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SawDoc.com Troubleshooter

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A friend of mine had a job checking the quality and quantity of dairy herd production.  He was just out of High School.  One day, he went to inspect a herd that had consistently been the best producing herd in three counties for more than twenty years.  As he walked into the barn, the farmer asked him "What am I doing wrong?"  Of course my friend was taken by surprise. "It is hard for me to think that there is much I could tell you.  You have done the best of all the farms I've ever seen." he told the farmer.  "Well," said the farmer, I've been at this for over twenty years.  I've learned a lot and tried a lot.  But maybe there is something I'm missing.  Some habit that I've fallen into that isn't the best.  Something I've forgotten.

We all know a lot.  We all have tried many things, and forgotten some.  And we all have our habits and ways of doing things.  On a mill, there are many things to remember, a lot of things you know to make things work right.  When a problem comes up, we know what to try to get things going again.

The troubleshooting list that follows is just a little reminder of some of the things that we might otherwise not think of.  I have tried to include everything that I know of for fixing a problem with the mill.  But I've not seen every problem, nor fixed everything that could go wrong with a mill.  The list is of the main things I've seen work to make the problem go away.

After the problem, you will see a list of things to check, with a number after it. The number tells you where to go in this guide to get more information on that particular item.  Click on the cause to go to that section of this guide.

 

Symptom Cause

Saw leads into log  1.   Bad collar
2.   Too much lead

9.   Saw heating in rim 
See "Saw runs hot in the rim"
3.   Teeth sharpened into the log side
3.   Teeth swaged more to the log side

3.   Teeth damaged on board side
5.   Shoulders bent into log
6.   Feeding too slow
7.   Board side guide too close
8.   Saw out of plumb
4.   Shank edges worn
12. Saw running faster than it is tensioned for
11. Saw dished out of log

Saw leads out of log 1.   Bad collar
2.   Not enough lead
9.   Saw heating in rim 
See "Saw runs hot in the rim"
3.   Teeth dull
3.   Teeth sharpened out of the log

3.   Teeth swaged more to the board side
3.   Teeth damaged on log side
5.   Shoulders bent out of log

7.   Log side guide too close
4.   Shanks edges worn
8.   Saw out of plumb
12. Saw faster than it is tensioned for
11. Saw dished into log

Saw leads in and out of the log 1.   Bad collar
2.   Improper lead
5.   Shoulders weak
7.   Guide too far in from the rim
7.   Guides not set properly
9.   Saw heating
3.   Dull or damaged teeth
4.   Shank edges worn
12. Saw running faster than it is tensioned for

Saw runs hot near the eye 1.   Bad collar
2.   Not enough lead
3.   Dull teeth

9.   Hot bearing (nearest to the saw)
Loose bearing (nearest the saw)
12. Saw running slower than it is tensioned for
11. Saw dished out of log

Saw runs hot in the rim 1.   Bad collar
2.   Too much lead
3.   Teeth not swaged enough
4.   Shanks worn
6.   Feeding too fast or too slow
7.   Guide pin or pins too close
10. Arbor bent
11. Saw dished into log
12. Saw running faster than it is tensioned for

Saw scores log when sawing 2.   Not enough lead
5.   Teeth and shanks not lined up
5.   Shoulders bent into log
7.   Guide pins not adjusted

Saw scores log on return

2.   Not enough lead
3.   Teeth dull
Loose track
Side play in carriage
9.   Saw heating in the rim
see "Saw runs hot in the rim"
12.  Saw tension off  

Saw throws sawdust from the back 4.   Shanks worn
2.   Not enough lead
3.   Teeth dull
6.   Feeding too slow
5.   Teeth and shanks not lined up
Side play in the carriage
9.   Saw heating

Saw hammers, pounds, or chatters on the guide pins 1.   Bad collar
Saw speed fluctuating
9.   Saw heating
10. Sprung arbor
12. Saw bent
Drive train pulley out of balance
Loose arbor bearing
12. Saw running slower than tensioned for

Variation in the thickness between boards (not the dog board) Set works not accurate
Gears worn on Set works
4.   Worn shanks
3.   Teeth dull
Saw not maintaining a constant speed
Husk not secure
Incorrect scale setting
Dogs not secure
Side play in carriage
7.   Guides not set properly
6.   Feeding too slow
3.   Cutting edge of teeth to narrow
12. Saw tension off

