How is bar length measured?

[ejb 2370]

It's probably pretty obvious,but here's why I wonder.
I have a Echo cs670 that came with a 20" bar.I recently bought a Jonsered 625 with an 18" bar.After trying to get a new chain I discovered that they both measure 18 1/2 inches from the front of the saw to the end of the bar.The echo chain has 70 links and the 625 has 68.
Did they give me an 18" bar on the echo?
Thanks

 

[TimberPig]

The "called length" is from the front of the saw to the tip of the bar, roughly, which is what is actually usable bar length. It sounds like it is indeed an 18" on the Echo, not a 20". The bar may have a code on it as well that tells you what the length is. I believe Echo bars are relabelled Oregon bars, but they are often labelled different than Oregon bars in the bar number coding. If you look near the tail of the bar, there is likely a number stamped there. If you post it, someone who is more up on Echo's than I am should be able to help you confirm this.

 

[computeruser]

They did give you a 20" on the Echo.

A quick glance at my trusty old Bailey's catalog suggests that the bar length/drive link counts that you came up with are correct for a 20" bar on an Echo and a 18" bar on the Jonsered you have.

As for the difference in claimed versus actual length, some saws have more of their bar hidden in the powerhead body than others.

 

[THALL10326]

It's probably pretty obvious,but here's why I wonder.
I have a Echo cs670 that came with a 20" bar.I recently bought a Jonsered 625 with an 18" bar.After trying to get a new chain I discovered that they both measure 18 1/2 inches from the front of the saw to the end of the bar.The echo chain has 70 links and the 625 has 68.
Did they give me an 18" bar on the echo?
Thanks

Looking at your link numbers there are both chains 3/8 chains or is one a 325? I don't know much about either of those saws but on Stihl's bars vary not only in length but also how wide they are. A 025 with a 18inch bar uses 68 links of .325. A 026 with a 18inch bar uses 74 links of .325 because the bar on the 026 is wider, takes more chain to go around it. So I'm wondering if those chains of yours are the same pitch.

 

[ejb 2370]

I'll have to check on the links,but I think they'e both 3/8.

 

[cuttinscott]

70 driver is correct for the 20" echo and 68 driver is correct for the 18" jonsereds

of yesteryear a 3/8" 20" was 69 to 70 driver depending on the make saw
3/8" 21" was 72 driver. Now cause of being PC the standards have changed
18" was 64 to 66 driver now it includes 68 driver which i'd like to class as the old style 20". It just makes everything all the more confusing look at it from a dealers standpoint... A customer comes in says he or she wants a 18" chain for a saw what do you give them? I have over 30 varieties of chain rolls in stock. sure would be nice to have it easier thats all

Scott