Blade slot for backsaw handle.

[swagman]

Hi all. I just completed a trial using the slitting blade mounted to a router table to cut the blade slot in a backsaw handle. The end results were extremely good. The critical thing I found with the trial is getting the operating speed of the router correct. The router I have mounted in the table is a Makita 1/2" 22,000 rpm single speed unit. With the slitting blade mounted there was a slight vibration within the blade at full operating speed. Using the Jaycar motor speed controller I adjusted the rpm dial down to eliminate any of this vibration and at a speed I felt was adequate to complete the slot within the handle.



The slitting blade I was using was hss 75mm o.d. x 0.05mm thickness. The o.d. gave me an effective cut of 45mm outside the top flange of the slitting blade holder. The 0.05mm was slightly under gauge to the 0.020 thou saw plate I normally use for my backsaws. As it ended up this was ideal as I was able to slide the saw plate within the kerfed cut without having to open it up any further. I chose to use an old discarded backsaw handle for the trial and cut 2 slots well away from the original slot that was cut in the handle, flipping the handle over as I went. Here's the end results.





On each side of the handle I completed 3 passes to achieve an optimum outside penetration of the area I wanted slotted. It felt quite safe to run the handle through the slitting blade while guided the handle by hand. But I would not recommend likewise to others unless you have a high quality mounting for the router, a failsafe depth adjustment lock, and a means of slowing down the operating speed of the router. Continuing on:

The 1st pass in the correct feed direction.



The 2nd pass in the correct feed direction.



The 3rd and final pass in an opposing feed direction. I could not feel any obvious signs of heat build up on the slitting blade after completing all 3 passes.



The final step was to insure the slot was cut to the full and proper depth to allow the saw plate correct seating within the handle. This was done by hand using a dedicated high tpi backsaw that's had the set removed. As mentioned the results were excellent with the handle slots spot on to the horizontal plane of each of the handle faces.

I think I have covered most the important aspects of the trial. I hope you enjoyed the information. I should include that importance of wearing eye and ear protection and keep those fingers well away from the cutting blade.

regards Stewie

 

[nathandavies]

my mum said I wasn't aloud one of those blades

 

[baldpate]

...
The slitting blade I was using was hss 75mm o.d. x 0.05mm thickness. The o.d. gave me an effective cut of 45mm outside the top flange of the slitting blade holder. The 0.05mm was slightly under gauge to the 0.020 thou saw plate I normally use for my backsaws ...

Those thickness figures don't seem right - did you mean 0.5mm and 20 thou (0.02") ?

 

[morfa]

That's a good how-to. Really interesting to see how you do it.

Have you posted a full WIP on how you do your handles? I'd love to see that.

 

[MIGNAL]

Might be a good method but would such an exposed blade revolving at that speed be considered safe practice?

 

[swagman]

...
The slitting blade I was using was hss 75mm o.d. x 0.05mm thickness. The o.d. gave me an effective cut of 45mm outside the top flange of the slitting blade holder. The 0.05mm was slightly under gauge to the 0.020 thou saw plate I normally use for my backsaws ...

Those thickness figures don't seem right - did you mean 0.5mm and 20 thou (0.02") ?

Your right. It should be 0.5mm.

 

[swagman]

Might be a good method but would such an exposed blade revolving at that speed be considered safe practice?

Absolutely not. (hammer)

 

[swagman]

That's a good how-to. Really interesting to see how you do it.

Have you posted a full WIP on how you do your handles? I'd love to see that.

Not quite right. I have relied on a more traditional approach in the past. This new method would provide greater levels of accuracy.

Stewie;

 

[DTR]

Might be a good method but would such an exposed blade revolving at that speed be considered safe practice?

The method is commonly used on engineer's lathes, although one usually doesn't have to stick one's hands anywhere near the blade:

(photo borrowed from Harold Hall's excellent website)

Swagman, I'm curious as to what blade you used, as the engineering blades don't have any set?

 

[swagman]

Hi Dave. I am using engineers slitting blades.

 

[arnoldmason8]

Might be a good method but would such an exposed blade revolving at that speed be considered safe practice?

The method is commonly used on engineer's lathes, although one usually doesn't have to stick one's hands anywhere near the blade:

(photo borrowed from Harold Hall's excellent website)

Swagman, I'm curious as to what blade you used, as the engineering blades don't have any set?

They do not usualy have set- but the blade is slightly hollow ground which gives sufficient clearance for metal cutting.

Arnold