Lathe tooling

[trevj]

I'll reiterate the opinion that HSS is the way to go, and the stuff from Busy Bee, bought on sale, is as good as any.

At a buck or so per 1/4" square tool blank, you can afford to have a bunch of them, and practice your grinding. Get a couple of the 3/8 x 1/2 rectangular section ones too, they make great boring and internal threading bits.
A pair of vice grips to keep from burning your fingers while grinding, and don't quench the hot tool in water, until it has cooled in air to well below black heat. Quenching a red hot HSS tool can cause a micro-fracturing on the surface, that can limit tool life. A minor risk, but more probable than you softening HSS up while grinding it.

HSS will hold a cutting edge when it is red hot. The heat treat schedule, to anneal HSS runs into days long, at extremely high temperatures, the alloys used are not subject to losing their hardness by getting the tool hot on the grinding wheel. Tool holder suppliers like Armstrong, used to provide a holder to put your HSS bit into, so that you could lean on the bugger and make the grinder WORK. They had a ball end on the one end so you could brace it against your leg or hip, and LEAN on it! Go like heck, then allow it to cool in air, then grind it for pretty afterwards. Works very well, and cuts down your time sitting in front of the grinder, instead of doing productive work.

FWIW, once you gain some hands-on time, carbide is OK. There is a steep, expensive learning curve, as you get used to not touching the tool against a non-moving work, and you get used to feeding the tools in to the work with some confidence.

CCMT and CCGT are my two favorites. I have a couple of the Glanze (IIRC) Carbide lathe tool kits and boring bar kits from KBC tools, and they are relatively expensive sets for a hobby guy. The carbide inserts that come with, will get you started, then shop Ebay or Carbide Depot or similar cheapskate sources and go from there.
I would skip the Busy Bee house brand insert carbide entirely, and brazed carbide, while it has it's uses, is a bit of a trap, if you think it will save you from having to learn how to grind a cutting tool, as it really should be properly ground to suit the job, which requires a bit more in the way of tooling and grinders, as well as still needing to understand tool grinding, which gets you right where you were trying not to be.

Plain, high carbon steel, makes a really useful cutting tool as well, though heat management becomes a real issue. I make a lot of tools from water or oil hardening rod, that when run slowly to keep the heat from drawing the temper at the cutting edge, can often provide a better surface finish than HSS and take a sharper edge. But too hot for just a second, and done!

Cheers
Trev

 

[asa]

I use the Arthour R Warner HSS insert tools. I have been using these for 5 or 6 years and have no complaints.

 

[deadeyes40]

when I worked in the smaller shop we used a lot of inserts/carbide tools. we also ground/sharpened our own hss tools when we needed/used them. in the large production shop we had 1-2 guys who did the major sharpening/forming of the tools/bits/cutters for all the machines be it shaper/lathe/milling. even running a small hobby shop buy lots of hss tool bits and have more than 1-2 of same size/shape sharpened and ready. if the first one should dull/break you just switch out tools and sharpen all tools later

 

[lejarretnoir]

HSS are fine for intended use. I have a drawer full of them cut into various shapes for multiple tasks. Need to do a square thread? No problem, grind an HSS bit. HSS inserts are also available.
Carbide is fun when you crank up the horsepower and speed
I have no problem cutting beautiful threads with quality made carbide inserts and proper speed.

 

[Armedsask]

Carbide is pointless on any machine under 5 horsepower. Won't be rigid enough or have enough power to make it work.

 

[griffin86]

For most gun related stuff and hobby jobs HSS is fine. I still use some of it for form tools.
I primarily use carbide inserts though but it takes fairly rigid machines and some experience to get your money out of them. Lots of the myths about carbide are 30-40yr old stuff that is bs today. I've got carbides that cut plastic like HSS never could, that will take .0002" cuts on inconel and all in between. But fact is at $120-200+ for a box of 10. It's not every gunsmith or hobby guy that will be buying them for every holder... adds up real fast.

Gotta have the right tools for the job, hobby guys usually have lots of extra time to spare anyhow and most gun related work doesn't deal with high SFM.
Grinding HSS bits should be done on a decent A-O wheel. M-2 from China is actually pretty darn decent HSS, like the bit busy-bee usually sells. I've got Osborn and others fancier things and really, those M-2 hold up just fine or better in some cases.
A few brazed carbides never hurts to have on hand but I haven't used those in many years.

