rotery table

[Farmer DaveParticipant @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

[Farmer DaveParticipant @farmerdave]

indexing

[Phil PParticipant @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

[David Clark 13Participant @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.

[Phil PParticipant @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

[JasonBModerator @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

[Neil WyattModerator @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

[Ian PParticipant @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

[JasonBModerator @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

[David Clark 13Participant @davidclark13]

There are lots of online calculators online. Need to download them though. Don't work on my iPad.

[Phil PParticipant @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

[Farmer DaveParticipant @farmerdave]

Hi Guys Sorry for the confusion/mistake on my part ,my table is indeed 90:1 gearing. thanks for all the replies.

[Michael GilliganParticipant @michaelgilligan61133]

25 hole plate

Index every 18 holes

… I think.

MichaelG.

[Phil PParticipant @philp]

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

Phil

[Michael GilliganParticipant @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.

[Phil PParticipant @philp]

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

Phil

[John Stevenson 1Participant @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.

[Martin WParticipant @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

[Michael GilliganParticipant @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.

[JasonBModerator @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

[Martin WParticipant @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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