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Ratchet wheel

Designing, work holding and fly cutting

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Matt Andrews11/09/2018 17:24:30
11 forum posts
2 photos
Hello everyone,

I am trying to build a small scale elevator lift using clockwork mechanisms

I need to hold and fly cut a ratchet and am trying to figure out what is the best approach.

I have found little information on ratchet wheel design and fly cutting.

I get about 4 hours a week in my shop in increments so iam seeking advise to the best approach.

My design needs a ratchet that will wind the mainspring.

Iam not an engineer except in my heart but thinking a 1 1/2" ratchet on the diameter and about 3/8" thick.

My universal dividing head does not have a chuck so it will need to be held between centers.

How would you hold this blank knowing that you would be fly cutting the ratchet teeth or shaping them using a slotter.

Also looking for responses with regards to ratchet tooth shape design and approach.

The ratchet will be apart of the mechanism that winds the mainspring which is .018" thick x .75" wide and 120" long.

Any advise welcomed.
Best
Matt
Martin Connelly11/09/2018 18:23:58
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693 forum posts
71 photos

This task is not too dissimilar to gear cutting. You should be able to find plenty of examples on the internet. You have not stated what equipment or machines you have to do this but a spin indexer may be a good option if you do not have a chuck on a rotary table.

Martin C

Bazyle11/09/2018 18:24:32
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4064 forum posts
166 photos

Have you looked at clock making sites and clock pictures that will show you the shape and aspects of making a flycutter to cut it with. Also Meccano do one about 3/4 in diameter, again shows you the shape. There are some videos on youtube too specifically but not the one by Stefan which is not the type you want.

Michael Gilligan11/09/2018 19:16:55
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11612 forum posts
509 photos
Posted by Matt Andrews on 11/09/2018 17:24:30:
 
[ ... ]
My universal dividing head does not have a chuck so it will need to be held between centers.
[ ... ]
How would you hold this blank knowing that you would be fly cutting the ratchet teeth or shaping them using a slotter.

.

As the old saying goes: "if I were you, I wouldn't start from here"

But, if you must ... I think you will need the shortest and stiffest arbor that will accommodate blank and cutter, and some way of locking it against rotational creep. [sounds like a chuck of some sort would be very useful]

MichaelG.

.

This is on a smaller scale than you are working, but may be of interest:

https://watchmaking.weebly.com/ratchet-wheels.html

.

Please forgive the digression, but ... I've just found this and felt I must share it:

http://wiki.dtonline.org/index.php/2100_Animated_Mechanical_Mechanisms

Edited By Michael Gilligan on 11/09/2018 19:38:09

Jon Lawes11/09/2018 19:23:22
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160 forum posts

This might be heresy to say but have you considered buying one? They are available for steam engine lubricators and such.

I completely understand if you want to make one for the enjoyment of the process, however if you are not too wedded to that idea you can purchase one for not much money.

Neil Wyatt11/09/2018 19:33:27
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Moderator
14110 forum posts
600 photos
69 articles

3/8" thick! 1/8" should be plenty?

You have to fit it to a spindle, make an over length mandrel that fits the bore of the dividing head with the same fitting on the end.

Easiest shape is to use an ordinary end mill set to cut just past the centre line of the blank, depth set so each tooth cut leaves a tiny witness before the next one.

Neil

dscn2140[1].jpg

Edited By Neil Wyatt on 11/09/2018 19:34:08

JasonB12/09/2018 07:18:29
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Moderator
13228 forum posts
1203 photos

Your universal dividing head should have come with a drive bar so you don't need a chuck. Mount the wheel on a decent length arbor and support the other end with a tail stock (can be bodged up if you don't have one) and then just drive the arbor with the dog from the drive bar. The long arbor will allow easy access for the flycutter without excess tool overhang or running into the head/tailstock.

not done it yet12/09/2018 08:24:02
2044 forum posts
11 photos

Not sure what your ‘elevator lift’ actually is, or any specific details. One way or two? (like up only, or up and down)

Driving with a worm and wheel might be an alternative, as they can easily be arranged as a non-reversing drive.