Dog board varies in thickness from end to end 1.   Bad collar
Springy saw logs
Track alignment off
Side play in carriage
Knees not aligned
3.   Teeth dull
4.   Shanks worn
11. Saw dished
2.   If the back end of the board is thin, too much lead
2.   If the back end of the board is thick, not enough lead

Dog board varies in thickness from top to bottom Knees out of alignment
Tracks or head blocks out of level
12. Saw improperly tensioned
Bottom dog not working correctly
Bases of head blocks worn on the outer ends
8.   Saw out of plumb

Saw will not hold teeth 4.   Shanks worn
Saw worn
3.   Teeth dull
3.   Teeth have wrong hook
Defective sockets in the saw
 

1.  BAD COLLARS

     How the saw blade is held is one of the most crucial factors that affect blade performance, and therefore the performance of your mill.  You may have noticed that your saw hammerer often suggests that you check your collars.  Most of the time, that is where you should look.  Three out of four times, in my experience, bad collars are to blame for problems with the mill and the blade.

How to check

    The easiest check for bad collars is to hang the blade on the mandrel, then hand tighten the nut.  Set the guides so they are just slightly away from the blade (as you would set them normally).  Then tighten the nut with a wrench in the usual manner.  Make sure the blade does not move as you do this.  If the blade is forced over to one or the other of the guides, you have a problem. 

    Another check you might try is to use a straight edge.  As before, hang the blade on the mandrel and hand tighten the nut.  Put the straight edge on the blade and see if there is a dish.  (If there is, you may need to get your blade hammered.)  Now, tighten the nut and check for a dish with your straight edge.  If one shows up at this point, you have a problem.

    Before you decide that your collar is bad, it would be wise to try another check before you go to the trouble and expense of having the collars machined.  First, remove the blade.  Then rub chalk or a marking crayon all over the machined surface of both collars.  With a accurate straight edge, scrap off the markings.  If your markings are not removed from the outside 1/8 inch or so of the collar, and no where else, it is worn.  And worn in a place that is going to give you trouble.

   One last thing to check is that the diameter of both collars is exactly the same.

What to do

    If your collars are bad, there is only one way to cure them.  You will have to have them machined.  The following diagram will help your machine shop do it right.

   There is, however, a fix that might work for you. (This should be considered a temporary thing, however.  If your collars need to be machined, you should do that as soon as possible.)  Once you have figured out which of the collars is bad, a paper washer, cut from a medium weight sheet of paper (a manila envelope works fine) so that it is about 3/8 of an inch wide and no bigger in diameter than the outside of the collar, can be put on the bad collar.  Hold the washer to the collar with a little grease.  If both collars are bad, use two washers.  If the saw is being dished toward the husk (the teeth forced into the log), put the washer on the fast collar.  If the saw is being dished toward the log (the teeth forced out of the log), put the washer on the loose collar.

2.  LEAD

    Next to bad collars, improper lead causes the most problems with the mill.  Lead is put into the saw to overcome the tendency of the blade to saw out of a log when slabbing and to give clearance at the back of the saw so that the teeth do not hit so much on the gig (or return).

How to Check

    One simple way to check the lead is to mark a tooth on the saw. Loosen the guides. Measure the distance between the tooth and the end of the head block. Turn the saw and move the carriage ahead so that the marked tooth is exactly at the same relative position to the same head block and measure again. For a 48 inch saw or smaller, 1/32 of an inch is correct.  For a larger saw, 1/16 of an inch is desired.

    Another way to check is to run a string along the guide track so that the string follows the track exactly.  Then, using the same marked tooth, measure the front of the saw to the string.  Next, rotate the saw and measure from that tooth (that is now in the back) to the string.  This method also gives you an idea how straight your track is.

What to do

    Lead is adjusted by moving the saw end of the mandrel slightly.  Some folks call this "sluing the mandrel". Loosen all of the mandrel bearings from the husk and loosen the belts as well.  You need to do this so that the mandrel is not put in a bend or bind when you move the saw bearing.  Now, move the bearing block nearest the saw to the left or right as needed to put in the proper lead.  Make sure the blade is not touching the guides for all this.  Never use the guides to put lead in or out.  When you have the lead that you want, tighten the bearings.  Check the lead one more time to make sure it hasn't moved by tightening the bearings.  

