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View Full Version : do boring bars need hardening?



lowcountrycamo
06-08-2012, 03:45 PM
Making a couple of 3/4" boring bars out of hardened rod. Annealing now. Should I re-harden after machining. Bars will be 10" and 6". Thanks.

justanengineer
06-08-2012, 04:31 PM
If you think you might bend them in use you can, otherwise there is no point. Usually the work gives first tho. ;)

Thomas Staubo
06-08-2012, 05:41 PM
If you just want it to be stiffer (to resist chatter), don't bother as hardening it won't make it any stiffer (search a bit on the forum if you like, it's been discussed before).


.

rohart
06-08-2012, 07:21 PM
Hardening will stop it getting scratched to bits by the swarf it creates, and may help to stop the seat of the insert suffering, if that's the way you are making it.

Hardening is a good idea, but the downside is that after hardening it may not be as straight as it was before the heat treatment. But since it's not a part that has to fit with other parts a slight bend shouldn't be a problem if it happens.

Forestgnome
06-08-2012, 08:17 PM
My thought would be to not harden it, or if you do temper it well. A boring bar can take quite a load at times. I know hardening won't make it stronger, but I wonder if it changes it's acoustic properties. It would be interesting to see if the resonant frequency changes at all. I suspect it doesn't, but don't know.

Evan
06-09-2012, 10:29 PM
To make it clear, hardening does not make the part stronger or harder to bend elastically. It only makes it harder. It will make it possible to bend it further before it deforms permanently but it doesn't make it harder to bend to the same point that the unhardened part would begin to deform. That applies to all steels, alloy or not. They also all have about the same resistance to elastic bending no matter what the alloy.

What does vary depending on alloy and condition is how much force it take to permanently deform the part.

In other words, hardening a boring bar makes no difference to performance.

A.K. Boomer
06-10-2012, 12:55 AM
To make it clear, hardening does not make the part stronger Uhm Ok ---------

It will make it possible to bend it further before it deforms permanently Yeah see that's that part that im having trouble with --- that would be called "stronger" because it takes MORE LOAD to bend it further


In other words, hardening a boring bar makes no difference to performance.


No, wrong "to make it clear" hardening a boring bar make's it not only stronger but more resilient, plain and simple it will be capable of handling MORE load without any permanent damage --- plain and simple it WILL make it stronger...

Also like stated --- it will make it resist gouging and as we all know boring bars choke on their own soup so this is important -------- harden the damn thing - set it and forget it.... it will make it BOTH stronger AND more resilient...

justanengineer
06-10-2012, 01:49 AM
Uhm Ok --------- Yeah see that's that part that im having trouble with --- that would be called "stronger" because it takes MORE LOAD to bend it further


No, wrong "to make it clear" hardening a boring bar make's it not only stronger but more resilient, plain and simple it will be capable of handling MORE load without any permanent damage --- plain and simple it WILL make it stronger...

Also like stated --- it will make it resist gouging and as we all know boring bars choke on their own soup so this is important -------- harden the damn thing - set it and forget it.... it will make it BOTH stronger AND more resilient...

You are correct Boomer, the yield strength does change, but the modulus of elasticity does not. As Evan explained, basically, until you reach the point of permanent (plastic) deformation of the bar, the bar will react, and deform (bend) the same amount given the same force whether it is hardened or not. Maybe others have, but I have never successfully bent an unhardened boring bar, nor broken one. Given that I have stayed within the elastic limits of the bars (never bent one), hardening would make zero difference on the performance of the bar for me. Regarding gouging/damaging the bar, I would much rather a boring bar get marred up than something expensive.

Evan
06-10-2012, 03:18 AM
No, wrong "to make it clear" hardening a boring bar make's it not only stronger but more resilient, plain and simple it will be capable of handling MORE load without any permanent damage --- plain and simple it WILL make it stronger...

It will not make it stronger in any way that matters to a boring bar. It also won't be more "resilient", whatever that is. Resilience isn't a property of metal and it isn't anything you want to have in a boring bar anyway. Hardening increases the metal's absolute failure strength, it's true. That is irrelevant to a boring bar.

oldtiffie
06-10-2012, 03:21 AM
I usually buy mine "ready to use" as a set with the holder/clamp and use them "as is".

If I have to make one I just use plain common old "hot-rolled" and drill/machine it as required. I usually use sound HSS bits (easier to make a round hole than a square one and I can "tilt" the tool to adjust side clearance and rake). I sometimes MIG well the tool to the bar or else silver brase it - what works works. Welding doesn't seem to affect the HSS tool too much if I am careful

If I ever have a problem its usually to do with tool shape or excessive speed or feed or depth of cut. I just "back off" until its woking OK and leave it at that.

Boring tools need to be dead sharp and hand-honed as required.

