Saw Cutting Crooked

[CTYank]

IME with chain off the bar, if you set one leg of a small machinist's square on the bar rails, you can easily see if the rails are even by looking at the other leg of the square. Easy and precise.

To true rails, I use a bench grinder. Set a tool rest so that a bar set on is in line with the center of the wheel. Gently grind the bar until the wheel makes even contact with both rails. Flip it and repeat. Really simple, and the marks from the wheel retain oil. It's worked great for multiple times with circle-cutters.

For prevention, sharpen chain often & avoid debris.

 

[flyboy553]

Just to be clear, the old timer Stihl dealer does indeed have a bar grinder setup. We put a machinist's square on it and to the naked eye, it looked square and burrless. That is why it was so perplexing. A lot of comments in this thread are assuming that only a homeowner looked at the saw, which is not the case at all. I also think a lot of folks didn't read my entire opening post, as all of these things were covered. And that is why I came across as having copped an attitude, which is kinda true, but only because people were answering without completely reading the OP. Not to mention the frustration at not knowing why it was cutting crooked. And people telling me to do what I had already done! lol
In the end, the bar is fixed, I am happy, the machine shop owner is happy (he got my money), and we all learned a little something from this! Well, except for Mastermonkey, he doesnt get my saw.

Ted

 

[jbighump]

new bar and chain......round here a forester 20" bar and full chisel chain is $35 out the door..i know its not a stihl but it does the same thing for much cheaper and I can afford to have a spareopcorn:

 

[RedFir Down]

For those interested in dressing your own bars this is what I came up with to dress them. If you already have a drill press it less than $20 in materials.



Here is the thread that goes into detail. http://www.arboristsite.com/community/threads/another-way-to-dress-a-bar.250111/

 

[Icehouse]

Have had 2 saws that did the same thing, both were saws I had bought from other folks. Took both bars to my stihl dealer and for $8 made them good. They have a very old bar machine that hammers the bar and trues the edge, cured both problems, like that machine has done for me many times over the years.

 

[SS Sniper]

that wouldn't cause the problem

see #47

It'll cause the saw to cut on a slight angle because the bar has more drag on a specific side.

 

[Icehouse]

It's the bar

 

[singinwoodwackr]

It'll cause the saw to cut on a slight angle because the bar has more drag on a specific side.

I disagree. A slight burr on one edge of the bar will not cause that kind of deflection. The issue is non square rails.

 

[Sean80]

Your bar may have a burr on it. Use a flat file to take it off and make it square again.

 

[Wood Doctor]

For those interested in dressing your own bars this is what I came up with to dress them. If you already have a drill press it less than $20 in materials.

View attachment 349940

Here is the thread that goes into detail. http://www.arboristsite.com/community/threads/another-way-to-dress-a-bar.250111/

Bravo! I've also been successful with a disk sander. You just have to be sure that the disk makes an exact right angle to the table and then make several passes. I also flip the bar over a few times on each side. And, I remove the sharp burrs with a mill bastard file before I start.

 

[StihlFroling]

If you think you fixed your own bar, your kidding yourself and or maybe got lucky. Did you read the part where the difference was only .003" don't think anyone can true that up by hand or on a homemade jig the way a shop can. It dresses the whole length of the bar and it's only taking off very small amounts. I believe its a 180-220 grit diamond wheel and maintains the original bar profile the whole length. This is how you scoop up bars that others think are junk. Straighten the bar on the press side, recrimp the rails to proper gauge and true the rail edges.

 

[RedFir Down]

If you think you fixed your own bar, your kidding yourself and or maybe got lucky. Did you read the part where the difference was only .003" don't think anyone can true that up by hand or on a homemade jig the way a shop can. It dresses the whole length of the bar and it's only taking off very small amounts. I believe its a 180-220 grit diamond wheel and maintains the original bar profile the whole length. This is how you scoop up bars that others think are junk. Straighten the bar on the press side, recrimp the rails to proper gauge and true the rail edges.

So you dont think my method works? Explain.
What machine/tools uses a 180-220 grit diamond wheel to dress a bar?

 

[Chris-PA]

0.003"? That is a very small distance. I am absolutely positive I have bars with much larger differences in rail height than that, and they don't cut crooked. I know it is important to have the bar edge be square, but given the abuse bars take, if it were required to hold better than 0.003" rail height difference we'd all be cutting circles.

 

[fearofpavement]

.003 may not seem like much to some but in the machinist's world, that's a lot. A chain travels at thousands of feet per minute and a little bit off multiplied by many thousands equals a lot.
I don't see why anyone with a vice and a file couldn't square up a bar. That's like saying someone can't sharpen a chain without a grinder.

