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  • Cut off blade designations ?

    I was looking at some T shaped cut off blades and saw the designation P1, P2, P3 etc. I tried to find out exactly what it meant but have not had much success searching this. The only difference I can see between them is the blade width. The smaller ones are P! for a couple of widths, then the next two widths are P2 etc. Is that all there is to it ? I even tried the Machinery's handbook with no success. Is there a good source for looking up this sort of thing ?
    Larry - west coast of Canada

  • #2
    I had wondered about that "P" designation myself when it was really T shaped. And then a few years back I came across a discussion that revealed the "P" referred to the "parallel" sides, as opposed to tapered sides on the "T" parting blades.

    Don't recall where I found that, but it struck me at the time as a pretty authoritative source. Now as to the numerical designations ...I plead ignorance.
    Lynn (Huntsville, AL)

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    • #3
      This page gives dimensions for various T-shaped (P-designated) cut off blades:

      https://www.sommatool.com/catalog/cu...off_blades.asp

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      • #4
        These work great for me . https://www.icscuttingtools.com/catalog/page_316.pdf

        Very cheap but unknown quality. http://www.cdcotools.com/

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        • #5
          Originally posted by Cuttings View Post
          I was looking at some T shaped cut off blades and saw the designation P1, P2, P3 etc. I tried to find out exactly what it meant but have not had much success searching this. The only difference I can see between them is the blade width. The smaller ones are P! for a couple of widths, then the next two widths are P2 etc. Is that all there is to it ? I even tried the Machinery's handbook with no success. Is there a good source for looking up this sort of thing ?
          There are 4 basic designs for HSS Parting Tool Blades
          1.Type P, which has a "T" cross-section and the numbers mean the size, with P 1 being the smallest and P 5 being very Large..I have seen "P" holders called "T" holders. This style can also have the top hollow ground for better chip formation.
          2. Type D, which is called a Trapezoidal Blade, A blade with two tapered vertical sides and top and bottom are parallel
          3. Type DA, Which is a 4 tapered angle, top and bottom - This is a very old style blade seldom seen today. The top and bottom tapers give very rigid mounting ( NO side shifting) , but the blade must be top ground to use !
          4. ? rectangular cross-section which is usually used after grinding both sides for a specific thickness or form. Similar to ground flat stock .

          See https://www.newmantools.com/huf.htm
          For type D and DA forms
          Looking at Lists shows the relationship of number to size.

          Be Aware ! There are False Type P (T) shapes being sold from China.
          The Top "T" section must have side relief (!) but these do not ..cheap, cheap and failure will result if buying these blades
          Here is a picture I posted a few years ago showing the defect , and which I have seen in other shops !
          Do
          not accept these profiles

          Click image for larger version  Name:	ENCO-New Blades A.jpg Views:	0 Size:	128.2 KB ID:	1949944

          Here is what should be seen in P Blades

          Click image for larger version  Name:	Old Cutoff Blades A.jpg Views:	0 Size:	81.9 KB ID:	1949945


          Here is a view of various Blades, but not a DA

          Click image for larger version  Name:	PC110012 A.jpg Views:	0 Size:	41.6 KB ID:	1949947


          Rich
          Last edited by Rich Carlstedt; 07-03-2021, 09:22 PM.
          Green Bay, WI

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          • #6
            I think the Supercoup 2012 cutoff blades might be DA style, they're painfully expensive and require holders
            specific to their shape.

            Click image for larger version

Name:	supercoup2012_cutoff.jpg
Views:	189
Size:	118.4 KB
ID:	1949964

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            • #7
              Rich, good information. I would have sent the Enco one back. A while back I bought a few blades, different sizes and styles just to have on hand. Not specifically for parting but more for grooving, snap rings etc.
              Two of them look like the one in your second picture that you captioned in yellow. The top (T) is tapered slightly on each side. They are OK. I have two smaller ones that look like the two in the center of your third picture, tapered from top to bottom but the top edge isn't ground flat, it's actually beveled or peaked in the center and the peak isn't even centered. On one of them the bevel is steeper on one side than the other. Almost like a reverse or convex chip breaker groove. I doubt they were designed that way. I'm more inclined to believe they were just poorly made. Not a big deal as I could grind the top flat if I can come up with a way to clamp a tapered blade square in my tool makers vise. If the tops aren't ground flat and square the blade is going to want to wander off or push to one side or the other, especially the thinner blades if extended too far out of the tool holder.

              Another mistake a lot of people make is they don't realize different style blades require different style tool holders in order for the blade to sit square.

              JL............
              Last edited by JoeLee; 07-04-2021, 09:07 AM.

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              • #8
                Thanks guys. Good information. I will definitely look out for these things next time I order some new blades.
                Larry - west coast of Canada

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