Tuning a Simington Square-Chisel Chain Grinder

The following information is mostly about tuning and does not cover much basic operation. If you are new to square-grinding and looking for entry-level information, the following may not be helpful. Most of the concepts require working knowledge to be meaningful. Even the terminology may be confusing to a beginner. On this web site, we've posted a lot of basic chain sharpening information available for free. We've also printed similar information in articles in previous editions of our catalog. These are both good sources.

How to Get Sharper or Blunter Inside- Angles

A good place to start a lesson on tuning a Simington grinder is with how to set it up to produce the inside angles you want on your chain's cutter teeth. This is important because this affects how efficiently your chain's cutter-teeth sever wood fiber and their ability to stay-sharp. In simple terms, acute inside-angles cut wood fiber most efficiently, but acute angles also make for weak cutting edges on cutter-teeth. The opposite is true about stay-sharp ability. Blunter angles work best here. So, the best setup is one that balances these characteristics; one that produces cutter-teeth that cut efficiently AND still have reasonable stay-sharp ability.

Once your grinder is setup to produce this balance, you may not retune it for a long time. However, at some point, you may want to make some changes. Why would you ever change a good setup? Well, you might find yourself working in a patch of easy-to-cut wood like Red Alder. Here you may wish to grind slightly more acute inside-angles to improve your saw's cutting speed. On the other hand, it might be winter and you are on a job cutting frozen wood. Here you may wish to change your setup to one that produces blunter cutting angles to improve your chain's stay-sharp ability. Yet another reason to retune might be that you have decided to enter a cutting contest at a local logging show. For racing, you'll want a setup that grinds very acute cutting angles.

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This adjustment is for making sharper or blunter inside cutting angles. Moving it towards the pivot will make the cutting angles on your cutter-teeth more acute. Moving it towards the back will make them more blunt.

The adjustment that affects the inside-angle the most is the arm length adjustment. The arm doesn't actually get longer or shorter, but there is an adjustment that moves the chain's mounting disk forward or backward. This causes cutter-teeth to contact the grinding wheel in a different location. So when you move the disk to a back position, it will make the inside-angle on your cutter-teeth more blunt. When you move it forward, it will make this angle more acute. Our advice is: if you are trying to develop a good baseline setup on a Simington grinder, set this adjustment in the middle of its travel. This is a good starting point for most users.

How to Keep From Cutting Into the Side-Straps Under the Cutter's Hood

There are actually two adjustments that control whether or not your machine cuts into the chain's chassis. The first adjuster is the thumb-screw on the underside of the swing arm. This adjuster raises or lowers the chain's mounting disk. The height of this disk affects the angle of the chain's top-plate relative to the grinding wheel. If this sounds complicated, a better way to describe it is: the height of this disk affects where the chain sits on the disk when it is being ground. Towards the top of the disk, the angle is slight, but as the cutter tooth moves down the arc from the top, this angle increases. When the angle gets too great, the grinding wheel will cut into the chain's side-straps.

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Use this adjustment to keep from cutting into the chain's chassis under the hood of the cutter-teeth.

This adjustment also affects the inside top-plate angle. This changes on a Simington 451C as the length of cutter teeth become shorter. Here's what happens: when grinding a new tooth, the chain will sit on the mounting disk at very little angle to the grinding wheel. But on a worn chain, short cutter-teeth will sit farther down the arc on the disk. This causes the inside top-plate angle to decrease.

This is somewhat of an advanced concept, so if you are still trying to get a good baseline setup, don't worry about it right now. But, if you are an advanced user and have wondered why the grind changes as cutter-teeth on your chains become shorter, this is what is occurring. If you choose to compensate for it, this adjustment allows you to raise or lower the chain holding mechanism, which changes the inside top-plate angle it grinds on your cutter-teeth.

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Because the cain holding disk is arced, the shorter the cutter teeth become, the more their fronts drop down the arc. This makes the inside top-plate angle more blunt. You can use the thumb-screw adjustment und the swing-arm to compensate for this.

How to Shape the Wheel and Adjust the Diamond Dressers

A few paragraphs ago you learned there were two adjustments that affect whether or not your grinder cuts into the side-straps on the chain's chassis under the hood of the cutter-teeth. The second adjustment is actually the feed adjustments on your diamond dressers. Among other things, these determine how thick the outside edge of your grinding wheel is after you dress it. On a dressed wheel, the side should be about 3/32" thick. If your wheel is thicker than this, it is likely you will cut into your chain's chassis.

If you are tempted to make the edge of the wheel thinner than this as a general practice, we don't recommend it. This is the portion of the grinding wheel that cuts the inside side-angle and outside side-angle on your chain's cutter teeth. It also removes the upper part of the gullet. You want to run it as thick as you can.

You will also find it's best to run a wheel with more edge thickness when you are grinding .404" pitch chain. The reason for this is .404" chain has a higher profile than 3/8". These taller cutter teeth like a thicker wheel and wider side-cut.

