Carbide Inserts For The Little Lathes

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.
 
Hi, regarding using inserts designed for aluminum to cut steel on a small lathe such as Sherline.
I'm working with 4140 around 0.25"...trying to improve my surface finish.
I tried Sherline's DPMT with a 1/64 radius and it didn't leave a good finish.
Just wondering if anyone has a suggestion for another insert to try...would a DCGT with 0.008 or 1/64 be worth trying?
The supplier I was searching didn't have any DPGT.
Confused since the supplier doesn't recommend G tolerance for finishing non-ferrous (recommends DCMT for finishing non-ferrous), but it seems from reading other posts the G tolerance has given better results for finishing.
Is it that these recommendations from supplier are more suited for larger lathes?
Trying to stick with DXXX style since I already have the holder.
Thanks for any help!
 
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okay thanks...I did grind some 3/8 HSS tools per the thread on this site...finish improved, but just doesn't seem right. So I thought would try some sharp inserts made for non-ferrous that others have mentioned here.
 
(recommends DCMT for finishing non-ferrous), but it seems from reading other posts the G tolerance has given better results for finishing.
The G tolerance is achieved by grinding and polishing. Grinding and polishing results in very sharp edges and lower cutting forces. None rigid lathes (bench top) will benefit from this.
I use this G type insert on aluminum ,brass, POM, etc with good results. If none of my inserts give a good result on any (hard,soft, stainless, etc) steel, I use this G type insert as a last resort and it rarely lets me down.
On my non rigid lathes, I can't use the recommended feeds and cutting depths. Most of the time I can use the recommended speed (RPM) but, for finishing, I lower the feed to 0.2/0.05 mm/rev and the cutting depth to 0.3/0.05 mm. (0.05 mm==0.002").
I mainly use 0.4 mm tool nose radius but for the G type inserts, I am going to use 0.2 mm tool nose radius for lower the cutting forces.
 
The G tolerance is achieved by grinding and polishing. Grinding and polishing results in very sharp edges and lower cutting forces. None rigid lathes (bench top) will benefit from this.

For low cutting pressure use G type (ground) inserts designed and ground for cutting aluminum. I have use them on all kinds of steel, including 4140 to good effect. They do wear out a little faster than inserts meant for steel, but cut with much less force.

Even the really cheap offshore inserts of this type seem to hold up well for me.
 
Hi, regarding using inserts designed for aluminum to cut steel on a small lathe such as Sherline.
I'm working with 4140 around 0.25"...trying to improve my surface finish.
I tried Sherline's DPMT with a 1/64 radius and it didn't leave a good finish.
Just wondering if anyone has a suggestion for another insert to try...would a DCGT with 0.008 or 1/64 be worth trying?
The supplier I was searching didn't have any DPGT.
Confused since the supplier doesn't recommend G tolerance for finishing non-ferrous (recommends DCMT for finishing non-ferrous), but it seems from reading other posts the G tolerance has given better results for finishing.
Is it that these recommendations from supplier are more suited for larger lathes?
Trying to stick with DXXX style since I already have the holder.
Thanks for any help!
Based on experience and conversations with Sherline a few years ago, they make their insert tool holders specifically to hold their inserts , not industry standards: in oder to use standard inserts you’ll need to modify the pocket in the holder.
 
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