Firt time at indexing

I set up my rotary table today and had a practice at indexing seven holes, it came out wrong I made some error, 12 turns with 19 holes or 18 spaces. I had a go at something easier for me, 8 holes,11 turns with 20 spaces which is half of the holes on the plate which came out correct. When indexing is it common practice to rotate the table in neutral, not in gear to the correct amount of degrees then use the indexing plate for what part is needed. I tried this and one turn is 4 deg x7 plus 20 spaces 2 deg equals 30deg, this seems a lot more easier than counting turns on the wheel.Beginners question but I can see a lot of errors when counting turns on the wheel.

Bob

Edited By BOB BLACKSHAW on 16/05/2020 17:27:01

Sounds like you are doing something odd as for the 8 holes I would expect 11 full turns (11 x 4 =44) plus a quater turn not half (1/4 x 4 =1) giving a total of 45degrees which is 1/8th of 360. This would be something like 5 holes on a 20 hole plate.

Edited By JasonB on 16/05/2020 17:19:14

Hello Bob,

Is that a Sorba table with 90 to1 reduction? If so it ought to have been 12 turns and 9 holes on a 21 hole circle.

Message me if I can help.

David

Bobs figures are correct David

12 x 4 = 48

18/21 = 3.428

48 + 3.528 = 51.428

360/7 = 51.428

Edited By BOB BLACKSHAW on 16/05/2020 17:29:17

Edited By BOB BLACKSHAW on 16/05/2020 17:29:36

In every shop where I have worked or visited ,rotary tables are wound via the handle and worm from index to index,I think that any one found rotating the table and using the worm as an indexing plunger would soon be in trouble with their superiors.It certainly is not good practice to use a rotary table in this manner.

Yep I made another mistake, in the manual 8 holes is 11 turns but the confusing thing it states part of turn 5/20 so yes its 5 spaces 20 states the holes in the plate.

Bob.

Edited By BOB BLACKSHAW on 16/05/2020 17:46:26

I do it like this - sometimes.

90 turns for 360 degrees so with a 21 hole plate that is 90*21 = 1890 holes

Each of the seven holes will be 1890/7 = 270 holes.

270/21 = 12.857.... So that many turns for each indexed hole.

So 12 complete turns and 0,857... of 21 holes = 18 holes (ie 0.857...*21)

I don't have a rotary table, but throwing an idea out there. Add a read switch to the table to trigger the count on one of these **LINK** and stick a magnet on the crank

Save having to count turns.

Good idea, but one only needs to count a very few turns. Fewer complete turns for those of us with 40 turns per 360 degrees RTs.🙂.

Red Face! The old adage is as true as always "fools rush in"

David

I'm guessing what you are doing here is very similar to using a dividing head.

A while back I needed to do some challenging divisions and ended up changing my dividing head so that it was driven by a stepper motor controlled by a Raspberry Pi. It really makes dividing very easy!

I wrote a short blog post on the subject which also links to a full article I wrote about making the stepper driver in the Horological Journal.

Another alternative if you wanted a ready made stepper motor divider is the Division Master however is does cost more.

Edited By Mark B on 19/05/2020 08:45:37

As Mark B says, you are effectively using the Rotary Table as a Dividing Head.

Firstly, if you want accurate spacing between the holes, keep the worm engaged at all times, and do not wind the handle back. If you do wind back "too far", and then turn forwards again, to take out any backlash.

The exact number of complete turns and holes will depend up the ratio of your particular Rotary table. The ration depends on what table you have, varying from table to table manufacturer, between 36;1 and 90:1; with many variations in between.

If you have a Soba or Vertex HV6, the ratio is likely to be 90:1. But check the chart supplied with the table. My elderly Vertex HV6 had errors in the chart.

I found out the hard way.

One of the errors was for the gear that I was trying to cut. It cost me a week before I got that sorted out having made a spreadsheet to make up a new chart.

So do the calculation for the number of divisions that you want to make, in case there is an error.

It is even possible that the Table is in error! There have been posts on here from folk whose Table was stated to have a 48:1 ratio, but actually found to be 47:1!

So DO check! Even if you have to count the number of holes in each ring on the plate.

If all your procedures are correct, the one thing that you don't check is bound to be the source of the error,

Howard