Slitting Saw Woes

H

HBilly1022

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I bought a cheap chinese cutter from Busy Bee tools for an upcoming project. I have never used one before so I figured I should do a test run and did a little reading about using one. I found a suggested method for an initial cutting sequence, in one of Harold Hall's books. The suggested cut was to take a 1mm depth of cut feeling and listening for any issues, then a second 1 mm cut and after that go to 2 mm. I didn't make it through the first 2" of 1mm deep cut in mild steel before it was obvious this thing was very dull and not going to work.

The saw is an HSS, 2 1/2" x 1/16" x 28 tooth blade. The blade is flat and there doesn't appear to be any rake (set) on the teeth. I ran it at 120 rpm using an arbor I made specifically for it. The blade didn't feel sharp before I started and is definitely dull now. I can see the wear on the sides of the teeth (both sides). It even felt dull on the outside edges of the teeth before starting.

Am I using the wrong tooth count, is this the wrong application for this blade or is there something else I need to be aware of?
 
Sorry, but I believe you answered your question in your first sentence with “cheap Chinese cutter”. I have seen them look like they were just stamped teeth and not cut/ground out. They were worthless….sorry.
 
HB can you give us a bit more info on what your application is. and how fast your are running the cutter. Dimensions of the work piece could help. 28 teeth could be coarse depending on the workpiece.

David
 
A slitting saw should be used to full depth where possible, not light passes. Maybe not your main issue, but it is one of them... You also must calculate the RPM of the cutter using the surface feet per minute (SFPM) of the wheel diameter to set the spindle rpm, and also calculate chip load per tooth to determine a reasonable feed rate. No cutter will survive a bunch of rubbing, a speed that will burn it up, or a too light or too aggressive feed.
 
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It was just a test piece of 1/2" mild steel and I was running the blade at 120 rpm (about 80 sfpm). I tried slowe and faster feeds but no luck. The blade appears to be ground, definitely not stamped. The blade was $12.

I found a thread where Jim Schroeder said he runs blades from Grizzly at 400 to 600 rpm and routinely cuts 0.5" deep. Maybe I need to run faster and deeper?
 
HBilly1022 said:
It was just a test piece of 1/2" mild steel and I was running the blade at 120 rpm (about 80 sfpm). I tried slowe and faster feeds but no luck. The blade appears to be ground, definitely not stamped. The blade was $12.

I found a thread where Jim Schroeder said he runs blades from Grizzly at 400 to 600 rpm and routinely cuts 0.5" deep. Maybe I need to run faster and deeper?
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80 SFPM is fast enough. If you double that you may well burn up the saw on mild steel. Figure your chip load and look for something like .001 to .002" per tooth with that few teeth. The feed must be enough to make real chips, not just rubbing and making powder. If making a long length of cut, feed per tooth cannot get too big or the gullets will fill up with chips and the saw will bind, goodbye saw. It is like Goldilocks, not too little, and not too much, just right...
 
HB,
I don't have much experience using slitting saws, but I'll tell you what has worked best for me. As far as I know, slitting saws come in two styles. One has straight teeth with hollow ground sides on the blade and the other has teeth with a set and the blade has flat sides. In my experience when cutting thin material like tubing, usually a max of about .125", I use the blades with straight teeth and cut at full depth in a single pass. If I'm making a deep slot in solid material I use the blades with set in the teeth and take multiple cuts (with cutting oil) to obtain the depth I need. The teeth with set seem to clear chips better and the blades don't tend to bind in deep slots. I have no idea if this is the "proper" methodology or not, but it works pretty well for me.

Ted

Looks like Bob and I are typing at the same time !
 
Thanks guys. I think part, if not most, of the issue is that this blade does not have a set.

My need for a slitting saw is for making some collets for the Harold Hall end mill sharpener. I guess if I can't get a slitting saw to work, I will make collets with 4 slits instead of 3 and I will use a vertical bandsaw to produce the slits. Just for the heck of it I'm going to try hand sharpening the slitting saw. After all it can't be any worse than it is now.

Edit: after looking at the blade again I decided it would be a waste of time trying to sharpen it. The teeth are worn round on the ends and as such I would have to grind / file them back a lot to get a full width tooth again. Maybe I can use this blade as some kind of Ninja throwing weapon ..... or just throw it in the scrap bin and see it there will be some use for the steel in a future project. What a waste of money.
 
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HBilly1022 said:
Thanks guys. I think part, if not most, of the issue is that this blade does not have a set.

My need for a slitting saw is for making some collets for the Harold Hall end mill sharpener. I guess if I can't get a slitting saw to work, I will make collets with 4 slits instead of 3 and I will use a vertical bandsaw to produce the slits. Just for the heck of it I'm going to try hand sharpening the slitting saw. After all it can't be any worse than it is now.
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You mean look like teeth on a hand saw…they will not. The teeth are flat. The clearance comes from the grind on the disc. It’s ground thinner towards the hole in the center. This is typical. But, I have seen very thin blades that are not ground this way and are just flat.
 
Hbilly, most slitting saws are hollow ground. As mentioned, they do not have any set to the teeth and clearance to prevent rubbing is provided by a thinner body. These saws work very well when used properly. For the slits in a collet, I would not use a saw with a set to the teeth.

I would suggest you buy a better saw blade. Martindale and Thurston makes good ones that can be found on ebay. I think a cheap blade is worthless; a good one will make slitting a simple procedure.

You need a good slitting saw arbor that fits the blade with very little clearance in the ID of the hole. This makes a difference in cutting efficiency and reduces wear on the blade.

As mentioned, speeds and feeds matter. For your blade that is now toast, about 300 rpm would have worked but you could go a bit faster with only 28 teeth. On a manual machine, feed is much faster than you might think. You can cut to produce amber chips and still be okay. I normally feed so I feel a slight resistance to the feed and the say goes right through. As Bob and Ted said, take full depth cuts; there is no need to make partial cuts with these saws.

On manual machines at low speeds, I prefer a sulfur-based cutting oil because I consider this a high pressure cutting environment like parting is.
 
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