cutting spur gears on a mill

[Martin ConnellyParticipant @martinconnelly55370]

There is no snobbery involved in wanting to make parts to standard dimensions or to a drawing. Such insulting language does not belong in this forum. Keep your prejudiced opinions to yourself please. You asked if this slapdash method of creating gears with some speed was a good idea and were then given lots of reasons why it wasn't by people who have had to make gears to meet specifications. You are still trying to push it as a good idea and are now starting to insult people who point out the shortcomings of this process. I thought some time back that this thread had gone far enough and I repeat that sentiment. This thread needs to be ended.

Martin C

[SillyOldDufferModerator @sillyoldduffer]

Posted by JasonB on 01/10/2021 18:37:37:

I have chinese hobby benchtop machines as do many amatures, I've not even got an engineering background like a lot of the members here just a bit of metalwork at school.

I have much the same kit as Jason, except my WM-280 lathe is a later, improved, model.

For some strange reason Jason's workshop is far more productive than mine and his work is better finished. How unfair! Then I remembered it's not the size of your tool that matters, it's what you do with it…

Dave

[Ian HewsonParticipant @ianhewson99641]

X2 Martin

[Anonymous]

Posted by brian jones 11 on 01/10/2021 18:32:32:

…..semi pro league with big machines DRO CAD CAM etc…..

That's as maybe, but I have a Myford in the workshop:

Does that make me a hobbyist?

Andrew

[brian jones 11Participant @brianjones11]

Caustic commentators on this thread must remember its Title "Spur Gears – a rogue method"

If you want to pursue the conventional route on this topic by making precision standard gears then this thread is definitely not for you – it has nothing to offer that mindset, walk away.

My examination of free hobbing is more akin to blacksmithery. The Artisan didnt have equipment to drill holes, he heated up metal and punched holes (even square holes). You would hardly have described it as precision engineering but it served its purpose. Just look at the craftsmanship in a horse shoe, note square holes and wrought square nails – dont twist and loosen. These are slightly tapered so that the thin ends curl up as they are hammered into the hoof and dont fall out – thats smart.

The pursuit of free hobbing which started with using taps – (as is done in making worm gears quite successfully btw – I dont hear any howls of disagreement on that score) and extended to spur gears has been roundly discredited for many reasons clearly explained as per foregoing posts.

And I agree – it results in a non standard form

Yet more by accident and in spite of the naysayers, I managed to produce some credible meshing model gears using the method of slitting a large bolt and this tool is currently under development , waiting for parts, and is showing promise.

I am hoping that with a more precisely made gr 8.8 tool I can predict the number of teeth I will get and also the workable distance between centers.

These rogue gears will never approach the quality of precision gears made by conventional methods and they were never intended for that purpose. I expect them to function as workable gears for light duty by a DIY method available to those with limited workshops who would otherwise never considered knocking up a gear train.

So to all amateurs, hamateurs amatures, armatures, armchairs and nearly 18,000 views, lets not resort to machinist' righteous bigotry give the Blacksmith some room maybe his tool might fly

WaM

[Grindstone CowboyParticipant @grindstonecowboy]

Could we perchance have a glossary covering some of the more obscure / possibly unique abbreviations?

I'm starting to feel like Jack Lemmon in 'Some Like It Hot' when he said "Nobody talks like that!"

Rob

[brian jones 11Participant @brianjones11]

Posted by Andrew Johnston on 02/10/2021 09:20:46:

Posted by brian jones 11 on 01/10/2021 18:32:32:

…..semi pro league with big machines DRO CAD CAM etc…..

That's as maybe, but I have a Myford in the workshop:

Does that make me a hobbyist?

Andrew

Well Gentlemachinists

An MG12 is hardly the kind of semi pro kit the home hobbyist might be expected to have in his shed

Remember why Myford took off post WWII – a 7" budget screw-cutting hobby lathe for the everyman

The DW diy vertical mill, hugely versatile which strips down into half doz manageable parts to go in a hatch back – can you do that with a Bridgeport? Doreen brought the milling world to the home hobbyist

Thank you Andrew for exemplifying my position – when does a hobbyist turn semi pro ( MEW rules as per F1 needed?) and his shed becomes a shop?

I rest my case – your Grace

WaM

[Anonymous]

Posted by brian jones 11 on 02/10/2021 11:03:39:

………………..and his shed becomes a shop?

When they emigrate to the US.

Andrew

[Nick WheelerParticipant @nickwheeler]

Have you considered that Andrew has thought about the parts his hobby requires and equipped his workshop appropriately?

[Pete RimmerParticipant @peterimmer30576]

Posted by brian jones 11 on 02/10/2021 10:29:40:

Caustic commentators on this thread must remember its Title "Spur Gears – a rogue method"

If you want to pursue the conventional route on this topic by making precision standard gears then this thread is definitely not for you – it has nothing to offer that mindset, walk away.

