Swingup external threading tool

[AdeV]

And if it is really really tricky I turn the chuck by hand - that's slow
and it makes my arm ache

Could you make/obtain a crank handle that goes in the back of your spindle? That would make turning the lathe easier; and would also mean you could turn right up to a shoulder with excellent accuracy. It'd also be great with a swing-up holder, because you're in total control of the speed & direction of the stock; so you just wind forwards to the end point, backwards to get off the thread, move the cross slide (or top slide, depending on how you're cutting) in a few thou, rinse & repeat.

[No1_sonuk]

I use my one on a Chester Comet minilathe , that hasn't got a brake and the lowest speed is 100 rpm.
I cut a runout groove with a parting off tool and I seem to manage.

Same for me, but Chester DB7VS (a 7x12 size machine).

[DaveH]

My lathe is the same as Chester Crusader only without the bells and whistles and 1990 ish,

The hand crank is a good idea - only in the past when I have looked at it - seems it maybe a bit of a stretch.

I think I must have short arms

Thank you all, I really appreciate your input 

I'm going to look at the hand crank again.

DaveH

[krv3000]

HI all well i have cut threds on my lathe witch is a emco compact 8 by hand crank i tride to cut a thred the way it tels you in the manuwel and it all went rong the lathe has a cluch so wat shud hapen is you hit your stope and the cluch cuts in and all stops but this did not hapen and at furst i thort i wood have to by a new leed scruw untill i fawnd out that ther is a sacrifishel pin that gives way  at the end of the chaft   from bob

[wheeltapper]

A hand crank is definitely the way to go, especially for short threads up to a shoulder, there's just no time to get into the swing.
I made mine so I can fit either a handle or a change wheel for indexing, there's some pics on here somewhere.

Roy

[DaveH]

Roy,

Thanks I'll have a look

 

DaveH

[DaveH]

Roy,

OK I found it - expanding mandrel, the way to go

Thanks

 

DaveH

[doubletop]

I am going to bump this thread up as there seems to be some new interest in this tool.

Don

Mike Cox has an article on his original design in issue 178 of MEW and has quoted this thread which is probably generating the interest.

Pete

[David Kirtley]

Well, I have been reading this thread for a while and wanted to try my own version.  It is a work in progress but I thought I would look for some feedback from people that know more. I am just starting out and this was my first attempt. I figure it was better to actually make something instead of just swarf.




I was under a bit of a constraint fitting it on a little mini-lathe QCTP (A2Z CNC).  Instead of a key, I just plowed a groove for it to fit in to keep it from moving left or right.

Here is with the tool holder in place It gives me about 0.25 room to adjust up to meet center height. The bottom of the tool holder is a bit thin but all it will be holding is the locking screws. The force will be on the main holder base. I left that as thick as I could.:



I milled a bit away on the swing arm to keep it from interfering when it swings:



I might put a shoulder bolt for it to swing on but for right now, I just have a cap screw. I doubt that my poor little lathe could develop enough power to snap a 1/4-20 screw.  I have not decided yet where I am going to trim off on the front and back. Right now it is way to long front and back so I had enough wiggle room to shape and finish.



Next up will be drilling for the lock screws for the tool holder and the adjuster.

[andyf]

Nice one, David  .

Might the width of the support to the left of the swinging part get in the way if you want to thread close up to the chuck jaws? I think that's why Bogstandard, when he reworked the original design, used a key underneath. Of course, if you only want to do RH threads, you don't need any support on that side (or a key) at all.

Screwcutting a shoulder bolt, with a plain shank to act as the pivot, should be no problem now!

Andy

 

[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]

Hi Andy,

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

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]

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

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

  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.   Cheers, mad jack.




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

[David Kirtley]

The largest bit mine can take is 1/4 in. I was actually switched to using an even smaller bit on the second test. By the time you add on the weight of the swing arm and the lock screws, the weight of the bit doesn't really make that much difference. If it doesn't prove to be enough to overcome friction, you can always add a weight or a spring.

The only thing I can see as a possible point of failure is for reversing with the bit engaged in the work piece and the pressure flaking off a chip of carbide.

[abinitio]

I would like to make this. Drg. with Dims would be usefull. some pics would be good regards AB

[Arbalist]

I would like to make this. Drg. with Dims would be usefull. some pics would be good regards AB

Have a look here mate:

http://www.modelenginemaker.com/index.php?topic=858.msg9461#msg9461

[drmico60]

Hi AB,

Also have a look here.

http://mikesworkshop.weebly.com/swing-up-tool-holder.html

I have also designed a swing tool for internal threading, see:

http://mikesworkshop.weebly.com/internal-swing-toolholder-for-threading.html

Mike