Slitting Saw Woes

Hbilly, good advice from Mikey. If your existing saw has 34 teeth, which is actually fairly coarse, and you take .001" per tooth, that is .034" for each revolution. Think about that, more than 1/32" feed for every revolution. That is one more reason to use a slow spindle speed.
 
mikey said:
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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Thanks for the info. I'm going to head out to the shop and Mic the blade to see if it is hollow ground. It didn't make sense to me that the teeth didn't have any set because that would cause the blade to rub. However your explanation makes perfect sense. I knew there needed to be clearance somewhere.

The 300 rpm you suggested. Is that for mild steel? If my calc's are right the sfpm for HSS on mild steel should be around 100 fpm and for a 2 1/2" diameter blade with 28 teeth that would be about 150 rpm and using a feed rate of 0.001" per tooth I would get a feed of 4.2" per minute and for 300 rpm a feed of 8.4" per minute would be right.

I did start producing amber chips but that was close to the end of the cut when I was trying a faster feed but by then the blade was already toast. Maybe because I was initially feeding too slowly. Man there is a lot to learn with this machining stuff. Seems like every day I find there is more and more stuff I don't know. I think I may be getting dumber.:D
 
Slitting saws seem to be a common problem with many of us while trying to get decent results. I have found that I have to do it by the book, because the answers come out much different than my guesses. The details of the setup also need to be correct. If the blade is wobbling, has runout, or other issues, then problems become more likely.
 
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Bob Korves said:
Slitting saws seem to be a common problem with many of us while trying to get decent results. I have found that I have to do it by the book, because the answers come out much different than my guesses. The details of the setup also need to be correct. If the blade is wobbling, has runout, or other issues, then problems become more likely.
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Thanks Bob. I checked the blade and the teeth are wider than the rest of the blade so I think there was another issue at play. I put the blade back on the arbor I made and checked the runout. It was about 0.003". Not sure if that was enough to cause problems but I'm going to make a new one for the blade just to be sure.
 
HBilly1022 said:
Thanks for the info. I'm going to head out to the shop and Mic the blade to see if it is hollow ground. It didn't make sense to me that the teeth didn't have any set because that would cause the blade to rub. However your explanation makes perfect sense. I knew there needed to be clearance somewhere.

The 300 rpm you suggested. Is that for mild steel? If my calc's are right the sfpm for HSS on mild steel should be around 100 fpm and for a 2 1/2" diameter blade with 28 teeth that would be about 150 rpm and using a feed rate of 0.001" per tooth I would get a feed of 4.2" per minute and for 300 rpm a feed of 8.4" per minute would be right.

I did start producing amber chips but that was close to the end of the cut when I was trying a faster feed but by then the blade was already toast. Maybe because I was initially feeding too slowly. Man there is a lot to learn with this machining stuff. Seems like every day I find there is more and more stuff I don't know. I think I may be getting dumber.:D
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I have cut a fair amount of mild steel over the years with slitting saws and it isn't difficult with a good arbor, a good saw and the right speed and feed. Slitting saws are actually quite effective little tools but you need to get the set up right.

I'm attaching Martindale's tech guide - see page 13 for useful hints. Note that the fewer teeth you have, the faster the saw can run. The typical RPM calc we use helps but you also have to consider the number of teeth on the saw. So yes, I would try 300 rpm for mild steel. For aluminum, I'm usually running 1000-1200 rpm.

Like all things metal, you need to try a speed and then feed for effect. If you cannot feed fast enough for the speed, slow it down. Feed so you have a slight resistance to the cut; you'll feel it, and it will be faster than you think. I do not use power feed with these saws because I'm usually doing a single cut but if I had to make many cuts then I would probably sort out a power feed rate in IPM.

Buy a decent blade and give it a try. And yes, there is a lot to this machining stuff but that's what makes it fun!
 

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If you are hand feeding the saw it will feel pretty jerky when it first engages with the cut so just feed steadily and once its fully engaged it will smooth out and you will feel better about using a higher feed rate. And ddickey is right so if you can rig up a steady flow onto the cutter near the arbor that will help.
I've had problems with the chinisium cutters not being a good grade of steel. Check ebay for a good hss cutter and see if you can find a tool and cutter shop in your area that can sharpen it.

