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  • Help with cost estimate of machining

    Hey folks,

    I need help estimating the time it would take to make the following pieces out of mild steel. The grey areas are what i need to machine away





    I have a 2" carbide face mill and endmills up to 3/4". I have 10 of each to build.

    I was thinkin of buying 30" of metal and then machining the groves, then drilling the holes. Millwork. Mark where i should cut them and then part them off in the horizontal saw. True up on the mill if necissary. Finally i would tap the parts that need it.

    How long would it take to maching the metal away? I have a 9x49 EXCELLO, with an R8. Power feed as well.

    Are my steps of production sound? Faster way? I don't have a coolant pump. I have until monday to get the price in so any input would be appreciated.

    Rob
    Last edited by spkrman15; 02-28-2009, 10:00 AM.

  • #2
    If you're making 10 and they are 3" each, you'll need more than 30" of metal. You have to take saw kerf and squaring up into account.

    What's the tolerance you have to mill to?

    Comment


    • #3
      I would suggest you saw the parts then mill the sides to dimention then drill and tap the hole then machine the gray areas off the parts in that order.

      It will be much easier to drill and tap before taking the gray areas off, believe me on this.

      Charge 1.5 to 2.0 hrs each if you want to make money on them. If you want to break even or lose then charge 45 min. to an hour.
      It's only ink and paper

      Comment


      • #4
        I would chop the stock at 6.250" lengths,mill the large step first,then chop in half.Mill the ends square to 3.00",do the small step with an end mill use the step and a vise stop to locate the hole.

        Total job would take me 2-1/2hrs tops,but I run coolant so dry would put me at 3hrs give or take a cup of coffee.That's $180.00($60/hr)+material unless it's a rush, then double that.

        Of course this includes things like stack cutting to save time.
        I just need one more tool,just one!

        Comment


        • #5
          I don't see how anyone can help with an estimate without knowing more about the machinery you have. Can you remove the material in one pass?

          Also, there's no tolerancing on the drawing. By dimensioning to 4 decimal places there's an implication of high accuracy. Typically something like +/-.001" with 4 place decimals.

          The drawing views are hard to understand. You say "grooves". Are they truly grooves or is the face material removed totally down the 3" dimension?

          If a potential customer supplied the drawing, watch out. It's definitely amateur time and those can be the hardest customers to satisfy.

          If the material is removed totally across the part you're going to have a good deal of distortion as the internal stresses are relieved if you use off the shelf material. The un-machined face will no longer be flat, it could be very badly cupped in the 2.25 dimension. Having the material stress relieved prior to machining will help control distortion, but no guarantee when that much is removed (add in $75 to $100 for the heat treater) . Depending on the flatness needed you may have to start with thicker material to allow skimming both sides to remove distortion. Chasing distortion by alternately skimming both sides is tricky, allow for extra trial and error blanks.

          Basically, the part could be a nightmare. Even holding it won't be easy, hardened steps jaws would be nice. Be very careful committing to making these parts, there are a bunch of "gottchas" involved.

          Comment


          • #6
            Buy material 3" wide, this will give you two sides finished.

            Cut to 4.5" plus and square off both ends. Do this for all 5 pieces

            Mark hole from either end, drill and tap

            Clamp to squared off jig plate on bed and measuring from both ends cut the large slot.

            Cut down the middle into two and square off.

            Hold in vise vertically by the 1.7500 face and mill small slot.

            2 hours tops for all 10.

            .
            .

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



            Comment


            • #7
              Originally posted by DR
              I don't see how anyone can help with an estimate without knowing more about the machinery you have. Can you remove the material in one pass?

              Also, there's no tolerancing on the drawing. By dimensioning to 4 decimal places there's an implication of high accuracy. Typically something like +/-.001" with 4 place decimals.

              The drawing views are hard to understand. You say "grooves". Are they truly grooves or is the face material removed totally down the 3" dimension?

              If a potential customer supplied the drawing, watch out. It's definitely amateur time and those can be the hardest customers to satisfy.

