Q About Indexable Cut Off Tools

mattthemuppet2

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Hi all,

busy thinking about tooling for my new to me 6 x 18 size lathe instead of working on an exam. I'm quite happy grinding HSS tools and get good results, but one issue I keep butting up against is parting >1in diameter parts. The HSS parting tool I ground from a 1/4x3/8 blank works ok, but I can't grind it to part larger parts without losing its ability to resist flex. I've been looking at those Iscar style indexable blades - Shars has a 3/4in tall one for reasonable money that uses GTN style inserts. Providing that the QCTP I plan on building can get the tip low enough to be on center, is there any reason to use a P or T style HSS blade over this?

thanks!
matt
 
There comes a point where the power hack saw or the band saw is more efficient than a cut-off tool. I too would like to be able to part off 2" dia aluminum, but even 1 1/2" dia is asking for trouble.
 
true, I just don't have either of those, at least ones capable of cutting steel :( The only power hacksaw I have is me :D I did buy some nice 14/18tpi Morse hacksaw blades which should make it easier, but the last effort took me at least an hour - 10min to go 1in into a 3in steel blank, then 1h+ to hacksaw through the rest. It was a good work out though..
 
I really like my gtn insert tools, but they are not from Shars they are name brand and cost. For that money, if you don't have a power saw yet I would put my money towards that, even a POS Harbor Freight saw can be tuned up and give you years of service cutting thousands of parts for you. First things first, a simple power saw long before you go to insert parting tools. I have 2 very rigid lathes, parting is a breeze with either HSS or carbide. I cant remember the last time I tried to part anything over 1.5". The drama is to great. Big stuff I try to leave extra material on part so it can be cut with power saw then remounted on lathe and faced.

michael
 
I bought some 13/16 4140 round stock, have been hand hacksawing off lenghts, not because I wanted to, but 1) 54 inches is too long to hang out the back of any lathe, and 2) my lathe is only 1/2" thru. Builds character. Muscles, too. 100 strokes at a time, about 5 passes for this stuff.
 
Don't want to offend you, but a 6x18 lathe is likely not rigid enough to run cutoff inserts on one inch shafts.

Save yourself some money and grief. Cut it with a hacksaw and face.
 
Don't want to offend you, but a 6x18 lathe is likely not rigid enough to run cutoff inserts on one inch shafts.

Parting requires a rigid machine... period! Even after you set everything up properly, if the lathe has any flex (tool holder,cross slide etc.) it will end up in a broken parting tool.
 
no offense taken Karl, that's why I'm asking :) A horizontal bandsaw is near the top of my list of things to get, along with a proper mill, but those will have to wait until after our next move. Doesn't make sense to pay for something twice! I do have one of those small benchtop bandsaws but it doesn't have enough power for cutting steel of any useful thickness. I actually tried it on this project and it just dulled the blade.

I'll stick with the short parting tools that I have and get cracking with the hacksaw. I'll make sure to change arms every so often so I don't get any rumours started :D
 
A quality bandsaw blade won't dull from one use unless what your cutting is very hard. Did you replace the wood blade with a metal cutting one? The tooth geometries are completely different and TPI is much greater on a metal one.
 
it was a generic Sears blade that came in a pack of 6 for $25, so most likely carbon steel. Fine for cutting alu and brass, not so much for steel. TPI was probably a little fine (8 or 10tpi, cutting a 1in piece) and I'm sure it was running too fast as the tiny motor bogged badly otherwise. Just the wrong tool for the job!
 
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