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goodscrap
10-20-2014, 05:26 PM
Has anyone made anything like this


http://youtu.be/QYm_CJFJEWs

Seems there is a bit of mystery on the mechanism at first but I found these detailed Pictures which help see what Is going on

http://www.cnctar.hunbay.com/HJozsi/Eszterga/SNAP-TAP/

Here is a shop made version but the mechanism is obscured unfortunately
http://youtu.be/TMZ9nu2HtR0

John Stevenson
10-20-2014, 05:48 PM
http://www.model-engineer.co.uk/forums/postings.asp?th=84556#1598838

Black Forest
10-21-2014, 12:20 AM
Not the same but works really well and would be easier to build. The lever that moves the threading tool forward and back is just rotating a cam.
https://www.youtube.com/watch?v=fxOqH9izVh4

dp
10-21-2014, 12:52 AM
Its a form of retracting tool like this kit: http://www.hemingwaykits.com/acatalog/Retracting_Tool_Holder.html

Here's an animation

http://www.micro-machine-shop.com/9x20%20Lathe%20Retractable%20Tool%20Bit%20Holder.h tm

awemawson
10-21-2014, 04:02 AM
Chap in the video is a walking disaster area! Loose cuffs, unbuttoned shirt and dangly bits. Accident waiting to happen in my view however good his threading may or may not be.

Mtw fdu
10-21-2014, 07:45 AM
Chap in the video is a walking disaster area! Loose cuffs, unbuttoned shirt and dangly bits. Accident waiting to happen in my view however good his threading may or may not be.

That was the first thing I saw as well when watching the video.

Mtw fdu.

vpt
10-21-2014, 08:16 AM
It must have been casual friday.

Hopefuldave
10-21-2014, 08:17 AM
Strange topslide angle, too... I prefer a straight in/out retraction as came from the factory on my lathe, about 3/8" movement of the cross-slide bearing that repeats to less that a half-thou", topslide at 29 degrees (or 27 for.whitworth threads).

DR
10-21-2014, 12:47 PM
Not the same but works really well and would be easier to build. The lever that moves the threading tool forward and back is just rotating a cam.
https://www.youtube.com/watch?v=fxOqH9izVh4

Interesting that he's leaving the half nuts engaged and reversing the spindle to bring the carriage back to the start. He's also feeding in with the cross slide rather than the compound, although the chip looks like it's coming off one side of the tool only.

Paul Alciatore
10-21-2014, 02:53 PM
Well, he just sharpened one side of the tool: the other side is just rubbing.

Seriously, there is a question there. He can not be feeding in with the compound because it is at the wrong angle, close to 60 instead of 30 degrees. So how is the in feed being done? The cross feed is the obvious answer, but is it? Or is there some trick there that we are not seeing?

As for the retracting mechanism, I suspect that the rod has a simple stop that it hits when the tool reaches the shoulder. Then the rod seems to release a locking pin on the side of the sliding part of the tool holder and then stops it's forward motion while it slides out of engagement. It would seem that the operator must then disengage the half nuts. I'm not sure what would happen if he is too slow at this. I would guess another stop, at the other end of the tool's travel, is used to move the tool back in and re-engage that locking pin. The operator is hand cranking the carriage back to the starting point and going far enough to hit that second stop.

It would be nice to see the whole mechanism and also the operator's hand motions from a better point of view.



Interesting that he's leaving the half nuts engaged and reversing the spindle to bring the carriage back to the start. He's also feeding in with the cross slide rather than the compound, although the chip looks like it's coming off one side of the tool only.

dp
10-21-2014, 02:59 PM
Interesting that he's leaving the half nuts engaged and reversing the spindle to bring the carriage back to the start. He's also feeding in with the cross slide rather than the compound, although the chip looks like it's coming off one side of the tool only.

If he used the compound the cutter would travel closer to the headstock with each pass before the mechanism withdraws it.

Here's the photobucket page for the tool. http://s399.photobucket.com/user/neilw20_2008/media/Lathe/SNC00317.jpg.html?sort=2&o=0

Black Forest
10-21-2014, 03:12 PM
Well, he just sharpened one side of the tool: the other side is just rubbing.

Seriously, there is a question there. He can not be feeding in with the compound because it is at the wrong angle, close to 60 instead of 30 degrees. So how is the in feed being done? The cross feed is the obvious answer, but is it? Or is there some trick there that we are not seeing?

As for the retracting mechanism, I suspect that the rod has a simple stop that it hits when the tool reaches the shoulder. Then the rod seems to release a locking pin on the side of the sliding part of the tool holder and then stops it's forward motion while it slides out of engagement. It would seem that the operator must then disengage the half nuts. I'm not sure what would happen if he is too slow at this. I would guess another stop, at the other end of the tool's travel, is used to move the tool back in and re-engage that locking pin. The operator is hand cranking the carriage back to the starting point and going far enough to hit that second stop.

It would be nice to see the whole mechanism and also the operator's hand motions from a better point of view.

Not sure but I think DR was referring to my video. I am cutting metric threads and so the half-nuts stay engaged. I always just use the cross slide to feed straight into the workpiece being threaded.

Black Forest
10-21-2014, 03:21 PM
Here is another auto retract threading tool holder.
https://www.youtube.com/watch?v=sn8av4Y1crU

John Stevenson
10-21-2014, 06:54 PM
Lift up tool.

http://youtu.be/YZkRNdXFYB8

Half nuts stay closed so you can do imperial on metric lathe or visa versa.
No winding back, only the infeed is applied and this can even be added as the tool is returning.
Easy to make, fits any lathe with no modification.

Why re-invent the wheel ?

DR
10-21-2014, 07:29 PM
Back pre-CNC we used an hydraulic tracer for high speed single point threading. The tracer template was straight, then at the end of the thread the template veered away at a steep angle. Depending on the response speed of the tracer head you could thread fairly fast.

Yondering
10-22-2014, 12:25 PM
Lift up tool.

http://youtu.be/YZkRNdXFYB8

Half nuts stay closed so you can do imperial on metric lathe or visa versa.
No winding back, only the infeed is applied and this can even be added as the tool is returning.
Easy to make, fits any lathe with no modification.

Why re-invent the wheel ?

More details? How does the tool lift up?

The ability to reverse at speed looks like a nice feature for this type of threading.

dp
10-22-2014, 01:57 PM
Here's the original thread from 2011:
http://bbs.homeshopmachinist.net/threads/38585-Swing-threading-tool

goodscrap
10-22-2014, 05:00 PM
Cheers for the replies, the first mech is clever in that it auto-retracts and doesn't matter if you overshoot a few revs, I rarely do any screwcutting, but it's always a palava when I do.

Brian