Evan
06-10-2012, 03:29 AM
I should point out that when I say "stronger" what I really mean is "stiffer". That is what a lot of people consider to be "strength", as in more difficult to bend below the point of permanent deformation.

Stiffness is an intrinsic property of metallic elements and the predominant metal in iron alloys is, of course, iron. The stiffness of iron will be the main factor although there will be some small differences in stiffness in very high alloy steels.

For very superior boring bars tungsten alloys are far better. It has about three times the stiffness of iron for the same dimensions. They cost much more but the difference is large.

A.K. Boomer
06-10-2012, 03:45 AM
Really depends how hard he's pushing his boring bar,

the OP is "do they need hardening" - for the most part I agree the answer is no, unless you make the occasional bottoming out mistake or something of that nature...

But - my beef was with Evans statement that it does not make it stronger - it does, plain and simple -- and if your maxing out your bar or have the occasional bottoming out against the inner facing wall then it can make all the difference in the world.

Resilience is the ability to bounce back after an "incident"

and a hardened bar has that ability more so than one that is not...

It is a term used in many of metal quality and properties books.

My new world dictionary describes just how I used the word;

Resilience; a) The ability to bounce or spring back into shape, position, ect.
b) The ability to recover strength, spirits ect.

Now --- you state that resiliency isn't even a property of metal? really?

definition "a" is widely used to describe certain metals and there properties...

And you also state that it's not even a property you would want in a boring bar anyways? really ? im stating BS, it sure the hell is....

Evan
06-10-2012, 03:48 AM
But - my beef was with Evans statement that it does not make it stronger - it does, plain and simple -- and if your maxing out your bar or have the occasional bottoming out against the inner facing wall then it can make all the difference in the world.


Never will it make a difference that matters. By the time the deflection is to the point of reaching deformation you already have a crash. Before that point there is no difference at all.


It is a term used in many of metal quality and properties books.

What is the "resilience" value of 1020 mild steel?

A.K. Boomer
06-10-2012, 03:50 AM
I should point out that when I say "stronger" what I really mean is "stiffer". that's all I was after - im not trying to badger you about it - I just wanted to clarify the difference


For very superior boring bars tungsten alloys are far better. It has about three times the stiffness of iron for the same dimensions. They cost much more but the difference is large.


What about carbide as far as stiffness - it's pretty good right?

Evan
06-10-2012, 03:54 AM
What kind of carbide?

A.K. Boomer
06-10-2012, 03:55 AM
Never will it make a difference that matters. By the time the deflection is to the point of reaching deformation you already have a crash. Before that point there is no difference at all.




your still not getting it --- if the inner facing wall is a crash of say .075" and just enough to bend the unhardened bar then the one that is hardened will make it through till you hit the feed release...





What is the "resilience" value of 1020 mild steel?

1020 mild steel is far less resilient than heat treated 4130,

are you looking for a number rating? don't - read the write ups about the qualities and properties...

beanbag
06-10-2012, 03:55 AM
Ummm, carbide is tungsten plus stuff. Carbide is like super hardened tungsten.

If this boring bar uses an insert, then yes, I would at least harden the insert pocket.

The one comment from Evan I don't get is why the ultimate yield (strength) of a boring bar doesn't matter. Isn't a hardened bar able to survive a light crash or oopsie without bending?

Jaakko Fagerlund
06-10-2012, 03:57 AM
Resilience is the ability to bounce back after an "incident"
What you are talking about is basically elasticity. This is a defined term in metallurgy and the values are known and measureable.

A.K. Boomer
06-10-2012, 03:57 AM
What kind of carbide?


Im not sure - just know they make large solid carbide boring bars - very expensive and supposed to be very ridged...

Evan
06-10-2012, 04:00 AM
It might survive a crash in better shape but that isn't the point. Boring bars aren't designed to survive crashes, they are designed to be as stiff as possible and still fit inside the work. Tooling is not usually designed with crashing in mind.

A.K. Boomer
06-10-2012, 04:01 AM
The one comment from Evan I don't get is why the ultimate yield (strength) of a boring bar doesn't matter. Isn't a hardened bar able to survive a light crash or oopsie without bending?

Yes - because in his own statement he even admits it can go beyond what the non-heat treated bar can -- this equates directly to higher yield STRENGTH,

the bar is simply more stronger and more resilient for the exact same given size and material - the only difference is the hardening ...

Evan
06-10-2012, 04:07 AM
Im not sure - just know they make large solid carbide boring bars - very expensive and supposed to be very ridged...

Carbide is an "alloy" (compound) of carbon and a metal. Tungsten carbide is just one of many carbides that are common in metal working. It's the tungsten that makes a tungsten carbide boring bar stiffer, not the carbon. There is also silicon carbide, iron carbide, calcium carbide, tantalum carbide and so on. They have very different properties.

beanbag
06-10-2012, 04:07 AM
Us ghetto machinists have mini-crashes, like simply setting the feed rate too high, too deep of a cut, accidentally bottoming out, etc. So my guess is that a boring bar that is "stronger" is more likely to survive.

