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Chainsaws

Which File Size for Chainsaw Chain?

Chainsaw chains dull in use, and must be sharpened every now and then. One of the best ways of doing this, particularly in the field, is by filing the chain with a round file.

But which size of a round file should you be using for your chain? There are at least five standard file diameters between 1/8” and 7/32” available, and finding out which to use for your saw is not obvious.

In this article, I am going to tell you how to quickly decide the correct file diameter for your chainsaw chains. The short answer is that the file diameter is determined from the chain pitch, which you can in turn determine from the chain markings, the saw model or through direct measurement.

Below, I will first give you the general lookup table from chain pitch to file diameter. Then, we will look at the different ways to find out the chain pitch. Finally, I will also present tables that allow you to fin out the right file size for your Husqvarna or Stihl saw based on the model alone.

File size vs. Chain pitch

The table below shows the recommended file size for each of the common chainsaw chain pitches. I have compiled the table based on recommendations of the major chainsaw and chain manufacturers.

Chain pitchFile diameter[mm]
1/4P4/32”3.2 mm
1/4”5/32”4.0 mm
3/8P5/32”4.0 mm
.325”6/32”4.8 mm
3/8”7/32” (13/64”)*5.5 (5.2)* mm
.404”7/32”5.5 mm
P =
Picco/
Low pro
*(Stihl recommended)

If you know the pitch, you can use this table pretty much regardless of the saw and chain brands; even if the manufacturer recommendations vary a little, you will not be off by much.

Some notes on the application of this table:

  • Round files go only with round grind teeth. Most chains have a round grind: if the round file shape roughly fits the tooth shape, you’re probably good. However, if you notice straight sections and multiple angles in the cutting edge, check the specific filing instructions for that chain model.
  • Tell regular and Low Profile chains apart. The 3/8” and 1/4” pitch chains come also in Low Profile (Picco) versions, which have lower cutters and take a smaller file. See instructions below.
  • Manufacturer recommendations vary a bit. Sometimes intermediate sizes 11/64” and 13/64” are recommended instead of the 32th-inch sizes.

Why does file size matter?

The chain file profile determines the top plate blade angle.

But you may also wonder why does it even matter what size of file you use? After all, they all grind, and you can just go around the cutting edges, much like you’d do when sharpening a knife.

The truth is that file size matters in chain sharpening because the round file profile is partly responsible for giving cutters the right sharpening angles. In chain sharpening, you are supposed keep the file in the same spot, and sharpen the entire cutting edge in a single action.

To be more precise, the file profile determines the blade angle of the cutter top plate. If you use too small a file, the top plate will be sharpened to a very small blade angle, which will make the cutting edge weak. If you use too large files, the top plate cutting edge will be too blunt and will not cut optimally.

How do I know the chain pitch?

You can find out the pitch of your chain by either:

  1. Checking the size marking on the chain, or
  2. Measuring the pitch directly

1 From chain marking

Pitch markings, from top to bottom, on Stihl, Carlton and Oregon chains.

The chain size markings vary from manufacturer to other:

  • Stihl: To check the size marking on a Stihl chain, look at front part of the cutter links (“tooth” links) in the chain. There, you should find a single digit stamped onto the metal.
  • Carlton: On a Carlton chain, you find a short number-letter code on the drive link – this will be on the “shark fin” shape part. The letter tells you the pitch.
  • Oregon: As with Carlton, look for a code on the drive link “fin”. There is a two-number code that tells you the pitch – see table below.

The table below shows what pitch each code on a Stihl, Carlton or Oregon chain corresponds to, and what is the appropriate file size for each; Husqvarna‘s lengthy coding is presented in a table of its own further down.

PitchChain marking
Carlton
OregonStihl
1/4”P7
1/4”Ex251
3/8”PNx90, 916
.325”Kx20, 21, 22, 952
3/8”Ax72, 73, 753
.404”Bx594
See table below
for Husqvarna

2 By measurement

Chain pitch is measured from the distance between two pins, leaving one pin between. This here reads 3/4”, which means a pitch of 3/8”.

Measuring the chain is relatively easy and certain way of finding out the pitch. To measure the pitch yourself,

  1. Take a ruler, caliper or tape measure
  2. Measure the distance of two pins in the chain so that you leave one pin between them.
  3. Then divide the measurement by two, and you have the chain pitch.

Note that pin spacing itself is irregular – this is why you measure over one and divide by two.

Low Pro or Regular?

A 3/8” Low Profile (Picco) chain (in front) has much lower teeth than a regular 3/8” pitch chain.

