Swingup external threading tool

[andyf]

Hi Anthony,

Hmm... I think it might have to be a bit more complicated, and rather more like Cleeve's version, to make it rigid enough to work with a boring bar-like tool for internal threading, which would (on your sketch) have to stick out to the left, rather than point straight up.

Andy

(in and wet blanket mode)

[bramley51]

Andy and John,I've just finished my self retracting tool,and I'm chuffed to bits.It works like a charm,even for an ijit like me. .Thanks for presenting the design,single point threading no longer scares the cr*p out of me.
I can highly recommend this tool to anyone to anyone who's never tried single point threading 'cause it's "too difficult".
Make this tool,and people will pay good money to see you at work
Thanks again,guys.

[troup]

Must be something in the water here in NZ, over half the people I know of from the interwobble who've run with this idea have been kiwis.

To whom I have now added myself, and will post more details, but I have a WARNING for those with a VFD who feel inclined to take the idea to the logical conclusion, and add some sort of automatic reverse.

What I'm talking about is a sort of self-acting "canned cycle", so you can thread pretty much like an NC lathe for the price of a switch or two.

Going directly from "full steam ahead" to "full astern both" used to be the preserve of turret lathes (eg Herberts with massive 4 speed motors and 'plug reversing') or the likes of John Stevenson's Tos, but now with VFDs it's as simple as adding a single changeover limit switch (a normally open pair AND a normally closed pair of contacts) or two simple limit switches. If either the switches or the dogs can be relocated, your lathe can automatically and accurately cycle through the threading zone ad infinitum, leaving you to simply increment the cut. (Runout grooves can be narrower, threading speeds higher > better finish, quicker job completion: all very enticing....)

HOWEVER this silver lining does have at least one cloud:

particularly when commissioning the reversing facility for such a setup, be aware that repeated reversals can cause a scroll chuck to self-open, to the point the jaws fly out. I learned this last night by almost having it happen. Yikes!

The scroll is the flat disc with a single spiral groove which engages with the teeth on the backs of the jaws, and also with the bevel gear pinions with the square recesses for the key.
The mechanism of the self actuation is that the scroll (at least on a bigger chuck) has a lot of rotational inertia if you're doing say 250 rpm in one direction. It wants to continue doing so even when the lathe suddenly switches to 250rpm in the opposite direction. Similar to the situation on a screwed spindle nose, where the chuck will happily unscrew when you go suddenly from forwards to reverse.

In the case of the scroll, it's switching from reverse to forwards where the problem occurs.
In my case, I was commissioning, with nothing clamped in the chuck, and trying to see how repeatable the reversing position would be (about 0.5mm before any attempts to refine the mickey-mouse lashup). The only symptom was a funny noise which sounded as though it came from the front spindle bearing. Picture yourself leaning down, (putting your head inadvertantly in the line of fire) to try and pinpoint the noise, as you flick the fwd-reverse switch with your thumb....

The jaws may open a considerable distance on each occasion, about 5mm in my case, and spinning at this speed they're essentially invisible. When I stopped the trial, they were almost fully out. This was a heavy industrial chuck and each jaw weighs about as much as a 1/2" Jacobs drill chuck.

Apart from the commissioning case or, say, threading between centres using the chuck only as a catchplate, when the jaws are not clamping anything, it's possibly even worth considering this scenario when you decide how tightly to do up the jaws of a job you'll be threading with rapid reversals.
I'm thinking particularly of threading, say, thin walled tubing, where there's little resistance to allow building up a decent amount of clamping pressure, and it seems to me the jaws could very easily release the work.

If I do jobs like this I'll either dial in longer decel and accel parameters, or make a closefitting plug for the work. (Note to self, DO NOT FORGET!!!)

[John Stevenson]

But this is with nothing in the chuck.

I use my swing up tool all the while now and I do a lot of screwcutting. Because the TOS is a dream to use with this tool I basically screwcut everything and finish off with a die if I have one or use the Coventry die inserts.

Last week for example I did 24 special M18 x 1.5 pitch bolts 60 mm long.

At no time have I had the chuck jaws come loose because of the quick reversal.

John S

[troup]

I'm relieved to hear that, John

Just to clarify, though: that contingency (inertial loosening when a lightly gripped part is reversed) was not the main thrust of my warning, nor was normal screwcutting.

What I wanted to alert people to primarily was the situation which might arise during COMMISSIONING or troubleshooting of any instant reverse facility: lots of reversals, dry running (so pushing the envelope speed wise) with nothing gripped in the chuck.

[Artie]

I hear whAT YOU ARE SAYING BUT AT THE SPINDLE SPEEDS AT WHICH SINGLE PPOINTING IS CARRIED OUT, THIS PROBLEM IS PRETTY UNLIKELY...oops sorry damned caps lock.....

Btw, thanks to Bogs, this item is HIGH on my list of tools I need to make ....

Cheers Rob T

[troup]

I hear whAT YOU ARE SAYING BUT AT THE SPINDLE SPEEDS AT WHICH SINGLE PPOINTING IS CARRIED OUT, THIS PROBLEM IS PRETTY UNLIKELY...oops sorry damned caps lock.....

It happened at only 250rpm or thereabouts on my lathe, which is well within the single pointing speed range for a fine thread, even on a totally manual lathe without any fancy bits and pieces. And it happened emphatically. not tentatively, although I reiterate that the chuck was empty.

I'm puzzled you would say that in any case; the only reason single pointing on manual lathes is done so slow is the human factor. From a process (and particularly finish) point of view the traditional speeds are woefully sub-optimal, especially for carbide.

