Formula for changing chain pitch?

[dewaynep]

Is there a formula that can be used for changing chain pitch? In other words, if I have a bar that I'm running .404 pitch chain at 60 links (hypothetically) and I want to switch to 3/8 pitch chain how can I figure how many links of 3/8 I need? I thought the following should work: .404*2*number of drive links(60)=48.48 that number then divided by the new pitch*2 (.750)=64.64 links (i would round up to 65). However, when I look at bars that list 2 chain pitch sizes my formula doesn't work.
For instance, a GB bar lists the following:

Gauge: .063

Length: 21 "

Pitch: 3/8 or .404

For .404" pitch it takes 68 DL

For 3/8" pitch it takes 75 DL

Using the formula above (which is obviously wrong) .808*68=54.944/.750=73.25 or rounded up to 74, not 75. How did they get to 75?

Anyone have a better formula or better knowledge?
Thanks.

Dewayne

[MCS]

You have it correct. Since the two pitch chains are not equal multiples, there will be a slight variation. That is what the chain adjuster is for ;D

[Supercharged86]

Guys, would this only work with a solid (non sprocket nose), since the sprocket teeth for say the 3/8 wouldn't mesh right with the .404, right??? Or do I got it wrong??? Thanks. Steve

[tommyhnavix]

This chart may help in chain conversion. Count drivers and look on chart for length. Find closest length in pitch you want to change to and see new link count.
Should be very close start.
Have in a larger PDF if this is to small .
Let me know and I can e-mail the PDF

[Brian VT]

Feb 12, 2012 10:56:20 GMT -5 Supercharged86 said:

Guys, would this only work with a solid (non sprocket nose), since the sprocket teeth for say the 3/8 wouldn't mesh right with the .404, right??? Or do I got it wrong??? Thanks. Steve

Correct. A bar nose sprocket needs to match the chain's pitch.