wheel cutters/cutting

[BoldminerParticipant @boldminer]

I have just cut the teeth on the great wheel of the above mentioned clock, ie. 96 teeth. This is my first attempt at clock-making and some how the end result dosn’t look right!……I sent for the rerquired 34 & 42 D.P. cutters from a well known supplier who quickly responded but sent me a 0.75 and a 0.6 module cutter. When  questioned, I was told that the 0.75-W cutter was to be used instead of the 34DP and the 0.6–W instead of the 42DP and everything will turn out OK. I also asked about the depth of cut as it was not indicated on the cutter as I had expected and was told to cautiously increase the depth of cut on 2 adjacent teeth until the radii on the top blend to make one continuous arc. I did this but to me the ‘space’ appears to be significantly larger than the tooth…..

I have studied the information and reference books which I have but all I have succeeded in is confusion!   Apart from returning the cutters and starting again is there any-one out there who can help resolve my problem/confusion? 

NB. the cutter blank was was exactly to size as required ie. 2.9″ OD and the teeth cut until the radii just met.

[BoldminerParticipant @boldminer]

John Wildings’ Elegant scroll Scroll frame Skeleton Clock

[JasonBModerator @jasonb]

Are they the correct number cutter for 96teeth, they should be No2

 

Also your OD sounds a bit large, OD is calculated by adding 2 to the number of teeth and then dividing by the DP

 

So 96+ 2 = 98

 

98/34 = 2.880″

Edited By JasonB on 03/06/2010 19:47:40

[JasonBModerator @jasonb]

As for depth of cut if you were using DP cutters the Addendum (hight of tooth above pitch circle) is 1/DP so 1/34 = 0.0294. Dedendum (ht below pitch circle) is 1.157/DP so 1.157/34 = 0.0340″

 

So your depth of cut should be the two added together 0.0634

 

Jason

[BoldminerParticipant @boldminer]

thanks for the reply Jason, as I said in the posting  the information in John Wildings consrtuction manual states :  Great Wheel 96 teeth – 43DP     P.C.D. 2.8″     O.D 2.9″ but I have been supplied with module cutters instead of DP.

[JasonBModerator @jasonb]

You are going to have to fudge it a bit as a 96T gear cut with a 0.75MOD gives a PCD of 72mm or 2.835″ which will muck up all your gear spacings, depth of cut will be in the region of 1.8mm or 0.070″

 

Maybe someone else can confirm what the OD should be but those figures from JW don’t look right, PCD should be 2.823″ and OD 2.880″

 

Jason

[kneedeepinswarfParticipant @kneedeepinswarf]

The module cutters you have been supplied are correct replacements for 34 and 42DP as

Module = 25.4/DP.

 

O/D of wheel = (No. of teeth + 2.7)M

 

So a 96 tooth wheel of  .75 M (34 DP) would be (96+2.7).75 = 74.025 mm or 2.914 inches, and for .6M (42DP) would be 59.22mm or 2.33 inches. So it would appear that JW has confused 42DP with 34DP when giving the O/D of the blank. Note that the O/D of the 34DP wheel should be .014″ larger than that given by JW. This could have had some influence on your result.

Other useful data:

Addendum = 1.35M

Dedendum = 1.55M

Tooth height, ie. depth of cut = 2.9M

PCD = No. of teeth X M

Tooth width and space width on the PCD are both 1.57M

As horological wheels have a cycloidal tooth form, with a pronounced “mitre” shape at the tooth tips, it difficult to judge exactly when the two curves actually meet and it is easy to feed the cutter too  far, giving a thin tooth. I find it is a good idear to coat the edge of the wheel blank with layout blue and the feed the cutter equally each side of the tooth until just the tiniest blue “land” can still be seen (use an eyeglass) and stop there.

Edited By kneedeepinswarf on 04/06/2010 21:28:07

Edited By kneedeepinswarf on 04/06/2010 21:30:06

[Sam StonesParticipant @samstones42903]

I’ve just been glancing through some of the threads about clocks, and am reminded of the time when I was cutting the 96 tooth Great Wheel for John Stevens `Skeleton Clock with Lever Escapement’.

