Oregon 21BPX ControlCut Saw Chain for 18 in. Bar - 72 Drive Links - fits Husqvarna, Jonsered, Makita, Poulan and others

Chain Pitch is the size of the chain, and is defined as the distance between any three consecutive rivets divided by two. Oregon chain is made in several pitches - 1/4" is the smallest, 3/8" is the most popular, 3/4” is the largest. Pitch is important because the drive sprocket must be the same pitch as the chain, and if applicable, the bar nose sprocket. The easiest way to determine the pitch of your chain is to look at the number stamped on the drive link..

Chain Gauge is the Drive Link's thickness where it fits into the bar groove. The gauge of the chain and the gauge of the bar must match. Oregon has several gauges for chainsaws - such as, .043", .050", .058" and .063". Normal wear can make it difficult to accurately measure chain gauge on a worn chain. Always order by the number stamped on the drive link of your old chain to assure correct gauge.

The length of your chain is determined by counting the number of drive links in your chain. Your drive link count has a direct correlation to your bar’s length. Be careful; a bar made by Oregon may take a different drive link count than that of another producer. Here’s a tip: count the number of drive links in the chain you have now, and write that number down someplace where you can find it. Or, if you have an Oregon chain in an Oregon box, the drive link count is stamped on the flap; you can save that flap for future reference.

Certain provisions of the safety standard known as ANSI (American National Standards Institute) B175.1 - Gasoline powered Chainsaws - Safety Requirements contain requirements designed to reduce the risk of injury from chainsaws sold in the United States. The following information should be used as a guide for the selection of appropriate replacement chains in order to maintain compliance with the ANSI B175.1 standard (United States only).
The ANSI standard B175.1 divides all chainsaw power heads into two groups:
- Under 3.8 cubic-inch (62cc) engine displacement, the chainsaw MUST meet the low kickback provisions of the standard.
- 3.8 cubic inch (62cc) and larger, the chainsaw MAY OR MAY NOT meet low kickback provisions of the standard.

Any chainsaw that does not qualify as a low kickback cutting system will bear a warning such as: “WARNING – This chainsaw is capable of severe kickback that could result in serious injury to the user. Do not operate this chainsaw unless you have extraordinary cutting needs and experience and specialized training for dealing with kickback. Chainsaws with significantly reduced kickback potential are available.Be sure to read the labels on a chainsaw before purchasing one.
When replacing chain on saws less than 3.8 cubic inches (62cc), any low-kickback chain of the proper pitch and gauge can be used. Oregon identifies and labels all low-kickback chain with green labels and all NON low kickback chain with yellow labels. Oregon safety features greatly reduce the hazard of kickback while maintaining high cutting performance. However, ALL CHAINS CAN KICKBACK, which may result in severe personal injury to the saw operator or bystander. Replacement guide bars and the ANSI standard.
The ANSI standard states:
Because of differences in replacement guide bars, the following guidelines shall be considered to determine kickback energy: Sprocket nose guide bars with the same effective length, the same number of sprocket nose teeth, and the same pitch may be considered to have equivalent kickback energy; A hard-nose guide bar having the same effective bar length, and the same or smaller nose radius as a sprocket-nose bar, may be considered to have equivalent or less kickback energy than the sprocket nose-bar; Kickback energy of all guide bar types may be considered to be less for smaller nose radius sizes.