View Full Version : sprocket tooth

charlie coghill
05-03-2004, 09:23 PM
Hi all;
I need some help. I need to order a idler sprocket for 40 pitch chain. In the MSC catalog they offer a 18 tooth and a 17 tooth sprocket. All other demitions are the same. Same diameter, same thickness.I must be missing something. Which sprocket should I order?
Unless the teeth are jamed closer togeather the 18 tooth sprocket should be larger and if the teeth are jamed closer togeather than the 18 tooth is wrong for a 40 pitch chain.
Thanks for any help you can give.

05-03-2004, 09:28 PM
What are the dimensions they give for each sprocket?

charlie coghill
05-03-2004, 09:53 PM
18 tooth width 0.72 bore 5/8 OD 3.14"
17 tooth width 0.72 bore 5/8 OD 3.14"

The sprockets are on page 3712 of the 2003 catalog, uper left hand corner of the page. The sprocket is mounted on a ball bearing.

Mike Burdick
05-03-2004, 10:34 PM
Must be a typo!

Their site list them as:

18 tooth width 0.72 bore 5/8 or 1/2" OD 3.14"
17 tooth width 0.43 bore 5/8 OD 2.98"

for a 40 pitch.

[This message has been edited by Mike Burdick (edited 05-03-2004).]

05-03-2004, 10:42 PM
Order by the number of teeth and bore you need. These are like gears so depending on the ratio you want, the number of teeth make the difference.

You can also buy the sprocket and hub separately. Get the hub in the bore size you need and the sprocket in the tooth count you need. You'll need a welder to join the two.

Ops! Just noticed you wanted an idler sprocket. Sorry. Tooth count won't matter. Get the bore size you need.

[This message has been edited by CCWKen (edited 05-03-2004).]

05-03-2004, 11:44 PM
Just a tip,at work I order a type"A"plate sprocket(sproket with no hub projecting out)then bore out and press in a 2nr ball bearing(bearing with two snapring grooves on the od)and snap them in.Sproket and bearing cost half of the idler cost and I can get whatever tooth count I want.

05-04-2004, 04:22 AM
That's a novel solution. How do you hold the sprocket while boring out the ID? Can you depend on the sprocket OD and PD being concentric, or does it matter that much?


charlie coghill
05-04-2004, 07:16 PM
Thanks for the replys. I called MSC this morning. The lady as predictable, did not know. She called the manufactor and we had a three way conversation. There was a typo in the catalog. The 17 tooth should have been 2.98 OD.
Wierd, that is a novel way of making an idler, I will remember that one, Thanks.

05-04-2004, 09:42 PM
Roger,I cheat and try to go with an even multiple of three 6,9,12,15,18,21 .etc so I can grip the spocket with the chuck jaws resting in between the teeth,this actually improves the runout on smaller number chain (25-40 pitch)since a lot of them are punched rather than milled.

On the other tooth counts I end up using the four jaw and the tip of a toolbit to indicate the tooth tips in.

If you have a bearing you want to use thats thicker than the sprocket plate all I do is weld on a couple of washers either one on each side or both on the same side in case I need the offset and tack them in place with tig,not much of a tack just three small ones equaly spaced are suficiant.

Also many times I find it unnessicary to even use a sproket,since you always put the idler on the slack side of the chain anyway there is no reason to even use a sprocket just a turned roller with a ridge in the middle so it rides on the chain rollers and not the side plates and a bearing in the middle.

05-04-2004, 09:47 PM
I wish I had a chance to take a picture of an idler I made for a customer last week,but they came in and got it while I was at lunch.

It was a #140 16 tooth double chain idler,I bored in two sets of 2.25"id Timkem roller bearings,oil seals the works,a fun job for once.

05-05-2004, 03:01 PM
Hey Charlie, check out the Machinery Handbook, you can make your own.

charlie coghill
05-05-2004, 09:08 PM
I haven't looked at MH but I will. Thanks.