A change is as good as a rest

[Martin WParticipant @martinw]

Ramon

 

How about taking the ball to orange heat and then burying it in vermiculite to cool down slowly especially if ash is a problem to obtain. What’s left over can be used for gardening, soil improvement, so you might be able to kill two birds with one done, so to speak.

 

Cheers

 

Martin

[Ramon WilsonParticipant @ramonwilson3]

Hi Terry

 

I would imagine the soak in a good fire as you describe and allowing it to cool overnight will do the trick alright. It’s allowing it to cool as slowly as possible which will let the hardness down.

 

A much revered, long missed and fondly remembered model engineer in these parts – Lenny Evans – used to case harden small parts in his coal fire. He would pack the parts in Casenit in a steel box fabricated from 1/8 flat bar and push it deep in the coals. Retrieved the next morning, they would get a swift reheat with a flame and the usual quench. He really was from the ‘old school’ – served a seven year apprenticeship with Garretts of Leiston and told me once that his first six months were spent scraping and polishing steel parts with files and emery and oil and the second six months doing nothing but sharpening drills – by hand. (Might have that the wrong way round)

He could put an edge on a drill down to the smallest quick as you like. Virtually all his home made taps were case hardened and not made from tool steel. Ah! but I digress…..

 

Can’t see why vermiculite wouuld not work either Martin but I think It might be better to crush it down into a fine powder to eliminate as much air as possible. I believe powdered garden lime will keep the heat too though have not tried it.

 

Regards for now – Ramon

 

 

[Sub MandrelParticipant @submandrel]

I made these cylinder balls from brass using a form tool made by drilling a hole in gauge plate. they were pre drilled 10BA :

 

:

 

 

[Ramon WilsonParticipant @ramonwilson3]

Hi guy’s,

 

I’m about to have a go at cutting the two bevel gears required for the governor. Though I have read about making gears from time to time over the years none of it other than the most basic points, if indeed that, has really sunk in so this time it’s actually ‘crunch time’

 

I have only one book on the subject – The Workshop Series one by Ivan Law and some info downloaded from a link seen on another posting on here elsewhere.

 

The gears required are 32 DP 12 teeth and 18 teeth. I intend to make the cutters using the two button tool method and forsee no problems there however the table in the book for bevel gear cutters shows the number of cutters for 20 degree pressure angle as 6 not 8 as is shown for spur gears
and starting at a tooth range of 17-20. Is it possible to cut lesser
teeth with this cutter ie the 12 tooth required or would I be right in
thinking that the cutter would need to be much thinner at the point. Can the dimensions of the no 8 cutter for spur gears be used?

 

The other question I have is other than going to depth from the point of touch on is how can you be sure the toothform is correct.

 

I know I will have to look into this subject to a reasonable degree but I don’t want to spend a great deal of time sifting through a lot of no doubt interesting but currently un-required info – I’d much rather get on with cutting the two I need so any help you could pass on here that would enable me to get cracking would be most appreciated

 

I now have the required balls for the governor – Neil thanks for the suggestion to use brass but I’d much prefer steel ‘coloured’. That’s a nice looking engine BTW – one of your own design?

 

I finished off the basic governor body today – the parts are all made form steel silver soldered together in a simple fixture. After the gears wil come the fiddly bits

 

Hope someone can help on the gear info

 

Regards – Ramon

 

 

[Sub MandrelParticipant @submandrel]

Hi Ramon,

I think I can help!

 

I have usd Ivan Law’s book for all the gears below. I extrapolated the gear tables for cutters 7 and 8 with a 20-degree pressure angle. The 13 tooth pinion in the pictures was made using the values D=4.50, C=5.65 E=2.25 (as per table on page 114).

 

You can only judge the form by the way the gears mesh! I have made a fair few now and only two were slightly tight and needed easing at the root of the spaces.

 

Note that on page 106 the bevel gear calculations should use COSINE not SINE – this is a well known error that only shows up when the two gears are of different sizes. The tiny pair of bevel gears (80 DP if I recall correctly) were done this way.

