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Gearcutting update
Hi guys,
Slowly working on the gear cutting projects but not fast enough for me.
Plan A:-
The original idea of turning the Victoria horizontal into a gear hobber by using a set of crossed helicals, a jack shaft and the dividing head has reaches a full stop.
I have the gears and the jack shaft but found that the input gears for the shaft input on the dividing head are missing. In effect it's a plain dividing head.
Started to look around for a new head but got sidetracked by Plan B:-
Plan B is to do away with the gears, jack shaft and drive train all together and replace this by an electronic drive.
What started this was seeing a small machine at the Midlands Model Engineering Exibition at Donington, UK in October. I have contacted the builder of the machine and he's agreed to build a larger version of the electronic box to drive my big Hoffman head driven by a large type 42 stepper motor.
I can't say a lot more about the driver box as I don't know anymore until late January when he'll have it ready.
This will be a genuine hobber able to generate geometrically correct gears from a commercial hob.
Also in the background is plan C:-
This is something I have been working on for a while and looks at the problem from a different angle. Biggest bugbear of cutting gears in the home shop is the cutters. Single point cutters are in sets of 8 and can work out expensive. Hobs are even more so.
Homemade cutters are not easy to make and suffer from poor materials. O1 is about the best we can use. Home made hobs are very hard and laborious to make.
I have come up with a way to work backwards from a single straight sided rack tooth to produce a geometrically correct involute tooth form. This cutter can be free hand ground, or done in a very simple jig, on a normal bench grinder from an old HSS end mill or slot drill. This cutter will be easy to make, of the correct material, require no hardening and will cut all the numbers of teeth in a range with just the one simple VEE shaped cutter.
Something similar has been done before where three or five cuts have been taken of each tooth space to form a tooth with a series of flats. My method if it works will do away with this and form a commercially acceptable tooth form
The idea is to build a purpose built machine but there is no reason why it can't be adapted to fit on say a Bridgeport.
I have one more problem to sort out with the feed and I can start trials. That's all I'm prepared to say at the moment as I may write this up for one of the magazines.
John S
[This message has been edited by John Stevenson (edited 12-23-2002).]
Slowly working on the gear cutting projects but not fast enough for me.
Plan A:-
The original idea of turning the Victoria horizontal into a gear hobber by using a set of crossed helicals, a jack shaft and the dividing head has reaches a full stop.
I have the gears and the jack shaft but found that the input gears for the shaft input on the dividing head are missing. In effect it's a plain dividing head.
Started to look around for a new head but got sidetracked by Plan B:-
Plan B is to do away with the gears, jack shaft and drive train all together and replace this by an electronic drive.
What started this was seeing a small machine at the Midlands Model Engineering Exibition at Donington, UK in October. I have contacted the builder of the machine and he's agreed to build a larger version of the electronic box to drive my big Hoffman head driven by a large type 42 stepper motor.
I can't say a lot more about the driver box as I don't know anymore until late January when he'll have it ready.
This will be a genuine hobber able to generate geometrically correct gears from a commercial hob.
Also in the background is plan C:-
This is something I have been working on for a while and looks at the problem from a different angle. Biggest bugbear of cutting gears in the home shop is the cutters. Single point cutters are in sets of 8 and can work out expensive. Hobs are even more so.
Homemade cutters are not easy to make and suffer from poor materials. O1 is about the best we can use. Home made hobs are very hard and laborious to make.
I have come up with a way to work backwards from a single straight sided rack tooth to produce a geometrically correct involute tooth form. This cutter can be free hand ground, or done in a very simple jig, on a normal bench grinder from an old HSS end mill or slot drill. This cutter will be easy to make, of the correct material, require no hardening and will cut all the numbers of teeth in a range with just the one simple VEE shaped cutter.
Something similar has been done before where three or five cuts have been taken of each tooth space to form a tooth with a series of flats. My method if it works will do away with this and form a commercially acceptable tooth form
The idea is to build a purpose built machine but there is no reason why it can't be adapted to fit on say a Bridgeport.
I have one more problem to sort out with the feed and I can start trials. That's all I'm prepared to say at the moment as I may write this up for one of the magazines.
John S
[This message has been edited by John Stevenson (edited 12-23-2002).]
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