Jim
 
I looked at several of my slitting saws and none of them have a "set" like a wood cutting blade. I have them from .015" to .250' and all have square teeth. Some are US made tools by various makers and a couple imports; I bought them as a lot along with an R8 arbor from a tool sale. They have all worked well but Bob is correct in suggesting chip load as a method of calculating speed and feed. Most of the ones I have have many teeth, especially the thinner ones. I have always found slowing them down and use of a good cutting fluid has helped solve issues I have had.

I said it in another post not too long ago and I will say it here again. In my experience where a tool is made is not the determining factor of how well it works but rather how it is made and what it is made of. Just this week I was looking for a 4mm ER16 collet. US made ones were $35 and up, I purchased an import with a spec of .0004" TIR. It arrived from its US seller and was well made, packaged and shipped. For fun it I checked and it ran my endmill with .0003" TIR as read by my trusty Intrepid indicator. It was $16 delivered. Would I have bought a US made if I could find one with the same spec at or near the same price, sure. I do this as a hobby and I am on a limited budget, what I spend effects what I can do in the shop.
 
I am a knife maker and use 3" jewelers slitting saws on my Bridgeport mill to cut the lock bar on titanium folder liners. I get my saws from Matco and they are a bit more costly. That said, I have used one repeatedly and have not had any issues. I run the saw at 120rpm and use plenty of cutting oil. If you would like that part numberer for the saws I use, let me know and I'll look it up for you.
 
TakeDeadAim said:
I looked at several of my slitting saws and none of them have a "set" like a wood cutting blade. I have them from .015" to .250' and all have square teeth. Some are US made tools by various makers and a couple imports; I bought them as a lot along with an R8 arbor from a tool sale. They have all worked well but Bob is correct in suggesting chip load as a method of calculating speed and feed. Most of the ones I have have many teeth, especially the thinner ones. I have always found slowing them down and use of a good cutting fluid has helped solve issues I have had.

I said it in another post not too long ago and I will say it here again. In my experience where a tool is made is not the determining factor of how well it works but rather how it is made and what it is made of. Just this week I was looking for a 4mm ER16 collet. US made ones were $35 and up, I purchased an import with a spec of .0004" TIR. It arrived from its US seller and was well made, packaged and shipped. For fun it I checked and it ran my endmill with .0003" TIR as read by my trusty Intrepid indicator. It was $16 delivered. Would I have bought a US made if I could find one with the same spec at or near the same price, sure. I do this as a hobby and I am on a limited budget, what I spend effects what I can do in the shop.
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I got sidetracked getting ready for camping and fishing season and haven't been using the machines for a bit but from all the info here it seems the problem is most likely the operator (as expected). It may be the import tool but after a little more research I don't think so. I found a post by Jim Schroeder whose work I followed for some time and he said that he uses Cinese slitting saws from Grizzly. From the pics on the Grizzly site they appear to be the exact same ones I got from BB. Both clearly state they are made in China. The Grizzly one may be a better quality blade but I doubt it. Next time I will try a full depth cut and cutting fluid ( I hate using it because of the mess). I will also make a better arbor and check the setup with a DI before using it, to make sure there is little or preferably no runout.

I'm not far away from start making the Harold Hall advanced grinding rest (right after I finish the end mill sharpener) and that will follow by his slitting saw sharpening jig. Then I can sharpen the slitting saw I have and see if there is any life left in it. I don't have any real machining projects that need to get done and don't see any in the near future. Seems that pretty much all my machining involves making tools to maintain my tools, just in case I ever find a real project to do.

I know what you mean about buying import stuff. If it wasn't for the greatly reduced cost of import machines and tooling I would've never gotten involved in this hobby. As it is I probably have well over $10,000 into it so far, just so I can make a tool to engrave lines on something or some other tool / jig I have no real need for at present. I'm really enjoying this and it has consumed most of my time since getting started. It is an expensive hobby but not as bad as fishing. Although it is catching up fast.
 
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