 

The engine is my own design (take a look in my galleries for more). I’ll pm you with a thought…

 

Neil

 

[Sub MandrelParticipant @submandrel]

Hi again Ramon,

 

Looks like you can’t be pm’d without a public profile.

 

I have written up the engine and produced drawings. David was willing to run a series on it, but encouraged me to contact Polly regarding supplying castings. they suggested I rework the flywheel a bit (they do have VERY high standards) but despite doing this circumstances have stopped me getting round to a set of test castings.

 

If you or anyone fancied borrowing the patterns and having a free set of drawings and having a go in return for some feedback…

 

A set of castings from ***** cost me about £44 several years ago (they took about nine months to be made, then they complained that I wanted to wait until pay day to send them the cheque!) I suppose I should be grateful they didn’t want payment in advance.

 

Neil

[Ramon WilsonParticipant @ramonwilson3]

Hi Neil ,

I have only just realised you had responded to my post. I was out till late on Friday and yesterday and today have had a ‘hard time’ moving a tonne of pebbles into the bottom of the garden plus sundry other accompanying tasks all perfectly designed to create abject tiredness and prevent access to workshop mode

I have however, found time to read a bit more and found Ivan Law’s book very descriptive and easy to understand but it appears – to me – to leave some areas a bit vague if you don’t know exactly what you’re doing – and I don’t

I can see now, given the cutter is correct that the form is defined by the depth of cut and understand the need to offset and rotate the blank when cutting bevels if that degree of accuracy is sought. (I believe, given perhaps some fine hand filing before fitting, this may not actually be neccesary on such small bevels as these?)

 

Where I’m stuggling at the moment is the apparent lack of information regarding the actual making of the cutters. As you are aware there are two charts in the Law book showing button diameter and spacing as well as depth of cut for making the form tools. The first is for 20 degree pressure angle and shows dimensions for 6 not 8 cutters and these only going down to 17 teeth. Is this because a bevel gear is being cut and not a spur gear?

This seems to be answered when he then mentions that pressure angles can be changed particularly when pinions of 10 or 11 teeth are called for and shows a chart for 30 degree pressure angle going down to 9 cutters beginning at 10 teeth.

(I wasn’t ‘prepared’ for the 30degree pressure angle as had previously thought that 14-1/12 and 20 were the only ones used. Is this chart what I should refer to to make cutters for these specific gears ?(12 and 18 teeth)).

 

There is no chart for the button dias for making form tools for eight cutters for spur

gears that I can find  either. On that note then, is there available anywhere, a definitive chart showing dimensions required for making form tools by the button method giving dimensions for all cutters in the normal 14-1/2 and 20 degree pressure angle both for spur and bevel gears ?

 

I would appreciate any help you ( or anyone else for that matter) can give to enable me to cut these two gears. Please appreciate though -and I’m not wishing to appear to be dismissive when I say – I don’t want to delve into lot’s of detailed theory/mathmatics if it isn’t really neccesary – I’m no academic and maths was never my best subject. What was there on that front is very much harder to get in gear now as the old grey cells seemingly diminish at an ever rapid rate. Hope you understand

 

Finally, Neil, not sure what is going wrong with the PM. I have recieved many PM’s to date so don’t think it’s because I don’t have a profle (as yet – something else I still haven’t got round to)

 

Regards for now – Ramon

 

Edited By Ramon Wilson on 11/12/2011 15:30:53

Edited By Ramon Wilson on 11/12/2011 15:35:47

[JasonBModerator @jasonb]

Can’t help much Ramon as I’ve only cut spur gears with commercial cutters, shame you could not get to teh MEX as there were 3 or 4 guys on the SMEE stand all cutting various types of gears using various methods, could have piucked their brains.

 

There was quite a bit of talk about bevel gears in Andrew Johnsons post a while back, I’ll see if I can find it.

 

As you say in the small sizes parallel depth bevels will be fine with a bit of file work if needed.

