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DaHui
03-08-2010, 07:20 PM
"Carbide inserts aren't for the home shop"

So I know this gets tossed around a lot. There are supporters in both camps. However, I use insert tooling almost exclusively on my Shoptask and Hardinge HLV-H. Why? Because it works.

Today I upped the ante. I've been machining a 303 stainless backplate for a 5" chuck. Outrageous I know, but you should see the surface finish! (I'll take picture soon, sorry) But that's not the story. I mainly wanted to try this notoriously difficult stainless machining myself.

That went so well I went out and bought some 304 because it's "less machinable." A good learning experience right? I turned and faced a 2" round in preparation to make a mounting hub for a diamond grinding wheel I bought. I was a little worried, cause you know, 304 is hard to machine. If I keep the DOC within the horsepower of my machine, it's a piece of cake! Once again, the surface finish is astonishingly good. Henceforth I'm going to make everything out of stainless until my bank account is dry.

Of course without carbide I wouldn't think about working this stuff. Based on the temperature of the little chips that landed on my arm I'm going to say HSS would burn up quick. To me, both the 304 and 303 turned quite easily. Of course hole drilling and milling could be different, but so far so good.

I also wanted to put another check in the "in favor of carbide on small lathes" column.

boslab
03-08-2010, 07:28 PM
you are of course suffering from surface finish madness, its common, knock a few tipped tools together whilst facing east, drink some beer and do some single point threading on a lump of 316L and behold the torn and mangled thread, you will be cured of stainless lust and crave rust forever [its an ancient Druidic ceromony so make sure you do it in the right order or youll render yourself sterile, you have been warned]
regards
mark

vpt
03-08-2010, 07:37 PM
I just turned some stainless with a carbide tip the other day in my atlas.

lazlo
03-08-2010, 07:46 PM
Oldie but goodie:

Carbide for the HSM (http://www.thegallos.com/carbide.htm)

Mark K
03-08-2010, 07:46 PM
Good info on turning SS with carbide. My light lathe wants your light lathe to say what insert geometry and grade it likes so well.

Pleez?

Mark

Forrest Addy
03-08-2010, 07:47 PM
303 and 304 stainless hard to machine? Not really considering the scale of things. You can't let the tool dwell and when cutting wth HSS, you can't run much over 55 ft/min. Otherwise 300 series stainlesses are fairly routine materials in the machine shop: tough to be sure but readily machinable using HSS or carbide.

If you want difficult to machine materials try some grades of inconel and the machinable alloys under the Stellite brand.

DaHui, It sounds like you're going through a phase where you have to try different materials just because. Go ahead. That'd how you learn. For the record, austinetic stainless isn't the best for chuck backing plates but it works. 300 series stainless is a bit ductile and it tends to gall and self weld. A better material for chuck backing plates is a medium carbon steel like 1040, a low alloy steel like 4130, or cast iron. But stainless if you have it, will work. It is expensive if it's purchased for the purpose.

The main problem with using carbide on small lathes is the lathe's low power and rigidity and slow spindle top speed. When you work materials about 1" dia with tooling intended for 350 ft per minute your optimum cutting speed is 1400 RPM or so. 1400 RPM x 0.008" per rev is 11" per min. if you have a 1" cut you're done in a second. Not much time if you have to blink.

I get the feeling for most noobs the big advantage to carbide is it's harder than HSS therefore: you don't have to sharpen it. Another is you simply replace the insert instead of sharpening the tool. And maybe subconcously the thought is if you're using carbide you get some brag rights like you're running with the big dogs. Well, not really.

Tool selection is all about the bottom line in a commercial shop. The more stock you remove in a given tooling applicaton the better the economics of parts manufacture work out. Carbide when run properly will last for about 1 hour of cutting time, same as HSS. This is for GP tools. Expensive-to-sharpen form cutting tools are babied to prolong their lives. GP tooling is used to max material removal.

A home shop machinist proceeds from a different perspective. It's the difference between shipping and yachting or model railroading. Carbide when used in a commercial shop is an economic decision because carbide when efficieently used quarters machining time (compared to HSS) and the cost per cutting edge is much less than HSS. Therefore carbide has dominated parts manufacture for several generations.

Using carbide on small low powered low top speed lathes may be counter-productive from one perspective but from the home shop user's it may just be an interesing problem.

I don't mean to trivialize the intentions of a home shop machinist using carbide tooling on his SB9 but I do hope to give him some perspective. Everyone has to learn hs business. That's part of the enjoyment: reviewing progress. Here's hoping the noobs in the home machine shop learn to use feeds and speeds appropiately to maximise both their enjoyment and productivity regardless of tool selection; carbide or HSS.

Carld
03-08-2010, 07:53 PM
You can use carbide inserts, brazed carbide or HSS on any metal turning lathe. Some metals require carbide to machine them and some may even require Boron, Ceramic or Diamond to machine them. The advantage of carbide is high speed, high DOC and heavy feed that you can't do with HSS. Carbide and HSS have their good and bad points and when used in the right application they do a good job. Knowing what range of SFM to start at will get you started and there is nothing magic about it at all.

