# I guess these are not very common/used, right?



## wquiles (Jan 13, 2009)

Just found these "round" inserts today while searching for something else:
http://cgi.ebay.com/1-LATHE-TOOLHOLDER-40-RNMG-RN-43-CARBIDE-INSERTS-K641S_W0QQitemZ120362710560QQcmdZViewItemQQptZLH_DefaultDomain_0?_trksid=p3286.m20.l1116

For wear, I guess you would continue to rotate the insert for the areas not used?

Will


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## precisionworks (Jan 13, 2009)

I use the round insert for a quick radius (although a CNC machine will interpolate that same shape). Since it has no single 'edge', they are nearly impossible to chip & last a long time.

Some face mills run the round inserts, like the Little Hogger:


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## wquiles (Jan 14, 2009)

precisionworks said:


> I use the round insert for a quick radius (although a CNC machine will interpolate that same shape). Since it has no single 'edge', they are nearly impossible to chip & last a long time.
> 
> Some face mills run the round inserts, like the Little Hogger:



Cool - thanks 

Will


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## KowShak (Jan 14, 2009)

Round inserts are usually used for turning hard or difficult materials, simply because they are the toughest, they we not really a shape of insert that you'd want to use for general tuning.


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## SafetyBob (Jan 15, 2009)

Will, thanks to you and Precisionworks, I have finally have ten times the knowledge about inserts, usage and such gained over the past couple of weeks. 

I frankly could not believe the prices of the inserts on that web site (l looked at about 8 pages before I decided to leave).....$1 to $2 per insert. That is certainly a deal. 

Here is a followup question for Precisionworks. After reading all the factory literature on inserts and what not, I think I need some basic advice that will be good for all of us very amatuer metalworkers (think newbee) and a good confirmation of tool usage for the experienced/professional metalworker. 

I noticed that the Sandvik and Seco catalogs had wonderful photos/diagrams of the tool holders for the inserts they sell. What got my attention was the type of holders....not diamond holding holders, but that there was a recommended holder to cut from right to left towards the lathe chuck and I think 4 more holders for specific cutting jobs like facing and such. Now that I have set it up, the question is, do I need to get all those basic types of holders to cover all the cutting types (I figured out the answer is yes, but a little more explaination with experience behind it would be great)? 

Only through spending around 4 hours or so looking, reading and studying those catalogs have I realized even though I have had my lathe for 15+ years, I really didn't know what I was doing, it was blind luck that so much of my stuff came out as good as it has. I really need to inventory exactly what tooling was given to me, organize it, see what else I need and get ready to blow some more money to improve my skills and most of all.....results.

Bob E.


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## wquiles (Jan 15, 2009)

Look in my PM12x36 thread as I just bought some cool Kennametal tools on special over the holidays. Honestly, you don't "need" all of that tooling, although some more specialized tooling can come very handy for the right project. For me, I had some specific needs based on prior projects on the 8x machine, so I had an idea of what to try next. Then again, experimenting only hurts your wallet - like Barry (*precisionworks*) said, some times you buy something and then gets resold on Ebay if it does not meet your needs/expectations 

Will


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## precisionworks (Jan 15, 2009)

> do I need to get all those basic types of holders to cover all the cutting types


In a perfect world, with a bottomless bank account, buy 'em all In the real world, which includes both home shops & busy commercial shops, you'll often see just a small handful of holders for any one machine.

If you think about most of the cuts you make, they are made from right to left - with the cutter traveling toward the chuck. Cutting toward the chuck puts the headstock bearings in compression, eliminates any bearing play on a worn machine, and provides the most stable cut. The type of holder is referred to as "right hand", as the cut starts on the right side of the part. It's used for profiling & turning to a shoulder located on the left side of the part.

For facing solids, you'll need a left hand holder, as solid facing cuts are made toward centerline. For facing tubes like a flashlight, either right hand or left hand is fine.

The left hand holder is needed when turning to a shoulder located on the right side of the part.

I find that grooving tools are often used. Straight tools can cut O-ring grooves, as well as flute heads & bodies. Right angle tools are used
for internal grooving.






There are all sorts of variations on the basic left & right hand holders, & you may have to buy (or modify) additional holders for special jobs. But one left & one right will get you started & do 90% of the jobs that come up.