I wouldn't know because I have never snapped or bent a bar.

Jaakko Fagerlund
06-10-2012, 04:08 AM
It might survive a crash in better shape but that isn't the point. Boring bars aren't designed to survive crashes, they are designed to be as stiff as possible and still fit inside the work. Tooling is not usually designed with crashing in mind.
Not crashes particularly (like ramming the tool in to the chuck), but most insert tools have a hardened and quite sharp seating piece under the insert that will cut most materials for a while before giving up. This gives the operator some seconds to react to a broken insert before ruining the whole tool.

Have ruined my share of boring bars and milling cutters with inserts that didn't have that extra protection (the seating piece) and it is always so nice to order a new 200 EUR holder...

Evan
06-10-2012, 04:09 AM
the bar is simply more stronger and more resilient for the exact same given size and material - the only difference is the hardening ...

Not below the point of permanent bending. In use, a boring bar should never even approach that point with even annealed metal.

A.K. Boomer
06-10-2012, 04:09 AM
It might survive a crash in better shape but that isn't the point. Boring bars aren't designed to survive crashes, they are designed to be as stiff as possible and still fit inside the work. Tooling is not usually designed with crashing in mind.


Boring bars are different that way Evan -- esp. in non-cnc production work where you hit the feed stop and then hand jog it up to your mark,

were not talking about an all out "crash" were just talking about not meeting your mark a couple of passes and then all the sudden you meet it ---- so instead of a .025" little wall you now have .075"

and it may only be .005" deep but it's enough to let you know... to me a good boring bar is designed to survive some fair abuse this way, at least for production work....

The point is - if it's better than its better...

Evan
06-10-2012, 04:12 AM
This gives the operator some seconds to react to a broken insert before ruining the whole tool.

The primary advantage is to prevent deformation of the seating area from the very high cutting forces exerted by the insert on the seat. That isn't at all the same as deflection of the bar. It's a wear issue of the insert seat.

Evan
06-10-2012, 04:13 AM
to me a good boring bar is designed to survive some fair abuse this way, at least for production work...

Hardening is not done for that reason. See above.


The point is - if it's better than its better...

It isn't better.

A.K. Boomer
06-10-2012, 04:23 AM
Hardening is not done for that reason. See above.



wrong - hardening can be done for multitudes of reasons --- overall strength for the same size package is important along with insert wear along with the resistance against gouging from cutting material...






It isn't better.

Of course its better - I just gave you three reasons why...

A.K. Boomer
06-10-2012, 04:27 AM
The primary advantage is to prevent deformation of the seating area from the very high cutting forces exerted by the insert on the seat. That isn't at all the same as deflection of the bar. It's a wear issue of the insert seat.


There's some bars that are heat treated just at the ends and i'll give you that - there's also bars that are heat treated their entire length and that's for overall strength everywhere...


Edit; His OP is asking if they need to be and the answer is NO,
I also would not recommend it at all if like stated earlier it deforms the bar and makes it crooked as then he may have trouble getting it into it's holder --- but if he's confident he can pull it off why not - if he's not then why not do just the end of it to protect the insert seat and also harden the threads for the insert screw - another big bonus for durability...

Jaakko Fagerlund
06-10-2012, 04:45 AM
That isn't at all the same as deflection of the bar.
Didn't say it was.

Evan
06-10-2012, 04:59 AM
The point is that hardening a boring bar will not improve boring performance.

philbur
06-10-2012, 05:36 AM
A tool that survives longer in a crash scenario may have the potential to cause more damage.

If the hardening, and more importantly, the TEMPERING is not performed correctly a heat treated tool will have a greater potential to produce shrapnel when it does fail. :eek:

Phil:)

John Stevenson
06-10-2012, 07:05 AM
The point is that hardening a boring bar will not improve boring performance.

Taken as purely looking at the bar this is true but what it does and will improve is the LIFE of the bar.

I have a commercial one here that has been well made, the insert fits true and is well pocketed, some aren't, but it's been professionally blacked but not hardened.

It's now got to the point were chips from boring into deep bores have eroded the side nearest to the bore with the result the insert side walls are nearly gone.

Black_Moons
06-10-2012, 10:35 AM
Taken as purely looking at the bar this is true but what it does and will improve is the LIFE of the bar.

I have a commercial one here that has been well made, the insert fits true and is well pocketed, some aren't, but it's been professionally blacked but not hardened.

It's now got to the point were chips from boring into deep bores have eroded the side nearest to the bore with the result the insert side walls are nearly gone.

How many holes did that take?

PixMan
06-10-2012, 11:01 AM
Taken as purely looking at the bar this is true but what it does and will improve is the LIFE of the bar.