Most carbide machining requires a gear head lathe to get the best results and performance out or carbide cutters, brazed or insert.

The biggest advantage to insert holders it that you can index the insert or replace it with different grades of carbide and other compounds. For almost every home shop job brazed carbide and HSS cutters are the best and cheapest to use. In fact for home shop machining carbide is rarely needed.

oldtiffie
03-08-2010, 08:19 PM
In amongst the clutter here is a Sieg 6" lathe. It has no rack - just a lead-screw that is operated from the tail-stock end of the lathe bed.

http://i200.photobucket.com/albums/aa294/oldtiffie/Shop_and_tools/Shop_tools2.jpg

It is an electronically controlled variable speed machine (~ 100>2,000RPM) with no back-gear for increased torque at low revs.

It is very accurate but has very little torque at low speed so machining say a 2" diameter bit of mild steel is a PITA as it stalls with any "decent" depth of cut or feed using low revs for HSS tool bits. The answer is to use TC (brazed) bits and up the revs - and it works fine. Using HSS for say brass or aluminium (any reasonable size) or smaller sizes is fine but for say mild steel - say up to 1/2" or 3/4" is OK with HSS but the TC is better most times.

A "spring" or "skim" cutt is usually done with a very sharp HSS tool-bit and/or a file or fine grade "wet and dry" (used "wet") paper.

The lathe is rarely used but when it is needed - when the larger lathe is "busy" - it is just fine and earns its keep.

I have all the attachments for it - and it works fine with an end-mill.

So, my limitation as regards using HSS or TC is governed to a large extent by the power requirements of that machine.

DaHui
03-08-2010, 08:25 PM
Here is the tool I have, takes 32.5x size DCMT inserts. I have been trying various inserts and frankly for multi-purpose turning they all work pretty well. I mostly use finish inserts for 'everything'...I have a light lathe.

http://www.the-alchemist.com/Images/Shoptask/Dropper/DSC04921.jpg
The insert in this image (below) is a SECO 32.52-F1 TP2000. I also have the same insert in the F2 chip breaker that is TM2000...I think. The grade is the new "black" SECO grade. I recently picked up some Sandvik DCMT-32.51PF CERMET inserts to play around with. That's what I used on the 303 but I hogged out my 304 backplate with the black F2 finishing inserts.

I know you don't "need" carbide in the home shop but if you want to spend more time making parts and less time honing/grinding/lowering SFM to use HSS, then carbide is the way to go. It's kind of like saying you don't "need" high quality tires on a car. Just so happens that I'm the kind of person that does. Heck I part off at 500 rpm with my insert tool. Try that with HSS. The satisfaction alone is worth the price.
http://www.the-alchemist.com/Images/Shoptask/compound_base/tool_tip.jpg

Oh and a pic of some of my HSS tools just in case anyone is wondering. I like to single point with a HSS tool that I ground, just because I ground it. The main point of this thread is not to dismiss the use of HSS but just to share my experiences with carbide and that it can be friggin' awesome in the home shop. I'd also note that I started out with one of those import triangular insert sets and it wasn't worth the money. The fancy SECO stuff is worth the money IMHO.

http://www.the-alchemist.com/Images/Shoptask/tools/group.jpg

DaHui
03-08-2010, 08:31 PM
"In amongst the clutter here is a Sieg 6" lathe"

Okay I'll admit, when I said "light" I guess I still meant something that was too heavy to pick up without mechanical assistance :)

To that point I just ground some HSS tools for a friend that has a sherline lathe. He was using carbide. Of course I told him he was crazy and that you can't use carbide on a light lathe :)

I'll redefine "light" as something around 1HP, hows that?

BobWarfield
03-08-2010, 08:41 PM
Carbide will be right at home on a Hardinge HLV-H.

Cheers,

BW

Mcgyver
03-08-2010, 08:44 PM
To that point I just ground some HSS tools for a friend that has a sherline lathe. He was using carbide. Of course I told him he was crazy and that you can't use carbide on a light lathe :)


your mistake is thinking it terms of 'camps', we're not sports fans here rooting for a team, we're engineers :) .....each material, work or tool, has its properties, characteristics and costs ....and the judgment of what's 'right' or 'works' is multidimensional. What matters is to pick the best tool for the job in the context of the constraints and objectives. Generally, small lathes don't like the large cutting force carbide requires, can't take advantage of its removal rate potentials and in the economics of the home shop. net disbursements are a concern while covering overhead is not....so yeah hss is usually the better choice...BUT...understanding the underlying reasons is important, because its NOT a matter of this or that will or won't work with a small lathe, its about knowing how to pick the right tool for the job

Mcgyver
03-08-2010, 08:45 PM
Carbide will be right at home on a Hardinge HLV-H.

