Author Topic: Gear making.  (Read 12499 times)

bogstandard

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Gear making.
« on: July 17, 2009, 03:18:02 PM »
I have just watched the most boring DVD. Almost four hours of continuous monotone talking, which to me sounds like a mild Mexican accent, coupled with very close up video.

If you can just get thru that monotone voice, you would find it one of the most informative guides to making gears the easy way.

It is called, you guessed it, 'Making gears the easy way' by Jose Rodriguez, which I think is where the accent comes in.

http://littlemachineshop.com/products/product_view.php?ProductID=2057

It answered a load of questions I had been mulling over for years, and could never get good answers to.


It is well worth watching if you have the chance.

Bogs

Offline John Rudd

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Re: Gear making.
« Reply #1 on: July 17, 2009, 03:29:21 PM »
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Offline John Stevenson

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Re: Gear making.
« Reply #2 on: July 17, 2009, 04:33:03 PM »
Sorry John,
Got to strongly disagree with you on this one.

it's crap, total crap  and before any one says it sour grapes let me explain why.

In no order it's monotonous, the quality of the video is so bad then when they do a close up the teeth could have been angle ground for all you know.

He uses a home made machine that to be honest isn't up to the job, it's part Sherline, part high tensile licorice but the main points are he uses tpi as his model to generate gears because he's using a tap or tap based geometry to generate his hobs [ which aren't hobs in the true sense ]

Gears are measured in DP or module if you are working in metric  but he doesn't cover this, neither does he cover pressure angles.

the killer though is he's got the value of Pi wrong in all his calculations so all his maths is for nothing.

Sorry but when you are charging punters serious coin, like 30 quid a throw in the UK for one of these coffee mats, sorry DVD's, you must give value for money.

On You tube is a guy called Hobbynut who has a series of 7 or 8 videos of gear cutting and hobbing.



These are well worth watching, clear precise and full of correct useful information, I see tonight he even has one on corrections to some of the videos already produced.

Download these, burn them to a DVD and throw the Rodriguez away.

John S.
John Stevenson

bogstandard

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Re: Gear making.
« Reply #3 on: July 17, 2009, 05:40:59 PM »
John,

I tried watching a few of that chaps you tube offerings, but his consistent beating of gums rather than showing anything stopped me from watching them all the way thru. All the articles he did could most probably be condensed into a quarter of the time, if only he could stop using that damned mouth of his and get on with the job in hand.

This DVD I watched however was full of interesting stuff. I am not on about making the cutters, as I know all his tooth forms are a load of crap, and he states that they are not the correct form, but they work for what he is doing. My interest lay in the way he used the hobs, and that to me was an eye opener. Also, I found the video quality was more than acceptable on a 42" plasma.

If you remember, a while ago I was looking to buy a set of gear cutting hobs, and everyone in the know who replied said that expensive machinery was required to use them.

http://madmodder.net/index.php?topic=511.0

In this DVD, the chappie shows how he got around the problem of the complicated and expensive machinery, and achieved very satisfactory results, and I am sure that if I used the correct form of hobs, I could produce correct gears as well, using his techniques.

But to get back to a point that has been raised about tooth forms.
 
If you are making a set of gears to go onto a small engine or a small workshop tool, does it really matter if the gear forms aren't correct? Surely if they have the right number of teeth and they run together well, does it matter if they are DP20 or MOD1.25? Only if you are trying to match existing setups are perfect tooth forms required, say if you wanted to make a few extra change gears. That is the reason I wanted to use hobs, one hob will cut all gears of the same pitch.

If this is the case, and you are just after making a cheap set of gears for small engines or home shop projects, then I would still recommend this DVD.

There is a large difference in what we need to do in the shop for our own use, and what is required for industrial use, or to satisfy the purists who require everything to be perfect and just so.

If there is anyone local who wants to watch it, I am sure I can arrange a viewing time for you, and then you can make up your own mind if it is for you or not. I won't even charge for the popcorn and coffee.
 
John

Offline John Stevenson

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Re: Gear making.
« Reply #4 on: July 17, 2009, 06:15:10 PM »
John,



If you remember, a while ago I was looking to buy a set of gear cutting hobs, and everyone in the know who replied said that expensive machinery was required to use them.

http://madmodder.net/index.php?topic=511.0

In this DVD, the chappie shows how he got around the problem of the complicated and expensive machinery, and achieved very satisfactory results, and I am sure that if I used the correct form of hobs, I could produce correct gears as well, using his techniques.

But to get back to a point that has been raised about tooth forms.
 
If you are making a set of gears to go onto a small engine or a small workshop tool, does it really matter if the gear forms aren't correct? Surely if they have the right number of teeth and they run together well, does it matter if they are DP20 or MOD1.25? Only if you are trying to match existing setups are perfect tooth forms required, say if you wanted to make a few extra change gears. That is the reason I wanted to use hobs, one hob will cut all gears of the same pitch.


