First lathe, tool bits

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Jmanb13

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I finally got my 1946 15" Leblond lathe cleaned up and running. I have added a CXA QCTP with holders.

I'm planning to buy a set of HSS bits to grind to shape. How many and what size would you recommend as a starting amount for the different profiles.

I was thinking of 3/8 by 3/8 Grade M2 bits.

What would be a good starting set of bit profiles to have on hand?
 
Right and left-hand cutting, R & L facing, single point threading.
 
Think about what work you are planning on doing, OD turn ,ID turn, face, chamfer and part are the most common, that is 3 or 4 tools. Internal thread, External thread, Internal grooving, External grooving and Face grooving both square and with a substantial radius, you are now at 9 tools. OD and ID back cutting adds a few more as does profile work. Buy or make the tools when needed not before you need them as they may never be used.

A single tool that holds many different insert profiles is useful, Kennametal Top Notch tools use square groove, full radius groove and many different thread profiles such as 60 Deg., 55Deg., Acme, metric trapizoidal and buttress in the same holder, very slick. Kaiser Thinbit has an excellent line of internal, external and face grooving tools including those pesky dovetail O-Ring groove tools, I can not even begin to communicate how much I dislike dovetail grooves.
 
This is the basic, standard set. It would be reasonable to grind these ahead of time if you feel so inclined, but other shapes beside these would make more sense when you need them. Starting with a dozen or more blanks would be a good idea, as you typically save money by buying larger quantities.

Types-of-Lathe-Tool-Bits.png

If you look on eBay you can typically find old HSS tooling lots for sale. Sometimes blanks, sometimes ground, sometimes mixed. Vintage Rex AAA, MoMax, and Firth Sterling tend to be better quality than the majority that you'll find today. May be others as well, those are just the ones I've dealt with.

Also note that T15, M36, and M42 (the latter two having roughly 5% and 10% cobalt added) are "better" (in roughest terms) grades than M2, but M2 is certainly good enough for most work. There are other grades as well, but they're less commonly available as tool blanks.


http://tomstechniques.com/ has a lot of good info about tool geometry, grinding, and use. His YouTube channel is good, but he generally advises people to start on his website because the information is better organized there.
 
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A 15" lathe can certainly use 3/8" blanks for bits, but can also usually handle larger ones, typically up to 5/8 or 3/4". They are more rigid, and more expensive. HSS tools can be had for very cheap prices used. I have several times bought fairly large amounts at about a dollar a pound, already ground into tools, just touch up or regrind as desired...
 
The line between reasonable and expensive seems to lie at about 1/2" tooling - go bigger and the cost goes up really fast. The same is true for grinding times - above 1/2" takes much longer. Unless you are going for really heavy cuts most of the time, I would just go for 1/2" HSS and/or cobalt bits.

The best cobalt bits, in my opinion, are Cleveland Mo-max bits (5% cobalt) or Super Mo-max (8% cobalt) but standard their HSS is fine for most work. I personally avoid Chinese bits when I can. Other names to watch for are Crucible, Rex (made by Crucible), Chicago Latrobe and Morse. ETM makes very high quality HSS tooling as well.

As for shapes, most hobby guys use a general purpose tool that can face and turn in RH and LH. A good facing tool is a knife tool, also in RH and LH. A zero-rake general purpose tool and a round nose tool for brass is handy, as is a good 60 degree HSS threading tool for external threads. I suggest you research and buy a blade-type parting tool instead of grinding one. Boring and internal threading tools are another discussion with many options.
 
Watch out for grinding lathe bits. Even the regular HSS tools contain cobalt. The "cobalt" tools have even more, and so do most inserts. Wear a dust mask and don't blow the dust around the shop. It is not high risk stuff, but still, why take a chance on making yourself ill.
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Wikipedia:
Precautions
Main article: Cobalt poisoning
Cobalt is an essential element for life in minute amounts. The LD50 value for soluble cobalt salts has been estimated to be between 150 and 500 mg/kg.[91] In the US, the Occupational Safety and Health Administration (OSHA) has designated a permissible exposure limit (PEL) in the workplace as a time-weighted average (TWA) of 0.1 mg/m3. The National Institute for Occupational Safety and Health (NIOSH) has set a recommended exposure limit (REL) of 0.05 mg/m3, time-weighted average. The IDLH (immediately dangerous to life and health) value is 20 mg/m3.[92]

However, chronic cobalt ingestion has caused serious health problems at doses far less than the lethal dose. In 1966, the addition of cobalt compounds to stabilize beer foam in Canada led to a peculiar form of toxin-induced cardiomyopathy, which came to be known as beer drinker's cardiomyopathy.[93][94]

After nickel and chromium, cobalt is a major cause of contact dermatitis.[95]

Cobalt can be effectively absorbed by charred pigs' bones; however, this process is inhibited by copper and zinc, which have greater affinities to bone char.[96]
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I have some old school Stellite 5/8" tool bit blanks that are around 60% cobalt, and some others with somewhat less than that, but still way more cobalt than tools have today. I am not excited about trying them out. Their scrap value is probably quite high.
 
I will go out on a limb here. I tried this with my first lathe. It was a mistake. I really didn't know enough, even after reading up on it a bit. Grinding your own tool bits is a skill and an art. Are you sure you want to try to learn that before you know how to machine with a lathe in the 1st place? If something doesn't go right, how will you know if it is the tool or one of countless other variables you might not be familiar with? Me? I really wanted to learn to make things FIRST. It really helps to have actually experienced using various tools to understand why this angle is that, and that angle is this, and so on. You say this is your first lathe. If I were you, I'd buy a tool holder set with indexable inserts. They work great and even to this day I do 95% of my work with them. They last long, they're a time saver, they're not expensive - and they just WORK so you can get to the business of learning how to make things. About the only cutting tool I take to the grinder on a regular basis are my parting blades.
A set like http://www.grizzly.com/products/7-pc-Deluxe-Tool-Holder-Set/G8787.

If you really want to grind your own, this looks like a nice compromise. Seeing a properly ground tool will really help! https://www.littlemachineshop.com/products/product_view.php?ProductID=4516&category=

I know the old timers all say "learn to grind your own tools". THEIR teachers HAD TO. I don't think it is a bad idea if it interests you in and of itself. It just isn't necessary to learn RIGHT AWAY to start really enjoying your new lathe. Old timers used to tell me I should learn to use a slide rule - but I grew up in the calculator age. The analogy applies. They were tied to the way THEY were taught but they were wrong. I've never, ever needed a slide rule.
 
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I'll keep an eye out on ebay for used bits.

My lathe came with a box of misc lathe bits that I could use. They are all pretty rusty, but with some grinding that should go away. I probably have about 10 or so 3/8 and 1/2, with a few 3/4 bits. However, looking at all the profiles, I couldn't find a single one that remotely resembled any of the standard profiles. If I were to use them it seems it would require a TON of grinding or somehow cutting off the existing profiles and starting over.

I tried using my bandsaw with a bi-metal blade to cut off the strange tips and start over, but it did not seem to be doing much and was probably ruining the blade.

Unless someone knows an easier/better way of getting rid of the existing profiles, I figured I would just grab half a dozen name brand bits from MSC and grind both ends to give me a dozen or so different profiles.
 
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