Multi Start Threads. What Are They ? What Are They Used For ? And How They Are Made On A Lathe.
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- Опубликовано: 11 сен 2024
- Discussion about Multi Start Threads and two methods of making them on a lathe with a practical demonstration using the second method.
EMAIL: -davesozzyworkshop@gmail.com
This is a CORRECTION to what I noted on the video. After sleeping on the matter and looking and playing with the thread, it IS a thread magnifier. The threads were cut as if it was a 16 TPI thread ( 4 TPI X 4 Starts ) My part thread length ended up at 3/4 inch, so 12 threads over that distance, the nut takes 3 turns to travel that distance. So it does Multiply the travel speed by 4. Please ignore the screen message that comes up when speaking about the bolt, also in my end chat I also mention it. Sorry for this misunderstanding on my part. Thank you to all the people who pointed out my error in regards to the multiple run out grooves causing the bad thread at the stop end. This being the first time I had done this on this lathe, I was not aware of the problems I would encounter. At least I now know that there is not a fault with my lathe, just in my operation of it. Regards from Dave.
I think the error in the thread is a result of using the stop on your lathe to cut the groove. Every time you advanced the compound you were cutting a new groove farther down the part. The carriage still stops in the same place, but because you advanced the compound, the tool is stopping farther down the part. The result is that you are cutting four grooves instead of just one. The error you see is the second, third, and fourth threads overlapping the previous grooves. I think, to fix that you would need to move the stop in the opposite direction by the same amount you move the compound. That way the tool will stop in the same location relative to the part (one groove). That is not a problem on a single-start thread because you are not advancing the compound so the tool stops in the same place. Or you can just make a big undercut as you did at the end of the video.
Hello Bill, thanks for the view and this comment. You are quite correct about the multiple exit grooves being cut, several other people have pointed that out. Never considered it as normal single start threads are no problem with this lathe. Still as I said, my first multi start thread in over 55 Years of engineering, so bound to make the odd mistake as a "Newbie" doing something for the first time. LOL Take care. Regards.
Dave, thanks for the video. It is good to see things that don’t always go to plan and the explanation for them. Keep up the good work.
Tom
Thanks, will do, Thomas. At least I got replies telling me what the problem was and not a lathe fault. Thanks for watching. Regards.
Hi Dave. Enjoyed watching the methods you covered. I've never needed to make them with the projects I've tinkered with thankfully lol. Tony
Hi Tony, Thanks for watching. I have never done it either in 50 + Years, that was my first go. Regards.
Hi Dave, great video, very informative. I have made about half a dozen multi start threads over my years....... None of them were intentional lol! It was a discipline not covered by my apprenticeship and I have never needed to make one. Learnt a lot here. Cheers, Jon
Thanks for sharing Jon, will you remember it when the time comes though ?? LOL. Regards.
Great video - I appreciate you showing us the whole process, even the problem with the runout grooves. One solution would be to invert the cutting tool, run in reverse and thread away from the chuck - allowing you to pick the start (end) point of tbe threads. Anyway - very informative video, thanks for sharing.
Hello Stuart, thanks for the view and your comment. YES upside down tool and reverse if you have a conventional lathe. This Hardinge is special when it comes to screw cutting, because of the way it is made the machine should NEVER be run in reverse when screw cutting. For left hand threads start at the chuck and come out. There will be a dedicated video soon on how and why the Hardinge threads as it does, by special request from a viewer. Watch this space. Regards.
Great! Thanks - it’s a beautiful machine I look forward to learning more about it.
That's a clever method. I thought of another but I haven't tried yet. I'm confident it will work. Mount square stock in a square collet. Turn the portion to be threaded round and to dimension. Cut one thread. Index the work 90 degrees in the collet, cut the next. Lather, rinse, repeat. This DOES require the depth of the stock in the collet to be consistent when you index, so face that end and use a collet stop. Should work!
Hi there, yes it does sound as though it should work, just need square stock and a square collet, not got square collets though.😢 Good luck trying it if you have the equipment. Regards.
great to see people having a go, and willing to share mistakes - absolutely everyone makes them! Well done, Dave, keep going.
Hello Rodney, thanks for the view and your comment. I think that people who say that they never make mistakes don't actually do anything. Regards.
Thanks, Dave. Another commenter correctly identified the cause of the different runout grooves, namely the successive displacement of the compound slide.
Your demonstration of the HLV forward and reverse clutch answers something I've wondered about since reading about the lathe as an apprentice 50-odd years ago. Thanks for sharing!
No problem Russell, Glad you now know about the threading clutch mechanism. Full threading instruction video to come shortly. Thanks for watching. Regards.
Hi Dave Very interesting video lesson on multi start threading. I may give it a go just to see if I can do it when I have some free time. Cheers
Hi Randy, be aware that you will need to do a tool runout undercut on your lathe. Thanks for watching. Regards.
@@daveticehurst4191 Thanks for the tip.
