Announcement

Collapse
No announcement yet.

Out of Spec Aluminum Flat Bar

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

  • Out of Spec Aluminum Flat Bar

    I gotta tell you its annoying. Some time back I had found a great source for 1/2 x 6 6061-T6511 flat bar. Smoking price. Almost every piece was warped across the width more than 0.010". I complained and the vendor sent me a spec source that showed that was allowable within spec. Before cutting a mold I take a 0.010" facing cut to get a flat starting surface. Some of their stuff a 0.015" facing cut wasn't enough. I quit buying from that vendor and I've never gotten another piece that was that bad. Sure some bar gets warped along its length from ham handed handlers, but across its width has to be from a bad extruder or processing line at the mill.

    A while back I got some 3/4 x 3 6061-T6 flat bar from a local metal vendor. I think I bought 4 sticks. Three of them were pretty good, No worse than expected anyway. One piece was more than 0.050 wider across its width than the rest. The rest was not under sized. I mostly use the 3/4 x 3 for hinged mold, and I often do the entire set of primary operations in one setup just adding hinge pins and handles afterwards. Then with that one stupid bar I'd be all done, and still have to do one more operation to face it so that they were the same width. I mentioned it to the vendor and the asked if I did that for a living like I didn't know I should expect that multiple bars in the same batch would be different widths. Well, I 've been buying most of my aluminum from a different vendor since than and I've experienced over width upto .010 a few times, but mostly its pretty consistent stuff. I've been buying most of my 3/4 x 3 from that vendor in precut lengths so I can get it on the mill faster when I am in the zone. Several thousand dollars worth. Haven't had a single one that was so bad I had to do one more operation after it was done. Not a single one that would cock over on one side when I set it on the counter top.

    Lately I've been using fixture plates instead of vises a lot on one of my machines. This way I can setup to cut multiple parts easily all at once. Its not uncommon to fixture 4 pieces at once to make two 3x6 molds in one setup. One smaller mold I make I do in batches of 6 at a time. 12 halves in one setup. I started out making fixture plates out of Mic6 and the last few have been made with ATP5. Basically a shelf with a stop ridge for one edge of the bar, and a flat shelf with an low profile Carr-Lane Tiny Vise edge clamp for the other edge. Those don't have much clamping range, but I make the fixture plates specifically for a particular width of flat bar so they don't need much.

    Well, I had to make an odd ball custom mold last week. 3/4 x 3 x 17.5 base stock size per side. I went scrounging through my stock pile of bar stock and found two pieces long enough to do the job. Into the saw, and then onto the mill where I found one of them was that damned 0.050 over width piece from the local vendor who question if I really did this for a living. LOL.

    Fortunately the shorter smooth side of the edge clamps held well enough to get the job done so I didn't have to put the vises back on the table and mill to width first.



    Last edited by Bob La Londe; 07-22-2020, 09:46 AM.
    *** I always wanted a welding stinger that looked like the north end of a south bound chicken. Often my welds look like somebody pointed the wrong end of a chicken at the joint and squeezed until something came out. Might as well look the part.

  • #2
    Originally posted by Bob La Londe View Post
    ...Almost every piece was warped across the width more than 0.10". I complained and the vendor sent me a spec source that showed that was allowable within spec...
    If you really mean .10" and not .010" I'm gonna call BS on that. No reputable supplier would allow that kind
    of twist across a 6" piece of material. Anything over .010" would have me calling my supplier for replacement
    stock...

    Keith
    __________________________
    Just one project too many--that's what finally got him...

    Comment


    • #3
      Originally posted by LKeithR View Post

      If you really mean .10" and not .010" I'm gonna call BS on that. No reputable supplier would allow that kind
      of twist across a 6" piece of material. Anything over .010" would have me calling my supplier for replacement
      stock...
      Fixed. Yeah I meant worse than 0.010" over a 6" width. I just quit buying from that vendor and never had another piece that bad.
      *** I always wanted a welding stinger that looked like the north end of a south bound chicken. Often my welds look like somebody pointed the wrong end of a chicken at the joint and squeezed until something came out. Might as well look the part.

