Announcement

Collapse
No announcement yet.

Annoying 'special' thread!

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

  • Annoying 'special' thread!

    I had to make a special 1/2" dome nut for an engine oil filter the other day, the original had gone missing years ago and a plain nut fitted, which leaked enough oil to be annoying.
    1960s British diesel, all threads on the engine are BSF, except for this 'bought-in' oil filter which was obviously finer. Must be UNF, plenty of it in use here at that time, so made a neat job of a nut to fit. Spindle measures a few thou shy of 1/2".
    Went to the vessel today to swap to the new nut, while the crew were doing an oil change, bl**dy thing wouldn't screw on.

    Brought the whole thing back here to measure properly, the thread is 19 tpi (UNF is 20, BSF is 16).

    Then after scratching head a bit as to what to do (no 1/2" - 19 taps in the house), noticed the male thread wasn't cut to full depth. Light bulb came on, 1/4" BSP is 19 tpi, and about 0.54" major dia.
    Grabbed a 1/4" BSP tap, ran it down the existing nut (sorry guys, no time to make a new nut!), job done
    There's plenty of engagement length, it's not a sloppy fit, should be plenty strong enough, but why do (did?) manufacturers bother??

    Tim

  • #2
    Not special at all. Oil filter - lube system - oil pipes - pipe threads - gas threads ?

    Come on man get your act together .............
    .

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



    Comment


    • #3
      Originally posted by Timleech
      Brought the whole thing back here to measure properly, the thread is 19 tpi (UNF is 20, BSF is 16).

      Then after scratching head a bit as to what to do (no 1/2" - 19 taps in the house), noticed the male thread wasn't cut to full depth. Light bulb came on, 1/4" BSP is 19 tpi, and about 0.54" major dia.
      Grabbed a 1/4" BSP tap, ran it down the existing nut (sorry guys, no time to make a new nut!), job done
      There's plenty of engagement length, it's not a sloppy fit, should be plenty strong enough, but why do (did?) manufacturers bother??
      Tim
      I've got a British made lathe c1945 (a William Findlay 'Electrolathe') which has fine threads for the adjustments on the leadscrews and feedscrews. It puzzled me for ages, because the diameters were strange. Eventually after some research I found they were electrical conduit threads.

      Richard

      Comment


      • #4
        Originally posted by John Stevenson
        Not special at all. Oil filter - lube system - oil pipes - pipe threads - gas threads ?

        Come on man get your act together .............
        Yes but it's 1/2" diameter, and it's not a pipe fitting, it's the central bolt, the thread is clearly cut to partial depth (probably with a pipe die).....

        It's a big filter, the pipe threads are probably 1 1/4" BSP

        Tim
        Last edited by Timleech; 03-16-2011, 02:09 PM.

        Comment


        • #5
          Originally posted by Richard Wilson
          I've got a British made lathe c1945 (a William Findlay 'Electrolathe') which has fine threads for the adjustments on the leadscrews and feedscrews. It puzzled me for ages, because the diameters were strange. Eventually after some research I found they were electrical conduit threads.

          Richard
          You mean the PG (Panzergewinde)? And that has been made "old" by replacing the standard with a 1.5 mm pitch metric threads Oh the fun with these threads...
          Amount of experience is in direct proportion to the value of broken equipment.

          Comment


          • #6
            Originally posted by Richard Wilson
            I've got a British made lathe c1945 (a William Findlay 'Electrolathe') which has fine threads for the adjustments on the leadscrews and feedscrews. It puzzled me for ages, because the diameters were strange. Eventually after some research I found they were electrical conduit threads.

            Richard
            Sounds perfectly reasonable on an "Electrolathe"

            RWO

            Comment


            • #7
              Originally posted by Richard Wilson
              I've got a British made lathe c1945 (a William Findlay 'Electrolathe') which has fine threads for the adjustments on the leadscrews and feedscrews. It puzzled me for ages, because the diameters were strange. Eventually after some research I found they were electrical conduit threads.

              Richard
              Richard,
              Are you sure it was a leadscrew and not a length of flexible conduit ?
              .

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



              Comment


              • #8
                Originally posted by Timleech
                but why do (did?) manufacturers bother??
                I have a theory that certain operations happen because somebody said, "the print doesn't say, so just grab any old (tap/bolt/shaft/etc) that works," and the one that gets grabbed becomes the standard. That's the great part about having a lathe and mill: there's no such thing as an unavailable replacement part, just an excuse to buy the cutting tool or attachment you need to make one yourself

                Comment


                • #9
                  19 TPI has got to be about as non standard as you can get without using pie.

                  Who even has gearing for that thread? I have a full set of gears for my SB, including three compounds and some extra gears not usually included. I have created a chart that shows all possible threads that it can cut. I can do 19.2 TPI, 19.33333 TPI, 19.5 TPI, and several really odd values starting with 19 and with infinitely repeating decimals. But I just do not have any combination of gearing that will do 19 TPI. It is a prime number and I assume you would need a gear with either 19 teeth or a multiple of that (38, 57, 76, etc.).

                  Does anybody have the ability to cut 19 TPI without making or buying such a gear?

                  On the other hand, it is fairly close to 1.333 mm: 1/19" = 1.337mm which is certainly well within the accuracy of measurement. Guess what, I have four different combinations of gears that can cut that. The simplest is 32 - 60 with a 100 - 127 transposing gear between them. (8 TPI lead screw). So it is probably a combination of English and metric.