With respect Brian you only started the thread, you don't get to dictate who may contribute or how. If that's what you want, write a blog. This is a community and participation is encouraged.

If there is an obvious flaw in the concept, the application or the result then it absolutely should be pointed out so that those who come across this thread in the future don't assume that a poor practice is perfectly acceptable just because it's gone unchallenged.

Edited By Pete Rimmer on 02/10/2021 12:19:52

[SillyOldDufferModerator @sillyoldduffer]

Posted by brian jones 11 on 02/10/2021 10:29:40:

…

I expect them to function as workable gears for light duty by a DIY method available to those with limited workshops who would otherwise never considered knocking up a gear train.

…

Unfortunately there's a nasty gap here between expectations and reality. Brian's DIY method is only useful when friction, distance between centres, low operating life, backlash, exact ratios, and low power transfer capability don't matter. All good if these can be ignored, otherwise free-hobbing is overly simple.

What does the customer want? Probably not a quick easy way of producing gear-like thingies with lots of shortcomings.

Much easier to design gear trains around proper gears. Anything else is an awful time-waster because fitting unpredictably dimensioned gears together is such hard work. Brian has yet to explore applying free-hobbed gears in anger: he'd find tackling John's 2:1 challenge educational. I suggest making the challenge a priority Brian – I'm sure you can make it work, but you need to experience the grief. And if by chance the first attempt goes well, try making 4 or 5 of them!

If WaM stands for 'Wet and Messy', I agree!

Dave

[brian jones 11Participant @brianjones11]

SOD I am working on the challenge but need to make a better tool and waiting for parts as I explained above

hold that thought

Q

Brian's DIY method is only useful when friction, distance between centres, low operating life, backlash, exact ratios, and low power transfer capability don't matter. All good if these can be ignored, otherwise free-hobbing is overly simple.

UQ

I am working on mitigating these problems Free Hobbing is Simple

There you said it SOD

Thats not fair PR the OP can object if a comment is OT. comparing the classic purist way of making gears to my rogue method is just plain "OT off topic"

I have always welcomed participation and indeed many comments have been instructional and helpful and I also fully acknowledge the shortcomings of the method

The enlightened viewer will judge the method by results and what it might do, while the bigot will get stroppy and slap me down saying "you can't do that here son , its against State Law"

WaM – off for an afternoon with Doreen

[Dave HalfordParticipant @davehalford22513]

Posted by brian jones 11 on 02/10/2021 10:29:40:

Caustic commentators on this thread must remember its Title "Spur Gears – a rogue method"

If you want to pursue the conventional route on this topic by making precision standard gears then this thread is definitely not for you – it has nothing to offer that mindset, walk away.

My examination of free hobbing is more akin to blacksmithery. The Artisan didnt have equipment to drill holes, he heated up metal and punched holes (even square holes). You would hardly have described it as precision engineering but it served its purpose. Just look at the craftsmanship in a horse shoe, note square holes and wrought square nails – dont twist and loosen. These are slightly tapered so that the thin ends curl up as they are hammered into the hoof and dont fall out – thats smart.

The pursuit of free hobbing which started with using taps – (as is done in making worm gears quite successfully btw – I dont hear any howls of disagreement on that score) and extended to spur gears has been roundly discredited for many reasons clearly explained as per foregoing posts.

And I agree – it results in a non standard form

Yet more by accident and in spite of the naysayers, I managed to produce some credible meshing model gears using the method of slitting a large bolt and this tool is currently under development , waiting for parts, and is showing promise.

I am hoping that with a more precisely made gr 8.8 tool I can predict the number of teeth I will get and also the workable distance between centers.

These rogue gears will never approach the quality of precision gears made by conventional methods and they were never intended for that purpose. I expect them to function as workable gears for light duty by a DIY method available to those with limited workshops who would otherwise never considered knocking up a gear train.

So to all amateurs, hamateurs amatures, armatures, armchairs and nearly 18,000 views, lets not resort to machinist' righteous bigotry give the Blacksmith some room maybe his tool might fly

WaM

All this implies you are on the same level as a blacksmith after serving his 5 year apprenticeship in the accidental production of usable metal goods. You wouldn't catch a Blacksmith making anything in plastic that had no real use.

[brian jones 11Participant @brianjones11]

This Greek Blacksmith stole my idea

Not a DRO in sight, just pure skill

WaM

[JasonBModerator @jasonb]

Also in the first two videos not a spur gear in sight as they are worm wheels.

Also notice how in all the videos he is using a properly formed hob so he gets the correct profile teeth and also pre gashing the gears so he gets the correct number of teeth two vital elements that your "copied" method seems to lack.

WaM (What a Muppet) you must be to have missed those.

Edited By JasonB on 03/10/2021 18:28:13

[brian jones 11Participant @brianjones11]

Sorry MEW board dumps your text at the slightest excuse so this got lost

 

ca 10.00 he is making a spur gear as he uses the vertical slide

Even with gashing his free hob method is so much quicker than gear cutting with a dividing head.