      Comment


      • #4
        We got a "great deal" on some 4x4" 6061 extrusion many years ago that was a parallelogram, and out of square by over 0.05". If you measured across the sides it was about 0.01" over like it should be. It cut like **** too. Was next to worthless for the stuff we needed it for as it would only clean up square to around 3.900. The "great deal" was more than lost in all the time spent compensating for the missing material. I think it came from Estonia, but I can't remember for sure. Had to be 8-9 years ago now.

        Sometimes things make it out and get into a secondary market where it just might be good enough. When they get passed off onto unsuspecting buyers is when it causes issues......

        Comment


        • #5
          I asked for some stainless off the drop rack at a local metal vendor to use as backers for aluminum welding. One piece of flat bar is a parallelogram at best. Its certainly not rectangular. The guy then went to look up book price on it, until I objected reminding him it came off the drop rack and it was not parallel.

          Their drop price is usually still higher than Midwest or Xometry.
          *** I always wanted a welding stinger that looked like the north end of a south bound chicken. Often my welds look like somebody pointed the wrong end of a chicken at the joint and squeezed until something came out. Might as well look the part.

          Comment


          • #6
            How long have you been in this business?
            No one would expect a mill finish product to be accurate, you buy it big and make the parts accurate.

            Jig plate is not mill finish, it has gone through a second operation.
            TGP is not mill finish by definition.
            If you require high accuracy stock buy it either pre-ground or have it ground before use.
            You really should have known this.

            Have you ever wondered why much stock shafting is supplied in 1/16 th's less then a 1/8" whole size, such as 1 7/16, 1 15/16, 2 7/16, 2 15/16 and so on?
            Start with a 1 1/2 nominal mill finish bar and grind it to 1 7/16.
            Last edited by Bented; 07-27-2020, 08:20 PM.

            Comment


            • #7
              Originally posted by Bented View Post
              How long have you been in this business?
              Hahahahahahaha...did you not read how changing vendors resulted in better stock, or were you just trolling the forums looking for an excuse to be judgmental. Note the lack of a question mark. That's deliberate.

              You remind me of the guy who refused to get 5-inch stock in for me even though it's readily available and instead told me I should buy 6-inch stock and throw away 17.3% of it. Another vendor got me what I actually wanted for less than the difference by weight DELIVERED. LOL.

              How long have you been in this business? Hahaha. And yet some vendors consistently provide a more consistent product than others. Usually for less money. Weird.


              *** I always wanted a welding stinger that looked like the north end of a south bound chicken. Often my welds look like somebody pointed the wrong end of a chicken at the joint and squeezed until something came out. Might as well look the part.

              Comment


              • #8
                I have never seen extruded aluminum rectangular shapes larger then 4" that are close to flat and straight from the machine, the thinner it is the more likely it will be off when it comes out of the die during extrusion and cooling, heat treating and tempering.
                Cast jig plate is milled after casting, you may want to look into shops that supply ground material, this saves a good deal of facing and squaring.
                This is an excellent vendor https://www.dixmetals.com/standard/aluminum.html

                Do your customers not specify an order of machining processes?

                I find this on customer drawings often, cut stock, stress relieve, rough machine, harden to RC 55, finish grind to size.
                My employer often leaves out the stress relieve part to save money, this sometimes bites him in the ass when the parts come back with a big red tag that has NOT COMPLIANT printed on it.
                This is not my problem however.

                Comment


                • #9
                  .. and yet somehow the flat bar from some vendors is always better than from some other vendors. Less beat up most of the time too.

                  I don't just have to accept it, and I don't have to just buy the size stock they want to sell.

                  YES!!!!!! I get that its not precision bar, but some mills produce better more consistent stock, and some vendors seem to buy from those mills.

                  I don't worry to much about the cost of customer specified materials. It gets added into the price and if I don't get the job I'm perfectly ok with that. Since I also make both custom and inventory (cut library) parts where I am the one specifying material I do worry about all aspects of the cost of producing those parts. Material cost, stock quality, design time, setup time, and machine time. I can machine a part efficiently in one or two setups it costs a hell of a lot less to produce than if I get ****ty stock that has to be machined in six setups.

                  Not withstanding tooling costs, its more material cost effective for a mill to produce parts more consistently close to nominal dimensions. 50 thousandths oversize on one piece of stock may be minimal, but 50 thousandths oversize on thousands of pieces of stock is thousands of dollars wasted. Interestingly those vendors who stock that more consistent material tend to have better average pricing. Also interesting is some vendors understand this basic principal too. I've found my two most cost effective sources ship precut pieces very very close to the dimension ordered, and their cuts are always very square. They can cut closer to on size and save a lot of money over time by cutting square. If you keep your equipment well maintained its no faster to cut crooked and it wastes material.