DAHui, you're a beginner right? how many lathes do you have :eek:

airsmith282
03-08-2010, 08:55 PM
i had a 7x12 metal master was my first lathe junk but it was the first anyhow carbide tooling was ok on it runing 500 or so rpm in stainless 303 316 and 316L

my 10x18 busy bee lathe B2227l is great with cabide on any speed, but i do not like to use them often cause i do get better fininsh on HSS cutters that i make my self..

tonight i started a project on chipping hammer iam making for a firend, any how HSS 550 rpm on 3/4 mild steel 9/64 cut each pass and the hss cutter is still all good and sharp..


tried the same deal on the carbide and was ok but did not leave as nice of a finish, even on the fininshing passes the HSS cutters worked best

stainless steel i always get the best results with HSS cutters,,

i have not tried the carbide on a higher speed then 550 but they are ok on home shop machines,
i should mention i usally dont take large cuts on my machine but fiqired why not this time...any how its all good

Black_Moons
03-08-2010, 10:44 PM
I run a 1000lb 12x36, and I STILL love HSS for verious uses.
For one, a couple HSS blanks in the toolbox = any tool my mind can come up with, without a trip to the store.

square bit holding boring bars and flycutters make good use of HSS.
Sometimes I grind unique tools with them, like a two cutting edge grooving tool designed to make a deep square groove 2x or bigger then the tool with a flat bottom, without using more then a small cutting tip to prevent chatter/loading. (ie, not using a form tool)
And by 'deep square groove' I mean on the ID of a hole, tool held in a boring bar.

Or maybe I wanna turn some plastics, sharpening a HSS bit with some insane rake like 45~60 degrees makes a nice razor bit for peeling plastics

I don't see many carbide inserts with such rake. though you can get some 'supersharp' for aluminum inserts, they are usally expensive and not avilable for all size holders.

Of course, I'll not think twice about grabing my carbide inserts for roughing out a few square inchs of mild steel. Might go back to HSS for the finishing pass however!

My threading bits are also all HSS, mainly because I can grind a really sturdy bit and keep it razor sharp easily. you don't want a dull form tool. Also can easily make a few diffrent ones that are offset right or left and diffrent nose radiuses as needed.

a lot of my boring is done with those cheapo brazed boring bars. they work amazingly well. the cheapo brazed carbide square shank tools.. Not so much as they did not seem to come sharpened and where too hard to sharpen with hand hones. Likey work a lot better if you paid for decent ones and had a real diamond wheel grinder to sharpen/form them on.

Its all about the job at hand.

dp
03-08-2010, 10:50 PM
What are the insert holders made of that makes them so expensive? The shapes don't qualify as rocket science, so the material itself must be some kind of rare cubic unobtanium.

DaHui
03-08-2010, 10:52 PM
your mistake is thinking it terms of 'camps', we're not sports fans here rooting for a team, we're engineers :) .....each material, work or tool, has its properties, characteristics and costs ....and the judgment of what's 'right' or 'works' is multidimensional. What matters is to pick the best tool for the job in the context of the constraints and objectives. Generally, small lathes don't like the large cutting force carbide requires, can't take advantage of its removal rate potentials and in the economics of the home shop. net disbursements are a concern while covering overhead is not....so yeah hss is usually the better choice...BUT...understanding the underlying reasons is important, because its NOT a matter of this or that will or won't work with a small lathe, its about knowing how to pick the right tool for the job

Wow that's one of the most well balanced and reasonable paragraphs I've seen on here yet. I thought people loved to camp :) I'm definitely the "right tool for the job" kind of guy. Many opinions (in general) seem to be black or white. I posted the pic of my HSS tools to show that I wasn't a camper but an experimenter. Best way to learn.

And yes, I'm a beginner. Only about 5 years of machining experience. I have a heavily modified Shoptask (my first car) and a 1973 bridgeport and a 1977 HLV.

Mcgyver
03-08-2010, 10:58 PM
And yes, I'm a beginner. Only about 5 years of machining experience. I have a heavily modified Shoptask (my first car) and a 1973 bridgeport and a 1977 HLV.


thanks... 5 years, you're more than a beginner but we're all learning, that's what makes it fun. No offense intended on the the beginner bit, I just guessed from the tone of that post that you were earlier on in the age of discovery, my mistake :)

DaHui
03-09-2010, 12:28 AM
Mcgyver, no offense taken. I'll take myself off the beginner list when I get to ten years :) I often feel like it's my first day. For example, when machining stainless for the first time :)

OldRedFord
03-09-2010, 01:57 AM
What are the insert holders made of that makes them so expensive? The shapes don't qualify as rocket science, so the material itself must be some kind of rare cubic unobtanium.


I wonder about that my self.

macona
03-09-2010, 02:12 AM
They are well machined hardened steel. The ones I have machined down to different thickness have taken carbide endmill to do anything. Made some of the prettiest chips I have ever seen. Each chip had a mirror finish to them.

