Fretsaw novice in need of advice.

[davethesax]

What blade TPI recommended for 3mm hardboard? At the moment I’m using normal pin-end Proxxon 25 TPI and I keep breaking blade. It’s always at the same place i.e. about 6mm above the bottom clamp. I have checked the alignment of the clamps and all seems to be ok.
I’m sure the breakage has nothing to do with the TPI and is most likely me, :? though any advice would be appreciated.
Regard, David

 

[Clockie]

Just a few thoughts about your predicament: A lot of cutters use the American system of blade numbering, including myself. All my blades come from America. For 3 mm ply I would use Flying Dutchman (FD) Ultra NO. 1 or Pegasus MG NO. 1. You can make very tight turns and nice sharp corners with lots of detail. The 25 tpi seams to be very fine, not unlike metal cutting blades. The breakages could be due to too much tension or too much feed pressure or a combination of both. All blades will break in time due to metal fatigue and in my experience it is usually near the bottom clamp. Hope you sort it.

 

[Chippygeoff]

I agree with Clockie and feel you have either too much tension on the blade or you are pushing the material to hard or a combination of both. It's not so much the TPI of the blade as to the number of the blade that is most suitable for various materials. Let the blade do the cutting and just apply enough pressure to guide the material being cut. Having the right speed also helps and all of this will come with experience so just keep at it.

 

[mac1012]

Hi I cut 4mm plywood with a number 7 blade which is quite coarse and is fine it reverse tooth meaning a couple of teeth at bottom of blade point upwards so you don't get splintered edge as long as you got couple of teeth covered by the width of wood you should be fine I would say a no 5 should do you which is a popular size to use ALS dont over tighten clamps as that could be causing it to break near the clamp which you said had happened also not to much tension a nice ping and a small amount side ways movement

Mark

 

[davethesax]

Thanks Clockie, Chippygeoff and Mark for your replies.
The breakage usually occurs when making a 90° even executed slowly. Not sure about blade tension though after reading Mark’s post maybe I have it too high
I’m at the bottom of the learning curve. As Chippygeoff said it all comes with experience.

 

[chrispuzzle]

Thanks Clockie, Chippygeoff and Mark for your replies.
The breakage usually occurs when making a 90° even executed slowly. Not sure about blade tension though after reading Mark’s post maybe I have it too high
I’m at the bottom of the learning curve. As Chippygeoff said it all comes with experience.

If it is a sharp corner you're turning, the turn is easier if you go past first and then back the blade up a little. Of course you cannot always do this, but I always try to back up very slightly anyway - disengaging the teeth from the cut, and taking the pressure completely off the blade - before starting the turn. This gets a nice, sharply-defined angle and helps to reduce the stress on the blade.

That said, the blade is always going to flex when turning and so it needs enough give in it to do this adequately.

 

[davethesax]

Thanks chrispuzzle I will just keep practicing and buy blades by the gross rather than the dozen.

 

[davethesax]

Hello All
Thanks all who gave advice on the blade breakage problems I was having.
I have now got a just a little more experience and I’m now using Olson crown tooth No 620 .024 wide, .011 thick, 20 TPI, they seem very forgiving and really stand abuse I find them just right for me and though a novice I would recommend them to anyone who lacks experience and finesse like me.