I buy a bit from KBC, watch for their specials/discounts of which they're doing quite a few of this year. Doesn't take long to sign up on their website and you can get the emails of new offers.
I also like dealing with local vendors specialized in dealing with shops, mainly DGI, but most cities have quite a few choices.
Buy good taps... I like OSG cause they're easy to get around here. Cheap taps can cost a lot...

How long would a typical carbide bit last? I haven't used a lathe before and I am just curious.

 

[trevj]

Carbide is pointless on any machine under 5 horsepower. Won't be rigid enough or have enough power to make it work.

That statement is only true if you fail to consider that there are carbide edge geometries out there that are actually very useful on a light duty lathe, with far less than your randomly applied five horsepower limit.

Negative rake carbide does not work well unless you can really drive the power to it. Outside of, say, an environment where you were turning production batches of barrels, or similar hogging operations, there is not a lot of call for that kind of chip making in gun work.

It is a disservice to try to apply any all encompassing rules to something that has as many choices of compositions, sizes, edge geometries, and coatings. There are carbide inserts out there for every use. Learn to read the catalogs, and the charts that give the recommended speeds and feeds and try, generally, to choose what fits the needs.

I suspect that the watchmakers that have been using hand held carbide tools to turn parts on watchmaker's lathes, would be shocked to know that they were not able to do the work they did, on the 1/10th or less horsepower they used. Or when turning parts with a bow, operated by hand. Waller has been selling carbide gravers since before the Second world War, for that use.

How long would a typical carbide bit last? I haven't used a lathe before and I am just curious.

In hobby use, until you break it by trying to cut outside it's 'happy' zone of speeds and feeds, or you bump it against the work, or something else, or you manage to get the lathe to chatter, or... You will wreck far more than you will ever wear out. Sharp edged tools like the XXGT series, are easier to damage than a blunter edge such as is used on most other inserts. Easier to cut yourself on too. As you progress from the very sharp, positive rake inserts, to the very blunt negative rake ones, the forces, and horsepower to get them to work well, does go up. Choose the one that suits your needs.


In critical applications in a production environment, there are various tool monitoring methods, such as optical inspection methods and tests of the edges, as well as monitoring of the power required to drive the cut (which goes up, as the edge deteriorates) that are used to keep an eye on what is going on. In really expensive parts the cutters are changed out before they show enough wear to put them at risk. Normally they track the failure rates of their cutters, and can compare their prior records of cutting in similar conditions, and make a pretty good estimate as to when the cutter will have reached the level of risk they are comfortable with. When I toured through the Canadair plant in Montreal, they had pallets full of carbide inserts sitting awaiting recycling. For a hobby guy, they would have been considered as new, but they had done their time as cutters, were replaced, and were going to be sent out as scrap. Too much money tied up in a wing skin or spar forging to lose over a chipped cutter inset. They were producing wing skin sections for the RJ when I was there, and were making 12-14 pound parts from solid blocks of virgin aluminum that started out weighing several hundreds of pounds. Two guys with snow shovels were walking on the bed of that milling machine, scooping chips off onto the conveyor. It was pretty cool!

Cheers
Trev

 

[griffin86]

Thank you for taking the time to answer Trev!

 

[BCRider]

Kbc has good stuff , don't waste your time with HSS, takes lots of skill to sharpen it too work properly, something the hobby machinist lacks, takes long time to learn tool grinding skills

There you go again with your shop based "time is money" experience. For a beginner that does not understand how fragile carbide cutters are when used outside their rather narrow limits an all carbide tooling experience is likely to be a very expensive proposition.

And besides, if the guy reads a little about rake and clearance angles grinding an HSS cutter isn't hard at all.

HSS tooling also is far more resilient to cutting outside of it's limits and a mistake only costs a few cents worth of ground off metal to restore the edge instead of a $3 or $4 carbide insert thrown into the trash.

 

[SND]

Carbide is pointless on any machine under 5 horsepower. Won't be rigid enough or have enough power to make it work.

No trouble here on my cyclematic 618evs, its only 3hp and about 1800lbs total, but pretty tight/solid for its size. I turn and thread down to 0-80's with carbide, about 90% of it 316 stainless, some hastelloy and such.
There's carbide for nearly everything, right approach helps. It's more about a good tight machine than weight or HP.

