I hate to even bring it up again......took holder for Logan 210

So I understand that there is tons upon tons of information on this but I’m having a difficult time wrapping my head around this. I know that for smaller HP lathes I need a positive rake tool. So with that said I’m considering an SCLC toolholder like the one in the link below. However my questions are can you have to much positive rake like 11 degrees or would 11 degrees be preferred over 7,also is it better to go with a positive rake toolholder and neutral inserts or negative toolhoder and positive inserts, and lastly what would the preferred side angle be? With all of this being said I know HSS is the best option but my machinists skills aren’t quite to where I can grind them perfectly that’s why I would like to start off with carbide inserts. I’ll primarily be turning low grade scrap cold rolled steel and some aluminum. Feel free to shoot me straight because like I said I have limited knowledge. Thanks guys

1/2" RH SCLC Small Screw Lock Positive Insert Tool Holder

SCLCR1616H9 16mm Lathe Turning Tool Holder + 1pcs CCMT9T34 Carbide Inserts 659438785272 | eBay

Weads said:

So I understand that there is tons upon tons of information on this but I’m having a difficult time wrapping my head around this. I know that for smaller HP lathes I need a positive rake tool. So with that said I’m considering an SCLC toolholder like the one in the link below. However my questions are can you have to much positive rake like 11 degrees or would 11 degrees be preferred over 7,also is it better to go with a positive rake toolholder and neutral inserts or negative toolhoder and positive inserts, and lastly what would the preferred side angle be? With all of this being said I know HSS is the best option but my machinists skills aren’t quite to where I can grind them perfectly that’s why I would like to start off with carbide inserts. I’ll primarily be turning low grade scrap cold rolled steel and some aluminum. Feel free to shoot me straight because like I said I have limited knowledge. Thanks guys

1/2" RH SCLC Small Screw Lock Positive Insert Tool Holder

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most carbide inserts are designed for
1) a particular part material and condition (like annealed)
2) a certain depth of cut
3) a certain sfpm and feed rate
4) are you roughing, finishing and or both with same tool
5) part shape influences vibration or chatter limits
6) have to be aware of machine hp limits
7) some work better with coolant and others better dry
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some inserts can leave a mirror like finish if all conditions are just right and also be very bad if you want to do heavy roughing with it. general purpose are just that not the best for everything but a compromise for more different conditions
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by the way some negative rake holder take a insert with a groove in its top to give it a positive rake in a negative rake holder
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some holders take a bigger and thicker insert that can take a lot more (material removal rate) with out the corner or tip breaking off. of course bigger size inserts cost more.

Weads, based on my own learning curve, I would suggest that you are thinking about this backwards. You're worried about grinding the HSS "perfectly." Meanwhile, as you are finding out, there are a ton of different types and variations of carbide, and without a) lots of experience and b) lots of money, you are going to have to settle for a work-a-day set of holders and inserts that will NOT be perfect for most of what you will turn; they may be adequate, but not perfect. Meanwhile, keep in mind that carbide likes to run fast, with no interrupted cuts, probably faster than someone still learning will be comfortable with; it demands a rigid setup, which may well not be true for your Logan, if it has seen some use. As a result of all of the above, expect to break a LOT of inserts. If you buy quality inserts and holders, expect therefore to spend some serious $$$. If you buy inexpensive inserts and holders (i.e., cheap imports such as you have linked to), expect the results to be what you paid for. I say all of this from personal experience!

Meanwhile, you could be using a less-than-perfectly ground HSS ... that will be far more forgiving than the carbide and on your machine give you BETTER results. Learning how to grind HSS *adequately* takes very, very little time, several orders of magnitude less time than learning the bewildering array of carbide choices. And you can keep improving on the very same HSS tool, getting closer and closer to perfection, without having to buy yet another insert and/or holder. And you can make tools for every occasion - threading, narrow slots, facing, left and right turning, boring, trepanning, etc., etc., right at your grinder, without having to go to the store or (more likely) wait for the order to come in.

