivision by 4) and Yellow markers indicating the 60,120,240, and 300 positions (division by 6). It has the advantage of making use of an existing threaded hole and does not require the drilling of any extra holes. Applications requiring division by 8 are done using another set up with a 64T wheel held on a an expanding arbor fitted into the end of the mandrel. Removal of the sprung detent after use enables the supporting arm to be kept permanently in position as it does not interfer with the normal working of the lathe in anyway

I like the design and the neat way it it fitted, but I'm fascinated as to why you went to the trouble given that the VDH, which you already have, is fitted in under a minute which OK may be a few seconds longer than your bull wheel job but not much. Is the the extra time taken to wind the handle on the VDH when you only want to mill a square or drill holes on a PCD the consideration.

Even so I'm impressed with you going the extra distance. Once I can achieve a function with the kit I have it takes the promise of big advantages to persuade me to build more just for the extra finesse.

As I say this is certainly not a criticism of what it a very nice attachment just would be interested in your motivation.

best wishes Martin

Hi Martin,

Good question!

I guess it's because the plates and sector arms etc. are normally on the Timmins head on the mill (and I don't have to wind the the handle 4 x 15 times to mill a square)

Cheers,

Rod

Edit OK, 3x15 times

Edited By Roderick Jenkins on 04/09/2020 20:53:06

Some excellent ideas here for quick and simple indexing. Here is my GHT-inspired solution for indexing work in the ER chuck:

I have the HDA but it is slower to set up and the detent shown can remain in position when turning continues.

OK, I'm convinced.

I have to admit to digitising my HDA complete with dedicated controller so my plates can remain on the Versatile Dividing Head which does have the adaptor plates to fast fit to my mill so on reflection I suppose I have put more effort in than your bull wheel mod to acheive something of the same aim. I suppose my main motivation though was once the division number has been selected no mistakes can occur with a stepper system, which eliminates that heart stopping moment when cutting the last tooth of your 290 tooth clock wheel leaves half a tooth missing.

I tend to find the reason why someone did something as interesting as what they did. GHT was very good at explaining his thinking and I feel I learn more that way.

best regards Martin

PS (I realise I may have to calculate the relative chances of sector arm errors with that of power cuts for the new system but at least I can blame power cuts on someone else)

Edited By Martin Kyte on 04/09/2020 22:51:05