Question on chain saw bar and chains

[Winch]

I have a Stihl MS250 with 18 inch bar. I don't use it a lot but recently sectioned up an oak tree 24 inches in diameter and 50 feet long. I cut it into 8 foot sections no problem. Soon after saw got dull. I sharpened the chain but now it seems to only cut on certain spots on the bar. Mostly right next to the saw. I checked the depth of the groove and it's 7.5 - 8 mm everywhere. Specs I've read says that bar is good to 6 mm.

What about the width of the bar groove? Can that be a problem?

Also I started to buy an Oregon bar and chain that I thought the vendor said was compatible but now I'm not sure. A Stihl chain says its .325 pitch, .063 gauge and has 68 drive links. The Oregon is 3/8 pitch, .050 gauge and has 62 drive lengths. Is it compatible with my saw?

 

[Philbert]

It’s possible to put different length bars, and different pitch chains on saws.

The drive sprocket, guide bar, and chain work together as a system, and must be compatible. Change one, and you may have to change the others.

I would not put a 3/8 pitch chain on an MS250.

I would not give up on your current bar and chain: they probably need a little attention. Maybe bar maintenance?

Can you post clear photos of each? Maybe try a new chain on the existing bar, to see if it’s the bar or chain causing your current problem.

Philbert

 

[TRTermite]

You need to keep your bar - sprocket - "Compatible"With the chain So no not unless you convert them as well.
When you said 3/8" chain you need to clarify if it is 3/8" picco/low pro Or full size 3/8" (Not many people manage a 3/8" Full/regular chain on a Stihl 025. When you get all these numbers floating around make sure to keep the gauge in mind..

 

[Philbert]

When you said 3/8" chain you need to clarify if it is 3/8" picco/low pro Or full size 3/8"

Good point.

To clarify my comment, I would not recommend full size / standard 3/8 pitch chain on that saw. You could convert to 3/8 low profile chain, if you felt a need to.

Both Oregon and STIHL should have the 18”, .325 pitch bars and chains for your saw. Most STIHL dealers will stock the OEM sizes. Sometimes, less common Oregon bars and chains need to be ordered from an on-line dealer / vendor.

Philbert

 

[Winch]

I verified my bar is .325 pitch, .063 gauge and 68 drive teeth (18 inch). I checked all 4 of my chains and they match. The bar seems in good shape. I used a feeler's gauge to check the groove width and it is .063 all along. As mentioned the depth is 7.75 mm mostly. So I know what to get but I think what I have should work better than it does. I sharpen my chains on the electric sharpener in the pic. Then I file the depth using a little Stihl depth gauge. I had last set the sharpener to 30 degrees. Does that sound right for those chains?

 

[Philbert]

If you have several chains, you should stick to that size.

I use an electric chain grinder too. In person, I might be able to help you with your chains. If you can post some clear, close up photos of your chains (both sides, top), someone nay be able to offer some suggestions.

It helps to hold a white piece of paper or cardboard behind the chain, when shooting close up photos.

Philbert

 

[Winch]

Here's some older pics I took of the same chains being sharpened. I'll try to get better ones tomorrow if this doesn't help.

 

[Philbert]

Always hard to tell from photos. But, based on your description, here are some thoughts.

The ‘face’ of the cutters look ground, but the cutting edges (top plate and side plate) don’t look that sharp in the photos.

The shape also looks flatter than the ‘C’ shape of a new cutter.

Are you grinding with the profiled rim of the wheel or the side of the wheel?



It usually will take multiple passes to both sharpen the edges (first pass), then clean out the gullet (second/ third passes). Especially, with very thin wheels.

On your type of grinder I have had better results using thicker (3/16” for .325 chain) and coarser wheels.



The third picture (2 cutters from the top) also appears to show damage to the corner, where the top and side plate edges meet (could just be dirt). Any damage needs to be removed.

Philbert

 

[buzz sawyer]

Cutting better close to the power head indicates a dull chain to me - you can put more pressure on the chain there.

