Proper Cutoff Blade

I have used a number of different cutoff tools, have had too many scary breaks with the blade style.
If I can get away with it I have been using something like the following GTN-2 clamping holder.
The clamping style has much better retention and is stiffer than the blade GTN holders.
The only issue is the limited DOC, at about 1/2" on the radius. More than that and I head over to the band saw!
The GTN inserts are relatively cheap, and the GTN-2 is maybe 0.080" wide so is easy on the lathe.

 
machPete99 said:
I have used a number of different cutoff tools, have had too many scary breaks with the blade style.
If I can get away with it I have been using something like the following GTN-2 clamping holder.
The clamping style has much better retention and is stiffer than the blade GTN holders.
The only issue is the limited DOC, at about 1/2" on the radius. More than that and I head over to the band saw!
The GTN inserts are relatively cheap, and the GTN-2 is maybe 0.080" wide so is easy on the lathe.

Click to expand...

1/2” In practice is just slightly less than what I would feel comfortable parting in the first place., especially on a hobby sized machine.

More than that increases the moment arm to a degree that any miss step will lead to failure.
 
BanjoDude said:
In another thread, I was warned that the style cutoff blade I have is dangerous, in that when it breaks, it spits the back half backward. That's something I definitely don't want with the shop full of classic cars.... Is there another style that's recommended over these? I see that Shars has p/n 202-9575 that holds an insert. Is that a better option? Something else altogether?View attachment 497213
Click to expand...
first off that blade is not ready to cut you will need to grind it to include rake, i like to add side relief and a notch in the top then hone it to a fine edge. reduce the stick out to only what you need make sure it is perfectly aligned with the cutting axis and is slightly above center (very slightly).
now comes the hard part, if your compound slide is not solid you will never be able to part consistently, same for your cross slide and saddle. there is a positive feedback loop inherent with parting (well all normal rotation cutting but more pronounced in parthing) in that the point that the cutoff tool rotates about under load is below the tool so cutting load drives the cutting edge into the part increasing the depth of cut and increasing the load which increases the depth of cut and that breaks the blade. there is not really anything wrong with that holder considering what you have it in will not be that rigid. bottom line is that that holder is not the weak link in your setup (I'm guessing that if you have an 0XA sized tool you are on a mini lathe) as to that style being dangerous and you being worried about damage to your classic cars, if you are machining in their vicinity you have to expect parts to fly some times and would be advised to take precautions.
 
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