 

[SND]

How long would a typical carbide bit last? I haven't used a lathe before and I am just curious.

Anywhere from 0 seconds(chipping it before starting the cut...) to a few hours. AL and brass and most plastics will go all week.
Inserts are usually rated at 15minutes per edge, but that's on pretty ideal CNC conditions and pushing them to failure within 15mins for max removal rate.
Most run things a bit lower to change inserts less often as that's unproductive time, really varies with material and how supervised it all is, not things hobby/gunsmith stuff ever worries about.
With manual machines and every user/material being different there's no real telling how long they'll last, 20-60minutes per edge would be a good average. A guy could well go a year or more on 1 box of decent inserts that would likely do 80% of his needs.


On a small but somewhat tight machine 1 TCMT holder that takes 1/4 IC inserts, and a boring bar to take the same inserts, will do a lot of work without costing too much and you get 3 tips per inserts instead of 2 with cctm and dcmt's.
Usually best to stick to a medium toughness insert for manual applications(the numbers meaning change with some manufacturers), there's tougher grades too that will handles some chatter/abuse a bit better but aren't as hard/long lasting in terms of wear. It's a trade off, we mostly worry about how much material came off in how long, and keeping things accurate, I don't finish with any of my roughing tools. I might go a few days on 1 tip for a finishing inserts, but the rougher could be getting turned every hour.


Always good to keep in mind that DOC is free, wrong SFM is what kills most tooling, have it be HSS or Carbide. It has to run in its happy speed, too slow is usually not good, too fast is definitely not good.

Grinding HSS bits is pretty easy to learn and spending 15 minutes with someone who can show it would have anyone well on their way.
There's a very large community of people who machine as a hobby, no prior training and they do some pretty amazing stuff in the steam, clocks and other such interests and often on much less than ideal equipment.

 

[SND]

Biggest issue with smaller and looser lathes is trying to part things off. Most times you're better off putting it in the saw and properly face to length after.
But nothing like breaking a parting blade to make sure your heart is still in shape...

If your lathe has 2pc jaws, its great to have a few sets of aluminium soft jaws, make your own if you have a mill.
Lots of other good info on practical machinist and there's other forums more dedicated to hobby related stuff. There's many ways to get things done, main thing is to keep all your fingers and play safe.

 

[ciphery]

Only time id recomment carbide is for threading, makes it soooooooo much easier for set up and threading.

HSS is good for most stuff but requires coolant, not always an option when a lathe can go untouched for weeks if not months at a time. So carbide can be good there as coola t is not used with carbide inserts.

(Carbide)"is sooooo much easier to set up for threading"...can you explain how centre high adjustment and angular adjustment are different in setting up a carbide vs.HSS tooling? Both have to be set to the correct hight and squared to the work surface.

"Coolant is not used with carbide inserts".....Are you kidding?

"HSS is good for most stuff but requires coolant"......Again,are you kidding?

HSS can be run dry, in fact I just finished turning a 3" piece of 416 stainless @ 690 RPM with a .050" cut on.012"/rev feed with HSS and no coolant and have a decent surface finish, peeled that stock down to .750" over a 3" length and then finished it with out sharpening OR coolant use.
Also coolant can be oil based and actually provides lubrication and protection to a lathe. Try using monarch cutting oil sometimes. Works great!......but from your statement I would surmise that you don't actually machine anything.

Now if you are talking high feed rates and exotic or tough meterials such as inconel, 4140, induction hardened 1048 chrome rod, A2 tool steel etc then yes HSS does start to fall short of being adequate. But the OP is looking at hobby production gunsmithing jobs not production.

 

[ciphery]

Kbc has good stuff , don't waste your time with HSS, takes lots of skill to sharpen it too work properly, something the hobby machinist lacks, takes long time to learn tool grinding skills

LoL......Really? I would say that HSS is more forgiving to a beginer.
1) Learning to profile and sharpen a tool bit, drill etc is a neccessary skill for any machinist...first skill learned actually if I remember back to my first days correctly.
2) Pulling up a chart for relief/rake angles is simple with google...and if you don't have a machinists protractor/ combination square set to gauge the work you are doing then get one! Its a neccessary tool (probably one of the most used tools) for a machinist.
3) Takes very little time to learn and needs to be learned.

