Working with wood: how to avoid burn marks when ripping

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In this article, we’ll show you some woodworking techniques for your home workshop. You will learn how to properly debug the circular saw so that it does not spoil the workpiece when ripping. The article contains techniques and tricks when working with longitudinal blanks.

Working with wood. How to avoid scorch marks when ripping

The problem of burnt hardwood (oak, beech, birch) when sawing along the grain on a circular saw is solved only by grinding. And this is an additional operation, and quite time consuming. The appearance of burn marks is a sure sign of incorrect machine settings, while the overloaded engine suffers, the disc is worn out and the workpiece deteriorates.

Most likely causes of burn marks

  1. Resinated disc. The resin can be quickly removed with a special cleaner or washed off with ordinary solvent (this is a little longer).
  2. Blunt or broken disc soldering. They can be restored, replaced or sharpened in a special workshop, but it is easier and faster to replace the disc with a new one..
  3. Parallelism skew of stops.
  4. Incorrect workpiece feeding.
  5. Structural defects in wood.

Working with wood. How to avoid scorch marks when ripping

The first two are relatively easy and quick to eliminate by cleaning or replacing the cutting blade. The other three are more serious and below we will tell you how to deal with them..

Reception of setting the parallelism of the disk and the stop by improvised means

  1. Set the stop 100 mm from the disc.
  2. Take a block 60–70 mm long and screw a round head screw into the end. This head, when the bar is pressed against the stop, should cling to the disc tooth.
  3. Mark this tooth with a marker.
  4. Slide the workpiece with the screw to the other side of the disc and rotate the disc itself until the marked tooth is aligned with the head of the screw.
  5. The force when the tooth engages the screw head should be the same at the beginning and at the end. This can be determined by ear – the metal of the disc perfectly reproduces vibrations. If the sound at the beginning and at the end is different, you need to more accurately set the saw device in accordance with the instructions (methods will be different for different models).
  6. Professional models with stationary saws have workbench adjustment *. To do this, loosen a few bolts (with which the workbench is fixed to the bed). Carpentry machines allow for precise adjustment of the position of the saw unit.

* This refers to the part of the stationary saw, which is also called the “saw table”.

Precise parallelism adjustment with hour indicator

This is a more professional and accurate method, but it requires a special device – the ICh-10 hour indicator. In this case, the reference point for the stop is the disc groove.

  1. Install a rail or bar in the groove.
  2. Install ICh-10 between the rail and the limiter. Then reset the readings.
  3. Using ICh-10, adjust the stop according to the readings of the instruments – the difference in readings should be zero.

Working with wood. How to avoid scorch marks when ripping

As you can see, this method is much faster and more accurate (graduation 0.1 mm), but such a device costs about 20 cu. e.

The trick when aligning the disc

The saw unit is always fixed with several bolts. Therefore, when adjusting it, it is best to use one of them as an axis around which the entire mechanism or disc will move (by millimeters):

  1. Select the “axle” bolt based on the location of your saw mounts.
  2. Loosen it and then tighten it slightly more than hand tighten.
  3. Loosen the rest of the bolts carefully until they are free.
  4. Set the mechanism or disc to the desired position, focusing on the readings of the ICh-10 or the alignment device.
  5. Do not press on the parts of the mechanism to move it, but tap on reliable parts – this will be more accurate.
  6. After reaching the exact position, first tighten the “axle” bolt – this way the adjustment will not be lost.

This method is relevant for any stationary circular, reciprocating or band saws.

Riving knife trick

The final step in fine tuning the machine is to check and adjust the riving knife. This is a strip of metal behind the saw blade that opens the cut, preventing the parts from being pinched. It must be strictly vertical and parallel to the disc. Parallelism is checked by the usual rule. For safety reasons, on some models, pressure toothed plates are installed – they prevent the workpiece from retracing (the disc rotates towards the operator). Their adjustment is reduced to checking the spring force.

Sometimes, when the wood has a high density, the standard riving knife is not enough – the unfinished workpiece tends to return to its original position and a clamping occurs behind the riving knife and inevitable burn marks. In this case, masters use a simple solution that has no analogues in terms of simplicity and reliability: an ordinary spacer wedge on a leash.

Wedge for circular on video

How to make a spacer wedge:

  1. After the workpiece has passed the standard spacer knife, insert a wooden wedge into the cut.
  2. Next, complete a full pass of the workpiece and fix the extreme position of the wedge.
  3. Select a fixed point above the machine and adjust the length of the leader from point to wedge. It is advisable to use spring material.
  4. Tie the leash to a fixed point (details).
  5. After full passage of the workpiece, the wedge will be removed from it, and remain on the leash.

For convenience, when cutting many identical parts, you can adjust the leash length.

Correct feed of the workpiece

Marks and spoiled workpieces are the easiest consequences of incorrect workpiece feeding. Even well-set knives and stops will not help if the workpiece is not fed correctly – skewing, jamming, backward movement or uncontrolled jerking of the workpiece is very likely. Given the tremendous speed and strength of the circular saw, even a small, light workpiece can injure a person..

Correct filing rules:

  1. Vertical clamp. No matter what angle you start the workpiece, remember that it must be firmly pressed against the saw table at a distance of 30-100 mm from the blade.
  2. Horizontal clamp. Tight contact with the stopper will ensure a smooth run of the workpiece.
  3. Wind and control the workpiece with both hands. This rule follows from the first two – one hand presses to the table, the other to the stopper.
  4. For small parts, make or purchase a pusher – it will avoid dangerous proximity of hands and saw blade.

Working with wood. How to avoid scorch marks when ripping

  1. Apply the “clamp-comb”. This device is freely sold (price from $ 3), has many options. You can also make it yourself (especially if your circular is homemade) according to specific sizes. To do this, you need to make a lot of cuts in the bar and cut the “comb” at an angle of 75 °.

Working with wood. How to avoid scorch marks when ripping

Of course, when working on machines, you should not be distracted or do other operations in parallel..

Structural defects in wood

Defective timber is usually discarded during selection. Working with such blanks is fraught not only with burn marks (they will appear necessarily even on a precisely set machine), but also injuries. At the same time, the material can be clean, without rot and knots.

The main signs of structural defects:

  1. Longitudinal curvature across the thickness of the workpiece. Craftsmen call such blanks “saber”. If the curvature is small (the deflection height is up to 10 mm per 1 m), the workpiece can be pressed harder when cutting. Billets with a larger curvature are rejected.
  2. Longitudinal curvature across the width of the workpiece. The popular name is “rocker”. The rule is the same as with the “saber”, but the allowable deflection is 20 mm.
  3. The wood fibers are not parallel to the workpiece. The most dangerous type of defect is that there are significant internal stresses in the workpiece. When sawing, they are released and it can behave unpredictably. The only option to use such a workpiece is to level it with a thickness gauge (double electric plane).

Working with wood. How to avoid scorch marks when ripping

The first two cases can lead to burn marks, the last one will certainly. Sawing products of skewed wood will also have a curvature and must be in a relaxed state after installation..

Timely inspection of the machine will save you from the unpleasant obligation to remove burns and burn marks from the workpieces. Remember that all manipulations with the machine must be carried out after disconnecting it from the network..

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