having trouble with slitting saw

hardtail69 · Apr 13, 2017

I am slitting brand new DOM steel size 1.5 id. x 2.5 od. In other words half inch wall. the slitting saw was doing just fine and i completed one, but on the very next one the next day (so It was not over heated) it went in about half and inch and then started making a hellacious noise. i had been using plenty of cutting oil same as yesterday but when i took the piece out to examine it I noticed that just one side of the 4" x .125 saw every tooth was damaged, but only on one side. Now I had drilled several holes in this DOM and when it got to the first hole is when the damage occurred. The slitting saw was just HSS do you think that drilling the holes work hardened the hole wall and the slitting saw could not handle it? is DOM prone to work hardening? Would using a cobalt slitting saw work or would I need to go to carbide? Oh and I am doing this on my 1947 model 9a south bend lathe.below is the piece i am making. thanks for your advice in advance.

the clamp not the round thing

Conrad Hoffman · Apr 13, 2017

Maybe just hitting the edge of the hole was enough to damage it, or chips hanging up. What's the RPM? It's way easy to run slitting saws too fast- everybody underestimates the SFM. Does the arbor have exactly equal support on both sides? It's also easy to dish a saw with a bad arbor and that can lead to trouble.

sfriedberg · Apr 13, 2017

DOM tubing is not going to work harden. The A513 type 5 specification calls for a low alloy steel in the 1020 to 1026 range, and A513 type 5 is what typical DOM tubing is made from.

When you say all the teeth were damaged on one side, that often suggests you hit an inclusion or hard spot. However, since the damange apparently happened as you reached one of the holes, I suspect that as the saw broke through into the hole it created a burr which snagged or wedged between the teeth and the sides of the slot.

I would not have expected a 0.125" wide saw to suffer from chewing up a burr, so maybe there's more going on here.

hardtail69 · Apr 13, 2017

i was on the slowest of the fast speeds i dont know the rpm the arbor is about 1.250 steel cut down and threaded on the end for the 1" hole and yes it has a keyway in it. please note this is one of those rare 16 speed v pully lathes.

hardtail69 · Apr 13, 2017

oh and what speed and feed would you recommend? i am rather new to machining
and thanks for your help too.

rjs44032 · Apr 13, 2017

hardtail69 said:
I am slitting brand new DOM steel size 1.5 id. x 2.5 od. In other words half inch wall. the slitting saw was doing just fine and i completed one, but on the very next one the next day (so It was not over heated) it went in about half and inch and then started making a hellacious noise. i had been using plenty of cutting oil same as yesterday but when i took the piece out to examine it I noticed that just one side of the 4" x .125 saw every tooth was damaged, but only on one side. Now I had drilled several holes in this DOM and when it got to the first hole is when the damage occurred. The slitting saw was just HSS do you think that drilling the holes work hardened the hole wall and the slitting saw could not handle it? is DOM prone to work hardening? Would using a cobalt slitting saw work or would I need to go to carbide? Oh and I am doing this on my 1947 model 9a south bend lathe.below is the piece i am making. thanks for your advice in advance.

My first thought is why are you using oil? In all my years I have never used oil while slitting. Second, are you certain that your speeds and feeds are correct. For typical DOM tubing @130-SFM your spindle speed should be just 124-RPM. Feed would be @ 13-IPM for typical 36 tooth cutter and I would halve that as your depth on the workpiece is 1/2" thick.

Should be doable. I've never run into work-hardening problems with DOM, but you have to trust the supplier.

Edit: In the time it took me to type this post, several others already gave competent answers. Sorry if this seems redundant.

Best Regards,
Bob

Scottl · Apr 13, 2017

A long time ago when I was just a young man working in a shop as a machine operator I was tasked with slitting something very similar on a horizontal mill. The parts were stacked end to end and the saw run at low RPM and under power feed.

First thing that comes to mind is that you are doing this on a lathe that may have variable lash in the cross slide screw due to uneven wear. Are you perhaps unintentionally climb milling and getting a sudden aggressive feed when it hits a worn spot?

It is vital that a piece being slit is clamped axially so clamping forces don't compress the groove as it is cut. Also, depending on the lathe and how rigid it is sometimes it is better to approach the saw from the rear where the teeth are traveling upward. I know it seems counter-intuitive to have a lifting force on the cross slide when cutting but sometimes that works better on some lathes. The most important thing is to maintain a controlled feed with no sudden spurts that overfeed the cutter.

hardtail69 · Apr 13, 2017

it seems better now

ok here is what i did based on the advice I got here. I put the lathe into back gear and the feed is now on E and all the way over to the left .0027...It seems to be working fine i am also now using a 3" x .125 cutter because the two four inchers were ruined and all i had left was 2, 3inch cutters, but i made some modifications to the jig and it is working out ok. Oh and yes the clamping is axial. Clamping radially would really screw things up as the blade went through. I may be a newbie but I do have a firm grasp of basic physics lol

Scottl · Apr 13, 2017

hardtail69 said:
ok here is what i did based on the advice I got here. I put the lathe into back gear and the feed is now on E and all the way over to the left .0027...It seems to be working fine i am also now using a 3" x .125 cutter because the two four inchers were ruined and all i had left was 2, 3inch cutters, but i made some modifications to the jig and it is working out ok. Oh and yes the clamping is axial. Clamping radially would really screw things up as the blade went through. I may be a newbie but I do have a firm grasp of basic physics lol

Glad it's working out.

Dobermann · Apr 13, 2017

I would never use automatic or power feed to cut with a slitting saw. You're much, much better off to feed that by hand so you can tell how the cut is going and whether you need to ease off a little bit. Also, must cutting tools do NOT like sharp edges in their path, ie, the holes that you mention. I can't think of a better way to ruin a slitting saw than to power feed it through a hole in the workpiece.

moonlight machine · Apr 13, 2017

Dobermann said:
I would never use automatic or power feed to cut with a slitting saw. You're much, much better off to feed that by hand so you can tell how the cut is going and whether you need to ease off a little bit. Also, must cutting tools do NOT like sharp edges in their path, ie, the holes that you mention. I can't think of a better way to ruin a slitting saw than to power feed it through a hole in the workpiece.

I run a 6" carbide insert slitting saw on my CNC mill cutting 8620 every week. It is an interrupted cut through a 1 1/4" diameter. No problems at all.

traditional-tools · Apr 13, 2017

You didn't say what type of saw you were using. Some have approx 56-72 teeth (screw) and others have over 200 teeth (Jewelers).

If you're spinning a Jeweler's slitting saw at the lowest "fast speed", it's WAY TOO FAST!

More details needed!

hardtail69 · Apr 18, 2017

no it is not a jewelers saw it has 36 teeth to it. i have not had any trouble with slitting since i slowed it down and as to using power there is no way i an standing there for that long i need to get stuff done. any advice on a small Mill that could accomplish this task? must have power feed and be rigid enough to do this task of slitting a 1/8 inch sloth through 1/2 thick mild steel. with holes in it. i know lots of big mills that could do it but i am really pressed for space. i don't want some wimpy POS that i will have to "go easy" on. so i need small but powerful. LOL

hardtail69 · Apr 19, 2017

well i caved in a bought a G0704 mill today used but with only about four hours on it from a guy that simply changed his bussness to powdercoating from guns. well it came with a bunckof tooling a nice vice and even a small rotary table. all for 750 bucks itis not powerfull but should do the job . now i can use my beloved south bend lather for just lathe work lol thanks all you fine folks that helped me with this project i did complete the run nowi have to reset and work it out with the mill.

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