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Simple Carbide and Braze Joint Strength Tests
 This is a simple test to determine how easily your saw tips break and how good the braze joint is.
It is very simple. You braze a saw tip onto a narrow piece of plain, clean steel. Then you clamp the saw tip into a vise making sure that you just clamp the tip and not the steel bar. Do not clamp the tip too hard or you will break it before you start testing.
You lean on the end of the bar until something gives. In some cases the tip breaks, and in other cases the tip comes off. (Safety notes: you might want gloves or some sort of padding when you lean on the bar. If you do it right you have to put a lot of force to break the joint. Make sure that you are ready when it gives so that you don’t fall.)
You can also hit the bar with a hammer but be careful. It can really vibrate and it can really fly when it comes loose.
A good carbide braze joint is stronger than either the carbide or the steel. In this case you will break the carbide and will leave jagged chunks on the steel. There will be very little or no area where the carbide does not stick to the steel.
This is a good braze joint. If you do this with different grades of carbide you should be able to feel that some are harder to break than others. Most people can feel a difference.
When the tip comes off whole you can sometimes see that there is no braze alloy or very little braze alloy sticking to the steel. This usually means that the steel was dirty. It might also mean that the steel did not get hot enough but this is much less common.
If the tip comes off clean and there is no braze alloy sticking to the tip it often means a bad surface treatment on the tip or a good surface treatment that was badly pretinned. When this happens look at the braze alloy left on the steel. If the tip was badly plated you may be able to see a gray layer on the braze alloy. The braze alloy stuck to the plating but the plating came off the tip. Look for bubbles in the braze alloy to see if it was overheated.
Alloy tips We got started on this because we were asked to by a manufacturer of powdered metal saw tips. The tips were a bit hard for the customer to pretin but we solved that with our technology. Then the supplier asked if the tips were harder to break off than carbide.
When we tested these tips they came off clean and there was braze alloy stuck to both the steel and the tip. The braze alloy actually ripped in half. You can see a good amount of the gold colored alloy on both the steel and the tip.
It was very hard to rip the alloy but if you put enough force into a braze joint then something will eventually give. We do these with either our regular or our High Impact braze alloys. If you want a really strong bond we have a much stronger braze alloy but it melts at about 1800 F instead of the 1300 F to 1400 F for standard braze alloys. It is very, very strong but you do need to get the steel hotter.
Testing Finished Saws and Tools Hit it with a stick Put the tips on the saw then beat on them with a Stick. I like this because it is a good test, it worked very well and the guy that came up with it made a lot of money because his saws worked better. He was also criticized because he was having problems and no one else was.
Note: Many years ago this customer called me in because he was having problems with tip loss. On the way down I stopped to see another customer and asked him if he had a tip loss problem, the first guy said he didn’t have a problem. I talked to the second guy and then stopped into see the first customer again. Again I asked him if he was having a problem with tip loss. He said that he wasn’t having a problem. Sure the tips came off sometimes but it wasn’t a problem. The difference was in whether you considered tip loss a problem.
Hit it with a stick problem Put the tips on the saw then beat on them with a stick Problems: 1. No way to measure the force accurately 2. Everybody hits differently 3. This isn't the way impact is applied in actual use 4. Takes too long 5. Costs too much Benefit: It works
Testing Carbide for Impact StrengthImpact Test - Tinned tips versus untinned tips
Experiment and ResultsWe had a drop tower built with a weight. We drop the weight from different heights and measure where the parts break. This gives us a figure in foot-pounds. The weight is 20.665 pounds. We multiply that by the distance dropped. The saw tips were set on their sides so that the braze alloy wasn't on the top or bottom.
Untinned Impact at failure Pretinned Impact at failure Average 17.63 33.132 High 22.11 34.17 Low 11.78 32.44 Good carbide of any grade can take a huge amount of abuse before it breaks.
1. Wrap it in a cloth so the pieces don’t fly. Put the cloth on a concrete floor and beat the tips hard with a steel hammer. 2. Braze the carbide to a piece of steel. Clamp the tip in a vice and push on the end of the steel bar. You can break bad carbide with a light push. With good carbide you have to beat on it with a hammer.
Impact test 3 We took a tip, clamped it in a vise, put a chisel on the cutting edge and hit it with a steel hammer without chipping the edge.
Tip in vise Hitting tip with chisel and hammer
Impacted area at 10x and 60x. No chips even after being hit with a chisel.
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