Thread: Why did this stop cutting?????

The proper TCT holesaws for metal are much shallower and are generally aimed at sheet metal use; given that it lists cement sheet, ceramics and abrasive materials, I suspect it will be alright with cast iron if you don't push too hard.

The fact that cutting relief holes got it going indicates to me that it was a swarf issue; it's a very common problem/solution with holesaws in timber products. Or maybe just somewhere for the teeth to start biting again

Originally Posted by ptrott

Still have no idea at all why this happened, but the job is done now.

Out of desperation I drilled about 20 or so 3.5mm holes in the shallow groove that the holesaw cut before it started skating on the surface.

That got it started again, and I cut the rest of the depth dry, and very little heat was produced at all, 40-45 degrees according to the laser doohickey.
It never looked like skating again, just steady cut all the way to 32mm depth.

I'd say that confirms to me that it was skidding due to localised rolling of swarf dust rather than cutting through it. Having the hole there allowed the swarf dust to get out out of the way of the teeth....
I agree that the speed is too high for that not to happen.

Originally Posted by elanjacobs

The proper TCT holesaws for metal are much shallower and are generally aimed at sheet metal use; given that it lists cement sheet, ceramics and abrasive materials, I suspect it will be alright with cast iron if you don't push too hard.

The fact that cutting relief holes got it going indicates to me that it was a swarf issue; it's a very common problem/solution with holesaws in timber products. Or maybe just somewhere for the teeth to start biting again

Not a swarf issue, the teeth were still out of the groove, which measured 1.8mm deep. There was not enough depth to hold any swarf at all.
The holes I drilled were only 4 or 5 mm deep, just to get it started. I am certain that if it was a swarf issue, I would not have been able to go to 30+ mm without a swarf problem.

Originally Posted by jhovel

I'd say that confirms to me that it was skidding due to localised rolling of swarf dust rather than cutting through it. Having the hole there allowed the swarf dust to get out out of the way of the teeth....
I agree that the speed is too high for that not to happen.

How could swarf dust be an issue when the teeth were only 3 quarters of their height into the material, and there was no swarf visible in the teeth?
I scraped out the groove, got next to nothing out of it, and the teeth were clean, and it still skated in the groove, creating zero new swarf. It wouldn't bite enough to make any swarf at all..

For the benefit of those still thinking "Swarf"

This a a pic of the 1.8mm deep groove in which the holesaw was skating, taken immediately after withdrawing the holesaw. Note, no swarf.

Holesaw groove .jpg

This is a pic of the holesaw after skating in the groove, take immediately after withdrawing from the groove. Note, no swarf. )It wouldn't bit, so could not make swarf)

Holesaw teeth 1 .jpg

This is the holesaw in 30+mm. It could not have got there is swarf was a problem at less than 2mm. The "relief" holes I drilled in the groove were only about 5mm deep, so not there for the last 25mm+

Holesaw at 32mm .jpg

Originally Posted by ptrott

No heat, all cool to the touch. Had no issues until I sprayed coolant, lube onto it.

Given that the holesaw was painted to start with, I'm wondering if applying the coolant somehow combined with the CI to create a very slight buildup on the teeth and make them rub rather than cut. The photo you posted of the teeth almost looks like there's a bit of buildup.
The relief holes would likely have been enough to break that buildup off and you were good from then on.

Steve

Originally Posted by OxxAndBert

Given that the holesaw was painted to start with, I'm wondering if applying the coolant somehow combined with the CI to create a very slight buildup on the teeth and make them rub rather than cut. The photo you posted of the teeth almost looks like there's a bit of buildup.
The relief holes would likely have been enough to break that buildup off and you were good from then on.

Steve

That sounds plausible.
It was surprising how it cut ok until I sprayed it, then ceased within seconds.
I didn't connect the application of coolant to the skating at the time.
I removed the saw from the tail stock at one stage and rotated it back and forth by hand in the groove, and it was near frictionless in either direction, no matter how hard I pushed it into the groove. Quite weird considering how sharp the teeth are to touch.I tried it on a bit of mdf and it bit immediately.

Quite possibly a hard spot in there, drilling the holes around the edge just allowed the teeth to do there job and cut through it.
Sometimes a bit of "swarf" and lubricant combined is enough to grind things to a halt. DAMHIKT
Kryn

How well did it cut initially?
Just wondering if the surface of the CI was hard(chilled).
Or built up a hard surface which your drilled holes broke up.
H

Originally Posted by clear out

How well did it cut initially?
Just wondering if the surface of the CI was hard(chilled).
Or built up a hard surface which your drilled holes broke up.
H

Started cutting normally, a bit of chatter because it was biting in, but as soon as I sprayed it with coolant/lube, it stopped within seconds, which might be totally coincidental. No amount of feed pressure would start it cutting, even enough to stall the lathe which is 1hp and on the lowest speed, so plenty of torque.