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## precisionworks (Jan 15, 2009)

> get ready to blow some more money to improve my skills and most of all.....results.


My wife said if I spend any more money on tooling, she'll take the dogs & leave. Sure will miss those dogs

Boring bars are another lathe tool to study. My smallest is 1/4", the largest is 1 3/4", and all get used from time to time. Solid carbide bars are the nicest as you can go 10 diameters deep, but steel bars work fine as long as you extend the bar no more than 5 diameters.


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## KowShak (Jan 16, 2009)

SafetyBob said:


> Now that I have set it up, the question is, do I need to get all those basic types of holders to cover all the cutting types (I figured out the answer is yes, but a little more explaination with experience behind it would be great)?



The simple answer is "no".

Some toolholders are more versatile than others, some will do one type of cut where as some will do a few different cuts. As an example a "PCLNR" or "PWLNR" style toolholder will do facing and general turning, i.e. doing the end and outside diameter of a cylinder, where as some other types would only do one of the other (e.g. square inserts can't do both). Other toolholders e.g. for profiling, really need CNC control, profiling is something that can be difficult to get right without CNC.

You'll probably need a right hand tool to turn and face, few different sizes of boring bar, threading tools (internal and external) and a parting tool (that can double up as an external grooving tool). Assuming I've not forgotten anything essential, that list should cover most of your needs as a beginner and beyond.


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## precisionworks (Jan 16, 2009)

> profiling is something that can be difficult to get right without CNC.


The first practical metalworking lathe was invented in 1800 by Henry Maudslay, and machinists started making chips. Modern CNC machine design grew out of the work of John T. Parsons during the late 1940's and early 1950's. You have to figure that quite a few million (or billion or trillion) parts were made during the 150 years before CNC, and that most or many had profiles.

CNC does almost everything faster than manual control, and the machine doesn't get tired, so multiples are made quickly. But anything that can be done on CNC can be done manually - though it takes more time, more thought, some trig, a few form tools, etc.


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## KowShak (Jan 16, 2009)

precisionworks said:


> You have to figure that quite a few million (or billion or trillion) parts were made during the 150 years before CNC, and that most or many had profiles.
> 
> CNC does almost everything faster than manual control, and the machine doesn't get tired, so multiples are made quickly. But anything that can be done on CNC can be done manually - though it takes more time, more thought, some trig, a few form tools, etc.



The lathe I get access to has a hydraulic copier so it can copy a profile without CNC, however you have to make the original to copy, or the form tool etc. I suppose there is difficulty involved in setting up the CNC machine, programming it so it doesn't have any expensive collisions etc, 

I didn't say impossible, I merely said difficult, and perhaps something that a beginner shouldn't be planning on doing on day 1 of owning a lathe.


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## precisionworks (Jan 16, 2009)

Profiling a radius (for example) with CNC control is done by entering the start location XY, the end location XY, and the radius dimension. The control uses a trig algorithm to move the cutting tool in tiny steps to produce the radius.

Profiling a radius with manual control is not much different. On a sheet of graph paper, drawn the radius, the start location & the end location. Figure how big or how small you want to leave the stair steps, as that's how the semi finished radius will look. Trig out each step to give the X & Y moves, and write those down. Start the machine & cut the rough radius. Mount a radius cutter tool to blend the high & low points together and the job is done.

We made some axle hubs to mount on a coal mining transport car. Sealed lead acid batteries power a DC motor, which drives a hydraulic pump, which drives hydraulic motors attached to each of the four wheels. The battery pack weighs about 20,000#, and the car with battery is 65,000# - so the axle hub needs to be stout. The part started with a round bar 20" diameter and 24" long, made of 4140 prehard. After 8 hours machine time, most of the bar was in the chip bin & the axle hub was done, including some beautiful radius transitions that were finished with out shop built radius cutter. A CNC lathe could have knocked that out in two hours.

CNC control does the job faster, but the end result is an identical radius. Any part that is made by CNC can be made manually. You may not want to try that on Day 1, but it isn't a bad job for Day 2.


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## wquiles (Mar 31, 2010)

Found a really good article on the pros/cons of round inserts - definitely a good read 

Straight to a round ...


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