Creating a Hub for a D-shaft 6

[Helepolis]

Hi all,

At first it seemed like an easy thing to do, but not so sure now .

I need to assemble a Hub on a D-shaft of 15mm Dia., the Hub already has a hole of 10mm Dia. so it needs to be enlarged and create the "shelf".

.
Can this be done without creating large radius (anything over R1 mm) at the seem between the hole and the "shelf"?

 

[Tmoose]

"The torque is the issue."

How much torque are you transmitting thru a compromised 15 mm shaft?

Is an outboard bearing planned? The chain tension as a result the torque is trying hard to bend a cantilevered shaft, and if the D shaft in on a purchased part like a motor, the loading on the adjacent bearing may exceed what the motor manufacturer had in mind.

Any hub connection that is not clamped hard enough to resist micromotions due to torque variation and one direction radial loads is destined to experience progressive fretting wear, like the outside of this bearing race -

http://www.skf.com/binary/31-5621/ls401_48_tcm_12-5621.jpg

or this keyed shaft connection-

http://photos.motoiq.com/photos/685053521_4wehK-M.jpg

 

[mfgenggear]

Hi Helepolis

it is common to broach large quantity's with a "D" hole. and it is precision hole.
bear in mind core hardness can not be more than 43 HRc. approximately.
if core hardness is 50 HRc or higher the options to broached before heat treat with a core harness of 33-43 HRc.
then do a final heat treat.
but must importantly it has to be a very stable material with very little distortion.

wire cut is an option but only for small production lots because of cost. plus there is always the issue with recast
on the surface. but if the means override the cost it is a very practical method.

a key way or splined hole would require the same procedures, but it is common.
if the material (for an example) is 4340M or 300M is has very little distortion when it is vacuum heat treated and gas quench ( high bar )

the problem is the precision required at assembly. and if alignment is required. then the cost is justified.
might also consider a press fit between details. easy to grind the O.D. easy to hone or ID grind the bore in the hub.

Best

 

[MintJulep]

Almost always gear, sprocket, pulley manufactures have the option to add a custom bore.

Send you requirement to whoever you are buying the sprocket from and ask "How much?"

 

[tbuelna]

The tolerances shown in your OP sketch (.0004" to .0007") are pretty tight, but a good wire EDM machine can hold them. For 30 pieces, wire EDM is likely your best option. The only things you need to consider are making sure the sprocket is accurately positioned when you begin the wire EDM cut, and watching for any deformation of the bore D profile shape after the wire cut is completed in your hardened sprocket material.

 

[dvd]

Could possibly use one of these Ringfeder products with or without the d-flat.

http://ringfeder.com/en/international/products/ringfeder/?g=7334

 

[Helepolis]

Thank you everybody!
As usual, plenty of useful info.