Why Does This Slanted Angle Make the Fireball Hardtail Vise So Strong?

Vises
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There’s something very interesting going on with the jaw design on the Fireball Hardtail Vise, so let’s take a look. (to watch the video about this, go here: https://youtube.com/shorts/KXSpENIi8_0)

The Hardtail Vise has thick cheecks at an angle on its dynamic jaw
The Hardtail Vise has thick cheecks at an angle on its dynamic jaw1920×3413 391 KB

Have you noticed this angled shape at the front of the stationary jaw? It’s not just for aesthetics. That forward-protruding cheek isn’t an accident, it’s doing a lot of heavy lifting behind the scenes.

The Hard Tail vise cheeks extend past the jaws
The Hard Tail vise cheeks extend past the jaws1920×3413 333 KB

That area of the vise takes on a huge amount of stress when clamping. On older vises, that’s exactly where they tend to crack right in line with the jaw. But by pushing that angle forward and thickening the material, it shifts the stress path. So instead of the force going straight through a weak point, it now has to work harder to create a failure, essentially separating the material across a wider, more reinforced section.

Older Vises often break at this part
Older Vises often break at this part1920×3413 540 KB

This was confirmed with CAD modeling and testing, and it’s a simple but smart design move that makes this vise way less likely to break under load.

The Fireball Hardtail dynamic jaw is virtually indestructible
The Fireball Hardtail dynamic jaw is virtually indestructible1920×3413 439 KB

Wilton, Reed, and Yost vises will always have this issue. You’ll never see a Fireball Hardtail crack in that spot and this is why.

Pretty slick trick for such a small change.

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“This was confirmed with CAD modeling and testing”- The actual engineering technique is known as finite element analysis (FEA). I didn’t do FEA analysis but did sit between two engineers who did. FEA is one of those computationally INTENSIVE techniques (It is impossible to do without computers- You’d die before you could complete the math). But the assertion about putting the meat where the stress is is absolutely correct. I’d love to see a FireBall fan with FEA skills step up and do the model. We’d all love to see the color map showing the high stress areas of the two different vises….

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Sounds interesting to look at!

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FEA is really cool! I never actually did it but I did help the analysts around me who did. I wish there was someone to mesh and analyze the hardtail in comparison to "a “regular” vise (without the special angled bulge). It takes a lot of computing power.

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I did an FEA on my CNC frame design. Here is a screenshot of one of the earlier revisions:

image
image1049×1023 211 KB

I wanted it to comfortably hold at least 5500 lbs. From the above you can see how the lighter / green colors indicate the greatest stresses. This lead me to add supports under the four 4”x6” square tubes on either side and also thicken the top front steel plate.

There is a learning curve but I did this in FreeCAD with the FEM workbench. It is all open source and free so you don’t necessarily have to buy big expensive software. I could probably run one if someone had the CAD models already created.

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