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26th Dec 2021, 09:42 PM #1New Member
- Join Date
- Dec 2021
- Location
- NZ / Aus
- Posts
- 2
Clarification on Missing Gear - Required or not for cutting threads
Hi All,
New to the forum and the Hercus lathe... Mine is an Imperial Model A
Firstly Thanks to some smart people for other posts around cutting etc that have made things easier to understand but i am still slightly confused so figured i would ask and get clarification.
I am missing a tumbler gear (which easy fix) and know i require some new stud gears to cut metric (40,48,28 - https://metalworkforums.com/f189/t20...9-model-lathes).
My confusion is around that the idler has been setup with a 63 tooth gear (which from what i read can be used instead of the 100/127 gear for metric threads - but only seen setup instructions for 100/127) So i have no idea how it is meant to be setup and/or am i missing a gear to use that function & cut imperial threads as i see machines with "change gears" before the idler gear
Clarifiy the gears i have - 20,40 stud 80-63 idler and think its 56 screw (others i will sort out once i know the go)
See attached picture..
IMG20211226225833.jpg
Thanks for any help or a point in the right direction as this is going to be a life saver for my equipment when it can do its thing...I will be installing a DRO / Motor upgrade and possibly quick change tool post if and when it earns its keep or one of the boys toys sells.
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27th Dec 2021, 04:38 PM #2
Hi NZ - OldStuff
Welcome to the MetalWork forums.
You have joined a great bunch of people always willing to help.
ou will find plenty here who have the same interests as yourself.
Please take the time to navigate around the forums to view the varied and interesting subjects.
The is a large selection of places to see on our sub forums.
To do this, goto the the FORUM box in the top left hand corner of the screen. Click Forum Home and a scroll down page will come up.
Scroll down the page and the various help pages and sub forums shall be shown.
Please read the Terms of Use on the very top of the scroll down page - they are our rules.
To save time here's the link
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Many pages also have a sticky at the top.If you post its always a good idea to check the sticky ,if there is one there.
If unsure about procedures, the how to's of the Forum, I am happy to help if you wish to PM me.
Again, welcome to our forums.
Grahame
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27th Dec 2021, 10:24 PM #3Senior Member
- Join Date
- Aug 2015
- Location
- Adelaide
- Posts
- 239
Hi mate
The gears you have are right for the lathe except for the weird compound gear, not sure why there's a 63 tooth attached to the 80 tooth gear, as you said the 100/127 is standard for the metric but you can use this set as well https://australianmetalworkinghobbyi...et-500x500.jpg
Good luck and happy turning
Cheers Steve
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28th Dec 2021, 06:26 PM #4Golden Member
- Join Date
- Oct 2008
- Location
- Cairns, Q
- Posts
- 666
Steve,
100/127 = 0.78740...
63/80 = 0.78750, a very close approximation, often used to replace a 100/127 compound gear if the 100/127 compound gear is too big to fit in the available space.
If space does not even allow the 63/80 compound gear, a 37/47 compound gear = 0.78723... is also close enough for most practical purposes.
Frank.
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29th Dec 2021, 07:54 AM #5Senior Member
- Join Date
- Aug 2015
- Location
- Adelaide
- Posts
- 239
Thanks Frank
I read about the 37/47 compound arrangement but I wasn't sure about the 80/63, but after you mentioned it I do remember seeing a spreadsheet a guy did a long time ago with the different compounds and stud and screw gears, I know there are different ways of getting the same result with marginal error over a fair distance, Hercus had a 135/127 compound for cutting imperial threads on metric b and c models and I thought the 127 tooth was a big gear on the back.
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