How to figure chainsaw sprocket pitch?

[Philbert]

3/8 chain is .375 chain, not .365

Actually, is it .365. Just measured two 3/8 chains and got 0.730 across three rivets. One chain was a used Stihl chain from m MS361

Yeah, '3/8' is a nominal measurement, like '2X4', or 'foot-long' hotdog

Yes, but I don't have .354, 7/16, 1/2, 9/16, and 3/4 pitch chain.

3/4 pitch is easy to buy as harvester chain form many places. I bought some foot-long lengths to use as a teaching aid: they are 2X the pitch, and approximately 2X the gauge (0.122) of some of the 'standard' 3/8 pitch chains we use.

Philbert

 

[dsell]

Franny K, do you know the specs for 7/16, 1/2, 9/16, and 3/4 pitch chains to use your method?

 

[buzz sawyer]

Yes, but I don't have .354, 7/16, 1/2, 9/16, and 3/4 pitch chain.

How about this - For those of us who have these pitches on our vintage saws, lets take and share measurements of the clutch sprockets? I know I have 1/2, 9/16, maybe 7/16, .404, 325, 1/4". Or if anyone can contribute section of chains, do that.

 

[dsell]

Franny K said:
100 feet * 12 inches per foot / 1640 drive links per roll =0.732 inches between drive links. rounded off .7317......
For the 8 tooth spur, I did the math for 7 by accident first so will do for 8
5.856" circumference at rivet center, yes
1.864" diameter at rivet centers which should be measurable. Yes, that measures good, they rock a bit.
(1.864-1.667)/2=0.093" for offset notch at tie strap center to rivet center. That looks correct as best I can see with a caliper.

I used the same method for 3/4 pitch:
50 foot spool of 3/4 pitch has 383 drive links per Bailey's site.
50 * 12 / 383 = 1.5666 between drive links.
1.5666 * 8 = 12.5328 circumference @ rivet centers
12.5328 / pi = 3.989 diameter of rivet center circle.
Not sure what the distance would be from the sprocket tooth to the center of the rivet.
The diameter is nearly double mine, so 3/4 pitch is ruled out for this sprocket. Looks like 9 tooth is most common for 3/4 pitch.

 

[dsell]

I found some data in an old Windsor book. I'm guessing that the 50 ft reel is showing the number of drive links. It makes sense for 3/8 anyway. So, looks like 1/2 pitch 50ft is 596 drive links and 7/16 is 688.

It also shows the following for 100 drive link chain footage:
3/8 6.10 feet = .732 distance between drive links
7/16 7.28 feet = .8736
1/2 8.40 feet = 1.008

1/2 596 DL is 50ft = 1.0067 distance between drive links.
7/16 688 DL is 50ft = .872

 

[Philbert]

You guys are making my head hurt!

Philbert

 

[dsell]

I used the same method for 1/2 pitch:
50 foot spool of 1/2 pitch has 596 drive links.
50 * 12 / 596 = 1.0067 between drive links.
1.0067 * 8 = 8.0536 circumference @ rivet centers
8.0536 / pi = 2.5635 diameter of rivet center circle.
Not sure what the distance would be from the sprocket tooth to the center of the rivet.
I think we have a winner formula base on Franny K.

 

[dsell]

Per CAD, I haven't verified the distance shown between teeth.

 

[Rags]

You mentioned that the sprocket you have might be for a gear drive saw or a harvester. My Homelite Super 1130G with 1/2" chain has a sprocket that looks just like that, if I remember correctly the hole in the center is 1/2" & the two key ways are for 1/4" keys. I would like to one day find a .404 pitch sprocket for it at a reasonable price.

 

[dsell]

You mentioned that the sprocket you have might be for a gear drive saw or a harvester. My Homelite Super 1130G with 1/2" chain has a sprocket that looks just like that, if I remember correctly the hole in the center is 1/2" & the two key ways are for 1/4" keys. I would like to one day find a .404 pitch sprocket for it at a reasonable price.

.623 Keyed Shaft 8 Tooth .505 thick, 2.325 diameter.
Might be a Homelite 55593-3 sprocket for Super Wiz 55 66 80, 1130G , Wiz 55, XP1000, XP1100 but it's the same pitch as this other.

 

[dsell]

Per CAD, I haven't verified the distance shown between teeth.

View attachment 864592

.886 is right on, the .5782 actually measures closer to .6250

 

[dsell]

Found a few more rim variations.

 

[Philbert]

Found a few more rim variations.

View attachment 865338View attachment 865339View attachment 865340View attachment 865341View attachment 865342View attachment 865343

Nice to have an indoor COVID hobby . . .

Philbert

 

[dsell]

Nice to have an indoor COVID hobby . . .

Philbert

Takes much less room than saws!

 

[heimannm]

 

[dsell]

View attachment 865446

View attachment 865447

What are the large pin rims for?

 

[Woodslasher]

What are the large pin rims for?

really, REALLY, REALLY hot saws!

 

[heimannm]

For show mostly, but some serious guys use them for racing saws.

Mark

 

[Bwildered]

What are the large pin rims for?

Harvestor or processor bars

 

[Franny K]

I have Makita and Husqvarna battery chainsaw sprockets.

And the chip clearing aspect of some 1/4 rim sprockets.