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.
I see maybe ten kinds of problems here depending on how you sort them out.
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.
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.
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”
Ground & Unground Tips – At least some of the short tips are not side ground
One side got much more heat during brazing than the other 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.
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.
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.
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.
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.
Breakage – 2 kinds - Heat Stress & Impact
The smooth curves of these three look a lot like the standard heat stress curves
These four look a lot like impact damage