I have a commercial one here that has been well made, the insert fits true and is well pocketed, some aren't, but it's been professionally blacked but not hardened.

It's now got to the point were chips from boring into deep bores have eroded the side nearest to the bore with the result the insert side walls are nearly gone.

Would that happen to be a bar that takes TCMT/TCGT style inserts? That thin wall of the pocket on those boring bars is why I would prefer bars that take the CCGT/CCMT style inserts.

From 1980 through 1984 I worked at a shop where I ran a lathe with a 27-1/2" (750mm) chuck making parts with bores up to 8" diameter and 8" long. It was all 1020 hot rolled steel. The boring bars were shop-made from soft steel and used brazed carbide tools such as AL8 K21. The boring bars had large areas of worn-away steel from the chip flow, so I had to make new ones about once a year. Hardening would have slowed that down.

My dad's home shop (we share) has a mish-mash of commercially made insert boring bars, and a few Micro 100 solid carbide. The ones I tend to use the most are the 3/8" and 1/2" bars (2nd and 3rd down from top in photo), both take TCxT21.5x size inserts. The insert pockets have the most wear and damage (from the previous owners) right at the tip and to the bore wall side, just as Sir John has noted on his.

http://img.photobucket.com/albums/v466/kenm10759/Dads%20shop/IMG_1251-r.jpg

A.K. Boomer
06-10-2012, 11:38 AM
A tool that survives longer in a crash scenario may have the potential to cause more damage.



I don't believe it's good practice to use your boring bar as the fusible link,

try doing something like adjusting the tension load on the feed spring retention ball and if you don't have something like that then build a failsafe into your system...

Actually - a really good "resilient" boring bar could save your ass too as it will resist giving into the load beyond one that is lesser --- ever wonder why sometimes heavy cuts take even more material than the DRO states?

depends on the insert, rake and a variety of things but also is inherent to the geometry of the boring bar in relation to the part - the tool is being pushed down and torsionally twisted and this makes it drop below the maximum radius line of the part --- now you can have a snowball situation and if the bar fatigues you can have a self initiated crash even though the X and Y are well within safe limits the tooling is not...
This effect is more evident with doing large roughing cuts in smaller diameter bores - like when first starting out after drilling...

But take this with a grain of salt cuz im not a machinist at all - im just a mechanic :D





If the hardening, and more importantly, the TEMPERING is not performed correctly a heat treated tool will have a greater potential to produce shrapnel when it does fail. :eek:

Phil:)

Agree'd do it right or don't do it at all... although just doing the end is less critical than the entire bar...

loose nut
06-10-2012, 11:44 AM
If we accept that crashing a boring bar should be avoided then the biggest reason for improving a boring bar performance is to prevent or stop chatter and deflection. It might be what the OP wanted answered???

Maybe one of the more knowledgeable can answer this.

I have solid carbide bars that work very well, carbide insert boring bars (brand name not cheap crap) that are OK but not great, Heavy steel bars for HSS tool bits again OK but not great, a cheap set of the same that aren't worth getting out of the box and the ones I use the most are solid HSS or HS end mills with the extra teeth ground off. These seem to resist chatter the most and give a good finish to size.

Why is this. HSS versus ordinary steel?

Forestgnome
06-10-2012, 12:02 PM
The point is that hardening a boring bar will not improve boring performance.
Plus it's faster to make. You can get back to making whatever it is you were going to make a lot faster. If the boring bar doesn't quite meets your needs you havn't wasted a bunch of time hardening. None of the boring bars I have that use HSS bits are hardened and they work just fine. I would keep an eye out for a good deal on a carbide (tungsten) bar too, as they are really nice to use, very stiff!

A.K. Boomer
06-10-2012, 12:13 PM
Depends what you mean by "boring performance"

boring performance in a perfect world or what happens to boring bars after 5 or ten years of use in all different kinds of situation's

I.E. there's a reason why the really good ones are hardened - and they are a little more pricy due to that fact too ---- but you will have them longer - won't have problemo's with the insert seat and threads - they are far less likely to "get bent" and they will not "erode" from abrasive swarf around the insert area.
Also - if you have the set screw type bar with a flat on it then you do not have to keep going back and checking the tension of the screws as they dig their way into the soft bar material, those have a tendency to not look to pretty after awhile too...

Now - if that's not better boring bar performance then I guess I don't know what is...:rolleyes:

Here's a question that should shut allot of yaps on the subject --- your in the market for a good BB,

you go to your favorite supplier and he has two identical bars - same brand same good material except one is hardened and the other is not, but for this week and this week only the price on the heat treated bar is the same as the one that's not ------- seriously - which bar are you going to buy?

please - be honest, and if you say the one that has weaker threads and insert seat area and cannot handle as much load and get's eroded over time and on and on and on then at least give the miraculous answer were all waiting for as to why this pile of crap (sorry - inferior bar in comparison) is somehow better than the better bar... thanks for your time...

