Gear Hobbing (2025 Update)

gareth · 2015-02-28T12:54:34+00:00

Some of the early articles on gear-hobbing using a stepper motor turning the workpiece that was sychronised to the rotations of the hob used a series of belts and pulleys to up the speed of the hob so that a sufficiently high rate of pulses could be had to drive the stepper motor from an optical disc Now, those of us with an interest in amateur radio will know of the technique of using a PLL to resolve FM. Now, the rate of variation of audio is several orders of magnitude higher than the variations in speed of a cutter when it is subject to the force of cutting, so it seems to me that a PLL synchronised to an optical disc right on the hob axis, without the multiplying effect of the pulleys and belts, should do the same trick? What is needed is to divide down in the first instance so that the workpiece is turning at the same RPM as the hob, and then divied down agin for the number of teeth. This, of course, is for straight-cut spur gears for the division ratios for helical-cut gears are a nightmare altogether, and a second stepper motor is needed in any case for the feed. (I refer to my widely-available spreadsheet, "Hobnail" that calculates gear ratios for mechanical hobbing machines)

Clrob3437 3 years ago

Hello Gareth. I am very pleased to hear from you. I too got to know Giles Parkes and what a gentleman he was. He arranged for me to take his place demonstrating the Jacobs Machine at the annual Midlands ME Exhibition. Up to that point I was not aware of Hobnail and struggled to find much information on determining change gears for helical hobbing and ended up writing an Excel spreadsheet myself based on continued fractions. I am sure that it's not as accomplished as yours. Can you tell me what mathematical method you used for Hobnail? I would e-mail you directly but as I am not a member of this forum I cannot see your address. Yes, I would very much appreciate a copy. My address is snipped-for-privacy@clara.co.uk. The rules may not allow this address to appear in the post so could the moderator please send it to Gareth if it must be removed ? Thanks & regards, Chris.

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Adam Harris 1 year ago

Gareth I wonder if you might allow me a copy of your Hobnail programme for gear trains. It is mentioned favourably by the late John Stevenson on his site Johnfsworkshop.org and it sounds ideal for me (non-web dependent + filtering by my own stock of change gears + useable on Excel + no attached ad cookies or viruses!). I am new to this forum but have been searching for you and your Hobnail on Model-engineer.co.uk on which I am active. Adam

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Adam Harris 1 year ago

Gareth I wonder if I might too have a copy of your Hobnail software please. I am looking at making helical gears and following the late John F Stevenson's site "johnfstevenson.org.uk" he recommends Hobnail. From my perspective it sounds ideal however old it may be. It incorporates all features I want (operated on Excel spreadsheets + independent of web + filter by using only my available stock of change gears + free of ad cookies). I am active on model-engineer.co.uk website and have been trying to find you/Hobnail there without success . Kind regards, Adam

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Adam Harris 1 year ago

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Colin James 1 year ago

Can I have a copy of the Hobnail spreadsheet please.

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