Announcement

Collapse
No announcement yet.

Cheap Inserts with Full-Length Cutting Edge

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

  • Cheap Inserts with Full-Length Cutting Edge

    Hey guys,

    I've been mucking around with making insert holders for cheap ebay inserts, and so far it has worked quite well. I made a boring bar, a threading tool and a fly cutter, also tried out a indexable mill insert for a lathe tool and it stinks for chip breaking. Anyway, I want to make a dovetail cutter, countersink and deburring tools as well, but these inserts I have do not have cutting edges running the full length of the triangle.

    They are TCMT110204 (TCMT 731) and are only a dollar CAD apiece, 33c per corner.

    http://www.ebay.ca/itm/10Pc-TCMT1102...AAAOSw3utY6Hmu

    As you can see, the chipbreaker edge is only near the corners and not continuous.



    Maybe they did this because these inserts are too small to handle the forces they'd be under for a full length cut?

    Has anyone found any cheap triangle inserts from china which are full-length cutting? Any other details on useful geometries that are super cheap and available from overseas?

  • #2
    There are such things.

    http://www.carbidedepot.com/KENNAMET...KER-C1725.aspx

    In theory, only the leading edge will be doing the cutting, so you only need the 30% of the edge that your existing triangular insert has. You'd use it like you do an endmill, approaching from an edge.
    At the end of the project, there is a profound difference between spare parts and left over parts.

    Location: SF East Bay.

    Comment


    • #3
      Originally posted by danlb View Post
      There are such things.

      http://www.carbidedepot.com/KENNAMET...KER-C1725.aspx

      In theory, only the leading edge will be doing the cutting, so you only need the 30% of the edge that your existing triangular insert has. You'd use it like you do an endmill, approaching from an edge.
      Can you elaborate? I think once your dovetail reaches full depth you'll be contacting the entire edge, if the dovetail is going in a slot that is as deep as the insert is tall

      Comment


      • #4
        To elaborate....

        I was thinking about the bottom of the dovetail, not the side. For the bottom edge, it will act like a fly cutter, so the back half will not matter much.

        But for the side you will need a cutting edge the whole depth of the cut. A triangular insert does have a cutting edge, it might just be missing the chip breaker. You could also just use a bigger insert.

        Did you do a test to see if the chip breaker is needed for an interrupted cut like that?

        Dan
        At the end of the project, there is a profound difference between spare parts and left over parts.

        Location: SF East Bay.

        Comment


        • #5
          Originally posted by danlb View Post
          To elaborate....

          I was thinking about the bottom of the dovetail, not the side. For the bottom edge, it will act like a fly cutter, so the back half will not matter much.

          But for the side you will need a cutting edge the whole depth of the cut. A triangular insert does have a cutting edge, it might just be missing the chip breaker. You could also just use a bigger insert.

          Did you do a test to see if the chip breaker is needed for an interrupted cut like that?

          Dan
          I haven't but it would be easy to try. Ill give it a shot tonight

          Sent from my SM-G920W8 using Tapatalk

          Comment


          • #6
            I have a lot of older style TNMG inserts with full length chipbreakers. Most of the newer stuff uses bumpy or wavy top geometry. If the TNMG's will work for you, please PM me.

            Comment


            • #7
              I have a Dorian 3 insert dovetail cutter. It uses 3 flat top 20 degree relief inserts set sloping back and rotated slightly, and they have an indent in the bottom to index/lock them them in place. ... Shars has an "exact" copy. Geometry is tricky if you want positive rake cutting and a lot less chatter than just slamming the entire insert side into the work.

              Comment


              • #8
                You may have trouble cutting the whole side of dovetail in one cut.. If you had say 2 hp the mill may not be rigid enough. You can rough it by eyeball in two or three passes, then try a light finish cut.
                Finishing insert probably wont have full chipbreaker. 2nd from right is from a multi edge carbide insert endmill.

                Comment


                • #9
                  You may have trouble cutting the whole side of dovetail in one cut.. If you had say 2 hp the mill may not be rigid enough. You can rough it by eyeball in two or three passes, then try a light finish cut.
                  Finishing insert probably wont have full chipbreaker. 2nd from right is from a multi edge carbide insert endmill.

                  Comment


                  • #10
                    That's a TCMT21.51 insert, so it's only a 1/4 inch inscribed circle and 3/32 thick. That gives you about 1/2 inch per side. Horsepower will not be an issue for a single pass cut, but rigidity might be.

                    With my HSS dovetail cutters I always make multiple passes, so I don't see why you would not do the same with this.


                    Dan
                    At the end of the project, there is a profound difference between spare parts and left over parts.

                    Location: SF East Bay.

                    Comment


                    • #11
                      Just finished scanning Shars web site. They offer sever positive rake triangles with hole and a uniform width chipbreaker on the top. For milling dovetails is a chipbreaker really necessary? Chip length will be limited by distance the insert is in the cut. Probably shot chips like those from an endmill.

                      Comment


                      • #12
                        You guys are right, with an interrupted cut the insert doesnr seem to care. I ground a spot into some 1-3/77
                        8 1018 round bar scrap and it didnt seem to care what spot I used. The chips curl a lot more in the chipbreaker area but no discernable change in surface finish or chatter.

                        My mistake then, looks like I was worried about nothing.

                        Sent from my SM-G920W8 using Tapatalk

                        Comment


                        • #13
                          You don't need the chip breaker - but mount it highly positive in rake, which is why you need the 15-20 degree relief. Draw it in a circle; you'll see what I mean.

                          Comment


                          • #14
                            Originally posted by lakeside53 View Post
                            You don't need the chip breaker - but mount it highly positive in rake, which is why you need the 15-20 degree relief. Draw it in a circle; you'll see what I mean.
                            Hear Hear.
                            Look for TPMT inserts instead of TCMT.
                            Location: Helsinki, Finland, Europe

                            Comment


                            • #15
                              When ever you throw that word "cheap" into the formula there will be consequences. I hear it all the time with tools, DRO's, calipers, drill bits and the list goes on.

                              JL............
                              Last edited by JoeLee; 05-30-2017, 01:33 PM.

                              Comment

                              Working...
                              X