Retracting toolholder to fit QCTP

[bogstandard]

Before I can go any further with my lathe, I need to get the single point threading sorted. I have no trouble doing it, as it is one of the basic things you should learn very early on in your machining life. My problem is that because my lathe is a metric machine, but is also capable of imperial threading, the leadscrew half nuts need to be left engaged all the time for Imperial threading (and also some of the metric as well)
This is a common problem, and over the years a few people have come up with ideas to make the job a lot easier. I am not going to go into a lot of detail, only to say that being able to withdraw the tool quickly, and be able to put it back into the same position really helps to make the job a lot easier.

This is only the start of the project, and will not be picked up again for a little while, because I need to be able to work on my machines safely, and as yet, I am not in that position. But I am able to do a little bit to prepare for that time.

Here are a couple of designs that have been knocking about a while.

This first one is good in that it will retract for doing both internal and external threading, but that is about it, everything else is a non starter.

http://www.hemingwaykits.com/acatalog/Swing_Tool_Post.html


This one goes most of the way there, but is limited to external threads only.

http://www.hemingwaykits.com/acatalog/Retracting_Tool_Holder.html

So I will be coming up with something that does the same as the first, but operates very similar to the second one. There will be no plans or drawings (but I might measure it up at the end and make a few sketches), as I will be making it to fit, and of course changing my mind half way thru. Also, it will drop onto my QTCP just like a normal holder.


So to start.

I feel very guilty about this picture. A few months ago I let Ralph take away this lump of metal (over 6" wide & 1.5" thick) to cut some off for a job he had in mind. It is a piece of gauge plate, and is real tough stuff to cut. Anyway, I said that it wouldn't fit onto my saw, so he took it away and cut a piece off by hand.
Sorry Ralph, I have just found out that by turning it over half way thru, this saw will cut it (now crawling into the back of my cave in shame).

So anyway, I wacked a piece off, then chopped that into three pieces. About an hours easy work.




So here is my motley collection of metal, the three at the front will definitely be used, the bits at the back are there for backup, just in case I need something else to be made that I haven't thought of yet.




So that is it for now, just keep your eyes peeled for when I start to knock the lumps into some sort of shape.



Bogs

[websterz]

Good to see you up and about John! Can't wait for the rest of the project to unfold. 

[sbwhart]

Ha so its the gauge plate route your taking John. 

Looking forward to seeing what comes out of your shop of magic

Stew

[bogstandard]

Yes Stew, I just couldn't resist a bit of pain and suffering.

Luckily there should be no intricate stuff, just three dovetails and a jib strip to make, and the rest will be general hacking about.

John

[Pelallito]

John,
I think that you just wanted to give Ralph a chance to exercise his pint hoisting arm.   After cutting that gauge plate successfully, he should be a lot stronger and have no problems with quart mugs.
I too am looking forward to seeing this project develop.
I hope that you are feeling better.
Fred

[bogstandard]

Before anyone asks where this post has got to, and why has it stalled.

My time is a little limited at the moment, and looking forwards, I have to get a load of engines made or prepared for a show that is coming up in September.

So this has to be put on the back burner for the moment, to concentrate on more important things.

Bogs

[bogstandard]

This was due to be my next project, but due to needing something else more pressing and because I found that my lathe is very easy to work with when thread cutting, I have decided to put this right at the back of the queue, or it might even never make it into production.

I am telling you this as I think a couple of members were waiting for me to start this project.


Sorry lads.

John

[Ned Ludd]

i Mr. Standard,
I only joined this site to say Hi to Mr.B. Standard, so "Hi"
If a newbie to the site might be impertinent enough to make a suggestion. As a maker of the Thomas retracting tool holder, who hasn't, I find it a lovely tool to play with, but for the effort to make it I wonder if it was worth it. There is a much easier to make and better tool to use, which is a simple cross slide stop. It can be used for screw cutting if you use the offset top slide method, saves having to be careful zeroing the cross slide, just go back to a positive stop each time. If you make it adjustable, you can use it for the straight in screw cutting method or the "bit of in feed and a 1/2 a bit of top slide feed" method as well.
.
 I made one for my Colchester and wouldn't be without it for screwing, comes in handy for small scale production stuff too, as it has a five position turret stop. Yes for those who know, I copied the Colchester design, well it is long out of Patent by now!
Ned

[bogstandard]

Ned, Hi.

Your way of thinking has hit the nail on the head.
 
In my time, I have done more than my fair share of single point threading. It was only because I had never done any on my new machine that I thought I would require a retracting toolpost, but as it turned out, with the DRO setup, it has turned out to be dead easy. To such a point, as you said, my time is better spent making something a little more useful.

I made a cross slide stop for my old Atlas lathe, and it worked very well indeed. Unfortunately, there are no exposed dovetails on this machine to easily fit one, and I am not really into doing chop jobs on the lathe at the moment. Maybe in a few years when it has had a lot more use.

