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Lathe gears

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James Hannabuss16/12/2012 23:12:13
9 forum posts

Hey there I'm in need of some help I'm new to this site so I'm sorry if I put this in the wrong place. I've recently acquired a Clarke cl500m lathe and it's was in bits I've payed penny's for it as the previous owner had stripped it down almost completely, but when I fetched it he had lost all the screw cutting gears and gear from the spindle to the milling head. I was wondering if anybody on here has got one of these lathes could you please tell me sizes (outside diameters and number of teeth) of the gears so I can make a set. Also the gear that drives the milling head of the spindle is it the same size as the one on the bottom of the milling head?

Stub Mandrel17/12/2012 21:10:54
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4311 forum posts
291 photos
1 articles

Hi James,

I have found Clarke's spares service very helpful when I wanted to buy parts for my CL300M.

**LINK**

Neil

James Hannabuss17/12/2012 22:48:51
9 forum posts

Hey thanks for the response I've emailed them before for parts and for just the basic parts to get it running it was going to cost me well over 350 quid. (money I've just not got lol). So I've put my knowledge and skills into it and made some custom parts to get the machine running and it does quite nicely. . But I just need the screw cutting gears as i need to put power feed back onto it also I want to make my own set as a gear is something ive never made before and I want to learn how to do it and this would be perfect for it.

Siddley17/12/2012 23:02:38
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150 forum posts
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If you only want power feed I'd be tempted to take a different approach and power the leadscrew electrically.

James Hannabuss17/12/2012 23:16:47
9 forum posts

That was my first idea but I've been thinking about it a lot and I will need screw cutting on the machine.

Siddley17/12/2012 23:35:30
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150 forum posts
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They aren't the easiest machine to screwcut on - the lowest speed is a bit fast and there is no thread dial indicator so really you have to keep the halfnut engaged and reverse the motor after each pass.
I had a CL500 years ago and hated it to be honest, but if you bought it cheap then what the hell ? go for it and the best of luck to you.

Isn't there a sticker on it somewhere that gives you the tooth numbers of the change gears ? I'm pretty sure there was on mine. It's got to be in the manual or the parts list. That will get you halfway there.

John Stevenson17/12/2012 23:35:55
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5068 forum posts
3 photos

James,

Look here.

http://www.machinemart.co.uk/documents/060712520-CL430-500M.pdf

Page 21

John S

James Hannabuss18/12/2012 00:05:43
9 forum posts

I work on a Colchester master at work and that's what we do there just put the machine in reverse. I know what your saying about the speed doesn't really want to slow down to much for it and that's why I was thinking about a variable speed controlled motor so I can have lower to higher speeds, was just a thought gotta look into it. John Stevenson thank you Id only got the parts list one I'd never got the instruction one and completely forgot about it.

Right ok I'm going to sound like a right donut now as I know next to nothing on making gears (that's why I want to learn haha) is there a set rule for figuring out outside diameters of the gears?

John Stevenson18/12/2012 00:10:25
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5068 forum posts
3 photos

James,

You got any gears at all ?

Reason I ask is they all have to match in pitch.

James Hannabuss18/12/2012 07:13:08
9 forum posts

I have one that they forgot to take off the machine.

John Stevenson18/12/2012 08:30:09
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Moderator
5068 forum posts
3 photos

Count the number of teeth and measure the OD, everything can be worked out from this.

However after looking at a picture of one of these machines i reckon I have one here but Warco model and if the figures match i can take measure this one up.

Out all day so don't expect anything until tonight.

Terryd18/12/2012 09:19:57
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1935 forum posts
179 photos

Hi James,

The size of a gear is determined by the 'Diametral pitch' (used for imperial gears) or 'Module' (metric gears). The diametral pitch is the number of teeth per inch of its diameterm Module is DP / 25.4.

Of course it's not quite that simple (it never is) as the pitch diameter of a gear is not the same as it's overall diameter. Instead of 2 gears, imagine two wheels in their place running rim to rim, their diameters are the pitch diameters. To make gears you add projections to the rims of the wheels - the 'addendum', but in order to allow them to mesh you have to make cutouts to clear the new teeth - this is called the 'dedendum', but the pitch diameter is still the same. See, clear as mud.

The link below gives a simple introduction and may clarify my poor description above

for a simple introduction to gears and modules - which determines the number of teeth on a particular gear size see here. However they use the term 'circumference' which is the same as 'pitch diameter'.

For some more complex references see here.

Ivan Law's book 'Gears and Gear Cutting' is a good basic introduction - available from Amazon or MHS.

Regards

Terry

jason udall18/12/2012 09:43:59
2026 forum posts
41 photos
Posted by Terryd on 18/12/2012 09:19:57:

Hi James,

The size of a gear is determined by the 'Diametral pitch' (used for imperial gears) or 'Module' (metric gears). The diametral pitch is the number of teeth per inch of its diameterm Module is DP / 25.4.