Then there are solid carbide boring bars. You can guess why they cost a lot!

-Jerry

macona
03-09-2010, 02:37 AM
Heres a project I started over 10 years ago when I had one of the little 7x12 some-reassembly-required lathes. It was going to be a collet chuck. Never did finish it. Made from 4140 and turned with carbide on the lathe. Finish came out pretty darned good really.

http://farm5.static.flickr.com/4037/4419512254_39a6da2a67.jpg

http://farm3.static.flickr.com/2711/4418746149_1031172a0f_o.jpg

Black_Moons
03-09-2010, 05:43 AM
What are the insert holders made of that makes them so expensive? The shapes don't qualify as rocket science, so the material itself must be some kind of rare cubic unobtanium.

nothing fancy afaik!
All steels have about the same rigidity, so unless you are buying a solid carbide insert holder (Do they even exist? how do you make tiny threaded holes in carbide? or do you need a nut for your bolt?), tool rigidity is the same reguardless

Some may be hardened to help prevent damage to the part holding the insert and prevent/minimize damage on a tool crash, and prevent the tool holding set screws in your toolpost from marring the tool, but many people make thier own holders with good success out of mild steel, leaded steel or tool steels.

You can also buy carbide seats that go under your carbide insert to provide the hardened 'seat' for the insert, And you can easily buy the pro insert 'clamps' for a couple bucks. though they look easy enough to make your self, maybe they are really hard or something. Mainly its that $70~200 holder that you should make yourself IMO. the $2 screws, clamps and seats and whatever else you want to use on your holder you can easily buy.

websterz
03-09-2010, 06:29 AM
I have turned a fair bit of stainless on my 7x12 and recently made titanium wedding bands for myself and my wife on the same lathe. I use carbide for 90% of the stuff I run. :)

Mcgyver
03-09-2010, 08:00 AM
how do you make tiny threaded holes in carbide? .

with an EDM....but then problem becomes how do you keep then there :D

airsmith282
03-09-2010, 09:11 AM
nothing fancy afaik!
All steels have about the same rigidity, so unless you are buying a solid carbide insert holder (Do they even exist? how do you make tiny threaded holes in carbide? or do you need a nut for your bolt?), tool rigidity is the same reguardless

Some may be hardened to help prevent damage to the part holding the insert and prevent/minimize damage on a tool crash, and prevent the tool holding set screws in your toolpost from marring the tool, but many people make thier own holders with good success out of mild steel, leaded steel or tool steels.

You can also buy carbide seats that go under your carbide insert to provide the hardened 'seat' for the insert, And you can easily buy the pro insert 'clamps' for a couple bucks. though they look easy enough to make your self, maybe they are really hard or something. Mainly its that $70~200 holder that you should make yourself IMO. the $2 screws, clamps and seats and whatever else you want to use on your holder you can easily buy.


ok lets get a few things on the right track here
1. not all steels have the same or even close to the same rigidity,nor are any 2 pecies the same equally , 2.tool rigidity is not the same either.

as for your tool holders or incert holders for carbide incertes and other such ones they are very difference in quaility of metals used , some are harden some arenot some are made from junk steel good onse are made of other steels that are harden and ground differently as well.

if all things were equal or close to equal we would all be charged about the same price for a junk tool and a good tool but being the case that things are not equal at all and prices and quaility's are different shows in fact that they are not even close to the same

metals are not the same even 2 peices of the same listed grade are not the same strenghts or dencitys and so on , but yes the look the same seem to weight about the same seem to turn the same but there not,it does not take some one witht the IQ of 200 to prove this its plain commen sence and would only make sence to be found to be true,

if the hardness alone is looked at in say 4140 and A4 you can tell right off the start there not the same just by there identifed number code then trun them down also not the same, lets look at surface fininsh ,next a pressure bending test see how many foot pounds it takes to bend the fininsh part even,,,

here is another good exampl of the same steel not the same,

take 2 bars of mild steel for example 1 inch OD put each one threw a bender with a wieght guage and see how mich it takes to bend each bar there wil be a noticable difference, next make your self let say a hammer handel same steel.. turn one out at 350 rpm , the other at 550 rpm, no coolent now fluides of any kind then repeat using coolents and cuting fluids , takethem the back to the bender again you will see a noticable difference on each one how much it takes to bend each one..

the cooler you can keep your metal when building some thnig the stronger that metal is going to be over all.. yes its true some metal work hardens but also when that hardening takes place its going to have a brittle effect unless the harden process for that steel was done right its going to shatter rather then bend..

some steels can also become even softer when over heated as well. so once cooled they are now weaker then before they were cut into..

but hey what do i know i only work at this for a living, and i work alot more then 8 hours a day,speaking of which time for work have a great day guys ill pop in on my breaks..

willmac
03-09-2010, 09:48 AM
"not all steels have the same or even close to the same rigidity,nor are any 2 pecies the same equally , 2.tool rigidity is not the same either."