That was back in the early 70’s and I’m now 75, so please excuse any dithering in my notes.

With the second hand Myford ML7 which I bought around the early 60’s came a home-made dividing head with three plates. The ratio of the worm and wheel was the usual 40:1.

I was convinced that I had set up correctly so that the end result would display 96 teeth on a wheel measuring about 69mm diameter. This wheel engages with a lantern pinion so I took a chance and ground a fly cutter with a profile that might just pass as an involute.

I merrily progressed around the brass blank, and with manly pride, chose to check that the final move `into the first slot’ would prove that all was well. It wasn’t!

Before my eyes, the first tooth disappeared. Out came my Machinery’s Handbook from which I was to discover that with the plates I had, I could only divide to give 94 teeth.

Oh dear! or words of a similar meaning.

Then came the break-through. Of all the wheels in this particular clock, the number of teeth on the Great Wheel was not critical. Ninety four teeth was OK, so that’s where it rests.

Perhaps I’ll drop a Forum thread about my efforts at making the balance wheel.

I welcome any comments you chaps have to offer.

Sam

[NilochParticipant @niloch]

Sam,

I am unfamiliar with John Stevens’ Skeleton Clock with Lever Escapement; were the words and music in Model Engineer or another magazine ?

Issue numbers and any other information would be most welcome.

Thank you.

[Sam StonesParticipant @samstones42903]

Thanks to the help of several other readers when I was researching the archives, it was described in five issues of Model Engineer.

The first edition was dated 4 February 1972. The copies with the above clock are, Vol 138, issues 3434, 3435, 3437, 3438, 3439.

I hope this is a good starting point.

Sam

[DAVID POWELL 4Participant @davidpowell4]

I was thinking of making the beginners clock serialised in The Clockmaker some years ago and I’ve been reading the above and have 2 questions.

 

I want to know hoe you calculate the diameter of the blank used to make a clock wheel.

I know it is 2+the number of teeth divided by the DP, but how do you calculate the DP as this is the number of teeth per inch of the diameter and it’s the diameter I’m trying to calculate?

 

Second the author of this article in the Clockmaker suggests using a .6 module 42DP for cutting the wheels which have 100, 96 and 30 teeth, yet everything else I read on this subject indicates I should use a number 4 (26-34 teeth) and a number 2 (55-134 teeth)

 

 

[JasonBModerator @jasonb]

“Second the author of this article in the Clockmaker suggests using a .6 module 42DP for cutting the wheels which have 100, 96 and 30 teeth, yet everything else I read on this subject indicates I should use a number 4 (26-34 teeth) and a number 2 (55-134 teeth)”

 

Are yoiu sure it does not say use a 0.6module OR 42DP cutter as both these are similar pitches. The numbers refer to the range a teeth that an involute cutter will cover, you would still need different number cutters if using Module rather than DP but in both cases a No 2 & 4 cutter would be needed

 

OD equals number of teeth plus 2 divided by DP so for your 100t wheel thats 100+2 all divided by 42 so OD is 2.429″ You have been given the DP by the author.

 

J

 

Edited By JasonB on 30/10/2011 12:06:58

[DAVID POWELL 4Participant @davidpowell4]

Jason, thanks for your reply.as you’ve probably guessed I’m still a learner as far as this is concerned.

The article says, ‘ I finally settled on 0.6 module (42DP) as this is …………

 

As for the DP where did the author get it from?

[JasonBModerator @jasonb]

I’m not really a clock man but would assume the author started with the reduction ratios that he wanted, this would then give the number of teeth required and then decided how far the gear centres were roughly going to be.

 

So now we have the teeth and PCD its easy to work out the DP

 

No T = PCD / DP

 

J

[Stephen SpiceParticipant @stephenspice48575]

With regard to JWs skeleton clock. Could I ask for a little advise about the ratchet cutting.

I understand the book regarding the barrel ratchet. And a 5 deg of undercut mentioned for coarse teeth.

Having no access to Britten's book for the tables. I'm wondering what percentage of undercut applies to the maintaining ratchet wheel that has 120 finer teeth.

Jim.