Of course it's not quite that simple (it never is) as the pitch diameter of a gear is not the same as it's overall diameter. Instead of 2 gears, imagine two wheels in their place running rim to rim, their diameters are the pitch diameters. To make gears you add projections to the rims of the wheels - the 'addendum', but in order to allow them to mesh you have to make cutouts to clear the new teeth - this is called the 'dedendum', but the pitch diameter is still the same. See, clear as mud.

--------

Terry

Actually that is one of the clearest summaries ( and I have seen a few ) I have seen..

Now why cyclodial and envolute ?

Les Jones 118/12/2012 10:15:34
2161 forum posts
149 photos

Hi James,
If you are interested in experimenting there is an electronic approach to replace the lead screw gearing. I have considered the idea but decided that I did not trust the servo system to keep an accurate enough phase relationship between the spindle and the lead screw. If you are interested have a look at This forum.

Les

Russell Eberhardt18/12/2012 10:29:40
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2600 forum posts
85 photos
Posted by jason udall on 18/12/2012 09:43:59:

Now why cyclodial and envolute ?

Cycloidal gears give very low friction so are used in such things as clocks where the lkarge wheels drive the small pinions. However if the spacing of the centres is not exact (for example as a result of wear) they are no longer constant velocity and become noisy.

Involute gears are more robust, the spacing is less critical, and they are better for power transmission.

Russell.

Terryd18/12/2012 10:35:17
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1935 forum posts
179 photos

Hi Jason,

Thanks for the kind comment. sorry about the length of this posting but you did ask wink 2.

Cycloidal and involute are two types of geometric curve. A gear tooth in profile can have part of one or other of these shapes. Gears in mesh should have the same profile to prevent wear..

Imagine a bicycle wheel, the tyre valve at the bottom. When you roll the wheel along until the valve is at the bottom again. The curve that the valve makes is a 'cycloid'. If you roll the wheel around a circle it is an epicycloid, roll it inside a circle and it is a hypocycloid. clock gears are usually epi- and hypocycloids using a bit of the curve as the profile:

Cycloid

cycloid.jpg

Epicycloid

epicycloid.jpg

Hypocycloid

hypocycloid.jpg

Cycloidal gears - note the use of a bit of a cycloidal curve for the profile

cycloidal gears.jpg

To make an involute tie a pencil to the end of a thread on a fixed cotton reel then draw a line keeping the thread taut and as it unwinds you will draw an involute. Involute gears are the usual profile for power gears.

Involute

involute.jpg

Involute gears using a bit of the curve for the profile of the tooth

involute gear teeth.jpg

 

These gear profiles are used because the surfaces roll together rather than slide over each other so wear is minimized.

Hope that helps a bit.

Best regards and seasons greetings,

Terry

Edited By Terryd on 18/12/2012 10:48:32

Ady118/12/2012 11:03:27
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3852 forum posts
522 photos

All my gears are mixed DP and I've never had a problem, mainly myford and drummond gears

If you plan on running a 24/7 production line then it's an issue but if you're just a lathe dood who does stuff now and then then you've got at least a decade or two to sort out a perfect matching dp gearset

Until then I reckon you should be able to muddle along on a mixed set

 

Some gears and gearsets are getting harder to find on ebay

If you spot a weird one it can be worth grabbing it to use on an indexing unit

 

edit: T6 aluminium seems to be pretty strong if you want to make a lot in a hurry

I fixed my backgear with a chunk of T6 a while back and it's been fine

Edited By Ady1 on 18/12/2012 11:06:07

Versaboss18/12/2012 11:07:43
458 forum posts
51 photos

Yes, a good introduction inTerry's (first) link above. However, what irritates me a bit is the first sentence, stating that the module...indicates how big or small a gear is. In my - admittedly quite limited - understanding 'big or small' is referencing the diameter of a gear, or maybe the thickness or weigght (not relevant in this case)

My lathe has Module 1 change wheels, but the biggest has 127 teeth and the smallest 20, and certainly they have not the same size. But nonetheless their module is still ONE for all of them.

But I see how they derived that misleading definition (see 'reference diameter), but I would call the module a measure which indicates 'how big or small the gear teeth are'

Greetings, Hansrudolf

Ady118/12/2012 11:14:34
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3852 forum posts
522 photos

I found this book easy to follow when I first looked at gear cutting

jason udall18/12/2012 11:25:04
2026 forum posts
41 photos

Thanks Terry.. It was ment as an humorous comment... oh well missed again...

the generation of the curves I remember from TD. ( TOO many years ago) but no one has ever explained why cyclodial forms for clocks ( well the escapement to hands trains) but envolute for power transmistion.. I seem to remember (SOME) clocks use ep for drive to escapment and cy to hands ......now two sets of cutters?..... must have a good reason... and what form used in "clockwork" computers/ difference engins ...my guess CY.....

Regards Jason

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