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3.   TEETH FILING AND SWAGING

       No other task you do every day on your mill is more important than the maintenance of the teeth on the blade.  The teeth make the cut and the blade follows that cut.  If the teeth are not kept in good shape, you will not make good lumber. Bad tooth maintenance can lead to other problems with the performance of your mill, and can damage the saw blade.

How to Check

       Take the time to look at your teeth.  Except for being worn back, the shape, angle and width of the teeth should look like a new tooth.  It's that simple.  There are gauges to measure the proper angle and width of the bits and they might be of help.

What to Do

    Take the time to do it right.  There are some things you should not do.  Do not file a lead into the saw.  Do not file the back of the tooth.  Do not use a heavy hit when swaging.  

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  4.  SHANKS

    Some people call them rings, holders or gullets.  No matter what you call them, their job is to hold the teeth in place, and control and hold the sawdust until the tooth leaves the bottom of the cut.  When the shanks become worn or damaged, they can not do their job.  And if they are worn a lot, that can cause a dish in the saw , affect tension in the saw, and they will not hold the teeth securely.

How to Check

    As with the teeth, take a good look at your shanks.  You can see if they are worn or damaged. You will also need to check the amount of spring in the shank.  Even an old shank should feel tight when it is put in.  When you change teeth, take note of how much effort it takes to replace the shank.  If it is going in too easy, the spring may be gone.  

    To check for wear, use a micrometer to measure the shanks thickness.  If the shanks are more than .015" thinner than a new shank, it's time to put new shanks in, especially during the winter months.

    What to Do  

    If the shanks are worn thin, replace them.  If the corners of the shank are rounded, but the shank is not too thin, square up the edges with a round file.  If there is still enough thickness left in the shank, but the spring is gone out of it, you can peen the inside edge of the shank to tighten it up in the socket.

    If you need to replace the shanks, try to replace every other one and wait for some time later to replace the rest.  This will lessen the affect on the tension of the blade.

    If you are working with an older blade that has some wear in the sockets, it might be necessary to use oversized shanks if standard new shanks do not feel tight enough as you install them.  Try to wait as long as possible before going to the oversized shank as they might stretch the socket.  A saw that has stretched sockets and will no longer hold the teeth securely is no good, and should not be used.  The use of oversized shanks before they are needed will take years out of the life of a saw.

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5.  TEETH/SHOULDER ALIGNMENT  

Even with proper tooth maintenance, the cutting edges of the teeth may not cut properly unless they are aligned properly.  Many of the blades that come into my shop have teeth and shanks that are well maintained.  But the blade will not work well, even after it has been hammered.  I have rescued blades from the sign painter by fixing the teeth and shoulder alignment.

How to Check

    The first thing to check is that the teeth are aligned with the shanks.  This is easily seen by closely looking at the teeth.  Most filers do this as they install teeth in the blade.  Where the problem comes is when the shoulders are not straight.  Even with the teeth lined up with the shanks, if the shoulders are not straight, the teeth are not lined up properly with the blade.

    The best way to check the shoulders is to make or get yourself a gauge.  Holding the gauge against each shoulder (after the gauge has been set to account for any wear on the shoulder), you can quickly see where the problems are. (This same gauge, with a different adjustment, can be used to check the alignment of the teeth with the saw.)  You can also use a good straight edge held along the shoulder.  Make sure there is no gum on the blade where you are working.  When using the straight edge, make sure you compensate for the wear of the shoulder.  Use the edge on both sides of the blade to get an eye for the amount of wear.

    After years of use, the shoulders begin to wear.  As they become thinned, they loose the strength to stand up against dodging hard spots.  Older saws with thin or weakened shoulders will often stray in the cut.  These worn shoulders will need to be looked at and aligned more often.  

What to Do  

    When you are sure a shoulder is bent, you can straighten it using a hammer and a bucking bar.  Place the bar just above the guide line (be careful not to go in the guide line) on the side the shoulder is bent away from.  Hit the shoulder with the hammer near the outside edge of the blade.  It may take a few tries.  After each time you have tried, check the tooth's alignment with the shank and correct that before checking the shoulder alignment.

    Another way to bend the shoulders back to proper alignment is to use a wrench.  A good sized adjustable wrench or what was called a carriage wrench will work fine, but be careful it does not slip on you.  As above, it may take a few tries to get the shoulders back to plumb, and after each try, align the teeth and shoulders before checking.

