Having an issue cutting a Spur Gear. The index gears seem to be good. As I am cutting the right number of teeth. But the feed seems to be off as it is cutting a slight helical. Is there a calculation needed for the feed gears when trying to cut a spur, like there is for a helical?
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Barber Colman Gear hobbing
- Thread starter RkRider
- Start date
- Replies 13
- Views 1,562
Dan from Oakland
Titanium
- Joined
- Sep 15, 2005
- Location
- Oakland, CA
If you are cutting a helix, that tells me your index ratio is not exact. The Index ratio must be exact and equal to the machine index constant divided by the # of teeth. the Feed gear ratio will never have an effect on the resulting gear teeth if the index ratio is correct. Perhaps recheck your tooth count on the change gears.
I will take a look tomorrow. I am using the index gears from the table on the cover. But I will double check the numbers. The helix that is being produced is extremely small. Could there be something I am missing or a problem with the machine other than the index gears. Could I be setting the hob at the wrong angle?
I may be using the wrong terms.
We are presently using a 36 tooth DRIVER with an idler and a 48 tooth driven in the index gearbox
We have tried a multiple combinations in the differential gearbox.
The machine we have is a Barber Colman 6-10 with triple thread worm
Machine index constant is 12
Feed constant is .075
Diff. constant is 10/L
We are looking to produce a 16 tooth spur gear.
we have come close but always have a slight helix .
I haven't run one of these in over 30 years and can't remember how the differential gear box is setup for spur gears.
We are presently using a 36 tooth DRIVER with an idler and a 48 tooth driven in the index gearbox
We have tried a multiple combinations in the differential gearbox.
The machine we have is a Barber Colman 6-10 with triple thread worm
Machine index constant is 12
Feed constant is .075
Diff. constant is 10/L
We are looking to produce a 16 tooth spur gear.
we have come close but always have a slight helix .
I haven't run one of these in over 30 years and can't remember how the differential gear box is setup for spur gears.
David_M
Hot Rolled
- Joined
- Sep 30, 2014
- Location
- Midway, GA, USA
In your case, lock out the differential. Then, the gearing for the index looks good.
Richard King
Diamond
- Joined
- Jul 12, 2005
- Location
- Cottage Grove, MN 55016
Contact Bourne and Koch in Rockford IL who now owns Barber Colman and see if they can help.
Do you know how to lock out the differential on the Barber Colman 6-10
David_M
Hot Rolled
- Joined
- Sep 30, 2014
- Location
- Midway, GA, USA
Notice the red lever:
David_M
Hot Rolled
- Joined
- Sep 30, 2014
- Location
- Midway, GA, USA
I don't think anyone would cut a 16-tooth spur using the differential, but if they did, the math would look something like the below.
I chose a diametral pitch of 16 (the following won't work for other diametral pitches) and 30 thousandths for the feed rate.
The above would need testing using a light skim cut (It may have an idler count issue that doubles the helix angle instead of canceling it).
I think this is a convincing argument to do it the simple way by locking out the differential.
I chose a diametral pitch of 16 (the following won't work for other diametral pitches) and 30 thousandths for the feed rate.
The above would need testing using a light skim cut (It may have an idler count issue that doubles the helix angle instead of canceling it).
I think this is a convincing argument to do it the simple way by locking out the differential.
Last edited:
10 fingers
Hot Rolled
- Joined
- Mar 9, 2003
- Location
- Vermont
They would probably want a PO to give advise. That's IF they had a person on staff that has ever setup a 6-10. Can't blame them. Hobbyists earn them nothing.
Richard King
Diamond
- Joined
- Jul 12, 2005
- Location
- Cottage Grove, MN 55016
Email me and I can forward the email to the VP of sales who is a friend. Also I can ask Don Shadduck of The Gear Works in Springfield VT. who is an expert. All they can say is NO. It never hurts to ask. [email protected]
Dan from Oakland
Titanium
- Joined
- Sep 15, 2005
- Location
- Oakland, CA
Ah! you never mentioned the machine had a differential. Details. Diffs on a 6-10 are not that common and are a nice feature.
That red "lever" in the above picture is not really a lever but simply a link that slips over the differential change gear input shaft to prevent the shaft from turning. If you don't have it available, make up a plate that slips over both shafts and put a set screw into the side of the input shaft to lock it. Ideally, the link would have an internal spline that mated to the input shaft splines.
That red "lever" in the above picture is not really a lever but simply a link that slips over the differential change gear input shaft to prevent the shaft from turning. If you don't have it available, make up a plate that slips over both shafts and put a set screw into the side of the input shaft to lock it. Ideally, the link would have an internal spline that mated to the input shaft splines.
Peter Colman
Stainless
- Joined
- Sep 22, 2004
- Location
- Rugeley UK
I think we have the root of the problem but if you still get a slight helix it is time to check simple things, a slightly loose blank on the mandrel or a loose mandrel in the machine itself has given me this result.