Owning a micrometer and a lathe does not a machinist make.....learning the skills does.

 

[ciphery]

Where do you buy your zirconium belts?

Originally I bought them from a knife making and gun smithing supply company in Oklahoma....Jantz supply
I then bought indevidual belts from an ontario Knifemakers supply co., Jim Downey Supply
Now I buy 10 packs from Mikes Industrial supply or Fastenal

My favorite are Klingspur or 3M although wilton and others make decent products as well.

 

[ciphery]

I'll reiterate the opinion that HSS is the way to go, and the stuff from Busy Bee, bought on sale, is as good as any.

At a buck or so per 1/4" square tool blank, you can afford to have a bunch of them, and practice your grinding. Get a couple of the 3/8 x 1/2 rectangular section ones too, they make great boring and internal threading bits.
A pair of vice grips to keep from burning your fingers while grinding, and don't quench the hot tool in water, until it has cooled in air to well below black heat. Quenching a red hot HSS tool can cause a micro-fracturing on the surface, that can limit tool life. A minor risk, but more probable than you softening HSS up while grinding it.

HSS will hold a cutting edge when it is red hot. The heat treat schedule, to anneal HSS runs into days long, at extremely high temperatures, the alloys used are not subject to losing their hardness by getting the tool hot on the grinding wheel. Tool holder suppliers like Armstrong, used to provide a holder to put your HSS bit into, so that you could lean on the bugger and make the grinder WORK. They had a ball end on the one end so you could brace it against your leg or hip, and LEAN on it! Go like heck, then allow it to cool in air, then grind it for pretty afterwards. Works very well, and cuts down your time sitting in front of the grinder, instead of doing productive work.

FWIW, once you gain some hands-on time, carbide is OK. There is a steep, expensive learning curve, as you get used to not touching the tool against a non-moving work, and you get used to feeding the tools in to the work with some confidence.

CCMT and CCGT are my two favorites. I have a couple of the Glanze (IIRC) Carbide lathe tool kits and boring bar kits from KBC tools, and they are relatively expensive sets for a hobby guy. The carbide inserts that come with, will get you started, then shop Ebay or Carbide Depot or similar cheapskate sources and go from there.
I would skip the Busy Bee house brand insert carbide entirely, and brazed carbide, while it has it's uses, is a bit of a trap, if you think it will save you from having to learn how to grind a cutting tool, as it really should be properly ground to suit the job, which requires a bit more in the way of tooling and grinders, as well as still needing to understand tool grinding, which gets you right where you were trying not to be.

Plain, high carbon steel, makes a really useful cutting tool as well, though heat management becomes a real issue. I make a lot of tools from water or oil hardening rod, that when run slowly to keep the heat from drawing the temper at the cutting edge, can often provide a better surface finish than HSS and take a sharper edge. But too hot for just a second, and done!

Cheers
Trev

Well said. I would like too add for those that don't know and haven't corilated what you have said, that HSS. (High speed steel) is call so because it DOESN'T go soft when it gets hot enough to discolur when cutting OR being shaped at high speeds. This is what seporates it from standard high carbon tool steel.

 

[terry_g]

I have been an amateur lathe operator for over 35 years. I couldn't tell you how many carbide bits I have destroyed.
I replaced my 10K SouthBend a few years ago with a Busy Bee 12 x 36 Geared head lathe a much more ridged machine.

I use both HSS and carbide tooling with good results. I will use carbide if I have a lot of material to remove.
I can cut at over twice the spindle speed on my lathe with carbide. For most finishing work I will use HSS.
A HSS bit sharpened on a fine stone can give very good results.

I was in a second hand store in Surrey a few years ago and bought a hand full of 3/8" HSS tool bits for $20.00.
There were several different brands all American made. The American HSS is definitely superior to the Asian HSS.

Here are some of my most used tools.

Terry

The holders for the carbide bits were made from 5/8" key stock.

 

[SND]

(Carbide)"is sooooo much easier to set up for threading"...can you explain how centre high adjustment and angular adjustment are different in setting up a carbide vs.HSS tooling? Both have to be set to the correct hight and squared to the work surface.

