cutting spur gears on a mill

[Michael GilliganParticipant @michaelgilligan61133]

I'm impressed, Brian … "here are some data"

At last someone who knows that the word is plural

MichaelG.

[John PParticipant @johnp77052]

[JasonBModerator @jasonb]

I think the latest "secret weapon" is a step backwards, only having one turn of the helix will just cut a "V" shaped notch unlike the tap which will take a little off the gear teeth above and below giving a facetted curve to the teeth so you end up with an even less usable gear.

[brian jones 11Participant @brianjones11]

well this board crashed and dumped my text

so I will write it up another time

suffice to say this is the result of an M24 screwed rod piece with 6 slots milled in sides to make proper cutting edges

i used a 3mm carbide end mill, it lost its edge after 6 slots ie 3 inches – is that normal for MS?

Once set up it only took 5 mins to make a gear

45mm OD 3mmCP 47 teeth

I made two mesh ok

btw

the spiral flute tap wont work cos the flute in big ca 9mm and a 6mm blank gets orphaned and loses registration

bin that

My secrete weapon worked but only gave me 2.1mm CP

it was made from a spring washer

the largest in 30mm but would need lots of eng to hold it properly and i havent got a TIG welder – shelved

I can get an M24 HT bolt gr 8.8 but would probably have to grind the slots accurately somehow using a jig

Can gr 8.8 be turned with a carbide tool on Maureen?

[Nick WheelerParticipant @nickwheeler]

Brian's quick and simplified method seems to take a lot more time and effort for lousy results than spending a few minutes working out what is needed using the traditional maths and straightforward equipment. Or have I missed something in all the noise?

[brian jones 11Participant @brianjones11]

Well yes you have indeed

You see to make a gear by conventional methods requires expensive special equipment

a) Using a universal dividing head (£250 plus set of gear cutters £125) and all morning to set up and cut a gear

b) Using a hobbing attachment need a geared universal head linked to spindle rotation £££££

c)Using a gear shape DIY type as per the Eureka design – see YT

d) Using stepper motor etc all experimental

e) CNC mega bucks

f) 3D printed – proper Prusa machine is £550 plus a year getting learning to use the machine squirting plastic thread and then taking all morning to squirt one gear – look at the example above by NW

My method has its faults as amply pointed out in a loud chorus of disapproval and its not for gear snobs – only for light duty on non ferrous mtl but it involves a mill, a large bolt with 6 suitably ground axial slots (work in progress), a mandrel to mount the gear blank and you make a gear in 5mins

It has its limitations which I am trying to address but it makes useful gears for modellers and for light duty

BTW making a proper gear is eye-wateringly complex as I have discovered on this board.

So thats the mission – gears for dummies who dont need horological perfection, maybe kids toys, robots, automatons, RC stuff, experimental stuff etc

WaM

[John HaineParticipant @johnhaine32865]

So can you give us a "recipe" for cutting a pair of light duty plastic gears to realise a 2:1 ratio with a centre-to-centre spacing of 50mm please? That is, so someone can make a pair of gears to fit their design and do what's required rather than make a pair of gears and design the mechanism around them?

[Martin KyteParticipant @martinkyte99762]

Posted by brian jones 11 on 30/09/2021 19:26:09:

So thats the mission – gears for dummies who dont need horological perfection, maybe kids toys, robots, automatons, RC stuff, experimental stuff etc

WaM

If that's the mission you would be better off with a 3D printer. YYou can make most of the rest of the bits for the stuff you list too.

regards Martin

[Nick WheelerParticipant @nickwheeler]

But you haven't really acheived any of that:

Your gears are largely unpredictable in tooth count and form, both of which are essential if they are for any of the traditional purposes including your examples

Your hacked together cutter isn't much easier to make than an accurate hob

Much the same applies to holding the blank.

Some sort of dividing apparatus is essential for many workshop jobs, not just gearcutting

Small equipment and conservative speeds/feeds are the cause for much of the time taken, not the methods. I see the same with screwcutting; when I mentioned that I cut several M14x1 threads starting at 100rpm and was running at about 150 for the last one it was implied that I must have superhuman reflexes.

There have been plenty of demonstrations of homemade cutters that give predictable and usable results for little effort – a tool to make a tool for three parts only needs to be barely good enough, not polished to a finish suitable for chrome plating.

What you are doing is the same work prototype work that led to the established and published methods that have been in amateur and professional use for centuries.

[Anonymous]

Posted by brian jones 11 on 30/09/2021 19:26:09:

a) Using a universal dividing head……….