How's about getting a few shots of your stop, under it's own topic, to show the members what we are on about. I am sure they would be very grateful. Doesn't need to be a fantastic novel, just a couple of pics and a bit of text to give the general idea.

It might save me having to fire up the C-o-C when someone asks what we are on about.


John

[Ned Ludd]

Hi John,
If I can find the camera and then find the charger (more difficult) I shall give it a go. Since making mine a nice kind gentleman sold me half of a genuine Colchester one, I could take photos of the two together for comparison.
I wish I had a camera handy this morning, I did a little repair job on a friends broken door mirror. In true Bogstandard fashion, I made a new pivot to replace the broken one, then bored the main casting to take the new pivot. Again if I can find said camera I shall take some piccies before handing the repair back, tomorrow.
Ned

[bogstandard]

Ned,

It seems that if you need to post on here, a camera is a necessity, otherwise you get this  every time you open your mouth.


John

[Ned Ludd]

  I kind of knew that would happen, seen it before.
Will do my best, not to get it again.
Ned

[bogstandard]

Don't worry Ned, you should take things like that with a pinch of salt.

Sometimes we do act normal on here.

John

[Ned Ludd]

That makes a pleasant change from SOME sites. Which is why I am here, by the way
Ned
PS found the charger, now just the camera to find. New fangled digi things, bring back proper stinky chemical ones.

[Stilldrillin]

That makes a pleasant change from SOME sites. Which is why I am here, by the way
Ned

We`re all nice on `ere! 

Most of us...... 

Most of the time......   

David D

[andyf]

For screwcutting, a chap on a Yahoo group has made a swinging toolholder for his QCTP along the lines shown in the sketch below. Toolholder A is supported by the ledge on B, and by the adjacent vertical face of B, during the cut. When the saddle is run back ready for the next cut, the work rubs on the tool-tip, raising it to keep it out of harm's way. The motor (rather than the tumbler gear) must be reversed, so that the work runs backwards as the saddle is run back.

It does suffer from two pretty major limitations. First, it will only work for RH threads; on an LH thread, there would be no side support for part A. Secondly, it won't work for internal threads, and I suppose that those are where most help is needed because one is flying blind on instruments only. I'm mentioning it for just for interest, rather than as an altenative to a proper retracting toolholder.



Andy

[Darren]

These do look nice though

[bogstandard]

Darren,

Even though I have decided it is not time cost effective to make one, that one you have shown really saddened me.

With a slight design change that could have gone from being a mediocre outside threading one, to an all singing all dancing one for both internal and external threading.

That's what comes of following other peoples designs religiously. It is OK for what the original designer needed, but not for others who follow along afterwards.

As far as I am concerned, it is only half finished.

John

[John Stevenson]

One drawback I can see with the one in Darrens pic is that bloody lever would be very close to the chuck when working on short lengths of parts with large top hat diameters.

Not my idea at all but fitted to my CVA which in turn was robbed from the Monarch 10 EE [ sighs of reverence here .. Aaahhhh ] is that the hand wheel dial has the stop built in.



This is the hand wheel removed and reversed, the dog on the right is part of the dial, the other two are just floating dogs.



What happens is that you position the cross slide close to the work and screw the small side screw in then wind in.
Then what happens is the outer dog catches on the screw, then the inner and then the fixed one which gives you nearly 3 complete turns before it all comes up tight.

You then use the top slide set over at 1/2 the angle to position the tool.

At the end of the thread you wind out, no need to look, go back to start of thread, either manually or under power, and then wind in all the way, then apply new cut with the top slide.

This means the operation is machine controlled and not reliant on a special tool holder.

Depending on machine build up it may be easy or hard to implement.

John S.

[sbwhart]

We use to have Holbrook lathes that had a quick reatract handle on the cross slide, at the end of the cut you just pulled the handle up, go back to the start push the handle down, put your next cut on etc etc don't know if it worked for internal cutting though.

Stew

[Darren]

Thanks John, I was wondering how that worked on the CVA. Quite simple really, like most good ideas.

I wonder ...... 

[Gerhard Olivier]

With a slight design change that could have gone from being a mediocre outside threading one, to an all singing all dancing one for both internal and external threading.

Care to expand a bit John
I tried to think but all the mods I can think of to make it in/external is very complicated???  I ask because that spesific one is on my todo list.WHAYYYYY DOWN.
Gerhard

[bogstandard]

Gerhard,

Here is a very rough C-o-C of how easily it could have been modded to allow both internal and external tools to be held, and the cam would operate in the forwards mode for external cutting and rearwards mode for internal.


John

[Gerhard Olivier]

Thanks John -That would work - would need to put positive stop forward as well as rear.
And it would be a bit bigger to allow it to travel without play????


Hope I remember all this when I get back to the threading tools.

Gerhard

[bogstandard]

Gerhard,

Unless you are doing very large threading work, 0.187" (4.8mm) would be more than ample movement.


John