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Thread: Hercus Gearing Problem
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14th March 2011, 09:23 AM #1New Member
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Hercus Gearing Problem
I am restoring A Hercus 9in ARL 13007F, I hope that someone can help with the following:
I have a 56 tooth gear on the leadscrew, I suspect that the original gear was a 20 tooth gear with a shoulder???
The idler is 80 tooth, is this practical?
I intend to purchase a set containing the following:
127/100 transposing compound gear, 28,32,36,44,48,56. I figure that I will also need a 40 tooth gear.
Will this cover all the bases for basic thread cutting both metric and imperial?
Is there any other gear or anything else (i.e. another idler gear bolt) that would have come as accessories to this lathe originally?
All advice appreciated.
Thanks
DaveLast edited by jmk89; 14th March 2011 at 10:46 AM. Reason: Please obey the rules - leave in standard font, colour etc
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14th March 2011, 11:38 AM #2.
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Dave,
My ARL came with the metric transposing gearset in it's original cardboard box. I'll have a look tonight and report back in regards to the contents.
BT
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14th March 2011, 12:13 PM #3GOLD MEMBER
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Originally the lathe should of been supplied with a 20,40 and 56 tooth change gears,there would also be an 80 tooth bossed idler.
The 20 and 40 tooth change gears are changed between themselves on the Stud gear to give the desired Imperial TPI ,the 56 tooth gear remains on the Screw shaft.
For cutting Metric pitches rangeing from 0.20mm to 6mm you will require change gears of 28,32,36,40,44, and 48 teeth,you will also require the 127/100 tooth compound gear.This gear goes in place of the 80 tooth Idler.You will still require the 56 tooth gear,this will remain on the Screw shaft.the other change gears listed above interchange on the Stud shaft to give the desired pitch.
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14th March 2011, 02:56 PM #4New Member
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Thanks Pipeclay,
I didn't get a 40 tooth gear with the lathe. After reading you post and consulting the 'Textbook of Turning' the penny has dropped. I didn't realize that there are two separate gears on the stud. Now I see how the 40 tooth works on the stud and how the metric change gears would work.
Much appreciated,
Dave
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14th March 2011, 05:28 PM #5.
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15th March 2011, 07:50 AM #6New Member
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Thanks Bob. What's the general thought. Is it worth the effort and expense to buy and setup the gears for metric thread cutting? Are you still able to close the gear cover on a 9in Hercus with the 127 compound gear on the banjo? I recall from my tech training (45 years ago) that the method for cutting a metric thread was to reverse the lathe after each cut with the half nuts engaged. Is this a successful and practical option or should I look for a metric machine.
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15th March 2011, 09:03 AM #7.
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Dave,
Having the half nuts constantly engaged makes metric thread cutting a bit trickier. Most of my imperial screwcutting has utilized a runout groove. It's easy, you disengage the nuts when you hear the load on the motor change. Can't do that with a metric thread and the motor doesn't stop quick enough to enable the use of a narrow runout groove.
My answer has been to cut the threads without the motor, by turning the spindle by hand by means of a hand crank fitted to an expanding mandrel inserted in the spindle bore. It is laborious but it works.The mandrel was featured in one of my posts a few months back.
Hand turning works perfectly for threading to a shoulder or where you may not want a runout groove.
I don't know about the cover. I've left it open during my metric efforts.
Buying a metric lathe is an expensive option. Depends on the amount of screwcutting you plan on doing. I hadn't had the need to cut any metric threads until I acquired my metric mill six months ago.
Bob.
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