Lathe tooling
- Thread starter Rotaxpower
- Start date
I think most of the CNC lathe operators out there would be VERY surprised to find that they are not supposed to be using coolant. So would the whole of the Coolant Industry as well.
Coolant. Flood, or none, intermittent coolant can cause problems with some carbide grades and material combinations. Some. Not all. Applying some coolant or cutting oil to the work has inevitably improved, rather than made worse, the output on a small lathe, if the material is one that would normally use a coolant or cutting oil.
Most of the problems you seem to attribute to the use of coolant, are problems of pushing the cutters too hard, generally beyond the speeds and feeds that are reasonable. Especially in a home shop or gunsmiths, non-production shop environment, where set-up is the time suck and the cut is often a very small portion of the work.
Long curly chips jam up the chip conveyor, makes for a lousy return on investment while the guy or gal operating it cleans out a rats nest instead of making good parts, in a production environment. You can get past them if you have the horsepower, but you have to deal with them one way or another if you cannot push the cut hard enough to make a chip that curls and breaks instead of becoming a mile long razor blade.
Do some research into the heat treatment of High Speed Steel. You won't soften it at the tip, in use. You can, however, blunt the edges, by pushing it too hard and by exceeding the work harden your workpiece, and consequently grind the end off the cutter, if you are turning materials that are subject to work hardening, such as some stainless alloys, and Titanium, in particular. Ti. with HSS is a right joy (sarcasm) when you are pushing too hard, or not pushing hard enough. Getting past the hard surface layer of Ti. oxides is a Mo-Fo too. Great when it's cutting well, challenging when it's not.
Most, if not all, of what you say here, does not jive with my experience.
Cheers
Trev
That would depend on how much coolant they can use, and this is a discussion about hobby machinists, most of them aren't going to have a CNC with flood coolant. most are going to be using a spraybottle filled with coolant, in which case it is a BAD idea to use it on Carbide. if you can have a constant supply of coolant onto the cutter, of course use it, every bit of cooling helps with surface finish and tool life. but if it is intermittent than carbide is not a good idea.
Generally speaking with carbide inserts; above 400 SFM we don't use coolant, below 400 SFM we do.
But that's only a general rule. Sometimes if you are doing light finishing cuts using coolant will improve surface finish and/or prevent distortion in thinner walled or smaller diameter parts. If you're not pushing the carbide insert hard, adding a splash of coolant won't crack it.
In regards to coolant, specifically flood coolant; one problem that sometimes arises is you get an 'air bubble' (easiest way to explain it) at the edge of the insert and you can still get premature insert failure despite flooding gallons of coolant at the tool.
It really depends on the job/application/situation, etc etc etc. There is no one universal answer........
But that's only a general rule. Sometimes if you are doing light finishing cuts using coolant will improve surface finish and/or prevent distortion in thinner walled or smaller diameter parts. If you're not pushing the carbide insert hard, adding a splash of coolant won't crack it.
In regards to coolant, specifically flood coolant; one problem that sometimes arises is you get an 'air bubble' (easiest way to explain it) at the edge of the insert and you can still get premature insert failure despite flooding gallons of coolant at the tool.
It really depends on the job/application/situation, etc etc etc. There is no one universal answer........
Thought I might like to chime in ... After 41 years in a jobbing shop the greatest thing I have Learned is that hard and fast rules are not hard and fast. Always more than one way to get a job done. Thermal cracking is one issue the carbide manufactures have really addressed. Rarely see it happen any more. Even have ceramics that handle interrupted cuts with ease. HHS cutting tools still have a place in the shop and I suspect will for a time yet...
In 1974 when I started we had plenty of inserts on the lathes very few milling heads in those days. Thermal cracking was a huge concern. There were still carbon steel drills floating around in those days. Things have changed a lot since then.
Yep. If a fella learns all he knows, from a teacher that learned about the stuff 25+ years ago, then there is going to be some out of date information passed along.
When I was teaching apprentices the basics in the shop, one of the main things we worked on was grinding tools. Not because it was still relevant to a machinist in a production environment, which it pretty much isn't, and nor were we that, but because it gave the person that had the rudiments of the skill, the ability to KNOW that they were never going to be backed into a corner for lack of the right shape, size, angle, whatever, tool. I also spent time with each, digging through the catalogs we had, to show them how they could find the info they needed to choose a carbide insert for a particular application, as well as to familiarize them with the idea that we couldn't possible keep one of every kind on hand, nor did we need to.
Need a special thread form, easy. Need a special width groove, or one with radii at the bottom, easy. Form tools, same. Etc.
Not fast, not cost effective for a production shop. We made one or two parts, or repaired high value aircraft components, where the value was worth taking what time was needed. Spending a few minutes at the grinder, along with a few more at the optical comparator to check angles and sizes, was a LOT faster than waiting for yet another custom tool to be ordered in.
Our work was a LOT more in common with Hobby machining than production work. The jobs typical in a gunsmiths world are similar. Set up time eats the majority. The cut, we can afford the time for the cut to go slow, as it is the minor part of the work of getting the job done.