In the first picture, I see one ground cutter between two very dull (rounded over) cutters. Looks like you are running the chain into the ground. You should have been able to feel the difference (slower) in cutting long before it got rounded over that much. Can't see the other side of the ground cutter so I can't tell if it is sharpened correctly. Same for the second picture. In the third picture, I see a sharp cutter (again, can't see the other side) next to your thumb and a dull cutter next to your finger. I'm hoping the one next to your finger was not sharpened yet.
The top cutting angle also seems too flat. Follow Philbert's advice on grinding wheels.

 

[coffeebrk]

Here is the Oregon bar I run on my ms251

 

[coffeebrk]

Here is the Oregon chain.....

 

[coffeebrk]

Double check the setup angles for the type of chain you are grinding. From the pictures it looks like either the head tilt angle, and or the size or shape of grinding wheel or both are incorrect.

 

[Philbert]

Here is the Oregon chain.....
View attachment 1133205

OP is running 0.63 gauge chain. There is an Oregon model; semi-chisel 22BPX (Retail pack ‘L68’), full-chisel 22LPX (Retail pack ‘V68’) for 68 drive link chains. But, you may have to order from an on-line seller.

From the pictures it looks like either the head tilt angle, and or the size of grinding wheel or both is incorrect.

That type of grinder usually has a fixed head tilt angle (typically around 60°).

Philbert

 

[Winch]

My grinder has a fixed head angle. I have a 1/8 wheel on it now so I ordered a 3/16. I tried to grind one using 35* instead of recommended 30*. That was still using 1/8 inch wheel. Here is pic


How much should the wheel contact the cutter as it comes down? I've been just letting it hit the top of the cutter. Maybe take more of a bite?

 

[coffeebrk]

My grinder has a fixed head angle. I have a 1/8 wheel on it now so I ordered a 3/16. I tried to grind one using 35* instead of recommended 30*. That was still using 1/8 inch wheel. Here is pic
View attachment 1133256

How much should the wheel contact the cutter as it comes down? I've been just letting it hit the top of the cutter. Maybe take more of a bite?

What size of chain?

 

[Winch]

.325 .063 gauge 68 drive

 

[coffeebrk]

3/16" is correct. I always dress, (shape) new grinding wheels before using them to sharpen.

 

[Winch]

How do you do that?

I just watched a utube video on shaping a new wheel. He uses a silicon carbide block. I need to find one of those. Is there anything else you would recommend to do the shaping?

 

[Philbert]

See illustration in Post #8, above. Profiled rim should touch cutter just like a round file would.



Philbert

 

[fields_mj]

I have a Stihl MS250 with 18 inch bar. I don't use it a lot but recently sectioned up an oak tree 24 inches in diameter and 50 feet long. I cut it into 8 foot sections no problem. Soon after saw got dull. I sharpened the chain but now it seems to only cut on certain spots on the bar. Mostly right next to the saw. I checked the depth of the groove and it's 7.5 - 8 mm everywhere. Specs I've read says that bar is good to 6 mm.

What about the width of the bar groove? Can that be a problem?

Also I started to buy an Oregon bar and chain that I thought the vendor said was compatible but now I'm not sure. A Stihl chain says its .325 pitch, .063 gauge and has 68 drive links. The Oregon is 3/8 pitch, .050 gauge and has 62 drive lengths. Is it compatible with my saw?

This has already been answered, and I think you've understood the answer, but just in case, NO, the Oregon chain you asked about is not interchangeable with the Stihl chain you referenced, and will not work on the bar that's in your picture. If you try to run it, you will damage your bar, the new chain, and your drive sprocket or rim. If you bought that 3/8 pitch Oregon chain, give it away or throw it away before it causes you any more problems.

As far as cutting goes, that last close up pick looks like the cutter MAY not be sharp yet. Its very hard to take a pic of a cutter that's clear enough to tell, but it looks like there's light reflecting off of the cutting edge, but it may just be the quality of the pic. If you can SEE the cutting edge, it's NOT sharp and needs to have a little more material removed (with the correct size grinding wheel or file). It looks like you're using a semi-chisel chain. In my opinion, when you are learning to sharpen chains, its easier to learn with full chisel chains because it's very easy to tell if the point of the cutter is sharp. It should feel sharp like the claw on a cat. Semi chisel and full chisel don't have the point making it difficult for a beginner to know whether they need to remove more material or if they've made a mistake somewhere else. Hang in there, you'll get it!