Thread: your latest project

Hi All,

After seeing how well John Stevenson's modified threading tool worked, I deceided to modify my threading tool along the same lines.A while back I had a piece of black bar that was not deep enough to make my normal quick change holders out of, so I made up a couple of two piece ones for light duty jobs, like mounting dial indicators in etc. As the cuts used in thread cutting are fairly light I used one of these to carry the tool.
Since making the tool I have used it a few times, it makes cutting threads much quicker and less stress as you set your depth of cut on the cross slide and when you have reached the end of the thread just reverse the lathe direction and the tool raises up and rides back. You can set your next cut as the tool makes its way back. I only cut threads at 100 RPM this makes it easy on the lathe when you reverse directions and you can judge you finishing spot at this speed. I only use the cross slide for depth of cut.If you cut a few threads definately worth while having one. A few pictures to help clarify the above.

Bob

Nice job as usual Bob,
I have seen a few versions of that one getting around and will make one myself when I get around to fitting a brake to my lathe.
My Grandfather bought a home made lathe with the dovetails made just like that on the cross slide, and it works good.

Dave

Hi Dave,
Thanks for your reply.Making the dovetails in two pieces sure saves a lot of work and you do not need a dovetail cutter. I made a 60 degree blank long enough for four holders and just chop them off.I have one toolholder with a piece of HSS in it and take pretty heavy cuts (2.5MM depth) with it and it handles it OK. My lathe has a foot brake on it but I find it clumbersome to use for threading work, it is pretty hard to co ordinate the brake as you do not have much feel with your foot.With threading at 50-100 RPM I always cut a full depth of thread groove at the chuck end of the thread and when the carbide tool is nearly at the end just slip the lathe into neutral and let it coast into the groove by then the chuck has almost stopped and then select reverse, this way there is very little load on the gearbox and the carbide tip is not under load. As you know if you stop the lathe with the carbide still engaged it is almost curtains for your tip.
Bob

Hi Bob, thanks for the photo's, I have heard of that device before but haven't thought of making one. I do do a fair bit of threading & like the idea. Sometimes I do thread close to a shoulder & wonder how it would work because of the backlash in the gear train which would mean that the work would rotate backwards before the saddle bagan to move, does this cause a problem or does the tool holder rise up anyway? Looking forward to your comments,
Ian.

Hi tinkera,
The backlash would not cause any problems the tool rises up by itself as soon as the load is taken off it, and the tool rides on top of the thread all the way back. Have a read of the reply I just posted to Dave probably at the same time you were typing.
Bob

Originally Posted by tinkera

Hi Bob, thanks for the photo's, I have heard of that device before but haven't thought of making one. I do do a fair bit of threading & like the idea. Sometimes I do thread close to a shoulder & wonder how it would work because of the backlash in the gear train which would mean that the work would rotate backwards before the saddle bagan to move, does this cause a problem or does the tool holder rise up anyway? Looking forward to your comments,
Ian.

Ian, this has been discussed quite a bit on other forums, and is high on my project list. Madmodder is where I mostly saw it. I don't think anyone who actually tried it had any issues whatsoever, though there were armchair critics. There's a video on Youtube by John Stevenson. Will see if I can find it.

Edit:
[ame="http://www.youtube.com/watch?v=2F_AVx_JRlE&feature=mfu_in_order&list=UL"]http://www.youtube.com/watch?v=2F_AVx_JRlE&feature=mfu_in_order&list=UL[/ame]

There is an extensive thread over on MadModders that includes backlash as well. I can chase it up for you if you want.
It does not need to follow the thread on the way back and if you have backlash (like we all do), it will just ride up on whatever it comes across. When you reverse you go 10-20mm past the start of the thread, then as the tool moves toward the job for another pass, any backlash is taken up in the same direction as your cutting the thread like usual.

Dave

Hi Bob,
Have you thought about a tongue and groove set up to help hold the parts in alignment? Or you could just slot the 2 pieces you have now and put key in between them.
Another way would be to put 2 small V's 1 top and bottom, then tack weld them to fill the V, as well as the screws.The welds would then stop any movement of twisting, but the screws would support it as well.

Dave

Hi Dave,
When I first thought of making them in two parts I intended machining a groove along the entire top and bottom edges and then mig welding them in place. I deceided to try them out first with just the four counter sunk screws, I clamped the two pieces together and drilled all four holes (tapping size) on the mill using the DRO and noting the exact dimensions, I measured the exact diameter of the outside diameter of the screw threads and drilled and then countersunk the outer piece. After bolting together I ran a cutter along the top face so that I could pick up any movement, they have not moved. I originally intended them for light duty use only but they seem to be holding up OK. Your sugestions would work as well but the least amount of work you have to do the better.
Bob

Hi Bob,
It was just a thought as you said they where for light use only, so something like either of us was thinking would make them suitable to heavier use.

Dave