Gear Hob Callout

[rShell]

I am specifying a particular gear hob for creating a lead-in feature on an external gear. My supplier seems to be having difficulty creating the feature and it has me wondering if I am calling out the hob correctly. The not on the drawing reads like this:

LEAD-IN CREATED WITH
1 - MODULE, 45DEG PRESSURE
ANGLE, DIAM. 2.50 HOB IN
LINE WITH GROOVES IN THE
30 PRESSURE ANGLE
SPLINE

Does this make sense?

Thanks for your input.

Rshell

 

[MikeHalloran]

It makes no sense to me.
AFAIK, splines of 30 deg PA are rolled, not hobbed, so you may be specifying a tool that doesn't exist to be applied to a process that's not in use.

This would be a good time to visit your supplier and learn how he's attempting to make what you want, and then modify your spec/dwg so it reflects something he can make.

At the very least, make a big blowup drawing/model of what you think you have been specifying, and communicate that to your supplier.



Mike Halloran
Pembroke Pines, FL, USA

 

[rShell]

Mike,
Are you telling me that a "1 module, 45 degree pressure angle, 2.50 inch diameter hob" is a tool that does not exist?

Rshell

 

[mfgenggear]

rshell

are trying to make you 1 mod 45 deg pa spline inline with the 30 deg pa spline?
I am too having difficulty understanding your requirement.

Mfgenggear
if it can be built it can be calculated.
if it can be calculated it can be built.

 

[rShell]

Gentlemen,
I have attached a PDF with a pic of what I am trying to get my supplier to do. Hopefully this clears things up.

rshell

 

[mfgenggear]

rshell

if the supplier has a cnc hobber with a probe then it can be done easily.
otherwise it would be difficult to do on a manual machine but not impossible.
I would be resistant to do that on a manual machine.

It can be easily done on a manual gear grind to grind the lead in after spline hob, but not as efficient.

it is doable.

Mfgenggear
if it can be built it can be calculated.
if it can be calculated it can be built.

 

[mfgenggear]

rshell

why not call out chamfer instead of a lead in it would be much easier.

Mfgenggear
if it can be built it can be calculated.
if it can be calculated it can be built.

 

[gearcutter]

I don't think it's too wise to expect that anyone could successfully 'marry up' a generated 45deg PA angle profile with a generated 30deg PA profile.
For low production runs; lead in chamfers are normally done on a milling machine.
They can also be done on CNC hobbing machines but a modified profile is used on the hob.
The other option is to use the same hob that has been used to cut the spline but, in a second op, taper hob the chamfer.

Ron Volmershausen
Brunkerville Engineering
Newcastle Australia

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

 

[MikeHalloran]

It would be better to specify the feature(s) you want on the drawing, rather than telling the manufacturer how to make the features. Surely you can't really care about the exact profile of a lead-in, so why not just provide limits on the geometry you can tolerate?


Mike Halloran
Pembroke Pines, FL, USA