There is one key: you need a decent grinder and the right type of grinding wheel. The typical grinding wheel included with most grinders that you will find in big box stores or such is absolutely worthless - way, way too hard. You need a softer grade of wheel to grind HSS (yes, counter-intuitive, but true all the same). Specifically, look for something in the hardness range of H or I. As for a decent grinder - if your grinder slows down when you start grinding, it ain't decent. I started out with an awful import grinder that CLAIMED to be half a horse, but apparently the half of the horse that I got was all the gristle and none of the muscle. Coupled with the wrong wheel, grinding was painful. One of my first lathe projects was a spindle to fit some bearing blocks that I had on hand, with adapters to allow use of 7" grinding wheels (used on surface grinders) - much easier to source the right type of wheel in that size. Even running with an old half-horse washing machine motor (!) it is amazing how much easier and quicker grinding has become.

Here is my suggestion for your tooling.

SCLP right and left tool holders in 3/8” shank size.
SCLP right and left boring bars in 1/2” shank size.

CPMT 21.51 inserts will fit the above tool holders.
CPMT2151LF KC73

Get a boring bar that takes the 21.XX size inserts. Pay attention to be sure you pick tool holders that take the same insert.

One insert will fit all the tool holders and cover a lot of turning and boring work. Its all high positive and will work great on your machine. The KC730 coating on the inserts works well on many materials.

If all that costs too much, drop the left hand boring bar. You might not need it anyway if the spindle nose is threaded — unless you have a plan to lock it on.

These tools and inserts will work pretty well with a variety of metals on your small lathe. Not for hogging but will give a very nice finish with correct feeds and speeds. Follow directions from the maker as to depth of cut.

The trick is to buy tool holders that all take the same size insert. That way you only have to buy and stock one box of inserts. Later on if you need more you will end up with more and different tool holders and inserts for particular uses.

Also, soon enough you will discover that mystery metal may or may not be worth fooling with. If the tools above don’t give a nice finish when used properly, its the mystery metal.

I have no problem using carbide or HSS tools or grinding either. My take on the tools shown in his post are that they are so cheap he should buy them . They should be fine . And I think a hobby machinist does not need the high priced name brand inserts. Most home shops do not turn the really tough materials. Not to long ago 1 insert tool without inserts would cost more than the tools shown.

As far as aluminum inserts go some of the more popular Chinese sources have name brand Korean inserts for less than $1/ insert in most of the popular sizes and shapes. Whether or not they’re fake for aluminum they work as well as any of my name brand inserts and make it completely worthless to even think of firing up the grinder for HSS.

You don't have to grind it "perfectly". I never seem to. But it cuts and does what I want. And here's the key - if it *doesn't* do what I want, I go fix it.
Why is that a key? because grinding your own, you learn what works, and what doesn't, and why that is. So down the road, you end up with some carbide, and it won't do what you want it to do, you *will understand why that is and what you need to change*. You won't be buying stuff blind.

I have boxes and boxes of HSS I've picked up at estate sales etc. Some of the grinding amazes me. I wish I could do that good. Some of them I touch up a bit and use. You can get boxes of the same off ebay for example. Cheap.

The other thing is, that lathe was not designed for carbide. Not that you can't use it, but you won't be able to use it to full potential. Not enough speed and rigidity, and probably horsepower. My lathe wasn't either. I do use carbide sometimes, for hogging off metal, or cutting the skin off iron castings, I like the carbide threading inserts. But mostly I use HSS. With the right grind, you can sneak tiny little cuts of a thousandth if you are sneaking up on it. Carbide typically will not do this, it does not have a honed sharp razor edge.

The other thing is, I don't have to worry about breaking my last insert of a certain kind on Friday afternoon and being down till I can get more shipped in.

After a while, you get a "library" of ground HSS for different purposes. If you have an oddball job come up, you can grind a bit for that. So, no, I don't have to walk over and push a button on a machine every time I want to cut some shiny wood (aluminum).

IMHO, it is a really useful skill. It was hard riding a bike at first too, wasn't it?
Here, free download on how-to. Lots of videos out there too.

South Bend Lathe Works - Publication Reprints - 35 Bulletin How to Grind Lathe Tool Cutter Bits | VintageMachinery.org

Oh yeah, if you decide to get a threading kit, *DO NOT* buy cheap offshore inserts. I'll leave it to you to figure out why I am saying that with some authority on the matter.

Thank you very much for your reply. The sclp did interest me and I’ll certainly have a look at it!!!!