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View Full Version : Carbide, HSS, and those old textbook deep cuts....



J Tiers
07-16-2009, 01:40 AM
After the "carbide wars", and other discussins of lathe capabilities, it occurred to me that the old-timers seemed to have done much better than we do, despite our high-falutin' exotic grades of carbo-stellite-unobtanium with poso-negatory rake etc.

I often take a pretty deep cut when using the lathe, finding that it produces less bending on the part if the tool is ground right.

But....

Some of those old textbook pictures show small lathes using lantern posts taking off a D.O.C. of what looks like 0.25" or better. You know, the picture with a large coiled single-piece chip coming off the part, and a real whopper of a diameter reduction. The chip does not look like it is a thin ribbon, either, it looks pretty substantial, at least several thou thick.

Have any of you ever duplicated that sort of performance?

Fasttrack
07-16-2009, 01:48 AM
Yes. Next time I have the oppurtunity, I will take a video of my Pacemaker in action. I've not pushed it past .3 DOC (.6 off the diameter) but I've been told the larger Pacemakers could take a .5 DOC and not sweat it. It hums along like it's no big deal. You get a really nice surface finish, even on mild hot rolled steel when you take such a big cut. I was impressed, also, with the tool life. I could remove more material between sharpening taking large DOC than I could with smaller DOC.

Of course the Pacemaker doesn't really qualify for little ... :)

Forrest Addy
07-16-2009, 02:37 AM
They're called full HP cuts. If there is stock to remove the management wants it removed expeditiously. I recall running two heads on a 1960 era King vertical boring mill. This machine didn't have side heads but the rail heads were plenty stout. We had several elevator winch drums to machine for a replenishment at sea project. We're talking 45" dia here.

The machine had 75 HP and with both rail heads going I was removing a bit less than an inch per head at 0.070 feed or there abouts. The material was cast steel and machined beautifully - all 6's and 9's. You could fit about 4 to a coffee cup. As the chips flowed I shoveled them into an ever growing heap eventiually getting 3 ft high so some luckless apprentice could haul them off to the chip facility. The chips were still hot and radiated heat like a steam boler, so hot they scorched a hollow in the wood block floor about an inch deep.

Whenever I had a cut like that going the bosses would gather and grin. It did make a good show. It was fun back in them days.

J Tiers
07-16-2009, 09:59 AM
Hold on there.......

PACEMAKER?

That's cheating and you know it! :D

I mean cuts like that on a 9 or 10 inch SB, Logan, Atlas, etc, the same kind of deal as the old texts.....

Glenn Wegman
07-16-2009, 10:46 AM
Perhaps it's aluminum!

Edit:
..........and the machines were new.

DR
07-16-2009, 10:47 AM
.................................................. ....................

I mean cuts like that on a 9 or 10 inch SB, Logan, Atlas, etc, the same kind of deal as the old texts.....

But, what were they cutting?

Steels tended to be softer, freer cutting back in the day. I have cold rolled mild steel, 1018, purchased 30 years ago, no comparison to what we get these days.

Talk with some old timers in the screw machine industry about the quality of material available today.

BTW, usually when you complain about low quality steel these days someone will pipe in about it being low quality import material. Wrong... It's made in good old USA.

Evan
07-16-2009, 11:40 AM
A quick look in the chip pan of my SB9 reveals a good selection of almost entirely ferrous chips from the last two days. Many are from large diameter drilling but a good number are from turning including some .050 DOC roughing passes taken in 1040 medium carbon steel in high back gear. The really fine chips are from hard turning high RC treated steels with unobtainium inserts with imaginary rake angles.

http://ixian.ca/pics6/chips.jpg

lazlo
07-16-2009, 11:52 AM
Some of those old textbook pictures show small lathes using lantern posts taking off a D.O.C. of what looks like 0.25" or better. You know, the picture with a large coiled single-piece chip coming off the part, and a real whopper of a diameter reduction. The chip does not look like it is a thin ribbon, either, it looks pretty substantial, at least several thou thick.

