12x36 Lathe: CCMT21.51 or 32.51?

[Splat]

Need to turn some hardened steel on my 12x36 lathe and am looking to get my first set of carbide SCLC tool holders. For a lathe this size and being I don't take massive cuts on my lathe would I be better of going with the CCMT21.51 insert sized tools? I feel like the 32.51 would be ok too but at the expense of taking a toll on my machine? Thanks.

 

[mikey]

I own both sizes and they both cut about the same. On a 12" lathe, you probably won't be putting enough load to bend a tool holder so either will work. In general, I prefer smaller inserts because I can usually get them with smaller nose radii and that makes a difference in how small a depth of cut the insert can take. I am less concerned with how big a bite it can take.

 

[Splat]

Ah yes, I didn't think of small depths of cut. Definitely a consideration. Thanks Mikey!

 

[darkzero]

I have a 12x36 & I use 32.5x the most. Don't have to worry about your lathe not being able to handle them. Heck I use CNMG 43x also. I do use 21.5x for my boring bars though. My second to largest boring bar uses 32.5x & my largest boring bar uses CNMG 43x. I keep the worn out 32.5x inserts cause I have a face mill that uses the unused 100° degree corners so I really get my money's worth out of them. I don't think I'll ever need to buy another 32.51/2 insert again, I'm pretty sure I have a lifetime supply of them now.

 

[darkzero]

Most of the time I'm not too concerned with taking big cuts either. I'm just a hobbyist so no worry of a boss hounding me to get the part done. But it is fun to take big cuts when you can. For delrin you can easily bury the cutter without issue. Can in other plastics too but others tend to melt like PVC.

Feels so weird to take a .300" DOC (per side), followed by a finish cut & be done. Still had room for more DOC on the DCGT 32.51 insert but 300 thou was all I needed. It's nice when you can save so much time making something. Had to make 6 bushings & got them done in no time.

 

[Splat]

Nice. Yeah, I'm not worried about time constraints either. Just wondering about rigidity problems, if any. Sounds like I would be ok with either 21.51 or 32.51. Thanks guys.

 

[mikey]

Will, I have to get a Square Tool in your hands. It will surprise you to see how big and small you can cut Delrin, or most things for that matter.

 

[mikey]

Sorta bank, if you ask me. I think you need a LH and a RH turning tool. Boring bars are an individual thing. I would buy some cheap SCLCX tool holders and inserts on eBay and see what works best for you.

 

[Splat]

Yeah, I edited out the Grizzly set outta my post after your reply cuz I figured exactly what you said. I really only need the turning tools, and not even really the left one either for now. To heck with it. Gonna go to McMaster tomorrow and pick up a 1/2"shank SCLCR and SCLCL holders. Cstmr service just told me they're Dorian brand. At least I can get the needed work done tomorrow. Get one thing done and it all sets up for the next job, doesn't it?

 

[mikey]

When you decide on the size you want, ask Will for advice regarding which inserts to get. @mksj knows a lot about these things, too.