              If the material is removed totally across the part you're going to have a good deal of distortion as the internal stresses are relieved if you use off the shelf material. The un-machined face will no longer be flat, it could be very badly cupped in the 2.25 dimension. Having the material stress relieved prior to machining will help control distortion, but no guarantee when that much is removed (add in $75 to $100 for the heat treater) . Depending on the flatness needed you may have to start with thicker material to allow skimming both sides to remove distortion. Chasing distortion by alternately skimming both sides is tricky, allow for extra trial and error blanks.

              Basically, the part could be a nightmare. Even holding it won't be easy, hardened steps jaws would be nice. Be very careful committing to making these parts, there are a bunch of "gottchas" involved.
              "How long would it take to maching the metal away? I have a 9x49 EXCELLO, with an R8. Power feed as well"
              I just need one more tool,just one!

              Comment


              • #8
                I agree with DR, that part is prone to warp and the drawings are very unclear.

                Just glancing, I can see 2 different parts that "fit" the 1st drawing depending on which quadrant you put the tapped hole.

                Comment


                • #9
                  need more info

                  Comment


                  • #10
                    Originally posted by wierdscience
                    "How long would it take to maching the metal away? I have a 9x49 EXCELLO, with an R8. Power feed as well"
                    Yeah, so? Only he knows his machine. Will it take the cuts in one pass with his tooling?


                    Did he change the drawings? I could have sworn when I first replied they were both the same.

                    Comment


                    • #11
                      The drawings are a little vague to me and both drawings are the same as far as I can tell. I didn't say anything because when I do I get kicked in the dirt for asking a stupid question.

                      It looks to me like he is machining a steped bracket and not slots on the work. I guess Rob forgot he posted this and is off doing something else or gave up the job.
                      It's only ink and paper

                      Comment


                      • #12
                        How are you going to get the inside corners square? Or was that already covered.

                        Comment


                        • #13
                          Nevermind. Now I see what you're up to.

                          First off, come up with an hourly figure for your overhead costs. Heat, rent, water, etc.

                          How much you want to get paid per hour(You can break this down by how much eaqch machine used should cost as well. $10hr cutoff saw. $25hr lathe, etc.)

                          add the two above.

                          Figure the time for each operation ,that includes deburring and cleaning.

                          cost of materials


                          cost of shipping


                          add15%



                          Everyones situation is different.


                          Then again, just come up with an hourly figure you like and go from there.

                          Comment


                          • #14
                            My mistake(s)

                            Hey everyone,

                            Ok i posted the same part twice. I have since fixed the 2nd picture.

                            I have seen the parts. They are not heat treated, but rather look like they are desinged to fit into some kind of channel and clamped together. Hence the lip that probably fits into some kind of lip.

                            I am also learning Autocad and well i still have alot to learn on how to draw stuff so everyone can unserstand. Sorry but i am learning.

                            The tolerances are 0.000 because i was too lazy to change the settings, but i did not consider the impact that would have. I usually draw parts like that so it is easier to enter into the DRO.

                            My main concerns were

                            1) how long it would take to remove a 1-1/2" x 1/2" deep groove with a 2" carbide face mill.

                            2) Removing 1-3/4" x 1/2". I have no clue as to how long this type of work takes.

                            I was thinking of machining the parts in one long piece, as i read that is how alot of people build multiple quick change holders. They machine them out of a long block then cut them to size. Seemed like a good idea as i could get metal longer then i needed and set them up in the mill. Cut the 1-1/2"x1/2" in one set up. Same idea with the 1-3/4" x 1/2".

                            I see that most of you suggest parting off the pieces and machine them to dimensions. The general concencuss is 2 hours of machining for 10 pieces.

                            How does that sound?

                            DR & Hitnmiss, i will work on my scetching skills.

                            Rob

                            Comment


                            • #15
                              I agree about needing to get them relieved - it is going to creep when you mill out from under the face. Parts like this also really benefit from being able to be precision sawn, and with the economy in the crapper, nice cold saws are showing up for reasonable prices. I had lusted after one for the last 4 years, and now I have two.

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