Evan
06-10-2012, 08:57 PM
Now - if that's not better boring bar performance then I guess I don't know what is.

Performance is about making a hole in the work larger and how well that operation is performed, even just once. Note the words performance and perform have nothing to do with how long it will perform. The stiffness of any particular material cannot be significantly altered with usual manufacturing processes, including hardening.

Regardless of what material the bar is made from it will have the same boring performance no matter how the material is treated. Hardening has just as much effect on performance as painting or blackening the bar. How long the bar lasts and how it might wear is not performance, it's durability. Drag racing is a good example of the difference.

HSS and mild steel bars have the same stiffness per unit area. Some high chrome steels are slightly stiffer but no more than a few percent.

It is possible to significantly alter and increase the modulus of elasticity of some steels (mild steel for instance) by applying sufficient stress to cause severe strain hardening. The amount of stress required is just short of causing ultimate tensile failure. That also reduces other properties such as toughness.

BTW, the property "resilience" is a measure of how much restoration to original shape may be expected from a deformed material. It isn't a property of metals.

flathead4
06-10-2012, 10:30 PM
same brand same good material except one is hardened and the other is not, but for this week and this week only the price on the heat treated bar is the same as the one that's not

Price is not a property of metal, either.

Tom

A.K. Boomer
06-10-2012, 10:57 PM
Price is not a property of metal, either.

Tom


Metals not free, and neither is heat treating -- so it can effect your decision in what you buy,

So what - are you afraid to answer the question? what bar would you choose - the more durable and resilient one or the inferior one?:D

A.K. Boomer
06-10-2012, 11:25 PM
BTW, the property "resilience" is a measure of how much restoration to original shape may be expected from a deformed material. It isn't a property of metals.


What? valve springs are material - and they are metal, and they deform and change shape - in fact Valve springs are the king of resilience due to altering their shape and then springing right back to original sometimes over 150 times per second,

It is the same quality of a boring bar that get's pushed beyond what it would take to bend one unhardened of same material yet it will not bend and will retain it's original shape, it therefor is more resilient... that cannot be argued with - it's a plain fact.


I gave you the definition of "resilience" before

here is the definition of "resilient"

Resilient; 1. bouncing back or springing back into shape, position, ect. after being stretched , bent, or esp. compressed...



durability is also a quality of heat treating as it will resist scuffing and wear.
But that comes into play more at the insert end of the bar...


Open up a metallurgy book and read about the characteristics of metals esp. after they undergo a heat treat process and you will find the word "resilient"...

flathead4
06-10-2012, 11:33 PM
So what are you afraid to answer the question? what bar would you choose - the more durable one or the inferior one?

It is a common tactic of sellers to lower the price of their slower moving, higher priced mechandise to move it off the shelf. When they do, more buyers will jump at the lower price. I do, if I am in the market. One could make the case that most buyers don't value the added "durability" enough to pony up the extra cash since they will only buy when the item is on sale.

Tom

A.K. Boomer
06-10-2012, 11:39 PM
So you just answered the question,

given the same price you would choose the heat treated BB...

no further questions...

flathead4
06-10-2012, 11:52 PM
Actually, I said that I would not pay extra for a heat treated bar. I said I would only buy if it was on sale.

Tom

A.K. Boomer
06-11-2012, 12:13 AM
yes - on sale for the same price as the non-heat treated.

A.K. Boomer
06-11-2012, 12:28 AM
BTW, the property "resilience" is a measure of how much restoration to original shape may be expected from a deformed material. It isn't a property of metals.



Just like I stated earlier when it comes to metals you will generally find the words resilient and durable in regards to heat treating...

"Our blocking hammers are heat treated after they are CNC machined from 4340 steel to make them exceptionally durable and resilient."

http://www.fournierenterprises.com/cart/product.php?productid=16185

A.K. Boomer
06-11-2012, 12:44 AM
Regarding gouging/damaging the bar, I would much rather a boring bar get marred up than something expensive.


Yes but swarf is not something expensive ..:)

justanengineer
06-11-2012, 08:35 AM
Yes but swarf is not something expensive ..:)

I was thinking more along the lines of a tool holder or in my case, a boring tool post.

Your point about purchasing a boring bar is moot in many situations here tho. Im one of many on here that would never buy a boring bar bc I can make them cheaply and easily to fit the specific setup I need. Being that Im not a production shop, I have no need to use insert tooling and rather choose to use HSS and brazed carbide, and in my shop a boring bar has a good chance of outliving me.