[Stephen SpiceParticipant @stephenspice48575]

Just wondering if any of you chaps has actually constructed John Wildings Scroll skeleton clock and got away with the OD wheel measurements given.

I mention this because using Number of teeth + 2.7 (M. I make all of the diameters a little wrong

These would be :-

Great wheel JW 2.9 2.914

Third wheel JW 2.070. 2.048

Centre wheel JW 2.210 2.189

Minute wheel and reverse JW 1.000 .985

Hour wheel JW 1.780 1.764

[Neil WyattModerator @neilwyatt]

Isn't the thing about clock gear with cycloidal teeth that the exact diameters aren't critical and you adjust the centre distances to get free-running? Hopefully a couple of hundredths of an inch shouldn't be an issue?

Neil

[roy entwistleParticipant @royentwistle24699]

The usual suppliers of wheel cutters have one cutter marked Wheel and the pinion cutters marked with the number of teeth to be cut It is also usual to specify half mod size smaller for the pinion cutter buut to make the blank the same size as the wheel this gives stronger teeth For the pedantic one is actually cutting the spaces between the teeth

Roy

[roy entwistleParticipant @royentwistle24699]

To be a little bit clearer on mod sizes if the wheel cutter is .8mod the pinion cutter will be .75 If the wheel cutter is .6 then the pinion cutter will be .55

Roy

[Stephen SpiceParticipant @stephenspice48575]

Many thanks for taking an interest in my query.

Sill being Edu — macated in my 81 st year

Jim.

[andrew mcleishParticipant @andrewmcleish96372]

Yes stephen i have recently finished j ws ornamental scroll clock ,my first attempt at clock making.

I made my own cutters and division plates in fact the only bought in items were the dome and spring.

The cutters just entered the first space on all the wheels on completion of machining.

I followed all of mr wildings dimensions without problems that i can recall may be i was just lucky

Andrew mcleish

[JasonBModerator @jasonb]

Last post moved to new thread here

[Stephen SpiceParticipant @stephenspice48575]

I might usually be rather ashamed to add my latest photo's. Heath Robinson comes to mind. " Ingeniously or ridiculously over complicated in design or construction "

But I thought this might inspire the would be clock maker to have a go if they are like me not able to splash out about 500 quid for a dividing attachment. But can put their hand in a junk box and put together a few bits that will do the job. The electric motor is off a very old washing machine which I threatened to turf out many times. And this I control with the speed control borrowed from my honey extractor. The division plate was made just for this clock with hole numbers 45 32 26 30 and 21 which is ok for all the wheels and ratchets with my 60 to 1 worm.

Well done Andrew for making the cutters. I have managed this before but my attempts this time weren't good enough. I probably could have got ready made wheels for the price of my cutters but I maintain that if I couldn't cut the wheels then I couldn't really make a clock.

So the wheels and ratchets were my first job. But have since make most of the other bits for the clock. Where as most people would start with the plates, these being quite costly items I have still to make these wanting to prove the wheel cutting first.

Stephen Spice.

[Stephen SpiceParticipant @stephenspice48575]

Having made the dial for the John Wilding Scroll clock. I thought anyone following this project may be interested in my views regarding the initial marking out as I found the book rather over simplistic and could be a bit of a struggle.

At the onset I just couldn't find a pencil that was hard enough. And these marks were not going to be easy to follow.

As mentioned scriber marks were not advisable. And I advise blueing the entire plate and not just where the numbers are going. I found that a scriber made from soft copper made good marks on the plate that were very easy to see and these did not score the brass so were not visible afterwards.

I made 12 radial lines from numbers to the centre as a reference for the 1s to 4s etc and there is really no need to draw the numbers at all for these as these can just be worked by movement up or down of the vertical slide using the micrometre dial.

The Vs and Xs were drawn in at the appropriate places and if these lines are extended some way across the plate. then it is much easier to line up the tool on the extended lines rather than just the numbers drawn.

Stephen Spice.

[andrew mcleishParticipant @andrewmcleish96372]

Hi stephen i used a similar method when making my dial i also marked in the numbers with a uni fine line pen as a check.have you made your own bell ?. If you want to contact me my phone number is 01628 473140.andrew mcleish

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