Aligning Keyway to Tooth of Sprocket

[rs-forbes]

I want to use geometric tolerancing to ensure the alignment of a keyway to sprocket teeth but do not know where to start.
Can anyone give me some direction?

 

[drawoh]

rs-forbes,

I take your drawing is ISO rather than ASME?

I would use the keyway as a clocking feature, and apply a positional tolerance to one of the teeth.

--
JHG

 

[mfgenggear]

rs-forbes,

"I take your drawing is ISO rather than ASME?

I would use the keyway as a clocking feature, and apply a positional tolerance to one of the teeth."

to add to drawoh comment, I would suggest to pick a basic diameter on the sprocket such as pitch diameter, and make it a gage point on both sides of a tooth or in between a tooth space.
specify a true position to the keyway as a datum, in the old days it would be centerline of a tooth to the keyway. symmetry could be specified. follow ASME requirements pick a year.
for manufacturing I would machine a sprocket first then machine align the keyway to the sprocket. it depends on the equipment used and how sophisticated.

 

[drawoh]

mfgenggear,

I understand the inspection of involute spur gears over pins. How do you find the pitch diameter of a sprocket? Are they that accurate?

I could use datum targets to define which three (gaps in the) teeth were to be used to define the pitch diameter. When I want custom gears, I send my drawings to a gear shop. I assume they cut my datum features first, then they use these to fixture to a gear cutting machine.

--
JHG

 

[mfgenggear]

drawoh (Mechanical)7 May 21 18:13
mfgenggear,

I understand the inspection of involute spur gears over pins. How do you find the pitch diameter of a sprocket? Are they that accurate?

I could use datum targets to define which three (gaps in the) teeth were to be used to define the pitch diameter. When I want custom gears, I send my drawings to a gear shop. I assume they cut my datum features first, then they use these to fixture to a gear cutting machine.
--

Drawoh

I have had many planetary gears and other spurs and on that had alignment requirements.
with a cnc gear checker it very easy, it picks up the exact tooling diameter of gear tooth or tooth space, it can be either, and centralize it.
and will give an exact readout. on a printed sheet as well. same as inspecting the Total Tooth Variation, Tooth to Tooth Variation, It picks up the exact Theoretical Pitch Diameter as a gage point.
for the OP part I would fabricate an arbor with pin or equivalent manufactured to my design. the keyway would have to be manufactured constant such as broaching.
in the old days on the surface plate which I have personnel experience, I would put the part assembled with the arbor but first I would centralize the pin in the arbor
on a ultra precision ground magnetic v block, so when I flipped the vblock both sides of the vblock would measure exact with a height gage and and an .0005 inch indicator.
I would order a deltronic pin that would lay as close to the pitch diameter. I would then indicate both side of the Deltronic pin, and it would give the alignment. old school.
edit: same if the part has an alignment from gear teeth to an internal spline. tool to locate a spline tooth space.

 

[mfgenggear]

Drawoh

I wanted to add in the type of aircraft gears, I had to do a precision grinding of the datums for tooling purposes.
for roughing then the same for finishing. since most of the gears were case harden. if it is a through harden gear depending on the hardness
if it is higher than 45 HRc then the same process would have to be followed. but it is lower than 45 HRc it can be all machined
complete after heat treat.