There is one challenge in the direct measurement method, though: if your result reads 3/8” or 1/4”, you still need to determine whether you are dealing with a standard chain or a low profile version: the low profile chains take smaller files than the standard. The 3/8” Low Pro or “Picco” chain is particularly popular and easy to mistake for a regular 3/8” chain.

To tell if a chain is low profile or regular, measure the tooth height as shown in the image. The tooth height for a 3/8” regular chain is around 13/64”; for a 3/8” Low Pro/Picco chain, it is only around 9/64”.

In fact, the low profile chains are not only lower profile, but of much lighter construction thŕoughout. With some practice, you will learn to tell them from the regular versions just by the look and feel.

File size for Husqvarna saws and chains

Husqvarna offers plenty of information on file sizes for their saws and chains, but the data may be a bit hard to get to: I was able to find much of the info only on the UK and Australian sites and not on the US version.

For easier reference, I have condensed Husqvarna file size guidelines into the two tables below: one based on Husqvarna saw models, and the other on chain models. Links to Amazon for the original Husqvarna Intensive Cut files and file kits (w. handle, guide) included. (Workshoppist.com is an Amazon Associate. As an Amazon Associate we earn from qualifying purchases.)

FILE SIZE vs.
HUSQVARNA
SAW MODEL

Saw model
PitchFile
diameter
120 Mark II, 130, 135 Mark II, 240
T525, T435, 439, T540XP
535i, 540i, T535i, T540i
.325M
3/8M
5/32”
(4.0 mm)
file kit**
120i or other w. H38 chain3/8M11/64”
(4.5 mm)
file
435, 440, 445, 450, 450 Rancher
543XP
545 Mark II, 550XP
.325”3/16”
(4.8 mm)
file kit
365XP, 372XP, 390XP, 395XP
455/460 Rancher
555, 562XP G, 565, 572XP, 576XP
3120XP*
3/8”
(.404″)*
7/32”
(5.5 mm)
file kit
*3120XP is 3/8″ or .404″
**(links to Amazon)
FILE SIZE vs.
HUSQVARNA
CHAIN

Chain model
File
diameter
Husq.
files*
H00, H35, H36, H37, H39
SP21G, S93G
5/32”
(4.0 mm)
file kit
H3811/64”
(4.5 mm)
file
H21, H22, H23, H25, H26, H28
H30, H30R
SP33G
3/16”
(4.8 mm)
file kit
C83, C85
H42, H45, H46, H47(S), H48(S), H49
H50…H54, H56(S), H57(S), H58
H64(S), H65, H66
H70, H80, H81
7/32”
(5.5 mm)
file kit
H82, H83flat
*(links to Amazon)

File size for Stihl saws

The table below shows the pitch and the recommended file size for Stihl chainsaw models. Stihl recommendations are mostly in line with other manufacturers, but for 3/8” chains, Stihl specifies a 13/64” file instead of the more common 7/32”. Links to Amazon for the original Stihl files and the popular 2-in-1 sharpeners (files, handle, guide) included. (Workshoppist.com is an Amazon Associate. As an Amazon Associate we earn from qualifying purchases.)

FILE SIZE vs.
STIHL SAW

Model name
PitchFile
diameter
MS 150 C-E
MSA 120, 140, 160, 161, 200
1/4”P1/8”
(3.2 mm)
kit**
MS 170, 171, 180, 181, 193, 194
MS 201, 211
MSA 220
MSE 141, 170, 210, 220
3/8”P5/32”
(4.0 mm)
file kit
MS 250, 251, 261, 271, 291.325”3/16”
(4.8 mm)
file kit
MS 311, 362, 391, 462, 500i, 661, 880*
MSE 250
3/8”13/64”
(5.2 mm)
file kit
MS 880*.404”7/32”
(5.5 mm)
*alternative pitches
**(links to Amazon)

Chain file size Q & A

What size file for a Makita/Oregon/Poulan/Ryobi chainsaw?

The proper file size does not really depend on the make of the chainsaw, but rather on the chain pitch – see the size table above. Some application comments can still be given by brand:

What size file for an Echo chainsaw?

For the most part, Echo’s file size recommendations for Echo chains to be used on Echo chainsaws follow the general file size recommendations – see the file size table above.

The exception is that for a its 90PX series chains with a 3/8P pitch, Echo specifies a 4.5 mm, or 11/64” file. This is an intermediate file size between 5/32” and 3/16”, and is included in Echo’s five-piece file set. Note that Echo’s other 3/8P pitch chains (91PX and 91PXL series) take the smaller standard 5/32” file.

Which file size for 91 chain?

Oregon 91 chains are 3/8” Low Profile chains. As seen in the table above, these chains take a 5/32” (4.0 mm) file.