Cheers
Trev
The hard and fast rules are just fine for peopke who are nee to machining, improving and changing those rules are learned over time. Just like rpm and feed rate's arent set in stone, had one job at the last place i work where we were turning a piece of aluminum that eventualy turned out like a Frisbee, that thin area chattered like mad, i changed the direction of the cuts, helped some, next guy came in and changed the rpm and feed to what you might use for hardened tool steel, very slow rpm and slow feed for 6061 aluminum.
Same idea with turning a barrel between centers, standard rpm and feed is gonna make that barrel scream, slow it down and use a different tip. A follow along rest will help as well.
I run coolant on every part I turn on my cnc lathe, lathe removes a lot of material very fast with one incert edge doing all
the work, I've gone a whole day using the same edge of an incert cutting 4140 parts. If I had not used coolant the incert would of burned up on the first part. Heat kills !
the work, I've gone a whole day using the same edge of an incert cutting 4140 parts. If I had not used coolant the incert would of burned up on the first part. Heat kills !
I'm curious as to what inserts you're using and what contour you're turning.
Heat kills, but that's why the heat is supposed to be going out with the chip.
Steel, specifically, is one of the materials that is recommended to run dry with carbide inserts......
Brassman66
CGN frequent flyer
Grizzly Tools and Busy Bee.
Chinese made stuff I find to be general of better quality then Made in India.
Rarely use carbide tipped. HSS is easy on the pocketbook and easy to resharpen.
Cheers
Chinese made stuff I find to be general of better quality then Made in India.
Rarely use carbide tipped. HSS is easy on the pocketbook and easy to resharpen.
Cheers
lejarretnoir
CGN Ultra frequent flyer
- Location
- 162km from Connaught
I was in CNC shop last year and was surprised to see no coolant being used on steel with carbide inserts. Lots of blue chips.
I wasn't used to seeing that, but there it is.
I wasn't used to seeing that, but there it is.
We run, almost exclusively, Sandvik inserts for milling and lathe. (For the mill the insert tooling is only for facemilling and roughing, we use solid carbide for finishing and for that we always use coolant). But when I hog off a whole bunch of material on the mill with insert tooling, I can put my hand on the part immediately and it's, at most, warm. Don't touch the chips though......
I'm not saying you're wrong for using coolant. With the developments with carbide and coatings these days, you can realistically do it either way with steel (again, depending on your application).
WereWeasel
CGN Regular
- Location
- Albert County, N.B
If you're looking for cheap tooling; go to a machine shop and buy scrap tooling, there are lots of places out there now that don't even sharpen 1/2" and under drills. It's not worth their time. As for tool selection I like brazed carbides, they're easy to work with and you can run them fast moreover they're sharp. Inserts are based solely on geometry so yes they need the higher hp but good brazed carbide note the word "good" (which could also be had on the cheap when half of the carbide gets smashed off) can give you all the versatility of HSS with the the hardness and advantages of carbide.
It'd be good if folks sat back and had a sip of their beverage, and considered the differences between a Hobby user or gunsmith's needs, and those of a commercial machine shop, where the need is to make a profit for the owner. I see a lot of folks assigning the needs of a commercial enterprise, to the users that were, frankly, not needing that type of machining.
Not that a gunsmith does not need to make a profit, just that his needs as far as machining capability, are usually pretty far removed from commercial Machine Shop practice. Hobbyist's, even more so.
Cheers
Trev
Not that a gunsmith does not need to make a profit, just that his needs as far as machining capability, are usually pretty far removed from commercial Machine Shop practice. Hobbyist's, even more so.
Cheers
Trev
Trev, you aren't trying to inject a dose of common sense into this train wreck are you? 
I've been a on and off hobby machinist since I was in my teens 45 years ago. In all that time I've tried out the various carbide tooling here and there along the way. I found that for some things it is needed but for 99% of the machining I do I far and away prefer HSS tooling for the lower cost and ease of shaping the tools to suit my needs of the moment. And, odd though it seems to some around here, the HSS cuts most cast iron, most steels, aluminium, brass and plastic just fine.
On the other hand when I am forced to use carbide tooling for some materials I find that whatever tips or brazed cutters I do have are always the wrong ones for the needs of that moment. And that's something the carbide using shop owners are not mentioning is that we need to read up on the various grades of carbide as well as the shapes when picking out inserts or brazed tooling to do our work.
So I'll just continue to muddle by with my HSS for the most part.
I've been a on and off hobby machinist since I was in my teens 45 years ago. In all that time I've tried out the various carbide tooling here and there along the way. I found that for some things it is needed but for 99% of the machining I do I far and away prefer HSS tooling for the lower cost and ease of shaping the tools to suit my needs of the moment. And, odd though it seems to some around here, the HSS cuts most cast iron, most steels, aluminium, brass and plastic just fine.
On the other hand when I am forced to use carbide tooling for some materials I find that whatever tips or brazed cutters I do have are always the wrong ones for the needs of that moment. And that's something the carbide using shop owners are not mentioning is that we need to read up on the various grades of carbide as well as the shapes when picking out inserts or brazed tooling to do our work.
So I'll just continue to muddle by with my HSS for the most part.
