Slotting Saw advice please

Kennyd

Kennyd

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So, I have this R8 saw/arbor setup that came with my mill:
IMG_1857.jpg

And here is what I need to do: Slot this 1/4" walled 1.5"x1.5" square steel tubing so I can "pinch" a 3/4" rod in the hole. Here is the rough setup-staged for the pictures as I am not ready to make these cuts just yet:
IMG_1858.jpg IMG_1859.jpg



What RPM to run at, and about what feed rate? Is there a better way?

I admit being just a little intimidated by this tool and operation:thinking:

IMG_1857.jpg IMG_1858.jpg IMG_1859.jpg
 
At a glance, it doesn't appear that you have the clearance to make the cut. Using a slitting saw can be intimidating, and they can be broken relatively easily. If possible, it should be done climb cutting, with a little drag on the moving axis. You could cut it in either.

Other approaches could run between just bandsawing a kerf to machining a slot with an end mill. You probably have the most common solution there. If you actually do have the clearance, the speed should be fairly low, 125-150 RPM if you have good coolant. Less if dropping oil. I would probably plunge in from the end, with the spindle centered on the wall for the first side, and moving over to finish the other. It will get cut partly with the first plunge.
 
Slotting saws look intimidating but they're really just a saw. For a beginner start slow. You're not going to hurt anything by going 60. I'm going to disagree with Tony about the climb milling and say go conventional b/c you reduce the likelyhood of grabbing and you can feed into the part and 'feel' for feed (let the saw do the cutting) . Of course listen to your ears. If you hear a high pitch squeaking or chattering either reduce rpm or increase the pressure your putting on the handle your turning (turning it faster, but not by much, just till the squeal goes away, LET THE TOOL DO THE CUTTING).
As you get the hang of it you'll pick up the rpms slightly (100,150,200) and get a feel for feeding at those speeds.
Cutting oil is what I prefer to use as opposed to coolant but to each his own.
 
I'll be watching this thread close trying to figure out how to NOT break the slitting saw blades. The last time I was slitting something, the brand new blade that I had just bought, grabbed into the work & broke. I attributed it to the speed being to slow. I'm also hoping some one has a source on quality slitting saw blades @ reasonable prices.
Phil
 
I'm not going to insist on the climb cut position I take. The reason though, might be worth explaining. This applies to all climb cutting. It has to do with the formation of the chip. In climb cutting (also called "down" milling) The first point of contact in climbing is a spot on the material that is beyond the previously cut surface, and hence does not have any work hardening effect from the preceding tooth. Since the tip of the saw, of sharp edge of a mill cutter (where it is the most fragile and weak) touches there first, under the work hardened surface it is protected as much as possible. The "down" reference comes from the thickness of the chip. It is thickest at the beginning of the cut and drops as the cutter sweeps through the material. The opposite happens in conventional or "up" milling. The edge of the cutter has to force its way through the work hardened surface to start making a very thin chip which increases in thickness as the cutter progresses through the cut.

It does have a major drawback in machines that have backlash, as most all manual machines have. CNC machines, and certain manuals with backlash compensation don't have that problem so much. If you don't do something to mitigate the backlash effect, the risk of snagging a cutter is pretty great, and probably not worth it. I tend to just let the lock(s) drag a little and take a slow, steady hand feed. And I listen. I seldom break anything when I climb cut, but I don't take heavy cuts in climb mode. Mostly finish cuts with end mills, just because I get a better finish, with less pushoff a more accurate cut as well.

http://www.innovativetoolsales.com/ITS Techpage-Conventional v Climb Milling.pdf
 
I've always said if you ask 5 different machinists how to do 1 job, you will get 10 different explanations... That being said, I would avoid climb milling because you are running a manual machine, and I don't know how tight your machine is or how your workpiece is set up. Run her at 100+ rpm, and take a few passes. Use oil, and try your best to keep the cutter clear of chips.


I did edit this to explain my reason for not climb milling. If this were in my shop, and I ran a part to feel the cut and I was confident enough that the machine would handle it, I would attempt to climb. However, I would start conservatively by conventional milling.
 
Tony Wells said:
At a glance, it doesn't appear that you have the clearance to make the cut. Using a slitting saw can be intimidating, and they can be broken relatively easily. If possible, it should be done climb cutting, with a little drag on the moving axis. You could cut it in either.

Other approaches could run between just bandsawing a kerf to machining a slot with an end mill. You probably have the most common solution there. If you actually do have the clearance, the speed should be fairly low, 125-150 RPM if you have good coolant. Less if dropping oil. I would probably plunge in from the end, with the spindle centered on the wall for the first side, and moving over to finish the other. It will get cut partly with the first plunge.
Click to expand...


Yes, clearance is a issue for a straight through cut, but if I kind of go at it at a angle it will work (I hope that makes sense?)

I thought of the bandsaw or even hacksaw, but I guess I wanted a more 'elegant" solution and I already have this slotting saw on a R8 arbor.
 
Thanks to all others who responded, I will let you know how it goes, or if I chicken out:nono:

The info on RPM and milling direction is fantastic.
 
Philco said:
I'll be watching this thread close trying to figure out how to NOT break the slitting saw blades. The last time I was slitting something, the brand new blade that I had just bought, grabbed into the work & broke. I attributed it to the speed being to slow. I'm also hoping some one has a source on quality slitting saw blades @ reasonable prices.
Phil
Click to expand...

How did it break? Was it a violent explosion of shrapnel or did the teeth just come off the blade? Do I need a flack jacket?:lmao:
 
They normally just crack and the pieces fall off the arbor but with any tool the breaks there can be small pieces of shrapnel that fly.

If you do break a saw I wouldn't recommend trying to run another tool down the same slot because small pieces of broken high speed steel could have become imbedded in the material and ruin another cutter.

The biggest concern I'd have with slotting box tubing is making sure the weld seam isn't where you want work. The welded area can have hard spots.
 
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