Right, and those chips are always shown on museum piece South Bends, Clausings, Logans, ... where every surface has been lovingly scraped to 40 points per inch, and the toolpost has been expertly flaked by a master engraver. How come my lathe didn't come like that? :D


Have any of you ever duplicated that sort of performance?

The problem with questions like that Jerry is that it always turns into a "Ah caught a fish this big" free-for-all. The last time someone was complaining about the 7x10 mini-lathe, a guy replied back that he makes his living on a 7x10, and he takes .050" DOC on stainless steel. :rolleyes:

gnm109
07-16-2009, 12:02 PM
Perhaps it's aluminum!

Edit:
..........and the machines were new.

...........and there was no internet with nay-sayers telling them that they shouldn't make cuts like that. LOL.

.

lwalker
07-16-2009, 12:30 PM
That could have something to do with it :-)

I know I make cuts on my little minimill that I keep reading, both here and on the yahoo minimill group, shouldn't be done. I work mostly in 6061, but burying a 3/8 roughing mill full width and half depth is something I do pretty regularly.
Vibrates the living hell out of everything around it, but it removes metal very quickly. I don't get a lot of time to play with my mill, so I try to do as much as I can with the time I have.

When I use the mill as a lathe and chuck up a piece of steel (though I use 12L14 cause it's easier), blue chips go flying.

My philosophy has always been it only cost $400. Push it til it breaks then repair it.


...........and there was no internet with nay-sayers telling them that they shouldn't make cuts like that. LOL.

.

lazlo
07-16-2009, 12:39 PM
...........and there was no internet with nay-sayers telling them that they shouldn't make cuts like that. LOL.

Well, the flip-side is also true: everything/everyone is bigger, better, and smarter on the Internet than in real life ;)

ckelloug
07-16-2009, 12:59 PM
I think Fasttrack may be on to something. I believe that his experience with better tool life taking a larger depth of cut rather than a smaller one has some physics behind it.

I believe that the physics involved in the high depth of cut being easier on cutters is a phenomenon called adiabatic shear banding. In adiabatic shear banding, a very localized stress applied to the metal is intense enough to cause local heating so great that softening occurs. Failure (where the chip leaves the stock) thus occurs in a very thin region which has been heated to the point of softening by physical forces while the remaining material farther from the cut is still at normal hardness.

In short: ASB occurs when the energy deposited by the action of cutting forces accumulates much much faster than thermal conductivity can remove it from the point of failure. The intense mechanical heating with no loss mechanism on a small timescale causes even very hard materials to soften locally and in the machine tool sense cut at a lower than expected force.

ASB also is a dreaded failure mechanism in certain kinds of ballistic armor.

Regards,

Cameron

Mcgyver
07-16-2009, 01:07 PM
After the "carbide wars",

in the task of selecting the right tool for the job, there is no war, just shades of ignorance :D


....and other discussins of lathe capabilities, it occurred to me that the old-timers seemed to have done much better than we do, despite our high-falutin' exotic grades of carbo-stellite-unobtanium with poso-negatory rake etc.

I often take a pretty deep cut when using the lathe, finding that it produces less bending on the part if the tool is ground right.

But....

Some of those old textbook pictures show small lathes using lantern posts taking off a D.O.C. of what looks like 0.25" or better. You know, the picture with a large coiled single-piece chip coming off the part, and a real whopper of a diameter reduction. The chip does not look like it is a thin ribbon, either, it looks pretty substantial, at least several thou thick.







Your comment mentions the lack of modern cutters and DOC but not removal rates....old fashion hss or even carbon steel holds an advantage in DOC. Carbide's stays hard at higher temperatures; temp is a function (mostly) of cutting speed so carbide lets you do is spin faster producing higher removal rates. However with depth of cut the constraint (outside of machine and work rigidity) is spindle HP. As the nature of the cutter material allows a more acute cutting edge on hss, this in turn results in a short shear plane infront of the tool. The shorter shear plane, the wider it can be (for a given HP), ergo you should be able to get more DOC with HSS than carbide.

