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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
 

Steven Tarr

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Lots of interesting stuff presented. I appreciate the conversation. I went with using mod 8 gear cutters, with a 40T/80T ratio. Did not redrill the exhaust cam shaft hole. And you know what? It worked. As Mr. rkyle62 put it, "I'm over thinking the problem. Moving on to the next issue. Thanks to all.
 

Ken I

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Steven, Glad to hear it all worked out - like I said at the beginning you can cut fast and loose with gears - but I frown on the practice in real world engineering - but for model work you just go right ahead and do whatever works. (It's not like someone if going to come back with an order for spares is it ?)

When do we get to see a video of it running.

Regards, Ken
 
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SmithDoor

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I use gear gauge very simple.
If make mistakes distance between the gears just cut the teeth deeper.

There a lot gear boxes that some machinist made stake on center distance so they just cut teeth deeper. This only found out after the company is long gone and the gears need replacing.

Dave

FYI I work as a repair machinist and found out why companies all need the S/N. They keep notes on all mistakes and would seen you part fits

I am trying to address a mistake with my cam/crankshaft gears. I will be cutting mod 0.5 gears, 39T and 78T. I just checked the distance between shaft centers and found that I am 0.008" too short (should be 1.1515" and I have drilled them at 1.1435"). Since I have yet to cut the gears, I was thinking of reducing the diameter of the gears. The 78T from 1.575" to 1.569" and the 39T gear from 0.807 " to 0.805". My skill level is such that I can generally get +/- 0.001" if I am VERY careful. Is this going to work? Thanks in advance.
.
 

Master

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With the exception of the internal gear in my Edwards Radial I've made my own gears and cutters for years. "Gears and Gear Cutting" by Ivan Law has been a valuable source for me. I think gears can be a bit forgiving. Several times a bit of lapping compound has solved proper meshing.
 

TSutrina

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The .008 error to far may not be a problem. I had to assemble machined gears that were to the involute dimension and the center distance the sum of the two pitch diameters. THE GEARS DIDN'T MOVE AND WERE HARD TO EVEN MATE. I used a sand blaster to wear away the surface to get clearance. You need clearance for gears to work since nothing is perfect. If the load changes directions then less clearance is typically desired. But the only effect of a larger clearance when power is transferred in one direction is the actual contact angle changes a little, the average or value at the line between the center.
 

awake

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Lots of interesting stuff presented. I appreciate the conversation. I went with using mod 8 gear cutters, with a 40T/80T ratio. Did not redrill the exhaust cam shaft hole. And you know what? It worked. As Mr. rkyle62 put it, "I'm over thinking the problem. Moving on to the next issue. Thanks to all.
I'm assuming you mean .8 module, not 8 module ... :)

One of the advantages of involute gears over cycloidal gears is that involutes can tolerate less-than-perfect spacing.
 

TSutrina

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I'm assuming you mean .8 module, not 8 module ... :)

One of the advantages of involute gears over cycloidal gears is that involutes can tolerate less-than-perfect spacing.
Cycloidal gear also need clearance. Often more then one gear set has contact in involute gears then Cycloidal gears from what I have seen. This maybe wrong. When more sets of teeth contact then the tolerance of between teeths are important. Thus one reason for noise gears is this error between sets of teeth.
The advantage of the involute is the elimination of sliding. Worm gear have losses due to sliding. Cycloidal gear by nature of the forming of the teeth does not state that sliding is eliminated.
 

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