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Carbide Inserts For The Little Lathes

Sk8ter

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Mar 31, 2013
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#1
Hello guys I just wanted to pass along some useful information on very hi quality inexpensive tough inserts for your turning tools....

I have tested them abused them and they hold up do not chip or break because of (C2 grade) turn aluminum and brass and cast and mild steel very well...I like them so much i ordered another pack of 10 since these fit my 3" boring head bars etc....


I cannot say good enough things about these inserts....

here is the ebay link....http://www.ebay.com/itm/231896778452?_trksid=p2060353.m2749.l2649&ssPageName=STRK:MEBIDX:IT

if my posting is in the wrong place please put it right!


Lawrence
 

westsailpat

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#2
Thanks for the tip Lawrence , what would be a good holder ?
 

kvt

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#3
They look like the ones on the tools I have but How do I figure out what size they are, As Mine are on tools for my sherline. Lathe, so they are small. They work nice, but I did chip one recently so I need to find some replacements.
 

Sk8ter

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#5
I also wanted to say that the inserts that come with the above tools are really not too good....and IMO are more like C8 hardness very brittle and you will go through many
 

westsailpat

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#6
I kinda figured that , actually for me I think I should stay with HSS .
 

ExKenna

Ex cutting tool engineer for the "Big K"
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#8
Small positive rake inserts such as CCMT/CCGT and TCMT/TCGT work really well on mini lathes *IF* you pay attention to edge prep and the grade of carbide.

Hard grades of carbide wear longer but in a home shop where you're not trying to eek out the last 3% of tool life it's best to go with the toughest grade you can find.
With a lot of the import no-name inserts you have no idea what the ISO class of carbide it might be. But here's a clue: Steel grades are classed as "P" designation and the higher the number, the tougher the grade. So look for at least P25 or higher.. many times you'll find "P20-P30" thats the ones you want. Stay away from P10-P20, they are too brittle and break with no warning.

On edge prep (this is usually called "chip breaker): Roughing geometries often have a big hone or land at the cutting edge for strength. This helps the insert survive interrupted cuts, tough scale, or other adverse conditions. But! It also increases tool pressure and can cause push-off on small lathes. Look for a semi-finishing or medium chip breaker. These have a smaller land and usually the chip gullet is designed to roll and break the chip on depths of cut in the .010-.060 range.

To recap: Look for a tough grade in a semi-finishing or medium chip breaker for general purpose turning and a finishing chip breaker for finish cuts.
I did extensive testing on a 98 pound 7 x 14 mini lathe with a 550 watt motor. probably 12 different grades and 8 chip breaker designs. I found 2-3 winners, so don't let anyone tell you that indexable carbide tools aren't for small lathes. Like most anything else technical in nature.. if it's misapplied, don't expect good results.

Hope this helps

X
 

Karl_T

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#9
FWIW, I've had great results using inserts that say they are for aluminum on steel. You get more positive rake and a well defined chip breaker this way.
 

MachinistNick

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Nov 17, 2016
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#11
I was turning drill rod for a slitting saw arbor with the Harbor Freight indexable tools with the inserts they come with out of the package. I have had no problems with them and they seem to leave a nice finish. I only chipped one edge, but that was because of my mistake. I determined the inserts to be TPGH-731 when comparing these to a re-branded version if the Harbor Freight tools on Amazon, Ebay, etc.