 

I went the HPC route for the skew gears on the Benson

 

J

[Ramon WilsonParticipant @ramonwilson3]

Hi Jason, Thanks as usual for your input. Yes it was a shame I couldn’t get there, it would have been nice to meet up with you. I don’t think I shall be able to get to Ally Pally either as I have a date with the surgeon pending

I too looked in the HPC catalogue but there wasn’t anything that I could see would do – now that I’ve made the body – which is typical, but I have found some on the Huco site – unfortunately they have a £100 minimum order but have put me in touch with a local supplier who has promised to get me a price for two 1.5 : 1, .5 module gears on Monday.

 

That said I would prefer to make them if I can, if nothing else but because it’s something I have not tackled before, and on that note, surprise, surprise, guess what I have just found

Whilst looking in an old folder for some pictorial info on governors, in particular the linkage pins fastening as that’s whats being worked on at the moment there laid a copy of an article from ME, Sept 1994 by D.A.G. Brown showing three charts with the info I’m looking for. I haven’t read it through yet – literally only just found it – but it looks as if it fits the bill. Brilliant.

 

All being well should have this underway this week if other matters don’t get in the way

 

Thanks again though

 

Regards – Ramon

 

 

[Sub MandrelParticipant @submandrel]

Sorry Ramon,

 

I should have thought a bit longer; It was some time ago.

 

Yes for bevel gears the calculations are different as you use the cutter for an imaginary gear whose size can be found following Ivan’s methods – step by step.

 

I now recall that my figures for a 13-tooth 20 degree cutter were realised by drawing the tooth overscale using Corel Draw, finding a best fit circle and scaling off the dimensions.

 

Machinery’s handbook uses a two-circle method (for the tooth above and below the PCD) but it seems from other stuff I’ve seen that various combinations of circle diameter, spacing and infeed can be used and you still get a cutter within normal tolerances.

 

I have made a few gears by filling a bit of gauge plate to fit the gap between two teeth on a similar gear. Tubal Cain admitted this was his preferred approach.

 

I started off making cutters with two discs, but there is much more risk of chatter (especially as you are using them on 1″+ diameter silver steel) than with one disc, also I can easily move the topslide across with an accuracy of 1 thou for the second cut, try supergluing two cutters into drilled holes with that accuracy. You also avoid errors caused by the form cutter not being dead on 90 degreesand getting an assymetrical cutter.

 

Another tip – always take a tiny skim over the blank with the crosslide index set to zero. that way the infgeed of the form cutter will always be dead on.

 

I always, use single point cutters. I even bouight the stuff to make a eureka but cutting gears is so theraputic – gently turning the feed so it goes a thou or two for each tick of the cutter.

 

When making the gears, the cutter is DEAD on centre height of the blank, as close as you can get it, more critical than you might think, a small error gets doubled making teeth look wonky (though they will probably still work). Take care if cutting harder steels; I managed to blunt a cutter very quickly on medium carbon steel by going too fast.

 

If your gear blank is slightly undersize reduce infeed a little to maintain centre distances. Cut a little deep if you want extra backlash.

 

When cutting gears cut a whole ‘space’ in one go. Use gentle infeed to keep the cutting depth right.

 

Silver steel or gauge plate cutters work fine on brass or most steels.

 

Yes, it is possible to reset the blank and take another cut if the gear is too tight/you don’t feed in enough.

 

Some folk lose a lot of sleep over getting things 100% right when they haven’t even got equipment capable of measuring the error generated by a simpler approach. Don’t forget even Ivan’s cutters are theoretically all wrong as he forgot to allow for the angling of the cutter to allow for relief at the front, compounded by grinding the top of the cutter! Then there’s the angled relief you use to give clearance to teh cutter itself – it’s amiracle they work at all – but work they do…

 

Finally, just give it ago, it’s amazingly rewarding. My Fordson tractor is still decades away as I have only made the gearbox (above), but I love twiddling it and changing gear!

 

 

Neil

 

 

[Ramon WilsonParticipant @ramonwilson3]

Hi Neil,

Thanks very much for such a helpful post all of which sound advice I shall take on board.

 

Having spent the evening watching Wyatt Earp – I know but I’m a sucker for a good ‘wezzy’ – I’ve just been out to the workshop and searched through the old filing system only to find several more copied articles on gear cutting so I’m now well ‘resourced’ . Must be a sign of getting old as these ‘finds’ definitely came as a surprise – Cor, wonder what else is lurking in the dark reccesses of the workshop that’s been long forgotten.

