Slitting on a mill


I need to slit a piece of mild steel 0.500" thick and 0.875 deep to a
0.652 hole. This will be a clamp to attach to a motor shaft. Never
used a slitting saw before, therefore I am asking for any advice.
Using a drill/mill with a 3X1/16X1 30 tooth saw. Thanks in advance
Reply to
Gerry
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I hate slitting saws! Slow feed, robust rigid set-up, flood coolant, silent prayers! Can you use a hacksaw or a Sawsall?
Reply to
Buerste
I cannot cut straight with either. Hoping to get a cut better than I could do with a hacksaw
Reply to
Gerry
I cannot cut straight with either. Hoping to get a cut better than I could do with a hacksaw ***********************
Does in need to be straight?
Reply to
Buerste
I don't know about your machine - mine is a bit larger - but the only time I had trouble with a slitting saw was when I inadvertently ran the spindle in reverse. I used no coolant, I used the speed designated for that diameter cutter, and a slow enough feed that the teeth wouldn't load up - I was cutting stainless steel and had no problems, you should have no problems in mild steel - if you are worried about feed speed, hand feed it so it "feels right"
Reply to
Bill Noble
You *could* go into _Machinery's Handbook_ and look up all the formulas. But for convenience, my old McDonnell Douglas feeds and speeds calculator (slide rule type, plus built ALLOY: SFPM: Chip load per tooth Annealed alloys: 70-90 0.006 Soft carbon steel: 80-120 0.007
Let's be conservative, and pick Annealed alloys, so for the middle of the range (80 SFPM), and a 3" diameter cutter, you want about 102 RPM.
And for 30 teeth, you want about 1.83 in/min feed rate.
Now -- the first question is whether your drill/mill can get down to 100 RPM. If not, you will be burning up your cutter.
This is really the sort of thing at which a horizontal spindle mill excels, and I have my doubts about a mill/drill (or drill/mill as you show it). The fact that "drill" is before "mill" in the term suggests that it is more optimized as a drill press, and may not have spindle speeds slow enough for your task in steel.
And the inches/minute feed rate presumes a power feed, which you are unlikely to have.
What kind of spindle does this machine have? There are arbors for use with slitting saws and narrow mills which fit R8 spindles. If your machine has a Morse spindle, I'm not so sure what is available.
Use a cutting fluid -- at least something like Rigid high sulfur threading oil (sold for pipe threading). At this slow a spindle speed, you probably won't be throwing the coolant around at least. :-)
In any case, I would advise not going much more than about 1/16" (the width of your cutter) of depth per pass -- especially until you get the feel of your machine under this kind of loads. And it sounds as though you won't be doing enough cutting of this sort to really get the feel of it.
Good Luck, DoN.
Reply to
DoN. Nichols
With your equipment, Buerste has the best advice. With a bit of ingenuity, you can make saw guides out of shim stock and scrap rectangles. I frequently make clamping bushings this way.
Karl
Reply to
Karl Townsend
This is a good opportunity to learn. Use a new blade, mark the line on two faces, start at the corner and cut a shallow kerf down each line. The kerf guides the blade while you cut deeper. With practice you won't need it but it helps at first.
I have a lot of trouble with thin slitting saws. I set the drive belt fairly loose and reduce depth of cut if it jams.
jsw
Reply to
Jim Wilkins
Slitting is not difficult, but like all cutting operations, the number one problem is always chip clearance. In that respect, slitting saws have no kerf in the teeth, so chip clearance is critical. I use compressed air. If coolant is used, it must be a high volume flood. Full cut or small passes is the same for me. Steve
Reply to
Steve Lusardi
I found out a while ago that I get no points for neatness.
Reply to
Buerste
One problem that can give you grief is having stresses in the metal that will cause the cut to close on the saw. This doesn't happen all the time but when it does you will have a mess. If you properly clamp the work on both sides of the cut to keep it from springing and grabbing the saw you will not have this problem.
John
Reply to
John
Similar to what happens when you try to cut a well pipe off 5000 under water and your robot did't secure it properly.
Reply to
Paul Hovnanian P.E.
Yup, I've been burned many times by this. I just wish I had kept notes on what material and treatments closed up and which that seemed to open.
Wes -- "Additionally as a security officer, I carry a gun to protect government officials but my life isn't worth protecting at home in their eyes." Dick Anthony Heller
Reply to
Wes
LOL
Wes, when you make a list let me know.
Any metal with some built in stresses in it will clamp on the blade if it happens to be put on the saw with the stresses pulling the wrong way. Just stick a little wedge in the top of the cut behind the sawblade to keep the kerf from closing.
John
Reply to
john

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