What size file do you use for a 3/8 chainsaw chain?

What size file do you use for a 3/8 chainsaw chain?

A 3/8-inch standard chainsaw chain uses a 7/32-inch (5.5 mm) round file, which is the most common large-chain file size. Some manufacturers specify a 13/64-inch (5.2 mm) file for the same pitch, so the number on your chain's box or chart always wins over a general rule.

The catch with 3/8-inch chains is that there are two of them. Standard 3/8-inch chain runs on larger saws and takes the 7/32-inch file, while 3/8-inch low-profile chain, often branded Picco, is a smaller chain fitted to many homeowner saws and takes a 5/32-inch (4.0 mm) file. Using the big file on a low-profile chain, or the reverse, cuts the wrong hook into the tooth and ruins the edge.

The full pitch-to-file pairings are set out below for reference.

• 3/8 inch standard: 7/32 in (5.5 mm), or 13/64 in (5.2 mm) on some chains.
• 3/8 inch low-profile (Picco): 5/32 in (4.0 mm).
• .325 inch: 3/16 in (4.8 mm).
• 1/4 inch: 5/32 in (4.0 mm).
• .404 inch: 7/32 in (5.5 mm).

How do you tell standard 3/8 from 3/8 low-profile?

Standard 3/8-inch and 3/8-inch low-profile chains share a rivet spacing but differ in size, and you tell them apart by the saw they came on and the shape of the cutters and drive links. Standard 3/8 runs on larger, more powerful saws with taller, chunkier cutters; low-profile, often branded Picco, fits many homeowner and battery saws with smaller, flatter cutters.

The surest check is the number printed on the chain's box or loop, since makers mark the exact chain there. If the box is gone, the clues are the saw class and the cutter height: a compact homeowner saw almost always wears low-profile 3/8, while a mid or large gas saw usually wears standard 3/8. Our chainsaw chains guide shows how to read the markings stamped on the drive links.

What happens if you use the wrong file on a 3/8 chain?

Using the wrong file size on a 3/8-inch chain cuts the wrong hook into the tooth and ruins the edge. A 5/32-inch file on standard 3/8 sits too low and over-hooks the cutter, making it grab; a 7/32-inch file on low-profile 3/8 rides too high and leaves a blunt, back-slanted edge that will not slice.

Either error costs you cutting speed and chain life, because the next few sharpenings have to file the tooth back to the right shape. The one-fifth-above-the-top-plate rule is why diameter matters so much: only the correct file rests at the height that shapes a clean edge. When in doubt, follow the file size on the chain maker's chart rather than a general rule.

Does the 13/64-inch file really matter versus 7/32?

The 13/64-inch (5.2 mm) file is a genuine in-between size some makers specify for their 3/8-inch standard chains, and it sits fractionally lower than a 7/32-inch (5.5 mm) file. On a chain designed for it, the smaller file cuts the intended hook; the larger file rides a touch high and files a slightly flatter edge.

For most owners the difference is small, and a 7/32-inch file dresses a standard 3/8 chain acceptably, but if your chain's chart calls for 13/64 inch, using it gives the cleanest, longest-lasting edge. Keep whichever size the chart lists in your kit, and pick the matching file from our best chainsaw file picks.

How do you find the right file size without the chain box?

If the chain box is gone, find the pitch by measuring across the rivets: pick any three consecutive rivets, measure from the first to the third, and halve that distance to get the pitch. That pitch, not the saw's size, tells you the file diameter from the standard pairing chart.

For example, three-quarters of an inch across three rivets halves to a 3/8-inch pitch, pointing you to a 7/32-inch file for standard 3/8 or a 5/32-inch file for low-profile. Confirm which 3/8 you have from the cutter height and saw class above, then verify against the maker's chart before buying. The full method for reading pitch and gauge is in our chainsaw chains guide.

Confirm which 3/8 you have by reading the pitch stamped on the drive links, as explained in our chainsaw chains guide, then pick the matching file from our best chainsaw file picks. These are typical published file sizes, so verify against your chain maker's chart before buying.