Maybe look up why Fordson Standards killed so many operators, to see how effective they can be?

roy entwistle12/09/2018 08:44:52
864 forum posts

With a bit of careful marking out, a ratchet can easily be made with a saw and a file

Roy

Mick B112/09/2018 09:39:04
672 forum posts
42 photos

When my missus wanted an extra ratchet reel on her loom, I went to the local agricultural supplier and bought a couple of these fence wire strainers:-

tensioner.jpg

They might need tidying and modding for what you want, but perhaps they'd work?

Russell Eberhardt12/09/2018 10:28:32
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2298 forum posts
79 photos

This is how I do it:

dscf2351.jpg

Flycutter insert is made from silver steel to match the desired profile. The slight undercut required on the tooth form is achieved by setting the flycutter tip just below centre height with the ratchet direction as shown in the photo.

Russell

Ian S C12/09/2018 14:53:22
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6962 forum posts
224 photos

If you are taking a slice off a bar to make the disc, perhaps cut the ratchet first. Centre the bar each end. part part way through the bar at the required thickness, then set up between centres on the mill. After the ratchet is complete, put the bar back in the lathe, bore the hole for the shaft and complete the parting off. More solid than using a mandrel.

Ian S C

Matt Andrews14/09/2018 00:56:13
11 forum posts
2 photos
Not sure why but i responded to several responses and none had posted. Thank you for the different replies and the various ways to skin this cat.
I would like to cut it all out of one bar and transfer from lathe to dividing head but what a waste.

That is a nice set up Russel and something I want to replicate. I may have to take my 4 jaw and make it fit the dividing head.

Will that fly cutter cut all teeth without sharpening?

Best
Matt

Edited By Matt Andrews on 14/09/2018 00:57:13

Ian S C14/09/2018 10:55:20
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6962 forum posts
224 photos

Matt, the life of the tool depends on the material used for the ratchet, brass it will last for ever(well quite a long time), steel a bit less, but I'v fly cut gears the same way as Russell, in steel. I make my cutters from old centre drills, or the shank of broken HSS taps. I use a bar with a 20 tpi thread in the Clarkson Chuck, keep the bar holding the cutter as short as practical for stiffness, my ones are 5/8" dia, although I made a new collet for the chuck

that will take 3/4"

Ian S C

Michael Gilligan14/09/2018 13:23:44
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11612 forum posts
509 photos
Posted by Matt Andrews on 14/09/2018 00:56:13:
I may have to take my 4 jaw and make it fit the dividing head.

.

A good plan, Matt ... even if it does look rather like moving the goalposts devil

MichaelG.

.

" My universal dividing head does not have a chuck so it will need to be held between centers. "

Ian S C15/09/2018 13:38:46
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6962 forum posts
224 photos

You might have to turn up a spindle nose to take your chuck with a Morse taper to fit the dividing head, make it with a thread in the end of the taper to take a draw bar. Or you can do as I said earlier and you can do it between centres, and there isn't a great big chuck getting in your way.

Ian S C

Matt Andrews15/09/2018 15:49:45
11 forum posts
2 photos
I have opted to make a mandrel and do the whole operation between centers as you suggest. I am turning the mandrel down to size today.

I would like to somehow incorporate a positive lock via a collar clamp and a pin through the ratchet wheel.

I will post pictures of set ups when i can figure out how to post them.

Best
Matt

Russell Eberhardt15/09/2018 16:35:15
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2298 forum posts
79 photos
Posted by Matt Andrews on 14/09/2018 00:56:13:

Will that fly cutter cut all teeth without sharpening?

Yes, no problem in brass. I made the fly cutter insert insert from silver steel, hardened and tempered to a medium straw colour. It has cut a few ratchet wheels without sharpening.

Russell

Matt Andrews15/09/2018 18:21:21
11 forum posts
2 photos
I was going to do the ratchet wheel out of cold rolled steel and make a brass or cast iron pawl I will be winding this mainspring to the max. What do you think?

Thanks
Matt
Matt Andrews16/09/2018 02:00:32
11 forum posts
2 photos
Russell is it possible to see more detail of your fly cutter?

I have made one but i dont trust it in this application.

If possible,
Thanks
Matt

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