I think that this is very misleading. All steels have roughly the same Youngs modulus, but different steels and heat treats can have very different hardness and UTS.

Carld
03-09-2010, 09:52 AM
I don't agree that two bars of mild steel will vary in strength. There has been long threads about the bend strength here and the flex of the different alloys as used for boring bars.

If I remember correctly they don't agree with your opinions. When you buy a certain alloy of steel you can expect all that steel to meet the specs of the alloy mix. OTOH if it's made in someones back yard or a hack steel supplier you don't know what your getting.

Steel suppliers have to guarantee the quality of the alloys they sell and they have no trouble doing so.

I am not a metallurgist but there are several here and can give you the correct info.

EVguru
03-09-2010, 10:21 AM
The elasticity of a material (it's resistance to bending or stretching) is described by its Young's Modulus. It only applies until you get to the yield point when the material is permanently 'bent'.

Here's a chart listing Young's modulus, yield point and ultimate strength for a wide range of steel alloys.

http://www.engineersedge.com/manufacturing_spec/properties_of_metals_strength.htm

You'll notice that whilst the Young's modulus is the same for most alloys of steel and pretty close for cast iron and stainless.

The yield strength (permanently bent point) does vary a great deal, but for a tool holder we don't want to be getting anywhere close to the yield point. By definition the tool would be flexing too much!

Mcgyver
03-09-2010, 10:28 AM
nomenclature may be the issue here.....


I don't agree that two bars of mild steel will vary in strength.

what do you mean by strength? Usually taken to mean how much force it can take before it deforms ....and there are absolutely differences, 1018 mild steel is not as strong as 4140.



1. not all steels have the same or even close to the same rigidity,

the do.....if by rigidity you mean how much will it flex for a unit of force, they are all very close. This is for flexing or elastic deformation, ie it will return to its shape after force is removed...before plastic deformation). as willmac says, the Young's modulus are very similar for steels and its the Young's modulus that is used to calculate how much they flex for a given load

when you're thinking about steel and what happens when a force is applied, you've got divide things roughly into elastic and plastic deformation, or how it behaves before bending and when it bends....because the behaviors are different and you'll not understand things trying to lump the two situations together

knudsen
03-09-2010, 11:55 AM
I've used phase II 3/8 tools with carbide inserts over ten years, closer to 15, on all materials I turn (Al, copper, brass, SS, mild steel, and even plastics). I've also used braised carbide and hand ground HSS. Keep in mind, I probably spend less time in the shop than many of you, so take that 10 or 15 years with a grain of salt. I never understood how the inserts are inappropriate for HSM use. Perhaps you can get a better finish with HSS, perhaps that depends how good you are at grinding the tools and using them. I also have HSS inserts for the phase II's, US made. Last month, I did and experiment to determine weather HSS itself, under otherwise identical conditions, is indeed a smoother cutter, or if that's an urban legend. I was proving this to myself. I didn't take pictures.

So, I took a 1/2" piece of mild steel rod, chucked it in a 4 jaw chuck, and got the runout down to under .0005, about the best I can do without a smoother finish on the raw part and getting a DTI on it. Using Auto feed, I'm taking three cuts on the same part. I figure rechucking may introduce some sort of error, and if there is enough flex of the steel rod to effect finish, it should show on my control cut. I also changed the inserts, not the tool holder, and I marked the tip under test, so I wouldn't turn the tip, exposing a fresh or otherwise different edge.

Next, I wiped a coat of beeswax/kerosene on it and took a .75" long .020 cut on the end with a carbide insert (carbide test cut), dialed the tool away two full turns, went in another inch, advanced the tool in again two full turns and took another .75" cut (control cut), then I removed the insert, replaced it with a new HSS insert and repeated the cut between the two other cuts (HSS test cut). I could see no difference between the three cuts.

Repeated the cuts, this time at .010, and I still couldn't see or feel any difference between the three cuts.

Repeated the cuts, this time at .005, and I still could see a slight difference in color between the three cuts. Maybe not color, but darkness or contrast or something. Could not feel a difference with my fingers, or by running my thumbnail across the cut.

Repeated the cuts, this time at .001, seemed the same as .005, maybe a little more contrast or color difference, or maybe my imagination. It was not a big enough difference to know for sure if it changed.

The control and carbide cut always appeared and felt identical to each other, thus validating the test, If there were any differences between cuts, they were negligible. At this point the finish was better than I require for 90% of my work.

Next I sanded a cross hatch pattern onto the part using #80 emery and the diluted beeswax, sanding back and forth across all three cuts at low RPM. After sanding, all three parts looked the same again. I doubled the RPMs and went to #120 and moved slowly to remove the cross hatch. Finally I ran it full blast and hit it with #180, resulting in a very fine finish. I probably spent 10 minutes sanding the roughly 3" section. I concluded, under the conditions I normally use, the final cut may be different, but not better or worst. Any differences can quickly be removed by sanding. After sanding, the finish is better than I really need for anything.

