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Old 03-09-2019, 01:07 AM
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Default Education Please On How to choose the correct Carbide Inserts

Looking to get educated here on how to choose the correct carbide inserts
I know it's not one type does all... and would like to know more, Being I have now made the plunge into replaceable "carbide insert" cutting tools for the lathe.

And I have no knowledge of the proper types of carbide cutters to use.
I mean I don't need to get too far off into all the exotics of carbide cutters, as I am needing to get my feet wet first in more a basic grade school entry level.

How do you determine which inserts are best used for the type of material
Aluminum, S.S., bronze/brass, tools steel, chrome molly, and other types of turntable material's, including turnable plastic.
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Old 03-09-2019, 07:32 AM
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Inserts, vary in sizing, , styles, shapes and material composition, I use certain styles, based on what I’m cutting, material, shape being turned, whether it has grooves, slots or roundeded corners or sharp angles.

I use TNMG. CNMG, VNMG and WNMG inserts along, with What appears to be the home shop standard of CCMT. It depends on the job.

Some cut stainless steel great, but gnaw up aluminum, some cut aluminum to a mirror finish, but at about worthless on anything else. I have some that allow me to take a 1/4” DOC, but leave a rough surface to cleaned up with another pass, I have others that at best can do a .030” DOC, but the surface finish is great.

To me it’s been trial and error, lots of error. I have something like 23 different styles of inserts and holders, many I use, other are tool box hold down weight. My go to insert has been a TNMG 321 or 322, a basic tool, that for me just works. I also use the CCMT inserts, the are cheap, easy to acquire and work real well with smaller lathes.

To me it’s all based on experience, your material, DOC, speeds and feeds, insert design and composition and lathe rigidity. I’ve yet to see a perfect one size and shape does all insert, it may be out there, I haven’t seen it or used it.
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Old 03-09-2019, 12:27 PM
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So on plastics, one of my local buddies, tells me if turning the various types of turnable plastics. I should stick with HSS and grind my own over an insert tool/tooling...

So, I assume he might be right. as I was "trying" to search the net for carbide cutters and the first thing popped up was an S.S. insert. and of course tool steel blanks to grind away at... but yet I have watched him using carbide cutters in the past to mfg. production as well as one-off parts.

So it leaves me a bit confused I will need to order replacements and don't mind having the right tool for the job so to speak, But It being I know nothing about the particular types used for certain materials... I would without a doubt end up with costly cutters cheap, good or otherwise. that will be incorrect to the material type.

example, I would tend to order one because it looks like its the one for the job and in reality the one next to it is, in my way of "electrical brain shorts thinking" that appears to be less in appearance is the correct one to use...
(i.e.) blue nano vs' a basic coated or non coated carbide.

So is there some reading the tells about the various type of cutters for their general and variable use something with Pic or color, style or shape to help me grasp the idea of their use.
Or should I just go by the general info from BG site when looking at inserts
on there where it says on some designed for bla.bla and best use or results used on soft materials aluminum brass and cast materials?
To use as a general rule of thumb?
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Old 03-09-2019, 01:06 PM
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The only rule of thumb I know for inserts is " I don't have the one I want in stock"
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Old 03-09-2019, 01:38 PM
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Quote:
Originally Posted by terry lingle View Post
The only rule of thumb I know for inserts is " I don't have the one I want in stock"
Terry, that's not a "rule of thumb" my friend... That is "The Inevitable" you won't have It "because you need it" Rule...
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Old 03-09-2019, 01:47 PM
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Quote:
Originally Posted by MetalWolf View Post
....So on plastics, one of my local buddies, tells me if turning the various types of turnable plastics. I should stick with HSS and grind my own over an insert tool/tooling...
Not true. The uncoated, highly polished high positive rake inserts work great on all plastics--you can get excellent finishes. These inserts are designed primarily for aluminum but they work on plastics and you can also use them on steel for light finishing cuts.

Others will disagree with me but in today's world HSS is virtually obsolete. Except for a situation where you may need a specially shaped cutter there is just no reason to use HSS anymore.

