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  • #16
    Hopefully, I have returned to a more level of discussion.

    The problems with what you call "drill rod" pops up in the UK too. We call it silver steel is anyone's guess. It can machine with difficulty and one suggestion is to use Shell Garia H which is a neat cutting oil. There is little merit in recommending something which cannot be found and the following or something similar would also be ideal for deep drilling
    BP CFS 35
    Castrol Ilocut 173
    Duckhams Sulfcut 300
    Esso Dortan 12
    Fina Vulcit X C 12

    I hope that something from this list will assist



    • #17
      Threading takes practice. The tools must be sharp, and on center. Also the closer you can get to the optimum cutting speed, the better the finish will be. This has a direct correlation with your reaction time for engage/disengage the half nuts. Also 'Rapid Tap' or a 'chlorinated' ( and nn-healthy) cutting oil will give you optimum results.



      • #18
        <font face="Verdana, Arial" size="2">Originally posted by PaulG:

        My goofus lathe of course has the compound marked with 0 as parallel to the bed so it would need to be turned 60 from that position. But of course it's only marked to 40 degrees. So I had to use a protractor set to 30 and measure that from perpendicular to the bed. I suppose it could be a little off.

        My lathe is marked the same way. (Well, it goes to 45*.) I put a secondary mark om the compound 45* away from the primary mark, so for threading I set the secondary mark at 15.5*. It sounds confusing, but it's really not. I just take a bird's eye view of the compound and swing it to where it looks about right and say, "Oh, I remember now. I need to be a bit off 15*." Thinking visually about what I'm trying to accomplish tells me which way to nudge it, and I wind up at 15.5*.

        [This message has been edited by Randy (edited 06-29-2005).]


        • #19
          Back to material growing larger afer cutting on it. Cold rolled is actually drawn thru a die and is under stress, then when the outer surface is cut on the metal can expand. How about the ,6061 maybe extruded and under tension? Guy Lautard had long discussion on this in one of his books.


          • #20
            So that we are clear on what I'm about to say- the compound is what the toolpost is attached to and the cross slide is what the compound is mounted to. You feed in with the cross slide, NOT the compound for removing most of the stock. After feeding(in small increments per pass) in to full depth with the cross slide, check the fit. If the nut won't go on or the ring gage doesn't fit, feed in a thou or so with the COMPOUND and then check fit again. Run a file over the threaded portion with the spindle turning after each pass to remove any burrs, stop the spindle, and check again. Repeat as necessary to obtain the proper thread O.D. and depth.

            imakechips, yes, like somebody else mentioned, this is wrong. Lets not add more confusion. The cross slide should come back to a zero setting after every pass and then feed in with the compound.


            • #21
              Don't wish to muddy the waters further, but at 1/4" over any significant length, I'd be using the travelling steady.
              Rgds, Lin


              • #22
                Here's something I did on threading a while ago.

                Maybe it will be of help.


                Good luck!



                • #23
                  Thanks Kap, I didnt know about the final .001 move with the cross slide.


                  • #24
                    And I've never heard of "spit polishing" the final passes. I'll have to try that. I think I'll make a tool grinding fixture like the one shown, too.


                    • #25
                      Just a thought... i have almost no threading expierienc.e..

                      but opposed to engageing/disengaging the half nut... could you simply reverse the lathe keeping everything still engaged? This assuming you have a 'shifting' type action lathe where you can forward/reverse it immediately.. never tried but just a thought.


                      • #26
                        Lots of good tips above. I never heard of a " spit polish eather ". If you reverse spindle direction after the finish of a pass you must back out cross slide. Gearing backlash will crash the tool into the work if the tool is left in.


                        • #27
                          Yes, Derek, you can reverse the lathe to return to the start if, as Jim points out, you back the tool out for the return pass. In fact, that's the normal way when cutting metric threads on an inch based lathe. (Or conversely, cutting inch pitch threads with a metric leadscrew.) In this case you can't readily re-establish the relationship between the carriage and spindle if you open the half nut, so you simply keep it engaged and run in reverse to return.


                          • #28
                            Thanks to all for the help. It's embarrassing but the problem turned out to be a tool that was just a little high and on a 1/4 piece of course that can make a big difference in how it cuts. All my threads work great now.

                            Thanks to all.