Using a Dividing head

This topic has 7 replies, 6 voices, and was last updated 8 March 2023 at 16:56 by Clive Foster.

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8 March 2023 at 11:32 #636677
Tony Martins
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@tonymartins59025
Good morning all

I have a need to machine a length of 1.5" dia x 1" TPI straight cut thread, my 1800 Student lathe is not man enough therefore I dreamed I may be able to use my indexing head on the mill and mill a spiral thread but as my indexing head is not a universal head I would like to know if it can easily be converted in some way to manually power the mill table by using a timing belt type drive or should I go back to sleep again. Any ideas will be much appreciated.

Regards

Tony

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8 March 2023 at 11:32 #34187
Tony Martins
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@tonymartins59025
8 March 2023 at 11:37 #636679
JasonB
Moderator
@jasonb
Depends on how smooth the thread needs to be but it can simply be done in increments moving the table then rotating the work and depending on form you may need to make up a cutter.

I have seen other lash ups where the drive to the dividing head or rotary table was disengaged and various belts and pullies linked to the table handwheel so work turned when the table was moved which all seem to work OK and probably better than trying to drive the table from the dividing head

Edited By JasonB on 08/03/2023 11:39:57
8 March 2023 at 11:39 #636680
John Haine
Participant
@johnhaine32865
Prof Chaddock recommended cutting the column thread for the Quorn using a powered milling spindle on the lathe carriage, and driving the headstock mandrel from the leadscrew using a handle on the leadscrew.
8 March 2023 at 12:45 #636692
Martin Johnson 1
Participant
@martinjohnson1
Here is my set up for a steering box screw on a Tom Senior M1 and the usual Taiwan 6" rotary table:

Sorry dont know how to do a hyperlink.

Martin

Edited By JasonB on 08/03/2023 13:13:53
8 March 2023 at 14:15 #636717
Clive Foster
Participant
@clivefoster55965
Martin

Cunning set up. Driving the rotary table directly via a chain of gears was, for me, a classic "D'oh obvious" now someone has shown me thing. Would work just as well with a spindexer too.

Brilliant lateral thinking.

Many professional dividing heads, like my Cincinnati copy Edgewick have a drive shaft provided for this sort of use. Cincinnati had whole bolt on change wheel bracket, gear set and cover assembly to use their heads on their mills. My dividing head came with couple of chain and sprocket assemblies that were used to connect it to a Bridgeport for, as I recall it, some sort of mould making work.

Clive
8 March 2023 at 14:47 #636725
John P
Participant
@johnp77052
Without knowing what type of milling machine that you have or dividing head
it would be difficult to answer that question.
For example if the leadscrew on your mill was 8 tpi and the dividing head
was 40 to 1 ratio you would need to gear up from the leadscrew to the
dividing head at 5 to 1 .It is unlikely this could be done in one step
with a toothed belt as the pulley sizes will be large,some additional gearing
would probably be needed as well as a tumbler reversing for left and right
hand thread.

I have done here almost the same as what you are trying to do at 1.480" dia
and 3/4" pitch but with cnc which is a much easier solution as you can
get to any pitch with just a little number juggling.Cant remember what the slot width but was climb milled to finish leaving a perfectly finished thread.

John
8 March 2023 at 16:56 #636750
Clive Foster
Participant
@clivefoster55965
John P

Martins method of directly driving a rotary table, spin-dexer or simple spindle seems much more appropriate than attempting to drive a dividing head via its normal worm and wheel.

Direct 1:1 drive will replicate the feedscrew pitch.

Coarser pitches will need the rotary drive stepped down in the same ratio as the feedscrew and desired pitch. So, for example, if the feedscrew is 8 tip and the desired pitch 1" then 8:1 step down will do the deed. It's unlikely that any ratio be large enough to be wildly impractical. Its the method I shall adopt should I ever need to do "figure 8" oiling grooves.

Admittedly producing a metric pitch on an imperial machine or imperial pitch on a metric machine will be tricky as the conversion gear(s) need to be arranged. Arranging temporary metric or imperial feedscrew using decent studding might be more attractive in that case. As Y-axis feed will not be needed once all is set up an external screw is feasible with the nut clamped to the Y dovetails.

Clive
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