# Proper Rpm For A Plain Slitting Cutter



## tackit (Jun 22, 2016)

I hope to cut one side of a .0900thick plain steel 3" X 1 1/2" rectangular tubing off to make a tray from it, but I can't find the proper RPM for the cutter...  It's a 3" X  1/8" X 30 tooth plain slitting cutter. I find formulas but they don't give the RPM just the SFPM. Could someone please help me?  Thanks.


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## CluelessNewB (Jun 22, 2016)

Online calculator:
http://www.carbidedepot.com/formulas-milling.htm


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## tackit (Jun 22, 2016)

CluelessNewB said:


> Online calculator:
> http://www.carbidedepot.com/formulas-milling.htm


Clueless,   I don't know how to use the formula,   it wants me to enter numbers I don't have and don't know how to find.


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## Wreck™Wreck (Jun 22, 2016)

You did not mention the wall thickness of the tube, or material.
If your dimensions on the saw are correct, 3" Dia. X 3.141 =  9.432" / 30 teeth = .314" tooth pitch, this is a very course saw.

As a rule of thumb, especially with band saws try to keep 3 teeth in the material, for instance a band saw cutting 1/4" wall tubing one would chose a minimum .083" tooth pitch or a 12 tooth per inch blade, a 3" slitting saw would have 100+ teeth.

I have no idea of how many parts you require but this is doable just pay careful attention to the feed rate, start with a very slow spindle speed and increase from there. The sound will tell you when it gets too fast. Either way that is likely to be a noisy operation. As a side note some tubing will close up when cut through one side jamming the saw.

Good Luck


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## Wreck™Wreck (Jun 22, 2016)

tackit said:


> Clueless,   I don't know how to use the formula,   it wants me to enter numbers I don't have and don't know how to find.


100 RPM's with a 3" tool = 79 SFM

Morse Tools recommends 110 SFM for low carbon steels, 79 SFM would be a good place to start, increase it until the tools begin to fail quickly then back off.

This also somewhat depends on the machine used, a chattery  machine will increase tool wear. Also flood coolant will be required for decent tool life, do not slit the welded side if possible as the weld may sometimes cause anomalous  behavior.


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## intjonmiller (Jun 22, 2016)

tackit said:


> I hope to cut one side of a .0900thick plain steel...





Wreck™Wreck said:


> You did not mention the wall thickness of the tube, or material.


It seems to me like he did.


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## CluelessNewB (Jun 22, 2016)

tackit said:


> Clueless,   I don't know how to use the formula,   it wants me to enter numbers I don't have and don't know how to find.



You want to calculate RPM so use the second calculator on the page.  For example lets say you want 100 SFPM, and your cutter is 3 inches in diameter.   Plugging those numbers in and hit calculate you get 127 RPM.


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## Wreck™Wreck (Jun 22, 2016)

intjonmiller said:


> It seems to me like he did.


My mistake, missed that part of the post.


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## tackit (Jun 23, 2016)

Very informative and helpful,  thank you all for taking the time to help me out.  Those speeds seem slower than my round column 31 F Rong Fu mill can go. I'll have to go to the shop and check it out, I haven't used if for this purpose before so I could be very wrong.  Thanks again everyone.

I just checked,  it's speed range is 150-3000 RPM.   I'll set it for 150 RPM and go slow with blade lubrication.


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## mikey (Jun 23, 2016)

Rather than use the online calculator, this formula will give you the same result:

*RPM = SFPM X 3.82 / Diameter. *

100 X 3.82 / 3 = 127


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## Paul in OKC (Jun 23, 2016)

Run it on the lowest speed, with some lube. Should do fine.


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## tackit (Jun 23, 2016)

Guys my machine took way to much time to cut through the steel at 150 RPM, in five minutes i didn't make but a five inch long cut.   The cutter was jamming every-time I tried to add a bit more force. I readjusted the belt tightness a couple times and it still jammed.  I was using blade lube too.  I've given up,  I have  sheet metal I going to bend.


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## Wreck™Wreck (Jun 23, 2016)

tackit said:


> Guys my machine took way to much time to cut through the steel at 150 RPM, in five minutes i didn't make but a five inch long cut.   The cutter was jamming every-time I tried to add a bit more force. I readjusted the belt tightness a couple times and it still jammed.  I was using blade lube too.  I've given up,  I have  sheet metal I going to bend.


Was it loud with an annoying thrumming?

What feed rates did you try, if feeding by hand this will cause problems unless you are very experienced. I would think .006 or so per revolution of the saw would be a good starting point therefore 150 Revolutions Per Minute / .006 is  roughly 1" IPM  therefore a 5" long cut should take 5 minutes.


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## tackit (Jun 23, 2016)

Wreck™Wreck said:


> Was it loud with an annoying thrumming?
> 
> What feed rates did you try, if feeding by hand this will cause problems unless you are very experienced. I would think .006 or so per revolution of the saw would be a good starting point therefore 150 Revolutions Per Minute / .006 is  roughly 1" IPM  therefore a 5" long cut should take 5 minutes.



Wreck it wasn't loud at all... I kept lubing the cutter and cranking the table at the speed the cutter would take....seemed like forever to make five inches.      I have to find a better way,  it's to slow. 

I just talked to the SIL and told him when the AC/furnace man gets here I'm going to ask him to make a tray for me.... he's a tin knocker by trade and does tin work in his garage.


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## Wreck™Wreck (Jun 23, 2016)

tackit said:


> Wreck it wasn't loud at all... I kept lubing the cutter and cranking the table at the speed the cutter would take....seemed like forever to make five inches.      I have to find a better way,  it's to slow.
> 
> I just talked to the SIL and told him when the AC/furnace man gets here I'm going to ask him to make a tray for me.... he's a tin knocker by trade and does tin work in his garage.


Sometimes machining operations take a good deal of time, I do a recurring lathe job where the roughing lathe work, OD turn for a steady rest takes nearly 1 hour per pass, the part is 65" long, setup time will kill you.


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## Paul in OKC (Jun 24, 2016)

Unless you are needing both halves, just put in vise and use an end mill. Make a wood spacer to put in the middle for when you turn it around. Or saw it then machine the top edge to smooth/even it out


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## John Hasler (Jun 24, 2016)

tackit said:


> Guys my machine took way to much time to cut through the steel at 150 RPM, in five minutes i didn't make but a five inch long cut.   The cutter was jamming every-time I tried to add a bit more force. I readjusted the belt tightness a couple times and it still jammed.  I was using blade lube too.  I've given up,  I have  sheet metal I going to bend.


How are you holding the work?   You don't want to clamp in such a way that the slit will tend to close.   You could also try pressing a wedge into the slit behind the saw.


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## mmcmdl (Jun 24, 2016)

Use a carborundum cutoff wheel ! It would go thru it like butter ( if the sparks mean nothing )


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## tackit (Jun 26, 2016)

Guys I have shelved the tray project for now , I think I'll buy some 16 ga and bend a tray on homemade bender.   The 90 degree bend is 16 gauge steel.


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