Knew Concepts Blade Holding Improvement

[William Fretwell]

My Knew Concepts 5” titanium fretsaw was frustrating 2 days ago, sawing 7/8” Black Walnut. The blade would pop out at one or other ends with the knob as tight as possible.

Today I examined the holding surfaces, the end of a grub screw and the end of the knob screw. Shiny areas on each showed the contact area to be far smaller than that available.

Using an Allen key to hold the grub screw vertical I carefully flattened the end on a 1000 grit stone. The knob I held down on my sharpening table and used a 400 grit pad to flatten the end.

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The knob screw end was flat with a little hollow dot in the middle. I estimate that the available flat area was at least doubled, the blade width does not use the whole surface.

With the improved holding I was able to achieve scary tension on the blade, far more than previous.

Sawing the same wood I had no issue with the blade popping out as before over 2”. More cutting is needed but at the increased tension I’m sure it is much improved.

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So for all the design and expense it seems the quality of the screw contact ends is key.

If you try this and I do suggest you do! Keep the ends square to the stone, flat is the objective.
Will the ends work polish? Is it the microscopic scratches? Will they wear away? Time will tell.

[Assaf Oppenheimer]

Great tip, I think that the important thing isn't that the surface area be flat but that the two screw surfaces pinch at the same spot. Initially were the shiny spots on each centered?

I really wish a professional toolmaker would way in on this (@Rob Lee I would love your input on this). could you use a collet style locking mechanism? I realize a fretsaw blade isn't round, but I wonder if it could be adaptable...

[William Fretwell]

No Assaf the two curved streaks of shiny were lop sided, not remotely flat. They do need to be flat to meet, either that or one slightly domed and the other slightly curved in to match to increase the pinch. The domes would be very slight as the blade is very stiff over a short distance.

[Tom M King]

Thanks for that. I have one, and never could understand why people like these saws so much for that reason. The simple mechanism on the old standard German jewelers saw is much simpler, and holds much better. It has Many times the surface area in contact with the blade ends, and the flat sided thumbscrews are much easier on fingers.

[Assaf Oppenheimer]

fair point, I stand corrected

[Jim Koepke]

Most likely the Knew Concepts fasteners were purchased in bulk. The supplier may have been changed over time.

Not all fasteners are made with nice flat ends. In fact very few are made with flat ends without being special purpose screws.

My Knew Concepts saw has not been disassembled. Maybe something to look at next time in the shop.

jtk

[Phil Mueller]

Thanks William! I’ll definitely give mine a look. I’ve had the same problem as you.