If youre super concerned about lifespan of a boring bar, it really should not be machined steel stock regardless, it should be carbide or other harder materials. Personally, if I was to need a more durable boring bar, I would simpy acquire a few round stock forgings as I have access to a free source.

lowcountrycamo
06-11-2012, 09:37 AM
Thanks to all for input. From what I learned hardening might help around the margins but is not essential such as would be with collets, parallels, ect. I never imagined that I would bend it from a crash but was more concerned with chatter. I am making one for hss and one that takes inserts. Because I enjoy the process I might harden the seat but will leave the rest alone.

I also learned that price is an important quality in steel not mentioned in Machinery's Handbook.:)

A.K. Boomer
06-11-2012, 09:56 AM
double post.

A.K. Boomer
06-11-2012, 09:59 AM
I think that's a wise choice as it will make the seat and threads more durable and easy enough to do, and right you would not improve the chatter factor either way if you did the entire bar, although I will say this -- if it's a bar with a flat on top and your holding it with set screws - check those set screws for tightness after a really good chatter "sessions" because odds are they will have sunken into the "cheese metal"

It's not that price is a quality of steel - it just makes it more obtainable, and a good quality heat treat isn't free...;)

Evan
06-11-2012, 03:37 PM
I will ask you again. What is the resilience of 1020 steel?

Evan
06-11-2012, 03:40 PM
Price is not a property of metal, either.

I see you are not familiar with the gold market. :D

A.K. Boomer
06-11-2012, 03:53 PM
I will ask you again. What is the resilience of 1020 steel?


and I will tell you one last time --- 1020 mild steel is far less resilient than heat treated 4130,

are you looking for a number rating? don't - read the write ups about the qualities and properties of how the material is effected and takes to a proper heat treating... like the example I gave earlier,

"Just like I stated earlier when it comes to metals you will generally find the words resilient and durable in regards to heat treating...

"Our blocking hammers are heat treated after they are CNC machined from 4340 steel to make them exceptionally durable and resilient."

http://www.fournierenterprises.com/c...roductid=16185

this is all getting easier for me cuz I can just copy and paste everything --- have a nice day :)

Evan
06-11-2012, 04:18 PM
Find me an example.

A.K. Boomer
06-11-2012, 05:01 PM
Duh,,,

first I correct you on the definition of strength and how heat treating a boring bar adds it - then I correct you on how many ways heat treating makes a boring bar more durable - then I correct you that the words both resilient and durability are used to describe the characteristics of what happens to certain metals after they undergo a heat treating process - then you want an example and I give it to you, then you brain fart and ask again and I give it to you, then still one more time you ask again when it's hanging right above your post you just wrote,

so now it forces me to get personal --- did you have a stroke recently?

are you feeling ok? is there anything we can do for you?

If something like this happened please have you wife PM me with your address and I will put together a nice care package for you -- maybe some of the other guys will pitch in too,, good luck to you old friend... were all pullin for ya...

flathead4
06-11-2012, 05:11 PM
"Just like I stated earlier when it comes to metals you will generally find the words resilient and durable in regards to heat treating...

"Our blocking hammers are heat treated after they are CNC machined from 4340 steel to make them exceptionally durable and resilient."



Advertiser often use vague, unmeasurable terms like "exceptional." They might have well said it was "wholesome."



I see you are not familiar with the gold market.


Ha!

Tom

Carld
06-11-2012, 05:45 PM
A real pretty girl can make your boring bar hard.:rolleyes:

Arthur.Marks
06-11-2012, 05:54 PM
I knew there was a reason I hadn't clicked on this thread earlier! :D
I don't even know what is being heatedly argued over at this point, but it seems to center around the certain term "resilience". As such, I will add the following as it hasn't been mentioned yet:

resilience. (1) The amount of energy per unit volume released on unloading. (2) The capacity of a material, by virtue of high yield strength and low elastic modulus, to exhibit considerable elastic recovery on release of load.
p.48 Metals Handbook Desk Edition (2nd ed.). (1998). Materials Park, OH: ASM International.

If there will be a discussion, there must be an agreed upon definition and, preferably, one that is quantifiable. Otherwise, we can turn circles all day over what is "hot" and what is "cold." The reference above is the most authoritative one I have access to. The yield strengths for the two alloys are listed as follows:

ANSI No. 1020, cold drawn. Yield Strength = 350 MPa / 51 ksi
ANSI No. 4130, Water quenched from 855C and tempered at 540C. Yield Strength = 979 MPa / 142 ksi
p.154, 156. "

The Modulus of Elasticity for both is constant. Given this information, I tend to follow this line of thought: For a given material, "resilience" as defined above is a ratio of "high yield strength" to "low elastic modulus." Given that the elastic modulus is constant with these two examples, a higher yield strength would be defined as having more resilience.

Okay. So what does that matter? I guess it means that the heat-treated 4130 bar will take more stress* before being permanently deformed (changing shape). "Stress" here is being defined as, the intensity of the internally distributed forces or components of forces that resist a change in...shape of a material that is or has been subjected to external forces. p.56. " In other words, the strenth of the boring bar to "push back" before permanently changing its shape.