This is hardly promoting hss over carbide for production where matters is removal rate, however it does explain why the old pics can show a great big depth of cut without the benefit of modern cutter materials

drof34
07-16-2009, 02:31 PM
This certainly doesn't relate to a Logan or SB but it does relate to a large DOC.

I started work in a shop on 1-13-67 and was told about turning a bad soft cast iron roll off a shaft. The roll was about 3' to 4' dia and about 8' long. The shaft was 12" dia and still in good shape. They didn't want to press the shaft out for fear of bending it. So the decision was made to machine it off.

The lathe was a 48" Huston with a 100 HP DC motor.

Three tools were used in a single pass. A gang tool holder was made to hold three tool holders with the second tool 3/4" deeper than the first while the third tool was 3/4" deeper than the second. When the first tool was set for a 3/4" depth of cut, you removed 4-1/2" off the diameter in one pass.

This was before my time there so I didn't see this but I don't doubt it. I did run the lathe and I did see the gang tool holder. (The first liar doesn't stand a chance):D

Jim W.
ps; This isn't a lie.

Forrest Addy
07-16-2009, 04:02 PM
So ya got a 9" SB with a 1/2 HP motor or a 48 Betts Bridgeford with a 50 HP faceplate drive? It all means the same thing: getting the economical best you can from what you got. Good tool selection, technique, job planning, ect and making the cut appropiate for the machine, place in the work plan, and the work goes a long ways to ensure uneventful success and good machine durability.

You have a lot - a LOT - of factors to consider when undertaiking a job on a machine tool if you are to meet the work requirements, minimizing wear on the machine, and keeping the boss happy. Working the machine as near its cutting capacity when possible actually reduces wear and tear. Its the distance traveld with the ways system that produces wear. A dozen cuts where two would do means 7 times as much unnecessary back and forth. The load on the ways from cutting forces is but a small factor. It can't be all light cuts or heavy roughing cuts. Productive operation means the minimum of either that accomplishes the most effecctive work. Regardless it's a balancing act.

A fellow who can make a 1/2 shoulder bolt in a 9" SB with a 1/2 HP motor in an hour is as productive as his counterpart across the shop on a 4 head planer mill hogging inches off big forgings. They both working their machines to capacity. If the machine is running smoothly and the load meter is at or near 100% you really can't do much more.

Evan
07-16-2009, 04:15 PM
I think a big part of the problem is that people are becoming used to the limitations of very lightly built import machines. They don't build'em like they used to and that isn't just an old chestnut either. I went out to the shop and did a maximum effort slabbing cut on my horizontal mill on a big chunk of stainless steel bar.

DOC is about .4" at around 50 rpm on the 2" cutter with width of cut at the bottom 1.5", one pass taking about 2 minutes.

http://ixian.ca/pics6/slab1.jpg

http://ixian.ca/pics6/slab2.jpg

Before anybody asks the mill is an unknown make, probably Swiss manufacture, probably made early in the last century with a three phase 2hp motor and varispeed drive added later.

Liger Zero
07-16-2009, 04:19 PM
Perhaps it's aluminum!

Edit:
..........and the machines were new.

Now you know why that old South Bend on Ebay is beat all to hell.

"Half inch cut on SS, shuuure no problem"

*half hour later*

"Finished. So is the lathe."

:D

Jpfalt
07-16-2009, 04:33 PM
Part of the recipe for the deep cuts has to do with the cutting speed.

I have been able to take fairly heavy cuts on a SB 9 and a Sheldon 11 x 56, but they are done with a high speed steel cutter with the right rake, clearance and lead angles and also run in back gear to get the torque needed to make the cuts. It was done in 1970's produced 1018, 12L14 and 86L20.

A lot of those old really huge cuts were done with carbon steel tooling, also with the right geometry for the steel and run extremely slow. The rule of thumb for carbon steel tools was that if the chip showed color, the tool was wiped out. For HSS, the rule was that if the chip was glowing at all, the cutting edge was wiped.