Edited By brian jones 11 on 03/10/2021 18:44:42

[JasonBModerator @jasonb]

But he still had to pregash which takes almost as long as actually cutting gears with a div head and he also needed the div head. Only advantage is it's easier to make a hob than an involute cutter but that also takes time.

[JasonBModerator @jasonb]

I think I have worked out why it's taking Brian so long to come up with a workable set of 2:1 gears.

he posted this as his KP (nuts? ) method showing the tooth form from his single helix cutter

Now it may give a pair of gears with the same number of teeth that may just pass as usable but oh dear look what happens when the same cutter tooth form is used for different tooth counts, in this case a 48T "meshing" with a 24T

Looks OKish from a distance

But close up the lack of an involute and the thinner teeth that result from using the same cutter on a smaller gear start to give problems as the tips of the gear teeth either side of the meshing ones start to clash with the flanks of the other

Not a problem for Brian as he has not got any specific PCD or shaft centre distance to worry about so just move the gears further apart he will say. This is about as far apart as they need to go so there is no overlap.

But keeping them at the same PCD and rotating the gears shows a little bit of backlash may be present

This is why the spring washer of single turn of helix on the hob is no use to most people.

[John HaineParticipant @johnhaine32865]

But surely if the cutter is triangular it should cut an involute tooth?

[JasonBModerator @jasonb]

There should be some rolling that will give some curve which Brian has not included in his drawing but being just a single Vee will not produce an ivolute which is why a hob as several turns of the helix

[brian jones 11Participant @brianjones11]

Thank you John

took the word right out of my mouth

Indeed a Hob cutter has triangular straight faces which cut an involute as they turn

Will revert on this tomorrow as I try my 2:1 challenge

getting small gear blanks proved difficult without turning down much larger blanks but I have a cunning plan

I dont think Nylon blanks would cut very well do you? and you cant glue them together to make thicker blanks

OBTW for budding CADdies simulating revolving gears to examine close action at faces has baffled greatest gear minds around the world

eg the involute gears revolve by a rolling and sliding action across faces which is why clock makers favoured Cycloid teeth as they were nearly a perfect rolling action and lowest friction BUT only if they had loose axle holes

WaM

I must try and improve my microscopic photography

[JasonBModerator @jasonb]

Posted by brian jones 11 on 03/10/2021 20:30:49:

OBTW for budding CADdies simulating revolving gears to examine close action at faces has baffled greatest gear minds around the world

Really, have a click of gear/pulley constraint and rack & pinion Constraint on this page to see that it can be done quite easily in CAD. Though you may not get that with Freebie software.

[brian jones 11Participant @brianjones11]

Actually JB your spikey gears could have some merit

if you truncated the tops of the addenda say 5% and then run the gears together with a bit of load/speed in some abrasive flour or fluid of some sort I believe they would rapidly "run in" and settle down to be less noisy and become quasi involute

As you have the gear to make it so perhaps you could run a little trial for us to learn from

It could be quite cheap to make up a triangular tooth cutter – even a 20deg compliant one

WaM

PS

No JB  flashy animations dont do it, been there done that, you really need to be able to examine the precise motion as faces slide past each other.  Ive got that on hold while I try and get some gears made

Edited By brian jones 11 on 03/10/2021 20:51:43

[Michael GilliganParticipant @michaelgilligan61133]

Posted by brian jones 11 on 03/10/2021 20:30:49:

[…]

OBTW for budding CADdies simulating revolving gears to examine close action at faces has baffled greatest gear minds around the world

[…]

.

If you happen to have an iOS device, Easy Gear does [within its limitations] a remarkable job

**LINK**

https://apps.apple.com/gb/app/easy-gear/id1197863906

MichaelG.

[John HaineParticipant @johnhaine32865]

Posted by brian jones 11 on 03/10/2021 20:30:49:

eg the involute gears revolve by a rolling and sliding action across faces which is why clock makers favoured Cycloid teeth as they were nearly a perfect rolling action and lowest friction BUT only if they had loose axle holes

Good grief! No, traditional clocks use "cycloidal" gears to achieve "action after the line of centres" which is thought to minimise friction, though as the paper on fuze gears posted earlier suggests this is probably a myth. Anyway clock tooth forms are not really cycloidal, they generally use straight flanks on the dedenda and circular arcs for the addenda, because it's possible to make those whereas cycloids are very hard. "Loose axle holes" were a great way for cheap clocks to work without much fettling but the people making precision clocks with ball race bearings might find your characterisation a bit "loose" to say the least. A group of horologists in Australia cuts gears with precision Thornton cutters and lays out the plates to precise dimensions using CNC to take ball race arbor pivots – nothing loose about those! And There is a UK clockmaking company that uses involute gears.

My point about tooth form was that even though the "hob" has only a single turn it is still presenting the cuttng face to the teeth over a range of angles so should cut some of the involute.

[Author]

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