[b0gh0s]

I have an application for either carbon steel or 404 steel gears that I can't find as a stock part anywhere, would like to get an idea of how much it would be to make them as a custom product.

I am looking for helical cut gears, with a 9 or 10mm face width, Metric Mod 1, teeth, 5mm bore, (gear should have a hub and 2 M4 tapped set screw configuration). The larger gear should be 72 tooth, the smaller one 30 tooth (this would give about 51mm spacing between gear centerpoints). I am open to other metric pitches for the teeth but the spacing and ratio between the gears would need to be comparable.

I would like these to be as light as possible so cutouts in the dead areas would be preferable, but the actual design/look are not as important.

Can anyone with gear machining capabilities provide me with an idea of what prototyping (maybe 2-3 sets initially) and production runs (100 of each or more) costs would be? BTW I checked the usual sources (sdp-si), these gears don't seem to exist as stock parts...

Would also be willing to trade services, I have ability to CNC cut up to 14x25 inch carbon fiber panels if you wanted someone to do so.

Please call me directly at 847-778 0874 if you could provide me with pricing or guidance. Thanks!

[HuFlungDung]

FYI, the most teeth in a gear set of a given center distance, and a given pitch occurs when they are straight cut spur gears. As soon as you introduce a helical cut, the number of teeth are reduced. So, this will cause a change in the ratio if your center distance is fixed already.

Helical gears give the ultimate flexibility in choosing the shaft center spacing between the driver and driven, because literally any spacing (with slight variations in ratio) can be accomodated by a change in helix angle and number of teeth. Conversely, square cut spur gearing forces you to use center distances that are a multiple of the gear tooth pitch.

The circular pitch of a straight spur gear is the pitch diameter/number of teeth. This distance is determined by the thickness of the cutter creating the tooth space. So when you angle the cutter across the gear face, you can imagine that you are actually projecting this circular pitch onto the side plane of the gear, thus stretching it. It is a cosine relationship.

Also, there is a certain degree of flexibility in which helix angle you choose. Is this for purposes of a simple noise reduction? From what I've read, 22° is about maximum that makes a noticeable difference in noise reduction.

Helical gears produce a small bit of side thrust. Your gearbox needs to allow for this, by transferring the load properly to the bearings with proper thrust spacers or shoulders.

So you need to describe what, if any flexibility you have in design, because right now, it has only a straight spur gear solution.

[HuFlungDung]

To continue with an example, the total number of teeth you have called for is 102. The circular pitch of such a spur gear is pitch circle circumference/102teeth, so in this case, the circular pitch of each tooth is

(Pi*102mm/102teeth) = 3.1415927mm per tooth

Now if you drop 1 tooth so that you can get some kind of helical cut, what helix angle will it give you?

Okay, so now we have still got the same pitch circle diameter (because we have a fixed center distance) so we need to derive the new circular pitch:
(Pi*102mm)/101 = 3.1726976 mm per tooth as projected onto the side of the gear face.

Cos helix angle = 3.1415927/3.1726976 = .9902

ArcCos .9902 = 8.03 degrees

So, that would be the helix angle if you could drop one tooth out of the set, doesn't matter which one. But, that changes the ratio when you do that.

So, you need to make the decision. If you can change the center distance, then we can go back to using 102 teeth to maintain the ratio, and vary the helix angle to suit your whim.

[Mcgyver]

wow HuFlung, you are the gear man!

Given that you're specifying heat treatable steels, do you need these to be ground gears? you don't see too many job shops gear generation equipment around let alone one that can grind gears - that’s some pretty specialized machinery, why not google custom gear manufactures?

[HuFlungDung]

BTW, due to the infinite number of combinations of helix angles and center distances that are possible, plus right and left handed requirements for a meshing pair, this is why you cannot find listings in standard gear catalogues for anything helical except maybe 45 degree helix angles. This is a popular angle, because a pair of the same hand of these 45 degree gears can be run at right angles (a corner drive). Opposite handed 45 degree helical gears will mesh in the same plane.

[b0gh0s]

Sorry I should clarify (just reread my original post)
I am looking for possibilities for both helical cut and straight metric pitch gears, Huflung, sorry for the confusing requests, but thanks for the explanation on the sizing for helical cut gears.

In a mod1 straight gear set, 72t and 30t with a 9-10mm face width would be preferable, other possibilities for metric pitch could have different tooth counts but the ratio needs to be somewhere in the 2.4/1 range and still allow for approx 51-52mm center to center spacing.

I should have specified above, in a helical cut gear, I don't have requirements for tooth count or helix angle, I am open on these but as I stated a helical cut gear set would be preferable for the noise reduction and some efficiency gains, the spacing should still be 51-52mm, with a 2.4/1 gear ratio. Also these gears will need to be lightened either way (lightening holes would be fine). The gears should allow the smaller gear to turn clockwise, larger counterclockwise.

I am trying to determine if it is even economical to go down this path or not, need to understand the pricing for this type of gear done either custom or as a rework of another design.

[CURVEDMTL]

Hello, You might want to try Econo Belt and download there DP Gear file in Zip, and look for what you might want. I've done some part hunting with these people, and have found some, if not all success. They have other files of interest, in Loads and Tensioners, amoung others. Hope you find some use, and happy hunting.