Finally mastered slitting

After destroying several slit saws I am pleased to announce that I have now seen the error of my ways - too much speed! Run it nice and slow and it cuts lovely! Most of you will already know this, but this little insight might help someone. I blame it all on Harriet!!

Thanks Fizzy. Probably, a lot of seasoned members would know but there are many learners who wouldn't and it makes a big difference to them to have tips like that to help them "cycle around the potholes".

Indeed, we are used to circular saws flying round, so it seems unatural to accept they must go a lot slower than end-mills. But a 2 1/2" diameter slitting saw should rotate ten times slower than a 1/4" end mill to have the same cutting speed.

I must admit, I'm surprised Harriet didn't know that!

Neil

It also helps if you can keep the blade cool, it cuts a lot better i find.

regards

dave

..and buy or make a decent arbor so that it runs true.

Russell.

Yup I run slow and cool, but not sure of the best way of cutting. Do I do many passes with a small cut or is is best to just "plunge cut " but with a slow rate of feed ?

Thankyou Fizzy for this thread, i have always struggled with slitting saws, your comments will be very usefull.

I found that I couldnt get my x2 to run slow enough, simply lack of torque. I mounted the arbour in the lathe, made a draw bar and hold the work in/on the top slide. On my ml7 I use the slowest speed, I have tried the backgear but that was just too slow. Cuts nicely now, but its a slow process! Harriet did know butt is never awake long enough to take an interest!

Depnds on the job - how long, how deep, how thick the blade is and whether it's a new (sharp) blade.

Thin blades (50 thou or less) can be a problem because the cut can wander off line - of course the arbour won't let it so the blade twists and distorts. The deeper and longer the cut then the worse this problem shows up, and compounded if the blade is even slightly worn because it can end up cutting better on one side than the other thus increasing the likelyhood it will wander.

I found the best way is to take a shallow cut first (about twice the depth of the teeth) and the second the full depth. For the first shallow cut the blade is not under much stress so will (hopefully) cut straight, and for the second the shallow cut already made will help guide the blade for the deeper cut. Have only as much blade exposed as required to do the job - this might mean machining larger supporting collars which will help keep the blade stiff and aligned. Yes, use plenty of lube and take it slow.

With thicker blades (3/32" and up) the wandering cut problem starts to disappear, and if you buy blades with side-clearance teeth you'll get improved chip clearance and cooler running.

This link **LINK** has a lot of useful information on slitting saws on page 13. I think the important thing is that each tooth should be allowed to cut. If the feed is to slow, the teeth will rub and be blunted. If you run a low rpm, the feed should be adjusted for that.

I must admit I'm surprised you couldn't get an X2 to co-operate Fizzy. I have used mine to slit ER collets made in either EN18T or EN24T without noticeably blunting them. Were you using the low gear?

Neil

LOW GEAR, NO JOY...BUT I DONT KNOW WHAT IM DOING SO MAYBE BETTER NEXT TIME?

I always had a problem on my mill, lowest speed 400 rpm, until I fitted a three phase motor and inverter for speed control. Now, using about 100 rpm with a 3" cutter on steel, no problem.

Russell.

P.S., the three phase motor also gives a better surface finish than the old single phase one.

Edited By Russell Eberhardt on 02/06/2013 16:13:44

A useful starting point for HSS tooling in low carbon steels is a cutting speed of 100sfm. So for the aforementioned 3" cutter an ideal speed is 127rpm, but slower is no problem.

Fine pitch slitting saws are ok for shallow cuts like slotting screw heads, but useless for deeper cuts, as the gullets get jammed with swarf. For deeper cuts always use the coarse pitch saws. To echo Skarven I normally aim for a chip load of at least 2 thou per tooth with a slitting saw.

Regards,

Andrew