                  I buy both precut pieces and full bar stock depending on how busy I am and what the job is. If I have to make 100 casting bucket molds out of 1.25 x 3 x 3.5 pieces its a lot faster to order 100 pieces cut to 3.5 long. Marginally one might argue I could cut them faster by cutting multiples at once in bar fixture clamps, but its not true. I can do the same thing with precut pieces and waste less material.
                  Last edited by Bob La Londe; 08-04-2020, 08:47 PM.
                  *** I always wanted a welding stinger that looked like the north end of a south bound chicken. Often my welds look like somebody pointed the wrong end of a chicken at the joint and squeezed until something came out. Might as well look the part.

                  Comment


                  • #10
                    Originally posted by Bented View Post
                    I have never seen extruded aluminum rectangular shapes larger then 4" that are close to flat and straight from the machine, the thinner it is the more likely it will be off when it comes out of the die during extrusion and cooling, heat treating and tempering.
                    Cast jig plate is milled after casting, you may want to look into shops that supply ground material, this saves a good deal of facing and squaring.
                    This is an excellent vendor https://www.dixmetals.com/standard/aluminum.html

                    ............
                    Any reputable vendor of extruded material has specs on it. One of the specs IS the deviation from flat.

                    That spec is always more than you want it to be, and generally material comes in better than spec. Even when a piece comes in at the max spec, you have no reason to complain.

                    BUT, if the material comes in out of spec, you have every right to reject it with a nice big red "non-compliant" tag. What the hell are the specs for if the vendor can publish a spec, and then tell you to go pound sand if the spec is exceeded?

                    The customer may buy the material based on the max spec still cleaning up with sufficient "machining margin". When the vendor delivers material that is OUT OF SPEC, then the customer may not be able to use it. That is grounds for a rejection, and the vendor has to eat it.

                    If the vendor says "it will be like this, guaranteed", which is what a "spec" means legally, then if it is NOT that way, they have to make it good to the satisfaction of the customer, who just wants what the vendor promised to supply. It's no different than when your guys screw up and the parts come back to you tagged "non-compliant".

                    Not sure where you get this as just whining on the part of the customer....... Is that what your employers say when stuff comes back red-tagged?
                    1601

                    Keep eye on ball.
                    Hashim Khan

                    Comment


                    • #11
                      Was the spec ASTM B211 or something else? B211 says that for a 6in wide extrusion your flatness tol should be .004*W = .024" across the face max warp. Could be worse if you have a big longitudinal dimension and have to incorporate twist as well, however with the -T6511 designation means it's been straightened. Maybe the press operator went crazy and warped it worse?

                      source: https://www.mkmetal.net/images/uploa...0Tolerance.pdf sheet 8


                      I have been burned on a project where someone "helped" and "ordered material ahead of time" for us. It was a big box that we put a battery into, so that we could put it on a vibration table. The testing house said they wanted .003" flatness total across the entire box, which was three feet in one direction, so as to not distort their precious shaker platen. The material showed up and it was 1x12 extruded 6061, and had about .075" of warp on it. Naturally they accepted the material without pushing back on the vendor before us the chip makers got to it, so no takebacks. I would have gotten MIC6 and just sawed it to size and poked some holes in it and been done in 3-4 hours. Lesson learned.

                      That turned into close to 20 hours of flycutting, indicating, and creative shimming and clamping to get the damn plates flat enough to fly with the testing house. They didn't have the capacity to measure the flatness on the part anyways. We made best effort, got it close enough, and their machine (or our battery) didn't explode. Pass!
                      Last edited by psomero; 08-27-2020, 12:15 PM.
                      -paul

                      Comment


                      • #12
                        Pretty much only buy 6061-T6511. MIC6 and ATP5. (more ATP5 than Mic6) Occasionally I'll get some 7075 for personal projects or if the customer indicates the extra strength is needed.
                        *** I always wanted a welding stinger that looked like the north end of a south bound chicken. Often my welds look like somebody pointed the wrong end of a chicken at the joint and squeezed until something came out. Might as well look the part.

                        Comment

                        Working...
                        X