    One important thing to remember.  Never try to bend a shoulder that has been welded unless you heat the shoulder to 500 degrees Fahrenheit.  

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6.  FEED

    Different saws running at different speeds on different mills have different feed rates.  But every saw on any mill running at any speed has the same rate of feed per tooth.  Most operations I've been to tend to feed too slow.  This is inefficient and can cause saw problems.  So can feeding too fast.  You will need to figure what rate to feed your blade for your mill to get the best production and life out of your saw.

How to Check  

    What you want to find out is how far the log is traveling past the blade in the cut for each revolution of the blade.  Take a look at a number of average sized boards you have cut.  Even with the best tooth maintenance, there is probably a tooth or two that is cutting heavier than the others.  Each time that tooth cuts the log, it will leave a mark.  Measure the distance between the marks in the middle part of the board.  Unless you are feeding at the maximum rate the carriage will feed, measure a few boards to get an idea of your average feed.

What to Do    

  The manufacture's recommended feed rate per tooth is 1/10" for hard or frozen wood and 1/8" for softer wood.  The feed for your saw per revolution would be the per tooth rate times the number of teeth. A 52 tooth saw cutting oak should have a feed rate of nearly 5 1/4" (52 X .10" = 5.2") for instance. 

    If you cannot feed at the proper rate, you will need to change some things on the mill.  A blade with less teeth would feed at a slower rate.  Slowing down the revolutions per minute of the blade will give you more power to the blade.  More power from your motor or engine also could allow the proper feed. 

    If you are feeding too fast, you should slow down the feed.  Too much feed can pack the gullets, causing a build up of heat.  And if you pack the gullets full, the blade will quickly stop in the cut causing all sorts of problems.  If you have the power to consistently feed too heavy, you might think about getting a saw with more teeth.

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7.  SETTING THE GUIDES

    The teeth of the saw are on the rim of a relatively thin disk of metal.  The main support for the blade is the collar, which is some distance away from the teeth.  The guides help to keep the teeth straight in the cut.  The guide is used only to steady the saw.  Never use the guide to lead the saw.

How to Check  

    The guide should be set as high as possible to just clear the head blocks.  The pins should clear the bottom of the shanks by 1/4" or so.

    When the saw is turning, the guide should not touch the blade, but should be away from it just a little bit.  You should just be able to see a hint of light between the guide and the blade.

    The guide itself should be tight and securely mounted.  And the pins should not be too large.

What to Do  

    Move the guide to the proper position on the mill to be as high as possible and to 1/4" of the shanks.  Set the clearance of the pins to the blade when the saw is running.

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8.  PLUMB OF THE SAW, LEVEL OF THE CARRIAGE  

    The blade must be plumb and the head blocks level to make good lumber.

How to Check

    A blade that is not plumb with a carriage that is level will leave a dog board (the last board) that is wedge shaped from top to bottom or edge to edge.  If the top of the blade leans toward the carriage, there is a tendency for the saw to lead into the log.  And when the blade leans toward the husk, the saw will tend to lead out of the log.

    To check the plumb of the blade, use a good plumb bob and line.  Hook the line on a shoulder at the top of the blade, dropping down so as not to hit the collar.  The line should not touch the collar or a tooth or shank.

    A good spirit level is used to check the level of the head blocks and the carriage track. Move the carriage along the track to check the level along the entire length of the track. If possible, a heavy log on the carriage for this check will show up any weak or soft spots in the track. A line stretched along the guide rail and slightly above it can be used to check for any bumps or dips in the track.

  What to Do

    To plumb the saw, you can wedge the bearing blocks of the mandrel as needed, or you can level the husk itself.  The leveling of the carriage or the tracks depends on your mill and its set up.

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9.  SAW HEATING  

    A blade that is running properly will be only 5 degrees warmer than the air temperature.  That slight heating should only be in the rim from the friction of the teeth cutting the log.  If you have a blade that is heating more than 5 degrees, it will not saw properly.

How to Check

    After you have sawed for a while and suspect that the blade is heating up, stop the mill and feel the blade.  Take note if the blade is warm in the eye or the body or the rim.  Is it heating all around the blade or is it just in one section?  Where the blade is heating can tell you a lot about what is causing the problem.