Adjusting the Side-Cut to Remove Gullet Material

While on the subject of side-cut, we are often asked how to adjust a grinder so it removes the gullet material during sharpening. This is a reasonable question because if you are used to sharpening saw chain with a round file or round grinder, you don't create a gullet. Another reason to expect to be able to setup for this is that the manufacturer does it. The bad news is: you can't adjust any square-grinder to do it. Gullets must be removed in a second operation. So, why can the manufacturer sharpen this way and you can't? The answer is simple: They sharpen the cutter teeth before they assemble the chain. The chassis wasn't there when they sharpened the cutter teeth!

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Cutting on the chassis under the hood of cutter teeth weakens saw chain and should be avoided.

Adjusting the Dresser's Paths

The dressers are used for cleaning dull abrasive material from a grinding wheel. You also use the dressers to restore the corner in the grinding wheel and to control the thickness of the edge of the wheel. You adjust the "wing" nuts on the dresser shafts to move the dressers in or out. This is all part of basic grinder operation, but there is more tuning you can do with the dressers, and that is done by changing their paths.

Since the grinding wheel is ultimately what shapes the face of your chain's cutter-teeth, its shape has a big affect on your set up. The shape of the grinding wheel is in fact a "negative" of the grind it puts on your cutter teeth, so if you wish to change its shape, you must change the path of the dressers that shape it. To do this, loosen the bolt that mounts it to the grinder housing, pivot the mounting block, and then retighten the mounting bolt.

Why would you want to do this? Let's say your current setup grinds the outside side-plate angle almost perpendicular to the top-plate. You read information on Madsen's web site that says you should have a slight back-slope. You decide you want to try this, so you pivot the block that mounts the dresser that cuts the outside edge of the grinding wheel. You tilt the block a little towards the motor, tighten it back up, and redress the wheel. Now the wheel has a slightly different shape -- it flares out more at its base. Next, you test the new wheel shape by grinding a tooth on an old chain to test the change. Perfect -- the back-slope is just what you were looking for.

Yes, this is a little complicated. It may not be something you want to do if you are working on a baseline setup. However, if you are an experienced grinder operator or have help from someone who is, here is a little more advice about making adjustments to the dresser's paths:

1) If you are going to change the wheel's shape, make a small change, redress the wheel, and then test grind. A small change in a dresser's path can make a big difference, so do it in small amounts.

2) Mark the dresser block's starting position. You can do this permanently by etching the outline of the dresser block's in the main grinder housing with a metal scribe. For a less permanent mark, outline the dresser block with a fine-point felt-tip marking pen. These marks are important because they will allow you to go back to where you started from if you don't like the change you made. There is nothing more frustrating than trying to make a small tuning improvement and ending up with a worse set-up than when you started. You always want to have marks and notes that enable you to get "home."

3) Remember the shape of the grinding wheel is a "negative," so think about how you want to reshape the cutter teeth, then do the opposite to the wheel's shape.

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The dresser's paths are changed by pivoting their mounting blocks where they bolt on to the grinder's chassis.

How to Get a Crisp Corner in Your Cutter Teeth

The Simington grinder is built on a wonderfully simple swing-arm concept. Unfortunately, this simplicity comes with some costs. One, it is harder to grind a crisp corner in cutter teeth than it is on higher-end machines like the Silvey SDM-4 or Pro Sharp. These grinders have more sophisticated feed mechanisms that do not move the cutter-teeth across the grinding wheel. This characteristic causes the corner in the wheel to erode more quickly than it does on higher-end machines.

This isn't a problem when sharpening chains that are only "wood" dull. These chains require very little grinding to restore a fresh sharp corner. Unfortunately, sometimes you "rock" a chain and it requires a lot of grinding to sharpen. Our advice on sharpening these chains is: run them through twice. This sounds like a lot more work, but really isn't. It can also help keep you from overheating cutter teeth. On the first pass, focus on removing damage. After redressing the wheel, run the chain through a second time; this time restoring a crisp corner in the cutter's face. Since very little additional material will need to be removed, the wheel will hold its shape.

How to Tune the Grinder to get Similar Angles on Left and Right Cutter Teeth

Sometimes a grinder will not grind the same angles on the left-hand cutter teeth as it does to those on the right. This can be the result of a grinder being tipped over or rough treatment during transport. It can also be caused by an operator with bad tuning skills. Whatever the the problem, as long as there are no bent or broken parts, the problem can usually be fixed by shimming the motor. Shimming is how the plane of the wheel is matched to the sweep of the swing arm.

To measure whether shimming is necessary -- and if so, how much -- start by removing the chain. Next, swing the arm to one side. Back off the swing stops so the black plastic chain-holder is under the grinding wheel. With the thumb-screw on the bottom side of the arm, adjust the arm so the black plastic chain-holder just touches the underside of the wheel. With a pencil, mark the wheel where the chain holder touches it. Next, swing the arm over to the other side and rotate the wheel so the mark is over the chain holder. If the chain holder does not touch the wheel in the same manner as it did on the other side, you need to either add or remove shims from the motor mount.