Glenn Wegman
07-16-2009, 05:02 PM
Depth of cut isn't everything.

Cubic inches removed per minute is what counts.

I'm not so sure running in back gear to achieve a deeper cut is necessarily more efficient than a higher spindle speed and lighter cuts. I've noticed a trend in CNC machining toward higher spindle speed, high feed rate, and lighter depth of cut. Just something to consider.

Glenn

Peter.
07-16-2009, 06:11 PM
Well I for one am very pleased with my first foray into carbide tooling. I made a holder with 5 degrees of negative rake towards the point of a TNMP insert and set-about running some tests on various materials.

Some free-machining steel I have I can run interrupted cuts or normal turning at over .100" depth and keep cranking the feed rate until the drive belt slips. Finish is okay, but I can do better with a nicely radiused HSS tool.

22mm stainless bar cuts very freely - previously a source of frustration to me with HSS tools keep overheating and losing the edges/ workhardening the part. Finish is better than the mild steel, but again I can improve on it with HSS.

An aluminium motorbike handlebar I can cut at just about any speed and up to 1/4" DOC with the insert. Perversely I was expecting to struggle with the finish but it was mirror-smooth.

An induction-hardened excavator hydraulic ram hinge-pin that had previously foiled any attempt at machining I was able to cut through the hardening in .010" passes easily. It did jolt the machine when the cut was interrupted by a grub-screw hole. I tried a heavier cut but the load on the machine was very high and I could take another cut of at least a few thou on the same setting, and I was worried about damaging the machine cutting across the hole.

All in allI'm very pleased. I can use the inserts to remove material at a healthy rate compared to my HSS tools and when I've rouged the parts out I can use HSS to go for a nice finish. I'm going to try some TNMG inserts, and some others too, to see if I can improve on the finishes I'm getting.

aboard_epsilon
07-16-2009, 06:19 PM
I think a big part of the problem is that people are becoming used to the limitations of very lightly built import machines. They don't build'em like they used to and that isn't just an old chestnut either. I went out to the shop and did a maximum effort slabbing cut on my horizontal mill on a big chunk of stainless steel bar.

DOC is about .4" at around 50 rpm on the 2" cutter with width of cut at the bottom 1.5", one pass taking about 2 minutes.

http://ixian.ca/pics6/slab1.jpg

http://ixian.ca/pics6/slab2.jpg

Before anybody asks the mill is an unknown make, probably Swiss manufacture, probably made early in the last century with a three phase 2hp motor and varispeed drive added later.

i would be going a little more careful..and taking meek cuts with that set-up.you're inviting criticism.

all the best.markj

Peter.
07-16-2009, 06:46 PM
Seems to have worked - isn't that all that matters? :)

tattoomike68
07-16-2009, 07:26 PM
Seems to have worked - isn't that all that matters? :)


yep chip in the pan and good part on thier way out is what its all about.

I used to run a 60" king VTL with side heads (55 tons), cross heads, turrets and gang tooling for D&l foundry in moses lake washington. A 1" diameter cut was nothing. it was a 45 HP lathe with a range of .5 RPM to 56 RPM was balls out. at the end of my shift the boys from shake out would run a bobcat loader over to pick up chips.
.
Just so you know cast iron chips dont melt and just float with the slag so they go to the dump, you cant melt them down and make money.Cast iron chips are worthless.

They had a production schedule and some part they wanted 30 per 8 hour shift, after 2-3 month I was doing 100 parts by lunchtime, got a fat raise and would come in and set up all the lathes early mornings. the operators were freaked out at first and wired defectors onto the tool post to keep the chips from burning them all day long.

the owners loved my work and were way cool, the managers did not like me and were afraid of me, I had college and no fear so they would run away when I fired up a machine. It was damn funny.

Fasttrack
07-16-2009, 07:42 PM
So ya got a 9" SB with a 1/2 HP motor or a 48 Betts Bridgeford with a 50 HP faceplate drive? It all means the same thing: getting the economical best you can from what you got. Good tool selection, technique, job planning, ect and making the cut appropiate for the machine, place in the work plan, and the work goes a long ways to ensure uneventful success and good machine durability.