Thank You Dave...This is something I have not done for several decades. Your show jogged my memory & it felt good to think back. I think about this when I use the tooth past tube cap. That thread also has a force thread. Angled on one side and square on the other so it is not a symmetrical design thread but a load bearing thread. Seems like an overkill for a simple toothpaste tube cap? ... Love your Harding Lathe !!! TM
Hi Tuffy, Glad you enjoyed it. Thanks for watching. Regards.
The roughness at the finish is due to the different initial positions of the four starts leading to four different positions for the runout groove. The runout grooves and thread tails are crossing.
When cutting a 4 start thread using this method of advancing the compound slide 1 pitch for each start the run out undercut at the end of the thread needs to be long enough to accommodate the total amount that the slide moves, in this case 4 x .0625 + some extra clearance so that the leading flank of the insert does not crash into the shoulder. Alternatively on the Hardinge the stop which stops the saddle should be moved 0.0625" away from the headstock for each new start.
Hello Jon, You see that you do learn something new each day. As I said this was the first multi start I had ever done. Thanks for the information. Thanks for watching. At lest I do not now have to investigate my lathe. Regards.
Thanks for the view and your comment. Duly noted for next time, if there will be a next time. Regards.
Hi Dave, Great video once again! There is nothing wrong with you lathe, the ripped threads at the chuck side is a function of using the compound as you did. When you moved your compound dial 62 ½ thou you would also need to decrease your auto stop by the same amount to end in the gully that was cut by the first thread. You where running over the gully the first thread made then ran past the second end, the third end. I hope this helps, but there is absolutely nothing wrong with your lathe.
Regards,
Craig.
Hello Craig, Thanks for the view and your comment. Yes, several other viewers have said the same. But I did say that this was the first time I had ever done it, so lessons learnt all round I think ?😊 So used to doing only single start threads, that my mindset did not even consider what I was doing would not turn out as usual. Thanks again. Regards.
Very interesting. That's something I never got into. Using the compound instead of gear indexing is brilliant. I can see when multi start threading it requires ones full attention, no distractions. Good demo, well done. I hope all is going well for you buddy! Tc, Mike
Thanks Mike, glad I managed to find you something to watch to pass away your re cooperation period. I'm fine Mike, must drop you another email soon. Regards.
Hello Dave,
An enjoyable video and a real showcase for how cool your lathe is... I was wondering if you have to adject the STOP for the feed each time you advance the compound (Create a new start) to avoid the issue you had where the threads over cut each other.
Take care.
Paul,,
Hello Paul, someone else suggested the stop move, or do a long undercut groove before starting. Big learning curve as I had not done one before and probably never do again. LOL Thanks for watching. Regards.
If you're moving the compound 62 thou forward you would need to adjust the stop position to compensate.
Thanks for your view and your comment. Several other viewers pointed out the same thing. Never done it before in 50 odd Years and will probably never do again. Was a learning curve for me and others as well. On a conventional lathe you would have had an undercut to run the tool into so it would not have occurred. Regards.
Dave, thanks for the tutorial. I’ve never seen a multi-start thread in real life, that I know of. I like how your lathe automatically stops at the end of the cut. What brand and model is your lathe? Thanks again for sharing, have a great day!
Hi there, thanks for the view and comment. It is a HARDINGE HLV lathe. American but made under license in EXETER in England around 1950. Dovetail bed, manual variable speed, 5 C collet spindle, taper fit chucks. Was superseded by the HLV-H model. Wider bed and the variable speed change was done by an electric motor. If you get 1.5 hours spare, watch my shop tour. I explain how I got it etc. Regards.
@@daveticehurst4191 heading there now, thanks!
If you do not wish to make such a shoulder at the end of your thread cuts, you then need to move your hard stop back towards the tail stock by the same amount that you move the compound for each thread. So, for your demo, you should have moved back your hard stop by 0.0625'' for each new thread. This is where your mistake resides in with your first multi thread demo resides in.
On your second thread you compensated your mistake by making the shoulder 0.250'' wide to compensate for the pitch (4 times .0625)
Also, if your blank is not running perfectly true to begin with, then this is where you will get a difficult thread start as you engage the nut to a different thread start.
Try to reduce your turning speed as much as comfortably possible.
personally
Thank you for your excellent comment. Other people have also said the same. But I did say that this is the first time I had ever done it in over 50 Years so it was also a learning curve for me. Will probably never do it again. Regards.
I think that the problem with those 3 end threads is from the tool itself. In a laydown threading tool, its not a single toothed cutter, the 2 trailing threads are being cut off by the multipoint tool when left in the last position and the spindle continues to turn.
Thanks for the view and your comment. The threading tool was a single point insert. The reason the last treads were chewed up was because I was advancing the compound slide by 0.062" each time. I did not change my carriage auto stop point, so No. 2 thread over cut thread No,1. Then when I cut thread No, 3 it cut over threads 1 and 2, finally when I cut thread No, 4 that then cut over threads 1, 2, and 3. If I had done a long undercut of more than 1/4 " wide there would not have been a problem. As I stated in the video this is the first time that I had ever done a multi start thread, so a big learning curve for me. If you get a chance read some of the other feedback I have received, it will explain a lot and other options using a standard lathe. Hope this helps. Regards.