 

Hopefully if things go well this week I should be able to get on to them so will report back with the results, successes or miserable failures.

 

Many thanks for the input guys – all much appreciated as usual .

 

Regards – Ramon

[Ramon WilsonParticipant @ramonwilson3]

Hi Terry,

Just in case you or others are interested the balls were treated as described above and though still quite tough to drill softened sufficiently to drill a 2mm hole about 8mm deep – had to keep the speed well down though to prevent work hardening particularly when using the 1.5mm pilot drill. The balls oxidised quite a bit but after a soak in Hydrochloric soon ’emeried’ up to give a ‘turned finish’

No breakages however and as of tonight here’s how it looks so far

 

Having had a good read up on it now there’s a reasonable degree of confidence (???) regarding making the cutters and cutting the bevels so next session is to get ready for that.

 

Regards – Ramon

 

 

[JasonBModerator @jasonb]

Very Nice. Did you thread the balls or loctite them on?

 

J

[Ramon WilsonParticipant @ramonwilson3]

‘Morning Jason,

 

As you see it they are just pushed on for an initial trial but will be Loctited on final assembly. I baulked at threading them because it was still pretty tough material despite the annealing. Perhaps they should have been drilled out to 3mm or so and a threaded bush Loctited in, infact now you’ve put the thought into my head I think that’s what I’ll do

 

I’ve never paid much attention to the full size items – presumably the balls were separate from the arms and attached by threading it would certainly be a fair old job to make from solid that’s for sure.

 

Anyone have any pics of the full size weights and their attachment?

 

Regards – Ramon

[Ramon WilsonParticipant @ramonwilson3]

 

Well guys after a few trials and tribulations and thanks to Neils valuable advice I was finally able to make sense of the info I had and after a couple or three mishaps eventually managed to produce a set of bevel gears.

 

The information for the tooling to make the cutters was taken from an article by DAG Brown in the Sept 94 issue of ME and proved extremely easy to follow. They mesh and run well without binding or tight spots so I’m well pleased with the results asmaking gears is a first for me.

 

The balls are still held by Loctite – the nuts are false ones, the washers beneath are concave to sit tight against the surface.

 

Detail pics are on the HMEM site which I’m sure most visit so apologies to those who’ve already seen these.

 

Not far to go now – just inlet and exhaust plus the final fitting out – studs, nuts etc

 

Thanks again Neil

 

Ramon

[Sub MandrelParticipant @submandrel]

How do you get that sating finish on steel?

 

neil

[Ramon WilsonParticipant @ramonwilson3]

Hi Neil,

You are not the first to ask that but it’s not difficult and doesn’t take lots of work.

 

It helps if machining toolmarks are kept to a minimum however but a dressing with file where possible then emery down to 240 grtit, wet and dry to 400 and then the ‘secret’ – a finish off with Garryflex abrasive blocks. I have mentioned them on here elsewhere before and swear by them. They are very good on brass too and particularly so on ali.

 

They are an abrasive filled solid rubber block that come in four grades. They can be used dry, with water or, as I prefer, with paraffin. Another good thing about them is that being homogenous throughout pieces can be sliced off them with a scalpel to get into all sorts of nooks and crannies.

 

‘Cast about’ a bit for them as prices do vary

Regards – Ramon

[Sub MandrelParticipant @submandrel]

I have all the ingredients (including garryflex – I use it to clean PCBs).

 

But rather like plastic models where you needed ‘Skil, Patience and Humbrol’ I had plenty of Humbrol…

 

Neil

[Ramon WilsonParticipant @ramonwilson3]

Well its took a bit longer than anticipated but pleased to tell it is finally finished. There are several pics on here but for those who don't visit HMEM heres a couple taken as of today

 

 

And now – garden permitting – it's time to get back to another I/C engine – diesel of course

 

Regards – Ramon

Edited By Ramon Wilson on 28/03/2012 15:41:23

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