The KEY to remember here is that this has NOTHING to do with the deformation characteristic of the bar BELOW the yield strength. Both bars perform identically in this regard (Modulus of Elasticity). It only means that the point at which your boring bar is ruined from a big oopsie takes a bit more force than the non-heat-treated material.

I guess? I'm no metallurgist. Heck, I'm no "machinist!" I am just a guy that is trying to sort through the confusion in this thread with the available reference material on my shelf, a little logic and about two hours into it. I hope my "proof" was clear, correct and at least helped someone rather than fuel the argument :(

Carld
06-11-2012, 05:57 PM
This comes up so many times and is beat to death in each thread that at some point I just have to put a little humor in it.

jep24601
06-11-2012, 06:52 PM
I just had to look at this thread to see how a simple question "do boring bars need hardening? " could run to 7 pages when the answer to the question is "No, they don't need hardening""

lazlo
06-11-2012, 07:56 PM
ANSI No. 1020, cold drawn. Yield Strength = 350 MPa / 51 ksi
ANSI No. 4130, Water quenched from 855C and tempered at 540C. Yield Strength = 979 MPa / 142 ksi

The AISI 1020 is a red herring, IMHO, since mild steel's properties don't change substantially through heat treat.

Evan's original point was that the tensile and yield strength of an alloy boring bar increases via heat treat, but that's probably not desirable considering that a chromoly boring bar has vastly higher yield strength than the grey cast iron that comprises your topslide. You know all those lathes you've seen with the tool slot busted out? :)

That said, heat treating to resist screw bite marks and swarf flow is certainly desirable in a pro shop, probably less so in a home shop.

A.K. Boomer
06-11-2012, 09:42 PM
resilience. (1) The amount of energy per unit volume released on unloading. (2) The capacity of a material, by virtue of high yield strength and low elastic modulus, to exhibit considerable elastic recovery on release of load.
p.48 Metals Handbook Desk Edition (2nd ed.). (1998). Materials Park, OH: ASM International.

If there will be a discussion, there must be an agreed upon definition and, preferably, one that is quantifiable. Otherwise, we can turn circles all day over what is "hot" and what is "cold." The reference above is the most authoritative one I have access to. The yield strengths for the two alloys are listed as follows:

ANSI No. 1020, cold drawn. Yield Strength = 350 MPa / 51 ksi
ANSI No. 4130, Water quenched from 855C and tempered at 540C. Yield Strength = 979 MPa / 142 ksi
p.154, 156. "

The Modulus of Elasticity for both is constant. Given this information, I tend to follow this line of thought: For a given material, "resilience" as defined above is a ratio of "high yield strength" to "low elastic modulus." Given that the elastic modulus is constant with these two examples, a higher yield strength would be defined as having more resilience.

Okay. So what does that matter? I guess it means that the heat-treated 4130 bar will take more stress* before being permanently deformed (changing shape). "Stress" here is being defined as, the intensity of the internally distributed forces or components of forces that resist a change in...shape of a material that is or has been subjected to external forces. p.56. " In other words, the strenth of the boring bar to "push back" before permanently changing its shape.

The KEY to remember here is that this has NOTHING to do with the deformation characteristic of the bar BELOW the yield strength. Both bars perform identically in this regard (Modulus of Elasticity). It only means that the point at which your boring bar is ruined from a big oopsie takes a bit more force than the non-heat-treated material.

I guess? I'm no metallurgist. Heck, I'm no "machinist!" I am just a guy that is trying to sort through the confusion in this thread with the available reference material on my shelf, a little logic and about two hours into it. I hope my "proof" was clear, correct and at least helped someone rather than fuel the argument :(




Thanks Arther, very well written I might add:)

But the sad thing is is it most probably will fall on deaf ears... :rolleyes:

appreciate the time - don't feel bad, I bet I got more in than you :p

A.K. Boomer
06-11-2012, 09:45 PM
The AISI 1020 is a red herring, IMHO, since mild steel's properties don't change substantially through heat treat.
so don't heat treat neither of them and compare yield strength -- im not ascared :)


Evan's original point was that the tensile and yield strength of an alloy boring bar increases via heat treat,


Actually that wasn't his original point -- it was my point to point that out to him.

Any other questions?

A.K. Boomer
06-11-2012, 09:49 PM
They might have well said it was "wholesome."




Ha!

Tom



Really? are you reading any of this? what planet do you live on - Hostess?

is any switch being flicked at all? - a dim bulb? some kind of spark? are you getting anything from any of this yet?

jep24601
06-11-2012, 11:08 PM
"Is this the right place for an argument?"

lazlo
06-11-2012, 11:12 PM
so don't heat treat neither of them and compare yield strength -- im not ascared :)

Your missing my point about why that's a red herring :p

Mild steel has a yield strength of ~ 60 Kpsi, whether it's hardened or not. 4140 is 50% stronger than mild steel when annealed (95K yield strength), and wildly stronger when quenched and tempered (240K yield strength).
But even mild steel is 50% stronger than Class 40 Grey -- you'd be better off with a cast iron boring bar and a steel top-slide ;)


Actually that wasn't his original point -- it was my point to point that out to him.
Any other questions?