I thought perhaps the HSS got dull. So, I repeated the entire process except for sanding, using a new edge each cut on both the HSS and the carbide. Results were about the same. I also did the same test on Al, and the contrast between the cuts was definitely more so than steel and it seemed to have a little more shine to it, but again felt the same. Didn't bother sanding it. I'm sure the difference would just sand out. I don't recall what RPMs I cut at, but for each series of cuts, it was unchanged.

It would be interesting to see what results others get from the same tests, altered to your typical cutting conditions.


But you must always strive for perfection, get the best finish you can, blablabla...

Shut up, head.

fasto
03-09-2010, 12:43 PM
I use carbide on plastics. I mainly work PVC and CPVC. Plastics are surprisingly abrasive, especially the PVC families, because a clay-based filler is normally used. I can't get anything near the recommended SFM in plastic that is recommended for metals (the plastic just melts). I get very good, bordering on fantastic finishes running around 250 RPM on a 2.5" dia part, using those horrible TPG32x inserts in a zero-rake holder. Positive rake is really a no-no in soft plastics! I'll take as much DOC as I can, usually 0.100 or more, at as fast a feed as I can get away with, 0.040 IPR is as fast as my lathe will go. It is definitely under some load at those rates, but they provided 5HP and I figure I might as well use it. I have broken the brazing holding the carbide into boring bars until I switched to Armstrong - still using brazed carbide boring bars here.

Fasttrack
03-09-2010, 01:24 PM
we're engineers :) .....


Woah ... hey Mcgyver lets not go calling people names now... :D ;)

Carld
03-09-2010, 04:52 PM
Mcgyver, I said two bars of mild steel meaning the same alloy and that the strength should be constant from bar to bar. I said nothing about 1018 being the same as 4140, it must have been something you was thinking.

We are talking bending strength and the chart by EVguru, http://www.engineersedge.com/manufac...s_strength.htm is worth looking at.

From past threads there is little difference in the flex of metals when used as boring bars or insert holders. There are two different conversations going on here so don't confuse the two.

One group is talking bend strength and another flex strength.

Mcgyver
03-09-2010, 05:27 PM
Woah ... hey Mcgyver lets not go calling people names now... :D ;)


small "e", it'll be ok Tom :)

Carl, I see what you meant now

Black_Moons
03-09-2010, 05:35 PM
Its confusing but true.
the steel alloys all flex the same amount under the same force, its the point they no longer return from being flexed (ie get bent) thats varyed by alloy and heat treatment and such.

And iv still never heard of anyone who has made a mild steel carbide insert holder and bent it turning (Short of a tool crash, And in that case a harder/stronger alloy would surive a bigger crash)


but hey what do i know i only work at this for a living, and i work alot more then 8 hours a day

But what do I know, I just read silly books and listen to people who know more then I do and try to tell me things, since I don't have to work all day I have the spare time to do that.

aostling
03-09-2010, 05:41 PM
In amongst the clutter here is a Sieg 6" lathe. It has no rack - just a lead-screw that is operated from the tail-stock end of the lathe bed.


Tiffie,

You have a nicely organized shop. Now you need to organize yourself into the picture, for our Rogue's Gallery.

MaxxLagg
03-09-2010, 08:43 PM
I use Sandvik insertable turning,boring and threading inserts all the time on our HLV at work. I buzz off .100 on just about anything with no problem, great finish. 304 kinda sucks but 303 is a dream to work with.

lazlo
03-09-2010, 08:54 PM
ok lets get a few things on the right track here
1. not all steels have the same or even close to the same rigidity,nor are any 2 pecies the same equally , 2.tool rigidity is not the same either.

You're confusing stiffness with yield strength. The modulus of elasticity (stress/strain == rigidity) for all steels is ~ 30K PSI. In other words, a piece of rebar has almost exactly the same rigidity as a bar of 4340.

The yield strength (when the material permanently deforms) of steel increases dramatically from alloying element and heat treat.

oldtiffie
03-09-2010, 09:15 PM
This thread is diverging from "Myth busted: can't use carbide on a small lathe" - which seems to have got lost in the fog and more towards "properties of materials" and "big(ger)" lathes.

The topic was about using - or not using - carbide tips or inserts on a small lathe.

I have the same lathe as Airsmith - as do several others here. It certainly can be classified as "light" and so Airsmith is "right on the money" as regards his lathe - even if he may have unintentionally "re-directed" the discussion.

I suspect that the issue is more about the rigidity of the "small" lathe and its set-up as well as the speeds and power of it.

knudsen
03-09-2010, 09:28 PM
Well, Tiffy, my tests (post 31) were done on a 7 x, the flimsiest lathe since the 70's. It's fun to push it to the limit with carbide. It's been a while since I did that on steel, but it seems about .025 is the limit for higher RPMs, and I get nice poofs of smoke and tan chips that hurt and turn black. Like many 7 x owners, I yearn for a larger more powerful lathe, but this one works fine, pushed right up to the jagged edge.

oldtiffie
03-09-2010, 09:49 PM
Thanks knudsen.