HSS can be run dry, in fact I just finished turning a 3" piece of 416 stainless @ 690 RPM with a .050" cut on.012"/rev feed with HSS and no coolant and have a decent surface finish, peeled that stock down to .750" over a 3" length and then finished it with out sharpening OR coolant use.

With carbide threading holders all you have to do is dial the side of the tool itself (parallel with the cross slide of course). No messing around with a center gauge and eyeballing it. Tool is also ground right on 60, or full thread profile.
Height is same deal either way, dozen ways to do that.
A decent quick change toolpost always dialed in and left square comes in real handy, mostly with a DRO...

For threading I mainly use Vardex, inserts for which can be bought in qty1 from kbc and in many pitches and profiles.


As to turning at over 500SFM in 416 with HSS... well....

 

[Blastattack]

The biggest issue is most people haven't the slightest clue how to set up the machine before the cut. It is critical that people know some basic machining formulas to get optimal performance form their machines. The first thing that any budding machinist needs to know about his or her Material is the recommended Cutting Speed in SFM (Surface Feet per Minute). For example, using an HSS tool the cutting speed for 6000 series Aluminum is approximately 250 SFM. In another example, the cutting speed using a Carbide insert for 4140 Steel (up to 30Rc) is approximately 250SFM as well. All these numbers can be found in tables from your carbide insert manufacturer, or in the Machinery's Handbook. Once you know that number you plug it into the formula:

This formula applies to both rotating parts and rotating tools.

(4 x SFM) / (Diameter of part OR tool) = Optimal RPM

Here is an application of the formula:

You need to turn a 3" diameter piece of 6061 T6 aluminum with an HSS tool. Find the RPM

We know the Cutting speed for 6000 series is 250 SFM with an HSS tool, and we are given the diameter of the part.

(4 x 250) / 3 = 333 RPM

You now look at your lathe, and set the speed to the number nearest to that, the higher or lower speed depending on what type of cutting you are doing.

It can also be applied to all rotating tools;

You need need to use a 1/2" HSS drill to make a hole through annealed 1018 mild steel. Consulting the Machinery's Handbook, we find that the optimal HSS cutting speed is 110 to 120 SFM.

Plugging that into our formula:

(4 x 110) / .5 = 880 RPM

The drill press or mill should be set as close, and usually just below, to that speed as possible.

If you set your machine properly, you will all have way fewer problems, regardless of whether or not you are using hand ground HSS bits or carbide inserts.

 

[Aries-]

(Carbide)"is sooooo much easier to set up for threading"...can you explain how centre high adjustment and angular adjustment are different in setting up a carbide vs.HSS tooling? Both have to be set to the correct hight and squared to the work surface.

"Coolant is not used with carbide inserts".....Are you kidding?

"HSS is good for most stuff but requires coolant"......Again,are you kidding?

HSS can be run dry, in fact I just finished turning a 3" piece of 416 stainless @ 690 RPM with a .050" cut on.012"/rev feed with HSS and no coolant and have a decent surface finish, peeled that stock down to .750" over a 3" length and then finished it with out sharpening OR coolant use.
Also coolant can be oil based and actually provides lubrication and protection to a lathe. Try using monarch cutting oil sometimes. Works great!......but from your statement I would surmise that you don't actually machine anything.

Now if you are talking high feed rates and exotic or tough meterials such as inconel, 4140, induction hardened 1048 chrome rod, A2 tool steel etc then yes HSS does start to fall short of being adequate. But the OP is looking at hobby production gunsmithing jobs not production.

For threading im not talking hss inserts im talking hand ground.

In general a good way to crack kr chip carbide is to run coolant as the rapid heating and cooling causes the carbide to expand and co tract and crack.

On the flip with hss, if you dont use coolant and you take standard depth cuts, you are going to heat up and burn up the cutter, by removing the hardening in the tip.

And yes i do machine much, cnc machinist, and tool and die apprentice. And yes, an experianced machinist can run hss without coolant with the correct feeds and speeds but most hobby guys cant read the swarf coming off to see what they need to do. Many i know think the perfect chip is purple in color, and are totaly surprised that the chips i cut are gold and i get much better finishes than them. Or they foolishky think a great big long coil of a chip is awesome, when in actual fact its dangerous and terrible for surface finish.