Sorry AK -- it;s tough wading through the pissing contest :p

flathead4
06-11-2012, 11:22 PM
"Is this the right place for an argument?"


The argument is fun but the personal attacks are tiring.

Tom

P.S. - I just noticed your quotes. :D Perfect.

oldtiffie
06-11-2012, 11:42 PM
As I said earlier - I buy my boring bars and clamps (as a set) new and whatever material they are made of does the job. If the boring is not satisfactory then I reduce speed and/or feed or re-grind the boring tool or re-think or re-adjust the set-up.

"Stiffness" and "rigidity" are not restricted to the boring bar but to machine stiffness and set-up - to mention a few.

If I need to make a boring bar I use plain old cold (or hot) rolled mild steel. I prefer round HSS stock as all I need are round holes - no square ones.

On occassion I will MIG or silver braze a tool to a boring bar.

I have a quite good but "light" lathe is so I neither push it to its limits nor do I try.

I have plenty of time and my "tear-ar$ing" days are long gone and they are not coming back

A.K. Boomer
06-11-2012, 11:44 PM
Sorry Flathead just trying to get through;)

did maybe all this talk make resilience sound better than "wholesome" lol

I could say you like to waste peoples time - but then it would be noticed that I have time to waste...

A.K. Boomer
06-12-2012, 12:38 AM
Your missing my point about why that's a red herring :p

Mild steel has a yield strength of ~ 60 Kpsi, whether it's hardened or not. 4140 is 50% stronger than mild steel when annealed (95K yield strength), and wildly stronger when quenched and tempered (240K yield strength).
But even mild steel is 50% stronger than Class 40 Grey -- you'd be better off with a cast iron boring bar and a steel top-slide ;)

Lazlo I think im seeing your point on it being a apples to oranges comparison ----- so just take annealed 4130 and put it up against heat treated 4130,
The heat treated is both more durable and resilient. It has a higher yield strength...


Sorry AK -- it;s tough wading through the pissing contest :p

Don't be sorry - just realize that I generally don't have pissing contests all by myself -- I mean I may get a little lonely sometimes but I draw the line there...

John Stevenson
06-12-2012, 04:29 AM
Now this is one of those posts that's heading for a lock if for nothing more than AK likes to hear echo's

oldtiffie
06-12-2012, 04:42 AM
+1

This seems to be one our annual "storm in a tea cup" threads with a lot of people talking at but not to each other.

http://www.google.com.au/search?hl=en&gl=au&tbm=nws&q=storm+in+a+tea+cup&oq=storm+in+a+tea+cup&aq=f&aqi=d2&aql=&gs_l=news-cc.12..43j43i400.7392.16789.0.22368.18.4.0.14.14.0 .259.770.1j0j3.4.0...0.0.mBgGchfARBc

beanbag
06-12-2012, 05:14 AM
I would like to use this thread to express my opinions of others as well.

oldtiffie
06-12-2012, 07:05 AM
I would like to use this thread to express my opinions of others as well.

Quite some others seem to be using it as a vehicle to have a shot at or to try to shred some others.

There is any amount of precedence for you to join in.

For what its worth, the OP's heading is:


do boring bars need hardening?

the text for which is:


Making a couple of 3/4" boring bars out of hardened rod. Annealing now. Should I re-harden after machining. Bars will be 10" and 6". Thanks.

It seems to be a simple question that after all the number of times that this thread has been hashed around over time that there should easily be a short concenus answer without any of the "side issues".

mike4
06-12-2012, 08:08 AM
I have made a couple from annealed torsion bars , machined the pockets and cleaned the body back to give some clearence and then just hardened the first 50-70 mm so that the inserts dont chew the pockets out and to reduce the wear that Sir John described .
These are about 250mm long and 19mm diameter.

They should outlast me as they only get 8-12 hours use every six months.
No pics as they are packed away waiting for the next job.
Michael

JoeLee
06-12-2012, 01:14 PM
I made these little bars out of 12L15. I don't think you can really harden that material. They work fine as long as you don't try to take too heavy of a cut. If I had made these out of any other material they would have never come out as nice as they did...... insert pocket and 4-40 screw hole would have been tough to cut.

JL....................

http://i911.photobucket.com/albums/ac317/JoeLee09/Mini%20Boaring%20Bars/Image009.jpg
http://i911.photobucket.com/albums/ac317/JoeLee09/Mini%20Boaring%20Bars/Image003.jpg