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Spur gear meshing question.

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Richard Carlstedt

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Measuring Gears..
Several ways to do it , but they get pretty expensive equipment wise !.
A really low cost way is to buy a 5 dollar book , which is really a Catalog by the Van Keuren Company. Here is one on Amazon , but I got mine for $4
Pay no attention to the year ( 1952 in the ad) They are all the same- Its a catalog!
The Book has complete tables for measuring gears using pins ( similar to thread gages ) The tables give you the complet formulas for Even AND Odd Tooth Gears

When I cut a gear ( say a 35 tooth) I cut the first gullet and then index to either the 17 th or 18th position and make a second cut, drop in the prescribed pins ( make my own -simple) and use a mike or digital caliper and Bingo --I know immediately how much deeper to cut. The tables give you the required dimension for a true Involute gear . Works for 14 1/2, 20, 25, 30 PA and even has Spline data . best 4 bucks I ever spent
FYI - Van Keuren makes Gear measuring equipment
If you know a gear shop, they may give you one of their old ones.
Rich

Edit
FYI---When you measure a Commercial gear, you will find it undersize--they do that on purpose so you never have binding !
 

L98fiero

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Measuring Gears..
Several ways to do it , but they get pretty expensive equipment wise !.
A really low cost way is to buy a 5 dollar book , which is really a Catalog by the Van Keuren Company. Here is one on Amazon , but I got mine for $4
I couldn't find the catalog at much less than $20 and if you're outside the US it's another $20 shipping, on the other hand, here's a quick online calculator that I've used. http://salemcompany.com/cgi-bin/cabAS.py?a=./gears/pages/Salem1501HS.html&b=./gears/pages/Spur1501S.html&c=./gears/pages/Salem1501FS.html and Dimension over pins, balls or wire for external involute helical gear or involute splines.
 
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Richard Carlstedt

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Those online calculators are really neat, good resource .
There is one problem however in that it does not tell you the ideal wire size.
The Van Keuren book gives you wire size to match the Pitch Diameter Tangent Point of the specific gear.
You may want to check your used book stores, or try someone like Abe's

Rich
 

TSutrina

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Looking on the web can find the best wire size: As you see from the table that you can find the pin size. then use the on line calculating programs. Here is a source of equations and a image of the equations. Calculation of Gear Dimensions | KHK Gears they also have a gear calculation program.
 

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davidyat

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Ken,
Upon research, I found pictures like this. It looks like something that can be attached to a caliper. Just wondering if an attachment like this is available if you're unable to make one like yours.
Grasshopper
1603847513389.png
 

Ken I

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Ken,
Upon research, I found pictures like this. It looks like something that can be attached to a caliper. Just wondering if an attachment like this is available if you're unable to make one like yours.
Grasshopper
View attachment 120390
Why didn't I think of that - that will work well for most applications - although mine will cover a bigger range - I often have to measure partial "blend" type radii. So mine works for large radii over short distances.
You could probably machine or 3D print a range of "anvils" for smaller radii and blends.
Regards, Ken
 

L98fiero

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Those online calculators are really neat, good resource .
There is one problem however in that it does not tell you the ideal wire size.
Granted, you're absolutely right but most hobbyist machinists aren't going to have a set of gear measurement wires. Even if you have two sets of pin gauges and use the charts from the KHK site or one of the others and 1.7/DP or 1.7 x module for the pin size you should be able to get about as close as most people will be able to get using their home shop equipment and form cutters they made.
 

Ken I

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L98fiero - but most hobbyist machinists aren't going to have a set of gear measurement wires

That was the point I made about generating your own profiles in AutoCad - you can then project for whatever rods or drill shanks you have to hand and still achieve the same result. (see photo in post #10)

Regards, Ken
 

TSutrina

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The size of the pin determines where on the volute profile the measurement is taken. So the objective is to have a pin size close to the ideal size on the table or calculated. The equations and formula in the programs doesn't care about the pin size since it determines, calculates the location on the volute profile for the pins provided.
 

Ken I

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Whilst ideally you would want the pin to contact the pitch circle line - in some cases (small tooth count) the wire will not protrude above the tooth and you have to go bigger in any case.
Bottom line - who cares ? - if your profile is truly correct you can project off any (close) pin diameter and get the correct result.
If the profile is incorrect then measuring at the pitch circle line is no more "accurate" than anywhere else.
Don't get bogged down in formulae and "book-speak" knowledge - figure out what the heck it is that you are trying to accomplish.
If you are using "approximate" cutters - then you may as well use approximate measuring methods.
In spite of how the above sounds, I do take gear cutting very seriously.

Regards, Ken
 

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