I have re-posted that very good post of yours:

I've used phase II 3/8 tools with carbide inserts over ten years, closer to 15, on all materials I turn (Al, copper, brass, SS, mild steel, and even plastics). I've also used braised carbide and hand ground HSS. Keep in mind, I probably spend less time in the shop than many of you, so take that 10 or 15 years with a grain of salt. I never understood how the inserts are inappropriate for HSM use. Perhaps you can get a better finish with HSS, perhaps that depends how good you are at grinding the tools and using them. I also have HSS inserts for the phase II's, US made. Last month, I did and experiment to determine weather HSS itself, under otherwise identical conditions, is indeed a smoother cutter, or if that's an urban legend. I was proving this to myself. I didn't take pictures.

So, I took a 1/2" piece of mild steel rod, chucked it in a 4 jaw chuck, and got the runout down to under .0005, about the best I can do without a smoother finish on the raw part and getting a DTI on it. Using Auto feed, I'm taking three cuts on the same part. I figure rechucking may introduce some sort of error, and if there is enough flex of the steel rod to effect finish, it should show on my control cut. I also changed the inserts, not the tool holder, and I marked the tip under test, so I wouldn't turn the tip, exposing a fresh or otherwise different edge.

Next, I wiped a coat of beeswax/kerosene on it and took a .75" long .020 cut on the end with a carbide insert (carbide test cut), dialed the tool away two full turns, went in another inch, advanced the tool in again two full turns and took another .75" cut (control cut), then I removed the insert, replaced it with a new HSS insert and repeated the cut between the two other cuts (HSS test cut). I could see no difference between the three cuts.

Repeated the cuts, this time at .010, and I still couldn't see or feel any difference between the three cuts.

Repeated the cuts, this time at .005, and I still could see a slight difference in color between the three cuts. Maybe not color, but darkness or contrast or something. Could not feel a difference with my fingers, or by running my thumbnail across the cut.

Repeated the cuts, this time at .001, seemed the same as .005, maybe a little more contrast or color difference, or maybe my imagination. It was not a big enough difference to know for sure if it changed.

The control and carbide cut always appeared and felt identical to each other, thus validating the test, If there were any differences between cuts, they were negligible. At this point the finish was better than I require for 90% of my work.

Next I sanded a cross hatch pattern onto the part using #80 emery and the diluted beeswax, sanding back and forth across all three cuts at low RPM. After sanding, all three parts looked the same again. I doubled the RPMs and went to #120 and moved slowly to remove the cross hatch. Finally I ran it full blast and hit it with #180, resulting in a very fine finish. I probably spent 10 minutes sanding the roughly 3" section. I concluded, under the conditions I normally use, the final cut may be different, but not better or worst. Any differences can quickly be removed by sanding. After sanding, the finish is better than I really need for anything.

I thought perhaps the HSS got dull. So, I repeated the entire process except for sanding, using a new edge each cut on both the HSS and the carbide. Results were about the same. I also did the same test on Al, and the contrast between the cuts was definitely more so than steel and it seemed to have a little more shine to it, but again felt the same. Didn't bother sanding it. I'm sure the difference would just sand out. I don't recall what RPMs I cut at, but for each series of cuts, it was unchanged.

It would be interesting to see what results others get from the same tests, altered to your typical cutting conditions.


They are somewhere between but largely similar to what I'd expect of my lathes.

Here is my larger lathe 10 x 30 (milling attachment since removed) that is similar to what several here have:
http://i200.photobucket.com/albums/aa294/oldtiffie/Lathe_misc/Lathe1.jpg

http://i200.photobucket.com/albums/aa294/oldtiffie/Lathe_misc/Part_off4.jpg

hssmike
03-09-2010, 10:55 PM
Sorry for the delete, it was off topic.


Mike Warner
arwarnerco.com

beanbag
03-10-2010, 06:37 AM
Going back to the original topic a bit, I called Sandvik and asked them whether it was OK to use cermet inserts on a face mill. The guy there was worried that there was not enough rigidity, and that the inserts would be too brittle. Later, I had some questions:

1) how is it exactly that a not rigid machine causes inserts to chip?
2) on a face mill, it's an interrupted cut anyway, so why is rigidity even an issue?

knudsen
03-10-2010, 08:52 AM
I think the answer to #1 is that the spindal may flex back and forth. When it flexes towards the leading edge of the cutter, it digs in and flexes more. It may increase flex until the cut is too deep and break. Light cuts should minimize this effect, but how light? You won't know until you break some inserts.

lazlo
03-10-2010, 09:47 AM
1) how is it exactly that a not rigid machine causes inserts to chip?

