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Old 09-30-2010, 04:02 AM   #1
boxcarmj
 
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Default Building a Quick Change Gear Box, need help.

Is there a relationship between the spindle gear (40T) and the leadsrcrew (12TPI)? Is there a formula I need to work out? Thank-you Mike.


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Old 10-01-2010, 07:12 AM   #2
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Default Re: Building a Quick Change Gear Box, need help.

The ratio between the spindle gear and the leadscrew gear is what sets the pitch of threads when you are cutting them and the speed of the carriage movement when you are turning using the feed screw for horizontal feed.

With a spindle gear of 40t and a 12TPI lead screw you could divide 480 by the required TPI to get the number of teeth required on the feed screw.

For example, for a 24tpi thread divide 480 by 24 gives 20, so 20 teeth required on the lead screw. Intermediate gears will not change the ratio provided you do not use compound gears.

Thats my understanding of it all.


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Old 10-01-2010, 08:36 PM   #3
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Default Re: Building a Quick Change Gear Box, need help.

Thank-you, I'll add this to what I have.
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Old 10-01-2010, 08:56 PM   #4
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Default Re: Building a Quick Change Gear Box, need help.

Artful, what happens when you use compound gears, does this change the ratio, and how? Your answer was very helpful. Thanks, Mike.
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Old 10-01-2010, 11:41 PM   #5
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Default Re: Building a Quick Change Gear Box, need help.

Quote:
Originally Posted by boxcarmj
Artful, what happens when you use compound gears, does this change the ratio, and how? Your answer was very helpful. Thanks, Mike.
A compound gear is an intermediate gear which is comprised of two gears locked together on the same bearing.


The most common compound gears are those that convert metric to imperial pitches etc, for example a compound gear set of 127T and 120T.

There is a better explanation here:
http://www.schsm.org/html/gear_ratio_calculations.html
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Old 10-02-2010, 01:10 AM   #6
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Default Re: Building a Quick Change Gear Box, need help.

Basically - a 1:1 ratio (Spindle:Lead screw) would be 12 TPI. a 2:1 ratio would be 24 TPI and a 1:2 would be 6 TPI. Others ratios as required for the particular TPI.
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Old 10-02-2010, 02:50 PM   #7
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Default Re: Building a Quick Change Gear Box, need help.

Thank-you. I'll out the link, and this is all getting clearer. Mike


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