You can use thin washers or shim stock to shim between the motor and its mount on the main housing. We sometimes see business cards and matchbook covers used for shimming, but don't recommend using them. Some type of thin metal material is best.

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The plane of the wheel must match the plane of the swing-arm. This is accomplished by shimming the motor where its mounts to the base.

Before you begin shimming, know that the amount of shim material you add (or subtract) to the base may have a greater affect than you think because it tilts the motor. When you add a shim to one side of the base, the shim will raise the wheel, but remember that at the same time, it will lower the wheel on the other side. So do this carefully. If you make reckless changes, you may find yourself chasing your tail. Take good notes, shim in small increments, and measure often. It may take a few attempts to get it right, so be patient.

Another thing that can affect the grinder's ability to reproduce the same angles on both sides of the chain is the fit of the chain in the black plastic holding disk. On most grinders, this disk has a .050" groove in one side and a .063" groove on the other. If you are grinding .050" chain and using the .063" groove by mistake, the chain will be loose in the groove. When it is loose, the grinder may produce inconsistent angles. It is important to grind .050" gauge saw chain in the .050" groove and .063" gauge saw chain in the .063" groove.

Holding the Cutter-Teeth in Place

Now is also a good time to talk about indexing and chain holding in general. The Simington 451C has a carbide-tipped tooth-locator that pivots from side to side. This long-wearing component is adjustable and gives trouble-free service. The only shortcoming of this design is this tooth locator is the only indexing feature the grinder has. More sophisticated square-grinders have additional mechanism that clamp and hold cutter teeth in position during grinding. The good news is, this lack of a "clamping" mechanism can be mostly offset by operator technique. Holding down on the chain during grinding will hold cutter-teeth against the carbide stop and prohibit them from lifting during grinding.

Positioning the Chain Holding Disk

You already know one side of this disk has a .050" groove cut into it and the other has a .063" groove. We are often asked when you switch from one groove to the other, how you know the exact position the disk should be in when you re-tighten the mounting screw. The answer is, within limits, it doesn't matter. The arc is the same no matter where you tighten it. The disk is really a round object with the edges trimmed off. So if you like it tilted a little ahead, that is fine. Our advice is to set it so its cut edges are close to vertical, but if you are a little off one way or the other, it doesn't matter. The disk will hold the chain in the same position.

Setting the Swing Arm Feed Stops

The Simington 451C has two swing-arm feed-stops. The purpose of these stops is to help grinder operators duplicate cutter-teeth. The way to use these stops is to begin your sharpening with the shortest cutter-tooth on your chain. Since you can't add material to cutter-teeth, this will become your model tooth. If you are sharpening a chain that has never been filed, all cutter-teeth should be the same length. But if your chain has been filed a few times or ground by an operator that didn't set the stops, you will find that some teeth are shorter than others. For a chain to cut straight and smoothly, all cutter-teeth should be the same length. If they are not, some teeth will take more wood than others. This can cause excess cutting vibration. Also, if the total amount of wood the right-side cutters take exceeds the total amount of wood taken by those on the left, your cuts will pull to the right.

To set these stops, first sharpen your shortest cutter-tooth without setting them. When this tooth is sharp, set the stop so the grinder will not remove any more material from this tooth. From then on, grind all the other teeth to this stop and all the other cutter-teeth on that side will match the model tooth's length. When all the teeth are sharpened on one side, swing the arm around to the other side. This time grind a model tooth to match the length of the cutter teeth on the side you just sharpened. You can use a caliper or some type of measuring device or just remove the chain from the grinder and place the cutter-teeth side-by-side to determine when you have a match. When you have created a model match on this side, set the new stop and grind the rest of the teeth to match it. When you are finished, all the teeth on both sides will match.

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These thumb-screws are the feed stops. Once set, they help you grind each cutter-tooth to the same length.

While this is technically the correct use of these stops, we find that only about half the experienced grinder operators use them. With practice, most operators get good enough to "eye" tooth length well enough to get good results. Our advice is, when you are learning to grind or if you like the idea of sharpening precisely, use the stops. If you decide at some point not to set them, that's OK, as long as you are satisfied with how your chain performs.

Aligning the Corner of the Wheel with the Corner in the Cutter Teeth

The Simington 451C square-chisel grinder is very tunable. In the hands of an experienced user, it is capable of doing an excellent job sharpening square-ground saw chain. The one thing to always bear in mind is: aligning the corner of the wheel with the corner in cutter teeth is critical. No amount of tuning can make up for bad corner alignment. On the other hand, if corner alignment is good, a poorly tuned grinder will probably still produce chains that make chips. So pay attention to corner alignment on every cutter tooth.

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This is how a cutter face should look. When it was being ground, the outside corner was perfectly aligned with the corner on the grinding wheel.


Hopefully this information helps you tune your Simington 451C grinder to produce top-performing saw chain. If you have unanswered questions or have a problem you can't resolve about this or any aspect of getting the most from square-ground saw chain, please contact us. We are here for you.

Click here for video on setting up and tuning a Simington #451C.

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Click here for video on troubleshooting a Simington #451C.