Carbide has low toughness (amount of energy per unit volume the material can absorb before rupturing). If you have a lightweight machine that flops around like a wet noodle, the chatter, vibration, resonance, ... is applying an impact force on the carbide, even on an un-interrupted cut.

You know how boring bars chatter and sing? That's because the bar is flexing, vibrating and resonating. Increase the stiffness of the bar (shorten the bar, increase the diameter or use a stiffer material like carbide) or damp the vibration with a bag of lead shot, and it reduces the chatter.

High-speed steel has higher toughness than carbide, so you can have a sharper (more positive) edge, than an equivalent carbide insert, and still retain good edge life.

knudsen
03-10-2010, 11:22 AM
Here is my larger lathe 10 x 30 (milling attachment since removed) that is similar to what several here have:
http://i200.photobucket.com/albums/aa294/oldtiffie/Lathe_misc/Lathe1.jpg

Tiffie, interesting that you pulled off the milling head. Was it in the way, or just unused or ???

I find this one intriguing:

http://www.grizzly.com/products/Combo-Lathe-Mill/G4015Z

But at 1/8 the price of their 16" swing lathe, it's too good to be true. If you look at their page showing all hte lathes, it looks like a much smaller swing lathe with head and tail stocks lifted. I expect 7 X rigidity even if the cross slide and ways were beefy. Probably not capable of using half the swing. Oops, off topic again :p

airsmith282
03-10-2010, 12:59 PM
Going back to the original topic a bit, I called Sandvik and asked them whether it was OK to use cermet inserts on a face mill. The guy there was worried that there was not enough rigidity, and that the inserts would be too brittle. Later, I had some questions:

1) how is it exactly that a not rigid machine causes inserts to chip?
2) on a face mill, it's an interrupted cut anyway, so why is rigidity even an issue?

i have a carbide cutter in my fly cutter and its fine i also have an indeaxable endmill that i also use in my mill and all is good with it to.. you do have to run them fast and take small bites but they work just fine..the mill i have is a ct129 from busy bee with the MT 2 taper.

now i have chipped indexable cutters on my lathe so i dont use them to often i prefer the HSS cutters that i grind my self..

i also use on my mill HSS and Regular carbide cutters and both are also fine in fact the carbide ones are just great..

knudsen
03-10-2010, 04:33 PM
I use carbide, braised and inserts for both 7x lathe and x2 mill. Fly cutters, but no surface mills. The only time I chipped one at all was when I ran it into a piece of broken off carbide drill bit. Barely chipped the tip, and it actually seems to cut OK after the crash. The drill bit tip was maybe .020, likely smaller. I knew I was going to hit it sooner or later, but I kept on going. I have mangled plenty of HSS though. Especially China made HSS. Tried that on a fly cutter and it was a joke. Butter.

oldtiffie
03-10-2010, 05:36 PM
Tiffie, interesting that you pulled off the milling head. Was it in the way, or just unused or ???

I find this one intriguing:

http://www.grizzly.com/products/Combo-Lathe-Mill/G4015Z

But at 1/8 the price of their 16" swing lathe, it's too good to be true. If you look at their page showing all hte lathes, it looks like a much smaller swing lathe with head and tail stocks lifted. I expect 7 X rigidity even if the cross slide and ways were beefy. Probably not capable of using half the swing. Oops, off topic again :p

Thanks knudsen.

The only reason I pulled the milling attachment off the lathe was so that I could fit a new taper-turning attachment to the back of the lathe bed (still not done!!)

It was a very solid drill and mill device and worked very well. It just swung out of the way. The cross-slide has a large flat surface for a tee-slotted machining table to be mounted on. The lead-screw can be disconnected at a dog clutch without up-setting the gear train. The lead-screw acts a mill "X" screw via the hand-wheel that you can see at the tail-stock end of the lead-screw.

http://i200.photobucket.com/albums/aa294/oldtiffie/Lathe_misc/AirSmith09.jpg

http://i200.photobucket.com/albums/aa294/oldtiffie/Lathe_misc/AirSmith06.jpg

http://i200.photobucket.com/albums/aa294/oldtiffie/Lathe_misc/3-in-1connection3.jpg

I bought the lathe as an up-grade from my small 6" Sieg lathe and it worked very well. I up-graded the mill to a HF-45 square column mill but still kept and used the mill-drill on the lathe as well. After that I rather fancied the Sieg X3 mill (smaller square column mill) but decided to convert that to CNC (still to be done too!!!) but I needed the X3 at times so I bought a Sieg Super X3 mill for non-cnc use.

I then had 4 mills but I thought I needed a taper turning attachment for a job I had so I bought one and the mill/drill attachment was off the lathe but the job was needed and I found a "work-around" - so the milling head was off the lathe and the taper-turning attachment is still "in the queue".

The Sieg X3's are much better than the lathe mill/drill and so it hasn't been missed so far.

Drilling on a mill is not a big deal with me as I prefer to "mark out" and centre-punch all of my stuff and use the pedestal drill instead of a mill for drilling anyway.