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cutting spur gears on a mill

a rogue method?

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John Haine26/09/2021 17:00:55
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Quite a few I expect. There was certainly a prof of electrical at Bristol from 1911 (David Robertson), Osborne Reynolds was prof of mechanical at Manchester before 1900. A US "assistant professor" is more the equivalent of lecturer here today, not sure about 1911. Charles Parsons in a 1911 book on the steam turbine mentions a Prof Ewing at Cambridge. In fact a Cambridge chair in engineering was established in 1875 when it was called Professor of Mechanism and Applied Mechanics .

ega26/09/2021 18:42:07
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Posted by John Haine on 26/09/2021 17:00:55:

Quite a few I expect. There was certainly a prof of electrical at Bristol from 1911 (David Robertson), Osborne Reynolds was prof of mechanical at Manchester before 1900. A US "assistant professor" is more the equivalent of lecturer here today, not sure about 1911. Charles Parsons in a 1911 book on the steam turbine mentions a Prof Ewing at Cambridge. In fact a Cambridge chair in engineering was established in 1875 when it was called Professor of Mechanism and Applied Mechanics .

Thank you - good to know and I suppose one or more of those would have taken in machine design; it was the rather specific nature of the title of Roe's position that struck me and reminded me that by then America and Germany were overtaking the UK in this field.

Andrew Johnston26/09/2021 18:50:23
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I use the book on steam and heat engines by Ewing as one of my references when attempting to understand the underlying theory of steam engines. By the time my edition was published, 1926, he was Vice-chancellor of Edinburgh University.

Andrew

brian jones 1127/09/2021 14:07:15
347 forum posts
62 photos

Well dont break open the champagn yet

This is my first run with the secret weapon

20210927_123836 copy.jpg

and here is the weapon naked an unabashed20210927_123226.jpg

I had to use a bit of plumbing to stop the leaks from my secret workshop

cost of bits for tool <£10

time to make gear 5 mins

For the armchairs here are some data

OD 44.4mm

No teeth 54

I dont think I started with the right OD so result is iffy

more work needed

Cricket bats out already

WaMkiss

obtw I forgot to adjust the helix angle for the new CP

MK2 of tool is on drg board and may well have an adjustable CP

I need a better grinder set up to make a proper PA and cutting edge

Edited By brian jones 11 on 27/09/2021 14:10:48

Edited By brian jones 11 on 27/09/2021 14:28:28

Michael Gilligan27/09/2021 19:32:19
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I'm impressed, Brian ... "here are some data"

At last someone who knows that the word is plural

star

MichaelG.

John P28/09/2021 10:06:33
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all alone.jpg

JasonB28/09/2021 10:39:43
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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.no

brian jones 1130/09/2021 15:44:10
347 forum posts
62 photos

m24tool.jpg

m24gear.jpg

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?

Nicholas Wheeler 130/09/2021 19:00:21
823 forum posts
59 photos

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 1130/09/2021 19:26:09
347 forum posts
62 photos

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 Haine30/09/2021 19:42:57
4428 forum posts
264 photos

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 Kyte30/09/2021 20:05:29
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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

Nicholas Wheeler 130/09/2021 20:15:02
823 forum posts
59 photos

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.

Andrew Johnston30/09/2021 20:16:44
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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

JasonB30/09/2021 20:28:24
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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

SillyOldDuffer30/09/2021 21:23:29
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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 Hewson30/09/2021 23:37:42
315 forum posts
27 photos

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 1101/10/2021 05:22:04
347 forum posts
62 photos

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

JasonB01/10/2021 07:33:21
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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

JasonB01/10/2021 07:35:38
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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 easysmile p

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