Not so, you only need a means of indexing. It could be a rotary table or a plain dividing head. It doesn't need to be universal. You only need that for helical gears.

Andrew

[JasonBModerator @jasonb]

I've even used my spin indexer you can get them for under £50. Cheaper is a homemade spindle, detent and lathe change gear, even a printed out (ink on paper) division plate would be reasonably accurate and you would at least get a predictable number of teeth.

Edited By JasonB on 30/09/2021 20:28:56

[SillyOldDufferModerator @sillyoldduffer]

Posted by JasonB on 30/09/2021 20:28:24:

… even a printed out (ink on paper) division plate would be reasonably accurate …

Wrapping a saw blade around a mandrel and counting the serrations works too.

Dave

[Ian HewsonParticipant @ianhewson99641]

Why bother encouraging him, he very obviously enjoys winding people up, hi is so clever he will invent a circular object with a hole in and ask why it was not thought of before.

[brian jones 11Participant @brianjones11]

I think Jasons Spin indexer (hereinafter to be known as Maureen's method) shows promise and needs more work ie mixing and matching her change wheels on a spin indexer

Cant quite get my head around the permutations maybe some lively mind can assist

here are Maureens std change wheel set

,20,21,28,30,32,33,35,39,40,43,45,48,50,51,53,55,57,60,63,64,65,70,72,75,80,81,85,90,95,100,127,,

The paste up a paper printed dial is certainly promising when used with a junior hacksaw, you then only need a shaped cutter put into Arbor bench press like this for £10

https://www.ebay.co.uk/itm/124923302943?hash=item1d1602541f:g:IxkAAOSwdXlhUsLp

Now thats fair

OBTW you can only wind up Horologists

The Armchair Dragons in the Den are just waiting to see me fall over

but I have ordered an M24 HT bolt gr 8.8 (which I believe can be case hardened) together with a jig for my angle grinder then maybe get some sharp teeth into it

As for number of teeth prediction I have a polygon calculator in mind but need to back this up with some real models  of the non ferrous kind. I found that WD40 also helped on perspex blanks. So you must bait your breath a while

Edited By brian jones 11 on 01/10/2021 05:40:59

[JasonBModerator @jasonb]

Posted by brian jones 11 on 01/10/2021 05:22:04:

 

Cant quite get my head around the permutations maybe some lively mind can assist

here are Maureens std change wheel set

,20,21,28,30,32,33,35,39,40,43,45,48,50,51,53,55,57,60,63,64,65,70,72,75,80,81,85,90,95,100,127,,

So you can cut any of those tooth counts, anything that they are divisible by eg the 50T will also give you 25T and if you are cunning and make a point & notch detent you can then index the half teeth. All that before we get into compounding.

You already have the makings of an indexer, I'll let you work out what it is. Also no need to rush out and get a press that same tool can be spun in the DW or if you must you can use the mill's quill to cut the teeth (not fast so won't suit you) 

Edited By JasonB on 01/10/2021 07:39:43

[JasonBModerator @jasonb]

Posted by John Haine on 30/09/2021 19:42:57:

So can you give us a "recipe" for cutting a pair of light duty plastic gears to realise a 2:1 ratio with a centre-to-centre spacing of 50mm please? That is, so someone can make a pair of gears to fit their design and do what's required rather than make a pair of gears and design the mechanism around them?

You could have given him an easy one like 2:1 and 49.5mm ctrs, 50mm is not so easy

[brian jones 11Participant @brianjones11]

Holy Batmother are you using a DW quill as a shaping press (Doreen wouldnt like that) and the work is mounted on a rotary table? How long to chiv out each tooth? All morning jib then?

A 1 tonne Arbor press would chiv out a gear tooth in one swing of a bit of scaffold pole

As you have tickled my fancy with a Spin indexer, I fancy a 4" rotary table to mount my spare old chuck from Maureen to carry the mandrel plus fitting a digital angle gauge which has a resolution of 1 in 36000 ie 0.01deg so I could dial up what ever index I need. Way to go if needs be

I cant spare the time to construct a complete Table for 3-100 teeth that for the Armchairs

Now here is my first bash a the polygon approach to gear numbers from the example above

47 teeth OD 45mm CP 3mm. The diag shows a compliance within 130mu OD error almost negligible

IMHO it all depends on the quality of the bolt chivving and how the tool approaches the blank, ie it must engage quickly and firmly. I have to improve my mandrel – its a bit loose and must maintain tool sharpness

