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[4]

Source for (oddball?) flat sprockets?

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gr8legs

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#1
A couple of years ago I am pretty sure I found some flat chain sprocket blanks without a drilled center hole, just a located center drill point so I could bore out to the shaft size I wanted.

The sprockets I find now all are already center bored for the smallest shaft size the manufacturer thinks is appropriate - in my case I'm looking for a 40-series roller chain sprocket with 15 teeth. They come pre-bored for 1/2" and that's way bigger than I want.

Bushing down is not a great option because my plan is to bore to accommodate threading the center of the sprocket and then securing it to the shaft with a jam nut on each side. Can't really do that if I want a 5/16" shaft and the hole is already 1/2".

Has anyone seen a source for un-bored sprockets or am I imagining that I found them a couple of years ago?

Thanks in advance

Stu
 
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Ulma Doctor

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#2
Hi Stu,
unfortunately i only see 1/2" bores from my suppliers :(
i suppose you could get a standard 15t #40 sprocket and press fit a slug of cast iron or a steel of choice to a 3/4" or 1" bore #40 sprocket.
bore and face it to length.
you could then indicate, then bore the center to dimension and thread the center accordingly.
it's the next best thing to a fixed bore of the right size.
maybe others may have another suggestion!
all the best :)
 
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DaveInMi

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#3
#40 chain is capable of a lot more torque than a 5/16 shaft can tolerate. What is the application? Maybe there is an other solution that would present less problems. Would machining a hub to fit 5/16 to 1/2 with screws through the flange work?
 

Tozguy

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#4
Sorry don't know a source for such sprockets. I don't know much about your projected application. No offence intended but sometimes when I couldn't find the parts to make something my way its because there is a better way to go about it. How wide is the chain? Do you do any welding?
 

4gsr

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#5
Here's a shaft hub that would probably work. They don't offer one in 5/16" but do have it in metric 8 mm bore but it is out of stock.

https://shop.sdp-si.com/catalog/?brand=sdp&cid=p372

Here's the inch selections that they supply,too. Again, no 5/16 bore

https://shop.sdp-si.com/catalog/?brand=sdp&cid=p932

Edit:

Here's another one that will fit the bill perfectly. You not going to like the price on it!!!

http://www.fennerdrives.com/trantorque/_/Trantorque-Mini-5/16/?s=ZnwyNzI0

I'm sure if you look around and check with a local bearing distributor, you could get it at a much lessor price.
 
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gr8legs

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#6
Thanks all for the pointers - apparently I was dreaming when I thought I got un-drilled sprockets two years ago. Or maybe they were bored to 1/2" and I cobbled together what I have now which is rather ugly but functional in a hillbilly way.

The application is a cuckoo clock that the hands are driven by a pair of stepper motors through a 300:1 worm-drive and then a 2:1 chain sprocket drive to the hand shafts.

This current incarnation is a 'get-by' proof of concept. I figure I will use cogged belts in the finished design (quieter) but those pulleys are four times the price of simple chain sprockets and I need to get the design parameters tied down and tested before going that route.

I am getting in to 3D printing very soon and the actual cog belt parts will (I hope) be 3D printed after I crawl up the learning curve.

Stu
 

tq60

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#8
Make one...

Just get a 1/2 bolt and center drill it with your lathe for the shaft size.

Then drill from side on a flat for a set screw to lock to shaft.

Face of extra material from both head of bolt and nut body of bolt to make a bushing with locking set screw.

If you want to thread to shaft then thread the above assembly.

Sent from my SAMSUNG-SGH-I337Z using Tapatalk
 

silence dogood

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#9
Go down to your local bicycle shop and ask them for a old used sprocket the size that you want. They will most likely will give it to you free. Use that as a pattern on I seem to remember 3/16" flat stock. Add chain (careful, there are 2 different widths). Almost went that way, turned out that I could bore out the sprocket to fit the hub that I turned (in this case 1")
 

Silverbullet

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#10
With a rotary table you could mill out the sprocket itself. Even can be done by layout like us old guys use to do. With a couple dowel pins an easy set up to drill the holes to mill the points after .
 

Ebel440

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#12
I remember finding a lot of information about making sprockets and timing belt pulleys on bicycle websites many years ago. But don't know what size chain that is. Maybe 20?
 

chips&more

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#14
Am I missing something? A bushing will not work? 5/16” will fit into 1/2”? If not, then just make the 1/2” hole bigger. And then Loctite an appropriate bushing. If you are only turning clock hands for a cuckoo clock. Then low torque needs and mischievous accuracy is all you need…Dave
 
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