                  The only possible reason I can see for this is to prevent third party replacements. Inch OD makes you think English measure. Nobody thinks about metric thread. So a special gear is needed to make a special tap which is needed to make a special nut. Not many will copy it. More sales for the OEM.
                  Paul A.
                  SE Texas

                  Make it fit.
                  You can't win and there IS a penalty for trying!

                  Comment


                  • #10
                    My lathe has 19tpi on the gearbox plate and I think Tim's does too.

                    Michael

                    Comment


                    • #11
                      Originally posted by Paul Alciatore

                      Does anybody have the ability to cut 19 TPI without making or buying such a gear?

                      .

                      Yes




                      Comment


                      • #12
                        Originally posted by Paul Alciatore
                        19 TPI has got to be about as non standard as you can get without using pie.

                        Who even has gearing for that thread? I have a full set of gears for my SB, including three compounds and some extra gears not usually included. I have created a chart that shows all possible threads that it can cut. I can do 19.2 TPI, 19.33333 TPI, 19.5 TPI, and several really odd values starting with 19 and with infinitely repeating decimals. But I just do not have any combination of gearing that will do 19 TPI. It is a prime number and I assume you would need a gear with either 19 teeth or a multiple of that (38, 57, 76, etc.).

                        Does anybody have the ability to cut 19 TPI without making or buying such a gear?

                        On the other hand, it is fairly close to 1.333 mm: 1/19" = 1.337mm which is certainly well within the accuracy of measurement. Guess what, I have four different combinations of gears that can cut that. The simplest is 32 - 60 with a 100 - 127 transposing gear between them. (8 TPI lead screw). So it is probably a combination of English and metric.

                        The only possible reason I can see for this is to prevent third party replacements. Inch OD makes you think English measure. Nobody thinks about metric thread. So a special gear is needed to make a special tap which is needed to make a special nut. Not many will copy it. More sales for the OEM.
                        19tpi is normal for UK lathes, as 1/4" and 3/8" BSP use it.
                        All three of my lathes can do it 'straight out of the box'. Two are CVA 10EE clones, I think I'm right in saying that early CVA lathes must have copied the 10EE box slavishly and didn't include 19 tpi, (John?) later versions did.

                        Yes I have dealt with mixed metric/inch threads, this one I'm sure is basically a BSP thread. Laziness or perversity from the makers, I think.


                        Tim

                        Comment


                        • #13
                          Quote:
                          Originally Posted by Paul Alciatore

                          "Does anybody have the ability to cut 19 TPI without making or buying such a gear?"

                          Yes, my Chinese 13x40 will cut 19TPI. A lucky find in a friend's box of junk of an old but unused 76T spare 16DP gear for a long gone sickle mower blade sharpening grinder allows me to cut 19TPI on the old change gear lathe too.

                          Re unexpected threads, recently I removed the cylinder head from a 1940s British JAP 2S stationary engine. The head bolts looked too fine for BSF - surely not UNF on such an old British engine? The threads turned out to be 5/16 x 26TPI 60 degree British Cycle. Reasonable I suppose, considering the extensive use of JAP engines in older British motor cycles, but not what I expected on an engine usually used of fire pumps and similar applications.

                          franco

                          .

                          Comment


                          • #14
                            Originally posted by franco
                            Quote:
                            Originally Posted by Paul Alciatore

                            "Does anybody have the ability to cut 19 TPI without making or buying such a gear?"

                            Yes, my Chinese 13x40 will cut 19TPI. A lucky find in a friend's box of junk of an old but unused 76T spare 16DP gear for a long gone sickle mower blade sharpening grinder allows me to cut 19TPI on the old change gear lathe too.

                            Re unexpected threads, recently I removed the cylinder head from a 1940s British JAP 2S stationary engine. The head bolts looked too fine for BSF - surely not UNF on such an old British engine? The threads turned out to be 5/16 x 26TPI 60 degree British Cycle. Reasonable I suppose, considering the extensive use of JAP engines in older British motor cycles, but not what I expected on an engine usually used of fire pumps and similar applications.

                            franco

                            .
                            A while ago I was asked to find a nut for a big old Lucas headlamp, the type which fixes to a spherical seat for adjustment. Ones I've seen before had a tubular brass clamping bolt through the seating, to allow the cables to pass down the middle, but this one had a solid bolt with a fine thread. Assumed without studying it that it would be 1/2" UNF, in fact it was 1/2" x 26 - whether cycle or Brass thread I didn't discover, it's UNF now, as I didn't have 1/2" tap among my 26 tpi stuff

                            Tim

                            Comment


                            • #15
                              1971 Triumph motorcycle. Petcock bung on the fuel tank. I wanted to pressure test the tank and needed to fit a hose barb to the bung. I've got an inch thread pitch gage set with over 50 pitches in it and none of them fit, but it looked to be between 18 and 20 tpi. No metric pitches fit either. Finally verified 19 tpi by using the 38 tpi gage.

                              Turns out it is a standard 1/4" BSP fitting, but unless you know what to look for, it's hard to find in a thread listing.

                              Must be another example of that British odd-ball thread fetish they have.
                              For just a little more, you can do it yourself!

                              Comment

                              Working...
                              X