Announcement

Collapse
No announcement yet.

do boring bars need hardening?

Collapse
X
 
  • Filter
  • Time
  • Show
Clear All
new posts

  • #31
    Originally posted by Evan
    That isn't at all the same as deflection of the bar.
    Didn't say it was.
    Amount of experience is in direct proportion to the value of broken equipment.

    Comment


    • #32
      The point is that hardening a boring bar will not improve boring performance.
      Free software for calculating bolt circles and similar: Click Here

      Comment


      • #33
        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.

        Phil

        Comment


        • #34
          Originally posted by Evan
          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.
          .

          Sir John , Earl of Bligeport & Sudspumpwater. MBE [ Motor Bike Engineer ] Nottingham England.



          Comment


          • #35
            Originally posted by John Stevenson
            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?
            Play Brutal Nature, Black Moons free to play highly realistic voxel sandbox game.

            Comment


            • #36
              Originally posted by John Stevenson
              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.

              Comment


              • #37
                Originally posted by philbur
                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



                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.

                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...
                Last edited by A.K. Boomer; 06-10-2012, 11:08 AM.

                Comment


                • #38
                  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?
                  The shortest distance between two points is a circle of infinite diameter.

                  Bluewater Model Engineering Society at https://sites.google.com/site/bluewatermes/

                  Southwestern Ontario. Canada

                  Comment


                  • #39
                    Originally posted by Evan
                    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!

                    Comment


                    • #40
                      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...

                      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...
                      Last edited by A.K. Boomer; 06-10-2012, 11:48 AM.

                      Comment


                      • #41
                        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.
                        Free software for calculating bolt circles and similar: Click Here

                        Comment


                        • #42
                          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
                          Tom - Spotsylvania, VA

                          Comment


                          • #43
                            Originally posted by flathead4
                            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?
                            Last edited by A.K. Boomer; 06-10-2012, 10:27 PM.

                            Comment


                            • #44
                              Originally posted by Evan

                              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"...

                              Comment


                              • #45
                                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
                                Last edited by flathead4; 06-10-2012, 10:40 PM.
                                Tom - Spotsylvania, VA

                                Comment

                                Working...
                                X