German Involute Spline or Gear?? 3

[wratchet]

Hello all,
I've come to you guys, because I don't know where else to turn. Hopefully someone can steer me right?

I have a small DC Motor driveshaft that has, what I'd call a spline, machined into the steel shaft. It drives a set of planetary gears in a wheel gearbox. For the life of me, I can't seem to figure out what it is. Of course, I haven't dealt with gears that much anyways. Mostly the diametral pitch gears.

The dimensions that I find are as follows; the outside diameter is 17mm. The minor diameter at the base of the (gear) is about 12.5mm. I'd estimate the distance tooth to tooth to be about 3.75mm and the overall depth to be about 2.25mm, measured with a flat rule. I'm told there is a DIN standard called 5480 and that may apply here I don't know.I know it has an involute shaped tooth because I can see the curve of it. The module (pitch) appears to fall between 1 and 1.25, using a profile print that I got from Maryland Metrics site. I can place a 60 degree thread gage right in between the teeth, so I believe it is a 30 degree pressure angle.

Right now I'm considering making a flycutter to mount in a Bridgeport and grinding a cutter to match the tooth shape from a 1/4" lathe knife and trying to cut it this way with an indexer. May work, I don't know.

Does anyone here have any experience with this sort of thing? If you can help me out, you'll have my undying gratitude.

Best regards, wratchet.

 

[Occupant]

The pinion you are describing would fit a profile shifted gear M=1, x=0.5*M, pressure angle=20degrees. Usually there would be a tip correction factor for this type of gear, but apparently that was not done here. I can generate the involute for you, but that would not be of much help unless you have CNC. You can buy a form milling cutter modul 1.00 at ebay for about $75.- and then you don't even need the involute.

 

[israelkk]

Occupant

I am curious. can this form milling cutter give the correct tooth form with x=0.5 rack shift? If yes, how? I thought it can give only standard gear tooth not a long addendum tooth.

 

[mfgenggear]

standard off the self type mill gear form cutter will not cut a non standard gear to the correct whole depth.
and depending on the AGMA or ISO class quality required.
It will have to be special order to meet the specified attributes.

If the engineer is on the ball the whole depth is designed as standard whole depth with enlarged gear so a standard gear cutter can be used. if it's through harden and not over 45 HRc hardness, and if it is not case harden, A case harden gear will require added grind stock to finish after heat treat. thus requiring a cutter with a thinner tooth thickness and with a deeper whole depth.

an off the shelf mill form cutter will only obtain about a AGMA class Q7 gear. and with out knowing the original quality class of the planetary assembly. it may or not be accurate enough.

 

[Occupant]

You are correct, of course. I haven't actually seen a form cutter for M1.0, 14T, x=+0.5 on ebay. What I saw was without profile shift.
@wratchet: If the numbers are correct, the pinion should look something like the attached - if you can read *.dxf.

 

[dinjin]

This type of pinion is generally cut with a hob and by
withholding the cutter by .5M or 0.5mm on center distance for a 1 module gear tooth.

 

[mfgenggear]

to get an exact measurement over wires or span measurement
the machinist is told the whole or d+f required.
in the old days a drop indicator was placed where the tool
or part feed in movement could be measured.

the machinist will hold the center distance larger than is required. Rough out the gear, then measures and adjust for final cut. take final measurements of the part, make corrections as necessary, thus obtaining the correct circular tooth thickness.

The technology of today makes short work of this.

any one have an Idea what the quality class should be of the pinion gear.

 

[gearcutter]

This has been a very amusing thread to watch over the last couple of weeks or so.
While there has been a wealth of good quality information given; the original poster stated that he was going to try and fly-cut this pinion with (no doubt) a hand ground form tool!!!!!
In my opinion............there is nothing that anyone can say or do that will help create a more positive outcome here.
At the end of the day; the best this person will be able to do is to crudely try to copy what they have and hope for the best.
Due to the manufacturing procedure chosen; it would appear that the poster is not interested in producing a quality product for their customer.....for whatever reason.

If I sound annoyed with all this well I am, as I see this sort of (in my opinion) idiotic way of making gears being attempted regularly.
The end result is a 'mashed up' mating gear and in this case probably a bent motor shaft along with damaged bearings due to the debris released.
These people should be advising their customers to take the part to a gear shop and have it done correctly.
I’m sorry if I have offended anyone but I think things needed to be said.


Ron Volmershausen
Brunkerville Engineering
Newcastle Australia

http://www.aussieweb.com.au/email.aspx?id=1194181

 

[israelkk]

gearcutter

Well said!

The problem today is that no one doing the least effort to educate himself with the technical language, the correct terms, the manufacturing processes, etc. before asking questions. To ask intelligent questions one needs to have the minimum of the technical terms etc.

When I respond to such posts I try to reply in a way that the asking person will understand that he needs to do some homework before continuing. However, not always I succeed.

 

[mfgenggear]

the truth hurts eh

regardless of that a lot of good post are the results.

Any one making gears knows what it takes.
The right qualified personnel & the equipment.

I don't blame wratchet I blame the customer who contracted
the lowest bidder. I see this sort issues also.
The poster asked a question and regardless of circumstances.
he asked for help. It's up to him to learn.

 

[Javier72]

You have a 15 teeth, module 1 pinion.

DIN 867 U2.

x = 0

Dp = 15
Dext = 17
Df = 12.5
Db = 14.095
Alfa: 20º
S1 = 1.571

With no more data I can't say you any more.

Is very usual here in Europe.

 

[mfgenggear]

Here is a better way to explain it.

The electric motor should be returned to the original manufacture, and have it replaced or rebuild.

 

[wratchet]

I thought I would post back and let you guys that replied know how this turned out.

I did go ahead with the fly cutter attachment and made the gear that way. It seems to be working fine. If we ever do another one, we will replace the 2 gears that mesh with this shaft as those being worn makes the operation less than ideal we found.

Now that we have the machine up and running, I have sent the original gear and shaft to Ash Gear in Michigan and they confirmed that it is a module #1 with a 20 degree pressure angle. We will purchase the gear cutter from them and hopefully will produce a better piece next time. Also I intend to make the next one from a low carbon steel shaft and simply case harden it as the original was. Once the case is gone, the gear will probably be unusable anyway.

As you may have figured out, our Shop isn't equipped with the latest and newest tools, but we do seem to manage to do most of our repairs just fine.

I wasn't going to post back because I didn't care for the tone that some of these posts were taking. I simply came for some professional help from I assumed "professional" people and ended up being chastised for it. Some people here make too many assumptions, in my opinion.

Regards, wratchet