Oregon Micro-Lite 90PX chain sharpening

[GerrySM]

My Stihl MS170 came with a Stihl chain (Stihl Chain Loop PMM3 Picco Micro Mini Comfort 3, Stihl Part No. 3610 003 0056). This chain used a 4.0mm (5/32") file for sharpening.

I've been replacing it since with the Oregon 90PX chain (cheaper, also good quality). This chain, according to the chain's technical document, needs a 4.5mm (11/64") file.



(Interestingly, my new Makita XCU02 36V chainsaw also uses a 90PX chain from factory, and the manual states 4.5mm file is needed — although they may have got this info from the same source as the link above).

Now I want to change to using a diamond stone to sharpen this chain, and I'm finding that 4.5mm is pretty difficult to get, whereas 4mm is more common.

I went to the online Oregon Product Selector and it gives this contradictory advice: Is this an error by Oregon, or are the two sizes so close that it makes no difference?

 

[AVB]

5/32 0.1563 3.9688
11/64 0.1719 4.3656

I would the first manual is wrong as 4.5 mm bigger than 11/64 quoted. I don't about anyone else but I would stick with Oregon that the 5/32 is one.

 

[GerrySM]

Thanks, but both the manual linked and the website are Oregon, but they say different things. I have written to Oregon for an explanation, and I'll post their answer here.

 

[GerrySM]

Received a reply from Oregon, and it's as I suspected:

Thank you for contacting us and for your interest in Oregon(r) product. We recommend the 4.5mm file for the 90 series chain. Having said that, a 5/32" file can be used to sharpen the 90 series chains. In the event that the 4.5mm file is difficult to find the 5/32" file can be substituted. The 5/32" file is only slightly smaller than the 4.5mm. if you convert the inches to millimeter and vice versa you come up with: 4.5mm = 0.177165 (11/64") & 4.0 = 0.15748 (5/32"), & 11/64 = 4.36562 & 5/32 = 3.96875. Long story short, there is a small difference between the files and you can use either one to sharpen the chain.

Kind Regards,
Glenn Lxxxx | Sr. Technical Services Technician
Forestry Lawn and Garden
Blount International | 4909 SE International Way Portland, Or. 97222

 

[CR888]

I did hear some of Oregon's new chain requires a bigger file than the older model chain . Philbert posted something about this I think. Generally that size chain requires 5/32 size file. A bigger file will make it less aggressive in OZ hardwood which is a good thing. How one uses a file is just as important as the size.

 

[GerrySM]

How one uses a file is just as important as the size.

Yes, so true of many things in life.

 

[Chris-PA]

I've filed Oregon 90 with a 4mm file for years. It works fine. The radius is only 0.010" smaller.

 

[SawTroll]

5/32 0.1563 3.9688
11/64 0.1719 4.3656

I would the first manual is wrong as 4.5 mm bigger than 11/64 quoted. I don't about anyone else but I would stick with Oregon that the 5/32 is one.

As far as I know, 4.5mm is a nominal size, and the files really are about 11/64".

 

[GerrySM]

As far as I know, 4.5mm is a nominal size, and the files really are about 11/64".

11/64 of an inch is the same as 0.172"
An inch is 25.4mm, so 0.172 is 4.37mm
Likewise, a 5/32" file is 3.97mm

Therefore the difference between the two files is a tiny 0.4mm, not worth worrying about.

 

[SawTroll]

11/64 of an inch is the same as 0.172"
An inch is 25.4mm, so 0.172 is 4.37mm
Likewise, a 5/32" file is 3.97mm

Therefore the difference between the two files is a tiny 0.4mm, not worth worrying about.

I agree with the numbers - and a 1/64" "too small" file isn't a problem as long as you hold the file high enough. It will result in slightly more hook though, and a slightly weaker edge on the top-plate.

It is something I don't do unless I have to - except I routinely do it on the last third or so of the cutters "life". At that stage it actually is more correct than the recommended size.

 

[Philbert]

I was surprised by this too. I thought of Type 90 chain as 'smaller', since it is narrow kerf 3/8 low profile, whereas the Type 91 chain is 'regular' 3/8 low profile chain. Why would the 'smaller' chain use a 'larger' diameter file?

An Oregon rep told me that the Type 90 cutters are not just narrower, but also a different profile.

I tried the 4.5mm file/file guide on this chain, on my 40 Volt, battery pole saw, and it cut really well. Actually, pretty aggressive. The cutters also stayed sharp for a long time.

So, you can use the 5/32" file, but will probably get better performance with the 4.5 mm (11/64") file.