What to Do

    If the saw is running hot at the eye or at the rim, go to that section of this guide to help you find the solution. If it is heating only in a section, it may have a fold or lump in it that might need to be hammered out.

    Some thing to remember is that any heating of the blade can affect its performance.  If the sun beats down on the saw, it can heat it enough to make trouble.  If a slab gets wedged against the blade, friction will heat the blade in a hurry.  So look around for anything that will cause heat.  It only takes 5 degrees to make a problem.

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10.  BENT ARBOR  

    It isn't very often that this is a problem with a mill, but it can happen.  It would be something to think about if you have hung the blade up in the cut, or pushed a log over onto the blade.

How to Check 

    The most accurate method would be to use a dial indicator.  After you have secured the indicator, take a reading on the arbor at the place on the arbor past the fast collar where the blade would be. Turn the arbor. If the total indicator run out is more than .004", your mandrel is bent beyond tolerance.

    Another check that will isolate the problem, but is a bit less accurate, would be to set the guide pins so they are the same distance from the saw blade. Turn the blade until it hits a guide.  Take off the outside collar and pins and turn the saw 180 degrees without turning the arbor.  Replace the collar and tighten it up as you would normally. Again, do not turn the arbor.  Look at the guide.  If the saw is touching the same side of the guide as before, the arbor might be sprung.  If the saw is touching the other guide pin, the saw may be sprung (or "twisted" or "bent.)

What to Do

    If your arbor is bent, it will have to be straightened or replaced.  

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11.  SAW DISHED

     A saw is dished  when the eye of the saw is not flat with the rim.  That is, the saw is shaped like a bowl.  A dish can come from worn shanks, pushing a log over on the blade, running the blade with something wedged against it, running the blade with the lead forced in with the guides, excess tension and/or a bad collar.

How to Check

    Put a long (4 foot or longer is best) straight edge along the log side of the blade.  The straight edge should not rock nor show much clearance between the blade and the edge. (A thinner gauge saw or one turning faster than 650 r.p.m. may show a slight dish.)  To see if the collar is pushing a dish into the blade, do this check again with the collar nut loosened to only hand tight.

    Another check is to use the plumb bob.  If the saw is plumb, the line will show any dish if hung from a shoulder and not touching the collar or any shanks or teeth.  

What to Do

    Before you can fix the dish, you need to know what is causing it. If the saw is dished because of bad collars, you will have to deal with that (see the BAD COLLAR section ).

Saw Dished

         A saw can be dished when the shanks are worn.  As the shank wears, it loses its strength.  This allows the rim to shrink or contract causing excess tension in the body of the blade. Replacing the shanks can sometimes take the dish out as the new, stronger shanks will stretch the rim, relieving the excess tension.

    If the collars are good and the shanks are not worn too much, but you still have a dish, it is time to get the blade hammered.

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12.  SAW TENSION  

The amount of tension in a saw blade is determined by many factors.  When you get your saw back from the saw pounder, it has been tensioned for your operation.  If the saw runs on the mill for a short time and then begins to act up, there may be something wrong with the mill that is causing the tension of the saw to change.  If all things on your mill are close to perfect, the tension in the saw will gradually increase as the shanks wear.  Replacing the shanks may bring the tension back to where it should be.  Unless you have a wreck, the saw may not need to be hammered for years.  In practice, it seems I see saws back in the shop every year.  If you have to have the saw pounded more often than that, start looking for other problems with the mill.

How to Check

    When a saw is running and has the correct tension in it, it should stand straight with no weave, flutter or wobble.  If the tension is off, it will not stand straight.  It will also saw inconsistently, and may heat up.  If it begins to act up after you have sawed for a while, there may be some problem with the mill that is causing the tension to change (most likely something causing the saw to heat).

What to Do

    If the saw works well at the beginning of work, but soon acts up, check for other problems with the mill (collars, lead, tooth alignment and maintenance, guide adjustment, etc.).

     If the saw is "open" (that is, having too much tension in it), replacing the shanks may well cure the problem.       

  

Saw Running
Properly

Saw "FAST"
Too Much Tension

Saw "OPEN
Too Little Tension


     If the saw looks "open" or "fast" (not enough tension) from the time you first start up, and the shanks are not the problem, it's time to get the saw hammered.

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