MS881 ported 25in bar raker depth

[Grouse Hunter]

Acquired this saw through a trade and will be used for bucking large oak mostly...I realize it's a bit large and heavy for this application, but it's what I have.
How aggressive can I go on my rakers? 30, 40, 50thou?

 

[WoodmanSr]

Acquired this saw through a trade and will be used for bucking large oak mostly...I realize it's a bit large and heavy for this application, but it's what I have.
How aggressive can I go on my rakers? 30, 40, 50thou?

Read about 6° raker "progressive depth gauges" & FOP (Carlton File-O-Plate).

Old threads by BobL & Philbert

.. Are FOP really progressive depth raker generators?

If you don't find I'll lookup links.

Below is a very helpful recommendation. Easiest solution.

Sierra99 (AS, 2010) -- An old but good thread. It turns out that if you divide the gullet length by 10, you get the required raker depth to produce a 5.7 degree angle.
For example, a new chain with 0.25" gullet, divide by 10 you get a raker depth of 0.025", the "standard", that yields a good 5.7 degree angle.
If the gullet is 0.40" long, dividing by 10 gives you a raker depth of 0.040" (for the same 5.7 degree angle).

Try these links

https://www.arboristsite.com/threads/are-fop-really-progressive-depth-raker-generators.114624/

https://www.arboristsite.com/threads/raker-checking.69081/

https://www.arboristsite.com/threads/stihl-progressive-depth-gauge-tool.336757/

Edit... more.

Didn't answer your question. Right. Ms880 will pull huge. Just that at some point is dangerous & may damage bar rails or chain.

Read what Philbert references in old post. Good info on chain cutting action & wear effects.

Google -- Carlton Safety & Maintenance Manual.PDF
[CarltonSafetyMaintManual_EN.pdf / English download]

Okay, so no one biting. I'll just add angle targets are simply trigonometry (math).

1 in 10, divide by 10 is 5 71°, so, double that 1 in 5, divide by 5 is 11.31°. BobL made mention of milling certain species at 10° high angle. Recall saying the kerf wave (cutter separating from rail could be read in the wood).

So if 10° is a practical limit, multiply by 0.1763 [as = Tan(10°)].
.. new 0.250 gullet, 0.044" height gauge
.. worn 0.400 gullet, 0.070" height gauge.

Angle determination is independent of chain size. Only rise/run across gullet opening but chain style & wood species will respond uniquely. Good luck. This is the mathematical view not experience. Suggests starting at .040" not grossly extreme, about 10°. Then, can file & restore back to higher gauge height based on feedback.

 

[WoodmanSr]

Acquired this saw through a trade and will be used for bucking large oak mostly...I realize it's a bit large and heavy for this application, but it's what I have.
How aggressive can I go on my rakers? 30, 40, 50thou?

Do refer back to Carlton literature. An important point... when the low (high angle) Gauge Height become greater than the cutter top plate clearance angle... then you break function of cutters. You only forcing them to act as gouge planes vs see-saw wave removal of chips. Too low of height gauge binds the cutter into the wood, less efficient & hard on components (I'd think). Smooth cut & efficiency may rely on top plate clearance angle a few degrees excess of height gauge angle. Prehaps near a 10° practical limit to maintain cutter function as Carlton illustrates well. Your bar, chain, sprocket, & PTO bearing may appreciate also.

 

[Patrick62]

You added math to what I already suspected. and have been "doing" when sharpening chains. when the cutter is sharpened down to "end of life" it just don't cut good with raker, depth gauge at .025 so I have to make them a little deeper, then it works.

Now, to answer the origional poster question. the 880 is a beast. Run it if you want to, but... I would sell it, and get a 660.
Ok, the big saw was made to pull LONG bars with less rpm than the smaller 660 sized saws.
Run a large sprocket on it, and be patient.
Next part of this lesson:

a saw chain is only really capable of so much power. Torque and speed. I knew a guy back in the day got a lot done with a Husky 2100. His method was to run the rakers really low. However it s t r e t c h e d the chain mercilessly.
Now a days I demonstrate this by going to extremes. Get a chain and bar, and file off the rakers. Oh it will cut, but require like 30 HP to pull it. No problem, use a 390 Ford with a 4 bbl carburetor. no problem with power now!!!
13.2 seconds later the chain is broken.

The 880 could be running a .404 chain which is more substantial, and could take more power. In a longer bar it would be the hot ticket. but at 24 inch or so bar, my 660 would out run it and be lighter to handle.

 

[J D]

In short, that saw shouldn't have any issue pulling a chain with rakers set far lower than would be any good for ware & tare long term.
I'd start out somewhere between .030" & .040" & take a few thou off each cut until vibes increase or it starts feeling grabby... then after a couple of sharpenings it should be about right & you can work out your angles from there if you want to do the progressive thing

 

[NSEric]

I'd just keeping taking a swipe or two off the rakers until it cuts good, once you get it cutting good measure them.
On my 660 with a 20 inch bar I set the drags to about .040, you're going to be lower than that so start there.
Be careful with the rakers really low, the saw will fling smaller wood right at you if you're not holding it down good.