Philbert

 

[Chris-PA]

I was surprised by this too. I thought of Type 90 chain as 'smaller', since it is narrow kerf 3/8 low profile, whereas the Type 91 chain is 'regular' 3/8 low profile chain. Why would the 'smaller' chain use a 'larger' diameter file?

An Oregon rep told me that the Type 90 cutters are not just narrower, but also a different profile.

I tried the 4.5mm file/file guide on this chain, on my 40 Volt, battery pole saw, and it cut really well. Actually, pretty aggressive. The cutters also stayed sharp for a long time.

So, you can use the 5/32" file, but will probably get better performance with the 4.5 mm (11/64") file.

Philbert

The cutters on 90 are clearly taller than the cutters on 91. It's probably more aggressive filed with the smaller file, but 4.5mm files are like hen's teeth and I never tried one.

 

[GerrySM]

4.5mm files are like hen's teeth

And when you move to non-conventional methods, like those below, the lack of availability gets more irritating.

 

[Chris-PA]

And when you move to non-conventional methods, like those below, the lack of availability gets more irritating.

That stuff all seems silly to me - I use a file and a home made chain vice. And a good light. It's cheap, fast and the chains get very sharp.

 

[Philbert]

. . . but 4.5mm files are like hen's teeth and I never tried one.

Philbert

 

[Chris-PA]

View attachment 519947

View attachment 519948

View attachment 519950

Philbert

I know, but I can buy a 3-pack of very nice Stihl files at the local ACE for maybe $4 to $5. I'm really starting to hate having to get everything through the web.

 

[Philbert]

Hurry up and decide,'cause that e-bay deal is tempting me, even though I already have one!

Philbert

 

[GerrySM]

That stuff all seems silly to me - I use a file and a home made chain vice. And a good light. It's cheap, fast and the chains get very sharp.

Well, I've been using that for several years, and I also thought that a file was the way to go. But when I got the saw back from a service at the dealer it was so much sharper than I am getting it that I started wondering if there wasn't a quicker, better way. So I've bought a set of 4mm diamond stones, and I want to use them with a Dremel or drill to see if it is faster and sharper.

 

[Philbert]

Check out the stones in this thread if you want to use a rotary tool:

http://www.arboristsite.com/community/threads/grandberg-type-sharpening-stones.285808/

Philbert

 

[GerrySM]

Check out the stones in this thread if you want to use a rotary tool:

http://www.arboristsite.com/community/threads/grandberg-type-sharpening-stones.285808/

Thanks, those stones are made of a-BN (amorphous boron nitride), which is much softer than diamond (had they been made of Cubic Boron Nitride or c-BN, I'd be very interested).

Since diamond is much harder, the only thing to recommend them above the diamond stones I bought (above) would be if they have a much better adhesive

Cubic boron nitride (c-BN) Cubic boron nitride is widely used as an abrasive. Its usefulness arises from its insolubility in iron, nickel, and related alloys at high temperatures, whereas diamond is soluble in these metals to give carbides. Polycrystalline c-BN abrasives are therefore used for machining steel, whereas diamond abrasives are preferred for aluminum alloys, ceramics, and stone. When in contact with oxygen at high temperatures, BN forms a passivation layer of boron oxide. Boron nitride binds well with metals, due to formation of interlayers of metal borides or nitrides. Materials with cubic boron nitride crystals are often used in the tool bits of cutting tools. For grinding applications, softer binders, e.g. resin, porous ceramics, and soft metals, are used. Ceramic binders can be used as well. Commercial products are known under names "Borazon", and "Elbor" or "Cubonite". Similar to diamond, the combination in c-BN of highest thermal conductivity and electrical resistivity is ideal for heat spreaders. Contrary to diamond, large c-BN pellets can be produced in a simple process (called sintering) of annealing c-BN powders in nitrogen flow at temperatures slightly below the BN decomposition temperature. This ability of c-BN and h-BN powders to fuse allows cheap production of large BN parts. As cubic boron nitride consists of light atoms and is very robust chemically and mechanically, it is one of the popular materials for X-ray membranes: low mass results in small X-ray absorption, and good mechanical properties allow usage of thin membranes, thus further reducing the absorption. Amorphous boron nitride (a-BN) -- Layers of amorphous boron nitride (a-BN) are used in some semiconductor devices, e.g. MISFETs. They can be prepared by chemical decomposition of trichloroborazine with cesium, or by thermal chemical vapor deposition methods. Thermal CVD can be also used for deposition of h-BN layers, or at high temperatures, c-BN. ]