Thanks Rich - now where did I put that 247 tooth gear wheel to index it with? > Hi there Terry, > > I'd suggest the following (hoping my maths is correct):- > > Guess the number of holes - a good estimate would be to say that the > circumference of your 500mm sprocket is about pi*500mm, which is 1571mm, > and your pitch is 1/4"=6.35mm, which goes into the circumference about 247 > times. > > Divide 360 degrees with that number - leaving 1.4575 degrees. > > Now draw out a right angled triangle in front of you, with one angle very > small. > > Assume that this small angle is half of the 1.4575 degrees (0.7287 > degrees), and that the side opposite this angle is half of your pitch > (1/8"=3.175mm). > > The hypotenuse of the triangle should not be the RADIUS that you should > form the holes on for your sprocket for 495 teeth:- > > hole radius= 3.175mm/ sin 0.7287degrees = 249.633mm > > giving a diameter for your holes to lie on of 499.267mm. > > This doesn't allow for any clearance between the chain rollers and the > sprocket though. > > Hope this is of some use. > > > Yours, > > > Rich. > PS 247 HOLES!!! OUCH! > > On Mon, 30 Aug 2004, Terry Lane wrote: > > > I'm sure the info is somewhere but - have any of you got a quick way of > > calculating sprocket cutting. I got a job here that calls for a sprocket > > aprox 500mm diameter to drive 1/4" pitch chain. Now OK - the teeth gotta be > > one pitch apart, & the holes gotta be pin dia.+?, but how do I arrive at a > > pitch circle for the ring of holes? > > > > > > MODEL ENGINEERING DISCUSSION LIST. > > > > To UNSUBSCRIBE from this list, send a blank email to, > > modeleng-request@xxxxxxxxxxxxx with the word "unsubscribe" in the subject line. > > > > > > MODEL ENGINEERING DISCUSSION LIST. > > To UNSUBSCRIBE from this list, send a blank email to, > modeleng-request@xxxxxxxxxxxxx with the word "unsubscribe" in the subject line. > MODEL ENGINEERING DISCUSSION LIST. To UNSUBSCRIBE from this list, send a blank email to, modeleng-request@xxxxxxxxxxxxx with the word "unsubscribe" in the subject line.