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Saw Blade Analysis on a Bad Saw Blade

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Saw Blade Analysis on a Bad Saw Blade

John Gammelgard of Weyerhaeuser is a really good saw filer.  His command of analytical data is truly impressive.  Anyway someone sold John a saw blade that didn’t run well.  It came to us for analysis.  This had to be done in a few hours.  We did this visual inspection with a Proscope.  Visit our How to Braze Index  to find articles on brazing, and surface treating to see how the following situation could have been avoided.


Executive analysis


I see maybe ten kinds of problems here depending on how you sort them out. 


  1. Two kinds of tips - Most of them too long

  2. Uneven side clearance

  3. Not all tips were side ground

  4. Dirty plate   (Huge voids between the tips and the plate)

  5. Dirty and /or bad surface treatment on the tips

  6. Breakage – heat stress

  7. Breakage – impact – (there are certainly better grades)

  8. Brazing – one side too hot and one side way too cold

  9. Overheated braze alloy

  10. Probably wrong flux

  

Note: this was a pretty quick analysis and I didn’t have information on the carbide grade or source, the braze alloy or the flux used.    I didn’t do a whole lot of interpretation but, then, I didn’t really need to.  The pictures pretty well speak for themselves. 


Tom Walz

  

Two Sizes of Tips

Some tips are obviously shorter than others even allowing for the ATB grind.  The short tips also seem to be about 0.010” thicker. 

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Grinding

There is a difference in side clearance from one side to the other and grinding within a side varies as well.  Some of these measurements are open to interpretation due to rounding.    


We like to see the side clearance the same on each side and variance at least within .001” and preferably closer to 0.0005”

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Ground & Unground Tips – At least some of the short tips are not side ground 

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unground

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ground











Brazing

One side got much more heat during brazing than the other side. 

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Cold side Hot side   


These are pictures of two sides of the same four tips.  The top row shows significantly more flow onto the steel than the bottom row.  I think this is both heat and cleanliness. 

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Voids in the Braze Joints

On the cold side of many of these tips there are holes between the plate and the tips where there should be braze alloy.

Gaps 30 x std. light

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Gaps 50 x std. light

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Gap 50 x with wood in it

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Proof of Wood in the Gap

The left picture is a 30 x with standard light.  The gap shows up as a dark spot due to shadow. The right picture is polarized light.  You can see gold color of something foreign in the gap.  It is remarkably close to the color of the braze alloy in appearance but more orange. 

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Right is a picture of the same tip after I used a pin to dig out some material.  You  can clearly see where material has been scraped out.   The fact that you can scrape it out means it was not braze alloy.  

  

Plate Cleanliness

Brazing to a clean plate is very important to the quality of the finished tool.  There are many tips and techniques in our Cleaning Steel Before Brazing article.


This is good flow back onto the steel.  There is too much flow because there was too much heat but it is pretty nice even flow.

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Here the flow is uneven because the plate was not cleaned well.


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Right shows a big, obvious notch where the plate was dirty

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Breakage – 2 kinds - Heat Stress & Impact

The smooth curves of these three look a lot like the standard heat stress curves

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These four look a lot like impact damage


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