Gears again - identifying

I'm trying to replace some crashed spur gears in the QC box on an Enco
1024. Enco is no help. I downloaded a Martin Gear Catalog and am
trying to figure out what to order.
I'm measuring a Pitch Diameter = .773
How do I determine what the pressure angle is?
The valley between each tooth is radiused. Martin calls that a
Shaper-cut profile. Is that significant?
The guy a Purvis Bearing talked like this is rocket science.
Is there a better way to do this?
Reply to
Rex B
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One way is: If you have a gear with the same TPI and a _know_ pressure angle mesh them together and messure the distance. If it has the expected*) one, the unknown wheel has the same pressure angle, if not then not.
Also, if you look at the kind of gear (Norton?) chances are damned high that it has the standard pressure angle (don't know it for imperial based gears without looking it up in a book)
*
) Have to look in a book for the imperial based system, if you want. But it will take about 10 hours. It's time to go to bed right here. :-)
Nick
Reply to
Nick Müller
Me too, kinda (mine is a Jet 1024). I took the gear into a local bearing store (Eastern Bearing). The guy searched for the longest time and concluded that it wasn't anything standard and he couldn't help me. This place is a Boston Gear distributor, so I figured that it wasn't worth looking anywhere else.
Leigh (CATRUCKMAN) says that he carries Jet parts and I emailed him, but haven't had a response. I also emailed another Jet parts dealer that I found online. Haven't heard from him either. I'm leaning toward hobbing my own.
Bob
Reply to
Bob Engelhardt
Last time I ran into this I set the gear on my scanner, took a very large blowup of a few teeth, then compared the shape to the drawings in machinery's handbook. Mine was very obviously a 14-1/2 degreee pressure angle.
You can get a very accurate diametrical pitch by mating any two gears, measuring the centerline distance, and counting the teeth in BOTH gears. DP = total tooth count/distance.
These tricks work for inch gears, metric uses a different appoach. And anything from ENCO should be considered to have metric gears. If you calculate a DP that is not some nice even multiple (eg 6,10,20, 24 ,etc etc.), more than likely you have a metric gear.
If the valley is radiused, it has no effect on gear teeth meshing, it does reduce the ultimate load carrying capacity.
As for the rocket science, I've been experimenting with cutting sample and prototype gears on a CNC mill. Messy yes, Rocket science, no.
Rex B wrote:
Reply to
RoyJ
As the Enco 1024 is an import it is almost certain that you have module [metric] gears and not P.D. [inch] gears.
See Law's book on gear cutting for indepth discussion of P.D. v module. see
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I have this book and find it to be a valuable reference in addition to telling you how to cut both involute and cycloid gearing. Powell's is good to deal with.
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Reply to
F. George McDuffee
OK, I've been eyeing this book for a while, so I ordered it. With all respect to Powell, Amazon had it for half via some guy in Oklahoma. I'll probably wind up grinding a single-point form tool and making a couple of these on my minimill. I will also have to make a mandrel and find a reamer or two. I'll probably need a better grinder, or at least a new wheel. And I'll get to try out that indexer I lucked onto a while back. It's ratio is 1:48, so I won't even need to use the plate to cut this 16-tooth gear. Just cut a tooth, crank 3 times, cut, repeat 14 more times, right? Looks like I need to source some 1.375 round stock in leaded steel. What alloy do I need to specify? This is a quick-change gear, so doesn't need to be high-strength. I suspect a brass gear would do the job. I'd enjoy this project more if I had the liesure time to give up a day for it. I just hate having a nice tool partially assembled, so I'd better get on it.
Much thanks for all the help, guys. I'll let you know how it goes.
Rex Burkheimer Ft Worth
Reply to
Rex B
Just ran across this site.
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Pretty much exactly what I planned to do. I had not thought of using the boring head, but since I have a brand new 3" R8 head ($10) I can use that.
- - Rex B
Rex B wrote:
Reply to
Rex B
It will be a major project to machine a steel gear. Because of the low speeds/loading on the change gears we have found that aluminium work fine [we sued some 6061 T6 we happened to have] also the mechanical grade of micarta or formica makes good gears. This was a common timing gear material.
Drimel tool or 1/8 air grinder will be very helpful in hand grinding the involute profile into a single point cutter. Unless you like grinding use the smallest piece of tool steel you can. 3/16 is plenty for 1.0 module. You will need to grind the top of the tool down to center of the holder or grind in hook to avoid negative rake.
Reply to
F. George McDuffee
How about posting all dimensions you have? #of teeth, outer diameter, base diam., width (might give a hint to "metric"). So I (or others) can look up and see if I/they find out what it is?
Nick
Reply to
Nick Müller
That's good to know. I have some 6061 It would make it much easier, plus this gear would make a better "fuse" if it were AL.
I have some 3/16 cobalt steel stock which I'll probably use.
Thanks for the input
Reply to
Rex B
Sure: 16 teeth OD 7.890" Base Dia. 7.577" face width is .377" or 9.56mm
I've been trying to scan it, but I can't get enough contrast.
Reply to
Rex B
Eh, sorry, are you pulling my leg? 16 teeth and about 200mm OD with less than 4 mm height of teeth? Or am I dumb and wrong with thinking that 7.89" are 200.406mm? This gear would look _completely_ different from regular ones.
puzzled, confused and all Nick
Reply to
Nick Müller
LOL I'm doing too many things at once (supposedly to be working for my employer)
That should be .789" OK, .7577" base diameter, so tooth height is .031"
So this gear is about the size of a half dollar, and about 3/8" thick My apologies.
Rex
Reply to
Rex B
OK, this doesn't qualify for a module gear. Module 1 or module 1.25 are common and standardized and they both don't fit (OD wise). With 20° (the standard), that is. Tooth height would be way off (should be about 2mm or 2.5mm for Mod 1 / Mod 1.25). There also exists a Module 1.125 (have never seen that) that would badly match the OD (20.25mm compared to your 20.04mm). If the manufacturer quit the 20°, there is no standard to select from (AFAIK).
But there is a last chance. It is legal to play some tricks with tooth-height. If you take the time and mesh two of those gears together (may have different #of teeth, but i need to know. And no tricks this time! :-)) and messure the distance of the centers, I'll give it another try.
Nick, gonna have a beer in the meantime ...
Reply to
Nick Müller
Ok, I'll look at it tonight. Part of the challenge will be figuring out which gear meshes with it.
Have two. I know I will ...
Reply to
Rex B
Oh no! :-) OK, it's midnight here in ol' Germany. I'll have a sleep and you have to wait 9 hours to see me posting again ...
Nick
Reply to
Nick Müller
That's a great link, thanks.
I think you meant p 137.
Doesn't match mine. I scanned mine at high res and it appears as though the teeth are not even involute. I.e., they are straight sided. Why did they have to do it that way?
Bob
Reply to
Bob Engelhardt
Yup. Often true in machine tools as well, with the exception of change gears, which are usually standards.
Ned Simmons
Reply to
Ned Simmons
I think this gear was from the QC box. Its task is to produce exact output ratios by meshing between many gears on fixed shafts. I can't fathom how much fun it must be to design something like that, but I'd think using non-standard gears might be the easiest way to get it done.
Reply to
xray

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