All this is in hand

OBTW I will be the first to admit that the method may fail for smaller diameters say <20mm 21 teeth

and a correction factor may need to be applied TBA

OBTW there are those blinded by Mistic spray who think this thread is a waste of space, well it has had over 17,000 views and 339 replies (mostly temperate) so here's cheers to the silent majority (50:1) supporting the freedom to think out of the box

WaM

BTW for the punctilious Sailors who like a wind up I might make CP – Chordal Pitch

Edited By brian jones 11 on 01/10/2021 12:45:00

[JasonBModerator @jasonb]

CP (whatever it is an abreviation of) is not measured at the OD of the gear, after 18 pages I had hoped you had picked up and understood some of the basics

 

No DW in my workshop or Myford for that matter, it took a while but what's to rush. Even gives a 2:1 ratio and the correct eccentric throw

 

Edited By JasonB on 01/10/2021 13:03:00

[SillyOldDufferModerator @sillyoldduffer]

Posted by brian jones 11 on 01/10/2021 12:42:59:

…`

OBTW there are those blinded by Mistic spray who think this thread is a waste of space, well it has had over 17,000 views and 339 replies (mostly temperate) so here's cheers to the silent majority (50:1) supporting the freedom to think out of the box

…

I doubt anyone reads this thread in support of freedom to think out of the box! It's value lies elsewhere, mainly:

• Posts explaining why free-hobbing isn't used much. It's because the method is both unreliable and unpredictable. Practical rather than armchair reasons that can't be ignored for most gear applications. Choosing to ignore them solves nothing. John set a simple 2:1 challenge, and Brian needs to repeatedly solve it.
• Posts explaining various ways gears can be cut reliably.
• Posts referencing software, tables, and respectable gear literature.
• Entertainment – what new Snake Oil is on offer today! Will Brave Brian finally defeat his imaginary foes? (There are no Dragons in Armchairs!)

Brian believes he's invented a new method. Not so! Free-hobbing is as old as the hills. It works up to a point, but no-one has ever got it to work reliably. I don't see anything in the thread to change that.

Free-hobbing is caught in a pincer. It doesn't satisfy the need for gears that fit between design centres and mesh efficiently at a fixed ratio. And if a bit of slip doesn't matter, free-hobbed gears aren't as easy to make or as effective as pulleys, where the centres problem is fixed by the belt.

Dave

[duncan webster 1Participant @duncanwebster1]

But you must remember that the OP started from a position of knowing very little about gears, and judging by his latest post has not changed his position. Anyone who does know something is dismissed as an armchair engineer, and all the money spent by industry on machines to make properly shaped accurate gears has been wasted. Redefining accepted terminology is not really helpful

[brian jones 11Participant @brianjones11]

Well Sailors do like a bit of wind up dont they

For the record, I have NEVER disrespected any of the gear experts on this board nor claimed proprietorship of the free hobbing method. I simply had a box of large taps and wondered if they could be put to use

No John I havent ignored your challenge, I am just fiddling with my tool just now and how to grind it sharper. I will get onto it soonest

Well gear snobs are known for making convenient definitions so perhaps I,ll call mine KP as Kordal pitch. ~We wouldnt want to introduce any confusion into the world of gears

For me KP will be convenient and intuitive as it matches the concept of thread pitch (mm) for my tool and I hope will make an easy calc

This is after all Gears for Dummies

You should see the top of my head , its peened over

WaM

[John HaineParticipant @johnhaine32865]

Brian, I wait in hope! Just to make it easier, make the centre distance 49.5 rather than 50mm. Ratio has to be 2:1 but number of teeth etc up to you.

[JasonBModerator @jasonb]

Oh and I was so looking forward to those 1.010101MOD gears

Though there is an Imperial Circular pitch that comes close

Edited By JasonB on 01/10/2021 18:28:34

[brian jones 11Participant @brianjones11]

Jason I told Maureen and Doreen what you said – cocking a snook indeed on humble hobby machinists. You are off their Xmas card list. You are in the semi pro league with big machines DRO CAD CAM etc. Its not a fair comparison

No DW in my workshop or Myford for that matter,

All in hand John, I am struggling trying to fix a grinder using a 50mm x 5mm wheel so I can traveverse the slots and put a nice edge on the cutter faces. Ive figured a 5deg clearance angle by going off centre 5deg = neat

Will get there but its straining my brian

WaM

[JasonBModerator @jasonb]

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.

[Author]

Posts