You have a lot - a LOT - of factors to consider when undertaiking a job on a machine tool if you are to meet the work requirements, minimizing wear on the machine, and keeping the boss happy. Working the machine as near its cutting capacity when possible actually reduces wear and tear. Its the distance traveld with the ways system that produces wear. A dozen cuts where two would do means 7 times as much unnecessary back and forth. The load on the ways from cutting forces is but a small factor. It can't be all light cuts or heavy roughing cuts. Productive operation means the minimum of either that accomplishes the most effecctive work. Regardless it's a balancing act.

A fellow who can make a 1/2 shoulder bolt in a 9" SB with a 1/2 HP motor in an hour is as productive as his counterpart across the shop on a 4 head planer mill hogging inches off big forgings. They both working their machines to capacity. If the machine is running smoothly and the load meter is at or near 100% you really can't do much more.

Well said, as usual!

J Tiers
07-16-2009, 10:15 PM
Depth of cut isn't everything.

Cubic inches removed per minute is what counts.

I'm not so sure running in back gear to achieve a deeper cut is necessarily more efficient than a higher spindle speed and lighter cuts. I've noticed a trend in CNC machining toward higher spindle speed, high feed rate, and lighter depth of cut. Just something to consider.

Glenn

CNC can afford it.

I like large DOC cuts for a couple reasons.

1) I use them to make thin-stemmed parts like counterbore noses. The stems are so thin that you'd be forced to nibble them all day or spin 10,000 rpm, which I can't do. So I cut them in ONE pass to finish size, using a large rake cutter that has a small tip radius.

Almost all the cutting is on the END of the part, so there is very little force on the stem, and all that exists is right at the base.

I don't have any rotating centers with sharp enough points to get into a center on the end of a 3/32 stem, which needs a 5/16 nose on it so it is being cut from larger diameter stock.

2) I get bored and tired running back and forth for the 2 zillionth pass, and I am more likely to make a mistake.

With the one-step to finish, I turn a short part, mic it, and if it's good, we just go, otherwise adjust until it is good, and then go. Yes, the large DOC sometimes has a thin chip, but it seems to go faster than a few zillion "nibble cuts", no matter how fast they are.

lane
07-16-2009, 10:45 PM
Yes I have made those kinds of chips with my 10K South bend . 1/4 deep per side cut in the slowest feed and slowest RPM in crs and stress proof even some misery metal. Years ago ran a 21 inch Pace maker 3/4 deep per side in 4140 PH dont remember speed and feed but blue shavings roll up about 3 feet long and brake . Remembered measures some .025 thick and rolled about 3/4 diameter. All that with REX 95 tool steel.

Glenn Wegman
07-16-2009, 11:08 PM
CNC can afford it.

I like large DOC cuts for a couple reasons.

1) I use them to make thin-stemmed parts like counterbore noses. The stems are so thin that you'd be forced to nibble them all day or spin 10,000 rpm, which I can't do. So I cut them in ONE pass to finish size, using a large rake cutter that has a small tip radius.

Almost all the cutting is on the END of the part, so there is very little force on the stem, and all that exists is right at the base.

I don't have any rotating centers with sharp enough points to get into a center on the end of a 3/32 stem, which needs a 5/16 nose on it so it is being cut from larger diameter stock.

2) I get bored and tired running back and forth for the 2 zillionth pass, and I am more likely to make a mistake.

With the one-step to finish, I turn a short part, mic it, and if it's good, we just go, otherwise adjust until it is good, and then go. Yes, the large DOC sometimes has a thin chip, but it seems to go faster than a few zillion "nibble cuts", no matter how fast they are.

There are many different circumstances.

