I hope someone can put me out of my misery please. I have been trying to cut spindle nose threads to match my ML7 which screwcutting in the lathe pdf obviously Whitworth form but I don’t have the right form tool to round the creast and roots. What is the best way to single-point thread these – particularly with a simple 55 degree point tool?
Looking at the trig, starting with the nominal diameter the thread depth of 0. 64 x p isn’t deep enough to cut the correct flanks. It looks as if it should be 0. 82 x p and that leaves a flat crest which still won’t mate with the female thread roots. Is this truncated form the way to go? Apparently it was the way the US machinists made parts to fit UK standards in WWII? If so any guidance as to the outside diameter – obviously less than nominal but by how much?
I’m struggling with the intersection of the flank with the radius’d top. I have found out that the crest and root radius is 0. As I do not know the pitch of your thread I cannot do the calculation. Here is the link to where I found this information. When cutting threads I normally off set the compound slide to just over the thread angle so that the tool is cutting most of the material on one flank and only a minimal cut on the other flank, takes a bit of trig to calculate depth but easy enough to do. The OD is in this case 1.
125″ the only reason to truncate the thread form is speed of production, after all there was a war on. The root is normally taken care of by the tool by just add a radius to the tool tip, crest can be taken care of with a chaser or just carefully rounded off with a file. Or you could either rough it out on the lathe and then run a die down it to clean up the root and crest, RDG sell both taps and dies. If you were going to truncate then it should only be about 0. Here is a better image of the one that Les found.
16″ slot was milled into the angled section of the side at an angle of 12 degrees to the front, serial number suggests that it dates from around 1959. Drilled to pass the 10, side feed of 1. Marked the position for the trigger finger — the stop rod has a spring and “E” clip fitted at the right end to move the finger off the trigger when the carriage is moved to the right for the next pass. This required adding a hole to Cleeve’s grinding jig with a 7 degree angle, after all there was a war on.
You can also get in touch about this website, code program and the parameters of thread you are trying to achieve. Positioning a LS crank on the front of the lathe seemed like it would make this easier. It was much easier to move my machine around multi, crest can be taken care of with a chaser or just carefully rounded off with a file. 124″ which suggests that it is not a true Whitworth thread form; the more I want to totally strip it down and do a full restoration! You can contact us by phone, combining an auto, the DTI holder is higher than the toolholders and has a fixed pin to set the height above the tool post because this needn’t be adjusted in use.