Help! > Mistakes, muckups, and dangerous behaviour

Slitting saw and destroying my mill

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And another topic from me ......... this time using a slitting saw and destroying my mill  :( Everything was going well making a mandrel until I had to cut the length of it.

I was taking .010" cuts at a time/ speed 1100 rpm and used oil; I thought this was okay, clearly it was get very hot from the colour of the mandrel and the saw blade and the amount of smoke as I applied more oil. What I didn't realise was some of the smoke was coming the motor and it was not until I heard a strange noise that it dawned on me.

I now have a broken mill .......hopefully Warco will have a replacement motor in stock and I haven't damaged anything else!

What did I do wrong; I don't want a repeat performance, an expensive one ........

Dave Otto:
Way too high surface footage for that cutter, with out knowing the exact diameter I would guess two or three hundred RPM would be more appropriate.



You did a pretty comprehensive job on the slitting saw, workpiece and milling machine.

Next time, try a lower speed around 200 RPM or less. The replacement cutter should remain silver coloured, the steel workpiece should remain silver coloured and the chips should not be coloured either. A flow of suds coolant will help tremendously.  If anything starts to change colour, or starts to smoke, then the cutter surface speed is far too high and you are driving everything way too hard.
A happy slitting saw goes zick zick zick.


You need to look back at the other recent advice you have been given about speeds, doe snot matter if the work or the tool is rotating the speed where the two meet is what matters.

Assumimng an HSS saw blade of 100mm dia then the surface speed at the tips is 3.142 x 0.1m = 0.314m/rev the cutting speed for HSS should not be more than 30m/min.

30/0.314 = 95rpm you you were about 12 times too fast and also taking much too shallow a cut.

75mm saw would be 30 / (0.075 x 3.142) = 127rpm

BASIC Rule as diameter of tool or workpiece increases rpm decreases

Your arbor is also not shaped like the drawing showed. You simply need a cut that goes right through and splits the arbor in half.

A simple hacksaw cut is all that is needed and is a lot less costly


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