rotery table

This topic has 20 replies, 9 voices, and was last updated 30 October 2015 at 09:29 by Martin W.

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29 October 2015 at 19:06 #209755
Farmer Dave
Participant
@farmerdave
Hello all I'm needing a wee bit of help setting up my rotary table,need to cut 125 divisions. my table turns 90 degrees per turn of the crank , how do I calculate it and what index plate should I use. My chart only goes to 100 divisions . Thanks for your help. Farmer Dave
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29 October 2015 at 19:06 #17878
Farmer Dave
Participant
@farmerdave
indexing
29 October 2015 at 19:52 #209761
Phil P
Participant
@philp
Hi

A lot will depend on what indexing plates you have available, ideally you want one with 25 holes.

90/125 =18/25, so each division works out at 18 holes on a 25 plate.

Phil
29 October 2015 at 20:01 #209764
David Clark 13
Participant
@davidclark13
90 degrees per turn of the crank sounds a lot. Normal dividing heads are usually 40 to 1 giving a 9 degree movement or or ten turns for 90 degrees.
29 October 2015 at 20:01 #209765
Phil P
Participant
@philp
Just looked at the chart for my 90:1 Hofmann rotary table and there is no 25 hole circle plate with it.

So you might need to make that first. I am assuming you will have a 20 hole circle available as I do.

90/25 = 18/5 = 36/10 = 72/20 which gives 3 full turns and 12 holes on the 20 circle.

Then use that plate to do your 125 divisions as above.

Phil
29 October 2015 at 20:04 #209766
JasonB
Moderator
@jasonb
Posted by David Clark 1 on 29/10/2015 20:01:16:

90 degrees per turn of the crank sounds a lot. Normal dividing heads are usually 40 to 1 giving a 9 degree movement or or ten turns for 90 degrees.

90:1 which is quite common on rotary tables 4deg per turn

Edited By JasonB on 29/10/2015 20:04:34
29 October 2015 at 20:10 #209770
Neil Wyatt
Moderator
@neilwyatt
Sounds wrong, I suspect 90 is a typo and the OP means 9 degrees per turn (40:1 ratio).

Which gives (25*40)=1000 holes per rotation

1000/125=8 holes =per division

Or with a 50-hole plate, 16 holes per division.

Neil
29 October 2015 at 20:14 #209773
Ian P
Participant
@ianp
Jason its not 4 degrees per turn but 4 turns for 360 degrees.

Unusual to find rotary table or dividing head with 4:1 gears (well 1:4 really).

I feel a misunderstanding might be afoot here.

Ian P
29 October 2015 at 20:18 #209774
JasonB
Moderator
@jasonb
Its a rotary table many of which run a 90:1 gear which gives 4 degrees per turn.

40:1 – 9deg per turn is more commonly found on a dividing head but the OP is asking about a rotary table. I've never seen a rotary table with 40:1

The OPs typo is that he put 90deg/turn not 90:1

Edited By JasonB on 29/10/2015 20:20:10
29 October 2015 at 20:31 #209776
David Clark 13
Participant
@davidclark13
There are lots of online calculators online. Need to download them though. Don't work on my iPad.
29 October 2015 at 20:36 #209778
Phil P
Participant
@philp
If I knew how to add a spreadsheet to this page, I would show you how to work out divisions available using a system of factors.

Phil
29 October 2015 at 21:08 #209789
Farmer Dave
Participant
@farmerdave
Hi Guys Sorry for the confusion/mistake on my part ,my table is indeed 90:1 gearing. thanks for all the replies.
29 October 2015 at 21:27 #209792
Michael Gilligan
Participant
@michaelgilligan61133
25 hole plate

Index every 18 holes

… I think.

MichaelG.
29 October 2015 at 21:58 #209797
Phil P
Participant
@philp
What if he doesn't have a 25 hole plate though ?

Phil
29 October 2015 at 22:24 #209800
Michael Gilligan
Participant
@michaelgilligan61133
Posted by Phil P on 29/10/2015 21:58:44:

What if he doesn't have a 25 hole plate though ?

Phil

.

Make one

or improvise

MichaelG.
29 October 2015 at 23:13 #209813
Phil P
Participant
@philp
I'm just having a light hearted dig really, did you see my original posts at the top of the page.

Phil
29 October 2015 at 23:41 #209816
John Stevenson 1
Participant
@johnstevenson1
No 25 hole plate is a glaring error on the B&S style plates.

Once done everyone copied them and this was at a time when 125 and 250 division were ripe on inperial hand wheels.

Myford list doing a 125 division with their dividing head and to use 12/25 but they don't list a 25 hole on any of the 4 plates.

When we make the Myford plates No's 1 and 2 are direct copies but No. 3 has 127 holes extra and No. 4 has 50 holes extra.

Our B&S style plates have 25, 63 and 127 holes extra, one on each of the 3 plates.
30 October 2015 at 00:54 #209823
Martin W
Participant
@martinw
Hi

If my calculations are right then 125 divisions can be obtained as follows:-

For a 40:1 table then an index plate with either 15 or 20 holes can be used

15 hole plate Index at 24 holes or 1 complete rev plus 9 holes

20 hole plate Index at 32 holes or 1 complete rev plus 12 holes.

For a 90:1 table the same index plates can be used

15 hole plate Index at 54 holes or 3 complete revs plus 9 holes

20 hole plate Index at 72 holes or 3 complete revs plus 12 holes

The divisions will not be cut/marked sequentially but after 125 sequences the full set should be cut/marked.

Cheers

Martin

Edited By Martin W on 30/10/2015 01:00:03

Edited By Martin W on 30/10/2015 01:01:02
30 October 2015 at 06:37 #209830
Michael Gilligan
Participant
@michaelgilligan61133
Posted by Phil P on 29/10/2015 23:13:47:

I'm just having a light hearted dig really, did you see my original posts at the top of the page.

Phil

.

I must have seen but not Noticed … I had pretty much dismissed everything written in answer to the original [wrong] question as being idle speculation.

You were obviously correct, and may be psychic.

MichaelG.
30 October 2015 at 07:23 #209832
JasonB
Moderator
@jasonb
Posted by Martin W on 30/10/2015 00:54:07:

For a 90:1 table the same index plates can be used

15 hole plate Index at 54 holes or 3 complete revs plus 9 holes

20 hole plate Index at 72 holes or 3 complete revs plus 12 holes

The divisions will not be cut/marked sequentially but after 125 sequences the full set should be cut/marked.

Martin, on the charts 72 holes on a 20 plate is for cutting 25 divisions, surely if you keep going round the same all you are doing is recutting the same 25 divisions
30 October 2015 at 09:29 #209839
Martin W
Participant
@martinw
Jason

Just checked and you are correct and the error could apply to all the values I came up with. Evidently posting too late at night and not thoroughly checking my calculations . Thanks for pointing it out and readers please ignore my post above re division ratios.

Cheers

Martin
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