 

[singinwoodwackr]

If you think you fixed your own bar, your kidding yourself and or maybe got lucky. Did you read the part where the difference was only .003" don't think anyone can true that up by hand or on a homemade jig the way a shop can. It dresses the whole length of the bar and it's only taking off very small amounts. I believe its a 180-220 grit diamond wheel and maintains the original bar profile the whole length. This is how you scoop up bars that others think are junk. Straighten the bar on the press side, recrimp the rails to proper gauge and true the rail edges.

been doing this since the early '90s (dressing the rails) without one issue. I've also used a vise to close rails a tad, then dress and gotten lots more use out of bars.
I would agree that trying to see .003 deflection over 1/4" is tough w/o eagle eyes but some people can and do. I simply make sure my machine is dead square each time I grind a bar...no issues.

 

[Chris-PA]

.003 may not seem like much to some but in the machinist's world, that's a lot. A chain travels at thousands of feet per minute and a little bit off multiplied by many thousands equals a lot.
I don't see why anyone with a vice and a file couldn't square up a bar. That's like saying someone can't sharpen a chain without a grinder.

I'm not a machinist but I've spent a lot of years with a callipers in my hand, so I do have some feel for it. Whether a 0.003" tolerance is significant depends on what the part is and what the function is. Here we're talking about a 1deg angle on a chainsaw bar that may be 2' long, and there are so many other variables, including the chain itself and how it runs in the bar groove. How consistent is that 1deg angle over the length of the bar? I dunno - my gut tells me that a 1deg angle is not the problem. I can't see how the whole bar and chain cutting system could work in the field if it were that sensitive and the tolerances needed to be held that tight.

 

[flyboy553]

Well, it was enough to throw my saw off. Now, my saw wasn't getting pinched in the kerf at all, it was just not cutting straight down through the log. Just off a hair so the kerf wasn't nice and straight. After putting it on the surface grinder, it cuts straight now. Everything else is a constant, meaning I didn't put a new chain on or anything else. Just made the bar rails even.

I just didn't expect to see a slanted, cut after having the bar and chain all checked out and pronounced healthy, that's all.
I have only had the saw for about 7 months, so I don't know the history of the bar and how it was treated before, but on the day I bought it, it was in good shape and cut straight at that time.

Like I said, I probably wouldn't even had noticed it, or even cared, if I hadn't just had the bar and chain in to be checked out.

Ted

 

[singinwoodwackr]

Well, it was enough to throw my saw off. Now, my saw wasn't getting pinched in the kerf at all, it was just not cutting straight down through the log. Just off a hair so the kerf wasn't nice and straight. After putting it on the surface grinder, it cuts straight now. Everything else is a constant, meaning I didn't put a new chain on or anything else. Just made the bar rails even.

I just didn't expect to see a slanted, cut after having the bar and chain all checked out and pronounced healthy, that's all.
I have only had the saw for about 7 months, so I don't know the history of the bar and how it was treated before, but on the day I bought it, it was in good shape and cut straight at that time.

Like I said, I probably wouldn't even had noticed it, or even cared, if I hadn't just had the bar and chain in to be checked out.

Ted

you have to remember that when one rail is worn down lower than the other the chain on that same side will have worm as well. So, that .003 difference may in actuality be .006 or more on that one side. That's a huge difference over 1/4" of length.

 

[Wood Doctor]

And.

you have to remember that when one rail is worn down lower than the other the chain on that same side will have worm as well. So, that .003 difference may in actuality be .006 or more on that one side. That's a huge difference over 1/4" of length.

And, the measurement error could easily push it to +/- .01". Stand the bar up on a table saw right next to the fence, pressing against it. Now move the table saw's fence slowly to the right. Check the lean, if any. You will learn more from that than just about anything else.

 

[Wood Doctor]

This thread is old but worthy of posting again. I reminded myself of several of my own posts here. I just ran into trouble with a worn bar that had a left rail higher than the right. It eventually wore down new chains and even caused them to pull cuts to the left. Here's what materialized:

I replaced the old bar with a new one and tried to use the chain loops that were pulling left with the old bar. After only a few cuts with the new bar, they started pulling their cuts left again. By itself, the new bar could not save their cuts. Only when I used a new chain loop with the new bar did the cuts go straight down. The old bar with uneven rails had really done a number on the new chain loops. I suppose I could drop the right-side rakers and try to save these loops, but that seems to be a trial-and-error process.

My conclusion: a bad bar with uneven rails can ruin new chain loops rather rapidly and induce its problems to the loops, thus spreading the "virus". Dressing the bar may be just as important as sharpening the chain. Any suggestions or comments?