Quote:
...So is there some reading the tells about the various type of cutters for their general and variable use something with Pic or color, style or shape to help me grasp the idea of their use.
Or should I just go by the general info from BG site when looking at inserts
on there where it says on some designed for bla.bla and best use or results used on soft materials aluminum brass and cast materials?
To use as a general rule of thumb?
I've posted the chart below before but here it is again. Taken directly from the KBC catalogue. There are other sources of info on carbide cutters but this is the one I have used. It's relatively simple and will give you the basics of what you need.

At this stage of the game I wouldn't worry too much about the grade of the insert. With a low power, slow turning lathe you'll hardly notice any difference between grades. I would focus on insert shape and cutting geometry, always trying to find those inserts that have the most positive geometry. To start I would try TCMT and CCMT inserts in the appropriate sizes. They tend to be a bit more positive which is the single most important thing you're looking for right now...
Attached Files
File Type: pdf Inserts.pdf (194.5 KB, 27 views)
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Old 03-09-2019, 01:56 PM
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Quote:
Originally Posted by LKeithR View Post

Others will disagree with me but in today's world HSS is virtually obsolete. Except for a situation where you may need a specially shaped cutter there is just no reason to use HSS anymore.
I could not agree more, I haven’t used a HSS cutter is the last 15-20 years. The only HSS steel cutters being used in my shop are some HSS end mills. The only reason I use them is because I have scads of them, from the bulk Korean purchase made about 5 yrs ago.

I also agree, with your suggestion of CCMT inserts, they seem to be almost the standard for home shop use and is a good starting point for the starting of the use of carbide insert tooling.
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Old 03-09-2019, 02:17 PM
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Thanks, Jack and Keith the chart will help... I wanted to go with insert style tooling because I ain't worth a turd in grinding my own tooling let alone sharpening any of it although I have the means too.
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  #9  
Old 03-09-2019, 03:01 PM
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90% of my cutting on the lathe, is done with CCMT 2(1.5)x inserts. The X
can be a 0, 0.5, 1 or 2. The x value refers to the nose radius on the insert.
The 1 is 1/64" nose radius, the 2 is 2/64", 0.5 id 1/128" and a zero is
1/256" or 0.004" There are other designations and then the fancy wiper
inserts.

A couple of links to assist. Use uncoated carbide for aluminum and copper
alloys. You are running a manual lathe so you will not see much benefit to
running fancy high tech coating or PCD coatings for non-ferrous
applications. Also the uncoated carbide is good for plastics.

The TiN coatings will cause issues with aluminum as the aluminum will weld
to the TiN coatings. Running basic coated carbide on steels you will see
better tool life even on a manual lathe.

The C geometry will get most of what you need done, this is an 80°
diamond insert. The D (55° diamond) and the V (35° diamond) have there
place as well. They reduce tool pressure on the part, and should be used
when machining longer thinner parts where the tool pressure distorts the
part too much. I have some D's I run from time to time; I don't have an V
inserts, as never needed them bad enough to invest. You should also run
Postive (rake) inserts on a manual lathe to minimize tool pressure, negative
insert are more for use on CNC. Again tool pressure is your problem.

Do people run negative inserts on a manual, yes; I have as well, but I just
don't find the fight worth it.

http://www.carbidedepot.com/formulas-insert-d.htm

https://www1.mscdirect.com/images/so...faceFinish.pdf
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Old 03-09-2019, 06:44 PM
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The charts give a lot of information that leads you to select a particular insert but one thing not there is the tool you will use it in A CCmxxx insert is usless in any other holder.
If you are starting with a lathe and a wallet you should first buy thr toolholder best suited to the task at hand then select the insert for that holder that meets your requirements in each of the descriptor location.
Like all tools this will soon become a wallet emptying situation.
Inserts are cheaper than brazed tooling but when you have three or four pounds of them it is best that SHMBO be kept in the dark about them:
)

once you have a selection of tool holders you can buy inserts that fit the holder
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