What material is this gear made of?

Helicals are notoriously difficulty to reverse engineer. Even measuring the helix angle is not trivial, and this has a bearing on many other dimensions. The formula for the pitch diameter D, for example is: D = N/(Pn cos@)

Where @ is the helix angle, Pn is the normal diametral pitch (defined as being perpendicular to the tooth face) and N is the number of teeth. Note too that everything is calculated from the pitch diameter, meaning that you need to measure the helix angle at that diameter. It's really, really not easy to do accurately.

Try running some numbers through a calc or two, or consult the Machinerys Handbook to get a feel for it. Your chances of successfully making a high speed, highly stressed gear of that type based on measurement are not high, I'm afraid. Making a pair based on the centre distance you're tied to... that's another matter and probably more achievable, though still a fair task in a home shop. When you know and control every aspect of both gears in mesh, you're in a much better position.

A extract relevant overall from the excellent KHK primer here:

Helical Gears | KHK Gear Manufacturer

Helical Gears have teeth with a helix angle for higher torques and noise reduction. KHK produces various standard/special helical gears.
khkgears.net

"The helical gears made by KHK can be classified into two groups by the reference section of the gears being in the rotating plane (transverse module) and normal plane (normal module). If the reference section is in the rotating plane, the center distance is identical to spur gears as long as they are the same module and number of teeth. This allows for easy swapping with spur gears. However, in this case, they require special hobbing cutters and grinding stones, leading to higher production cost. On the other hand, if the reference section is in the normal plane, it is possible to use spur gear hobbing tools and grinding stones. However, the same module and number of teeth in spur gears no longer match the center distance of helical gears, and swapping becomes very difficult. In addition, the center distance is usually not an integer."

I don't mean to blunt your enthusiasm, more to hopefully guide your decision on whether it's an achievable job.
 
You might try contacting this company. They specialize in timing gears and ship world wide.

Login - We ship worldwide!

www.cvi-automotive.se www.cvi-automotive.se

If nothing else, they may be able to put you on the right track.
 
Suzuki4evr said:
The gear has 42 teeth,the OD=148.50mm =5.846". So 148.5/44=3.37mm and 44/5.846=7.52. So I am still not sure if it is Module or DP. Would that M3.5 or DP7. Not sure about the presure angle also and another question is at how do you determine the angle of the teeth correctly although it looks like 45dgr. Could you perhaps assist me with this?
Click to expand...
The calculations you made are baffling. The gear appears to be neither a metric or inch standard gear.. I looked at both the KHK and Boston Gear product catalogs and nothing is close. The formula for module or diametral pitch based on number of teeth and O.D. is exact, not an approximation. The measured O.D. may be off due to wear or machining variation but the calculations should be much closer.

Since this is a gear is from a Volvo, it is possible that they defined their own gear specification. A major automotive manufacturer would have the resources and possibly motive to do so. It would certainly discourage aftermarket parts. Your issue will be to try to finf appropriate tooling. Standard gear hobs won't work. It would be possible to cut the gear with a CNC mill and 4th axis capability. You still have to determine what the correct geometry is and that could be a difficult task.

Reverse engineering is bad enough when we can make some assumptions as to the intent (e.g., if a measurement comes out to 2.005, it might be safe to assume that the designed dimension was 2.000. Given your numbers, it doesn't appear that you can make any such assumptions. Maybe check the width of the gear. See if it comes out a nice number in either metric or inch. It's a stretch but it may provide a clue. The KHK metric gears have a 20º P.A. while the Boston Gear inch gears have a 14.5º P.A. The KHK gears have a 21.5º helix angle while the Boston Gear gears have a 45º helix angle.
Good luck!
 
RJ and Lo-Fi, thanks again for trying to guide me,but I think that I am must reconsider this project and rethink if this is worth persuing taking in consideration that the client added in the beginning that money was a problem. So I do not think it is worth spending a lot of time and money to help THIS time,although I am sorry that I can not help him. Spur gears are one thing,but helicals seems to be a different beast. I hate giving up on something I started,but it is what it is. Thanks again for putting things in perspective for me. Have a great day.
 
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