In re-reading my post, I realize I was not very clear. The point I was trying to make was that for general stock removal, it doesn't seem that sacrificing spindle speed for DOC is very efficient. I see references to dropping back into back gear to achieve greater DOC. I would run at a recommended surface speed range first and adjust DOC from there. In other words, I was not recommending a zillion passes, just that I would prefer to make two cuts at .100" doc at the recommended speed range than 1 cut a .200" doc at far less speed. Better chip control too. Keep in mind that I use Carbide nearly exclusively for turning. HSS may be a different animal due to it's more stringent surface speed limitations. I try HSS about once a year and it's like watching grass grow after using carbide!

Glenn

J Tiers
07-17-2009, 12:30 AM
Depends.... if you have HP and the belting/drive to use it, fine.

With flatbelts, you need to keep the belt speed up there, or the HP will stay in the motor. Then you are locked out from the middle speeds, you have to run fast and nibble, or slow and chow down.

The belt limits the HP transmission at the middle speeds, where it just isn't moving fast enough to add up to full HP. You may have a 1HP motor, but only 1/4 HP is gonna ever come through at some speeds.

Slow and chow down works pretty well.

I admit, I switch views every so often. I'll decide fast and more passes suits me for a while, then later I'll be back to deeper cuts and slower rpm, for a few weeks, or more.

For the thin stemmed parts, there isn't as much room for choice.

wierdscience
07-17-2009, 12:56 AM
Sometimes you have to decide.

Do I want to make 15 passes @ .050 and 150rpm,or do I want to make two passes @ .350 and 50rpm followed by one pass @ .050 to finish?

On low hp machines including some of the bigger conehead lathes it's faster to make a small number of deep passes at a lower speed.

Yes a 9"SB will make a .25" DOC pass in 1018,in backgear at .006"/rev.Assuming you know how to grind a tool to do it.

http://www.akpilot.net/How%20To%20Grind%20Lathe%20Tools/How%20To%20Grind%20Lathe%20Tools.pdf

That is from SB themselves,grind up a tool to match fig.26 "Roughing tool" and try it,you may be suprised.

.RC.
07-17-2009, 01:05 AM
Some decent depth of cuts in the video on this page -->> http://super-lathe.com/

wierdscience
07-17-2009, 01:32 AM
Some decent depth of cuts in the video on this page -->> http://super-lathe.com/

Well that settles it,if God has a lathe,it's a Super-Lathe:)

20,000lbs of CHIPS per hour,square tailstock barrel and 10,000 psi preloaded recirc ball ways,nice:cool:

J Tiers
07-17-2009, 10:15 AM
Is Binns still actually in business?

When did they sell their last "superlathe"?.

Probably in 1972, if the pictures are any guide........ the folks in them are all retired or dead now. Looks like a "zombie website" (I'm amazed they HAVE a website) , but I could be wrong.

lazlo
07-17-2009, 11:21 AM
20,000lbs of CHIPS per hour,square tailstock barrel and 10,000 psi preloaded recirc ball ways,nice:cool:

It's a cool video. This is the direct link:

http://super-lathe.com/media/superlathe.wmv

ckelloug
07-17-2009, 11:45 AM
Observations on the Binns web page:

The HTML on Binns' web page is of a fairly modern style and carries a DTD for HTML 4.01 Transitional. It looks like it was done by either a competent web designer or a non-stupid HTML editor program. It isn't MS Frontpage crap.

The site cannot be that old and is unlikely to be abandoned. For what looks to be an inward-looking industry, they may in fact be a leader considering they have a web page.

--Cameron

Evan
07-17-2009, 11:46 AM
It seems they are still in business. I looked up a company profile.



BINNS MACHINERY CO Description
BINNS MACHINERY CO is in the Machine Tools, Metal Forming Types industry in CINCINNATI, OH. This company currently has approximately 10 to 20 employees and annual sales of $1,000,000 to $4,999,999.

Fasttrack
07-17-2009, 12:00 PM
Well it ain't no 20,000 lbs of chips an hour, but it ain't too shabby for 1915...

http://i108.photobucket.com/albums/n22/fasttrack237/1915Adsm.jpg