Swingup external threading tool

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David Kirtley:
Hi Andy,

I thought about doing it like bogstandard but I was under one additional constraint. My tiny QCTP doesn't have much room in the vertical direction. I went down as far as I thought I could get away with under the cutter holder to get the cutter height below the centerline. 2.25mm just doesn't give me a lot of leeway to put in a key. I was already down to 6.8mm for the ledge for it to ride on and didn't want to go any thinner to keep it from flexing while cutting. For a real practical version, I would be much better off making my own toolpost that rides on the compound rather than using the QCTP or even move it all the way down to the cross slide. Then I could just go ahead and use big cutting tools and not even worry about flexing.

Not quite that worried about chuck clearance. I mainly use an ER32 collet holder on the faceplate that doesn't have as many spinny bits.

Honestly, it was just a fun exercise to practice cutting to dimension and play with a different approach.

andyf:

--- Quote from: David Kirtley on October 24, 2011, 10:56:19 AM ---Hi Andy,

Honestly, it was just a fun exercise to practice cutting to dimension and play with a different approach.

--- End quote ---
Hi David,

Well, out of something done for fun, you've produced a useful bit of kit! I look forward to seeing what you get up to when you are being serious.

Andy

David Kirtley:
Here it is in a bit more presentable state. All I have left to do is the set screws for the cutter and the threaded post for the adjuster. I might pretty it up finish wise but for now, I am staying with it. I guess I will stop by Harbor Freight and pick up one of their set screw sampler packs for some fiddly bits.

You can see where I have trimmed it off with a radius to give a bit of clearance.

David Kirtley:
Just an update.

I drilled and tapped for the locking screws for the cutter and the adjuster. Of course they were out of the cheap assortment of set screws at the discount store, so I just put some cap screws in for now. I also need to pick up a couple nuts for the adjuster.

Well, the only misfortune was one of the set screws is offset (Yes, I broke off the tip of a center drill)

Anyway, after setting the height by hand since I don't have an adjuster, I grabbed a piece of junk AL from the ziplock I keep near my lathe and tested out cutting threads. Swapped out all the gears to set up for M1 threads. I do have to say, it exceeded my expectations. Everything worked as advertised and threading was a simple relaxing exercise.

madjackghengis:

--- Quote from: Bernd on December 12, 2009, 06:44:49 PM ---
--- Quote from: bogstandard on December 11, 2009, 05:46:00 PM ---Bernd,

I have a shoe brake system on my machine, complete with a drum, just like a car, it is very efficient. I thought this was a lot of backlash on my machine since I had set it up, so just how bad is yours?

Bogs

--- End quote ---

John,
The old Logan I've got doesn't have a brake on it so I'd need to run it real slow for one thing.

Second, when I reverse the machine the chuck will start to turn and at about a 1/4 of a turn of the chuck the lead screw will finally start to turn. Then after the chuck has made almost a full revolution backwards the carriage will finally start to move. Have I made this clear enough to understand? That is one reason I think this tooling will not work in "my" machine.

I'm sure that the gears on the headstock probably have more backlash than they need. As far a the lead screw is concerned, I'll have to take a closer look.

In the mean time I guess I'll just have to resort to turning the cross slide out of the way.

BTW, I'm amazed at how nice that tool follows the thread groove backwards. Great job.

Bernd

--- End quote ---

I too have an "old" ten inch Logan, and Bernd's description and the backlash in my '48 are about the same. I built a Metal Lathe Accessories quick retract tool post twelve or fifteen years ago, and found it eased threading enormously, and use it for most of my threading, but compared to what I see with your tool setup, I'm working way too hard.
I had to turn a ten mm by 1 mm thread without transposing gears a few months ago, and figured one of my feeds was almost perfect, so I set up as per normal for threading, but with the feed clutch tight, retracting the tool bit at the end of the cut, and then reversing the lathe, and the thread came out perfect, worked perfectly to pull a very stubborn power steering pump pulley back onto the shaft, with the cut thread fitting into the shaft by hand snugly, but by hand all the way.
With your tool set up, I would have merely had to reverse the lathe, no retract, and set more feed. I have watched you with this tool, and watched when you were working on one some time ago as well, and I think the greatest worries you should have is making one to fit say quarter in tool bits, or smaller, so they are light enough to lift with the smallest of threads. I've watched the tool tip while reversing the lathe with it retracted, and while the tip ends up close to being in the middle of the thread, and not the cut groove, but I suspect the tool would ride there fine in reverse, and I'm going to try this.
The quick retract is a work of art, and works great, but if I can cut my threading time in half, I'd be very happy. I'm also looking for a place to attach a brake, I have long wanted one, but never got around to doing anything about it. Thanks for going through all the effort to show this off in all its capacity. :jaw: :beer: Cheers, mad jack.

**Edited by Stilldrillin. To show Jack's posting, clearer........
(If I've got it wrong Jack...... Let me know!).

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