 
John

OK but his method is not hobbing in the correct form as a hob has spiral cut teeth hence the need to gear the hob to the blank, a bit like a jubilee hose clip being tightened.

The method he uses which is also used by hobbynut is a 'hob with concentric teeth that produces a gaer with flats on it, the more cuts, the more flats and the better the quality.

Using this method to produce all the gears in any one range will work, it's nor new and there are some good web sites out there that explain this far better than Mr Rodriguez does.

Here's one from my good friend Tony Jeffree  http://www.jeffree.co.uk/Pages/multi-tooth-gear-cutter.htm

And one from Peter Harrison http://homepage.ntlworld.com/peter_harrison/workshop/gearcutting/index.htm

John S.
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Offline cedge

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Re: Gear making.
« Reply #5 on: July 17, 2009, 11:12:26 PM »
When I began this hobby I was in search of any available clues I could find to gain a foothold on the learning curve. I bought two of Jose's DVD's, one for the mini lathe and another for the mini-mill. John nailed it pretty cleanly with his boredom comments. Jose definitely provided the needed foot hold but his monotone delivery was excruciating and even with my elevated interest he managed to literally put me to sleep more than once.

He's the first to admit when he's doing something off the "standard" path, so its no surprise that he'd show an alternative to accepted practice when it comes to gears. Duclos did the same with his instructions for single tooth gear cutting. Like many things with our hobby, NASA specs are not required.... if it works we use it. The single tooth  cutter that I made from his instructions was not a perfect 32 involute shape, but it did produce a very usable and cleanly meshed set of gears. I'd be hard pressed to spot the differences in what I managed to cobble up and a set of commercial gears with the 32 involute profile.

I can live with not having to plunk down large dollars for special cutters if guys like Jose and Duclos are willing give me workable hacks that perform as needed. In Jose's case, he's also great for saving money on sleep medication. I recently tried to find his DVD's on LMS and sadly it appears they've dropped them from their inventory.

Steve

bogstandard

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Re: Gear making.
« Reply #6 on: July 17, 2009, 11:22:31 PM »
John,

I had already seen the first link, but not the second. Thanks for that.

I am not on about the straight toothed cutters, but the cutters that Arc Euro retail with spiral teeth.

He shows a freewheeling method that uses the spiral cutters to cut gear teeth, not worm gears.

I will be watching that part again, as he shows it being done with a freewheeling dividing head, but by looking at it, a normal simple rotating spindle will do the job admirably. All it would need is an angle adjustment on the base so it can be set to same angle as the helix of the hob, or I suppose I could set the head angle over to do the same sort of thing.

John

Offline John Stevenson

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Re: Gear making.
« Reply #7 on: July 18, 2009, 04:40:49 AM »
OK understood but one thing to take into account on the freewheeling  method is the gaps between teeth have to be narrower than the gear width or they can drop out of mesh when revolving but more to the point they can pick the next tooth up deeper on one side.
Home made cutters can have smaller gashes to offset this but bought ones are fixed, just a point worth noting.

There is a lot of good, free gear information out on the web, unfortunately not all in one place and there are many other ways to produce the same results.

It's even possible to produce perfect gears of any DP and tooth form, ie stub tooth, 20 degree PA 14.5 PA [ pressure angle ] and even splines on a Bridgeport type machine or clone using a 50p cutter that can be hand ground on a bench grinder if need be.

You could have a set of gear cutters for all pitches required in a home shop for under £5.00 in fact many have already got them but they don't realise it.

I know you have all the cutters John.  :poke:

John S.
John Stevenson

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Re: Gear making.
« Reply #8 on: July 18, 2009, 05:05:40 AM »
Somewhere! :doh:  On the web somewhere is a detailed article about cutting gears on a shaper using a taut wire to rotate the blank the result being perfectly formed gears using a basic tool shape.

If I recall correctly you start off as if cutting a rack tooth (which is the same as a gear with an infinite number of teeth) but as the blank is being rotated the result is a perfect gear tooth regardless of the number of teeth being created.  I presume that if every gear is a perfect fit to a rack they would also be a perfect fit to each other. :scratch:
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Offline No1_sonuk

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Re: Gear making.
« Reply #9 on: August 25, 2009, 06:25:21 PM »
I have just watched the most boring DVD. Almost four hours of continuous monotone talking, which to me sounds like a mild Mexican accent, coupled with very close up video.

If you can just get thru that monotone voice, you would find it one of the most informative guides to making gears the easy way.
The DVD player on my laptop can run at 2x speed with the sound active.
2 advantages:
1) The voice pitch is raised to a less soporific level.
2) The video lasts half the time. :)