To me the main attraction of this flip-up tooling idea is single pointing at speeds more like CNC than manual lathe practice. This in turn is the main reason CNC threads (particularly in gummy materials like mild steel or alu) are so much shinier in their finish, and when I saw that fantastic video of John Stevenson's I suddenly realised we mortals could have that too !
Check out the finish on John's photo, also (not the crummy material from the second, LH thread (?) test, but the first.

It's my hope, which I'm a few more hours of spare time from of testing,  that (providing reversing is accurate and automatic) it should be perfectly feasible to single point at speeds unthinkable on any manual lathe short of a Hardinge HLV with a highly sophisticated single tooth dog clutch. This is dedicated to providing an adjustable, reliable and automatic reversal cycle, specifically for singlepoint threading, even up to a shoulder. The manufacturers cheerfully suggest this facility should not be used at over 800rpm, or 1000rpm, I forget which...

A new Hardinge is about USD50,000, or 15,000 for a Taiwanese copy.

Compare this with:
Flip up toolholder: a few hours or days of work, depending on sophistication
Auto reverse sensing/switching and trip dogs: if you already have a VFD: maybe the same
In my case, I need to make a 'Dead man's pedal' for control and safety reasons (the inverse of a foot brake), and that's just about done.

I'd like to say a huge thank you  to the people who blazed this trail; to the guy from another forum (Mike Cox?) who revived (or independently reinvented) the idea, to the guy who brought it here, to the intrepid early adopters who so generously and inspiringly and thoroughly documented their investigations and implementations, including Darren who brought the good news from Ghent to Aix (ie posted on the PM forum, bringing it to a new audience again, myself included.)

I'd even like to thank the muppet who took umbrage at a perfectly reasonable response to his plea for drawings -- for having the decency (or truculence, or whatever) to leave the field before his hissy fit could give rise to any temporary tensions in the exemplary public-spiritedness of this forum.

[Bogstandard]

I have now finished reading the rest of this topic, and it seems to have generated a fairly large following and comments on other sites as well.

But I have noticed there are people who think nothing of changing the basic design and calling it OK to work with, then calling it their own 'new' simplified design.

I am not boasting, but I have had a very deep grounding in basic engineering design, which it seems a lot of people haven't, and in the unshown background, while developing this tool, lots of calculations were used to make sure the original design I did turned into a simple build exercise, where almost anyone with a bit of machining knowledge could make one, and get a tool that would work, and last almost indefinitely.

What has been done by other people, is basically doing away with the little block under the nose of the tool, the one that stops the tip of the tool swinging side to side, and are relying on a large washer around the rear pivot point instead.

WRONG.

Little would you believe it, that little block is one of the most important bits of the whole setup.

Without going into deep calculations about moments and stresses, and to explain it in easily understandable terms.

The block is there to take all the load of the side cutting action, and not allowing those loads to reach the pivot bolt. By doing away with it, that side load is instantly and drastically increased by the moment of the length of the swing arm and cutting tool, and is very likely going to cause the pivot bolt to break at the shoulder where the thread screws into the main block. Maybe, with dire results.

The things I show usually do take a lot more thinking about than you ever see, plus also I do try to simplify things so everyone can understand it.

So please, if you are going to change the design, look to the possible consequences that might happen before doing so.
 
I don't give a rat's arse about someone taking a design of mine, or anyone elses, but what I do object to, is people taking a proven and safe design, and modifying it to where someone just might get injured.


Bogs

[Boucher]

I don't give a rat's arse about someone taking a design of mine, or anyone elses, but what I do object to, is people taking a proven and safe design, and modifying it to where someone just might get injured.



--------------------------------------------------------------------------------

If you don't try it, you will never know if you can do it.

Somehow these two statements seem to be in serious conflict. I have no personal intrest in turning left hand threads and I doubt that the key is needed for right hand threads. As stated, "If you don't try it, you will never know if you can do it.

For a really simple swinging tool a dedicated tool post rather than the quick change holder appears to hold the advantage in simplicity and rigidity.

The description and detail of the cutting the quick change holder is very well done and should be preserved as a separate stickey for others to copy. John Stevensons inverted design and the way he makes the tool blocks in long strips makes one think about doing that for these tool holders as well.

This swinging thread tool is one of the best work saving shortcuts that has come down the road in a long time. If your machine has the features to use it you should try it.

 

[75Plus]

But I have noticed there are people who think nothing of changing the basic design and calling it OK to work with, then calling it their own 'new' simplified design.

Bogs

In all honesty John, I believe you took Mike Cox's design and made your "New and Improved " version to satisfy YOUR tastes. Not everyone feels the need for a "Rolls Royce" model so they build themselves a "Ford" which serves their need. It should be their choice and, if they choose to post their results, that should be OK also.

Joe

[Bogstandard]

Joe,

As I stated, they can do whatever they like with the design. Plus if you read this post thru, you will see where I posted a few pics about one that could easily be made, basically from bits and pieces in the average shop.

My gripe is where someone just comes up with an idea, not necessarily based on my design, and that design is basically flawed and so could become the cause of an accident.

When you post on a public site such as this, you will come under the scrutiny of everyone, so you must expect the criticism as well as praise.

If you do show what you have made, you had better make sure it is basically bombproof regards to safety. Because if someone should take on your idea, and make a copy of your flawed design, then you must be willing to take the responsibility if something does go wrong. Because if it does fail, and something nasty does happen, then where will the finger point?

Some people have no idea or common sense when it comes to safety in design, if it works, they are happy, with no thought of what might happen in the future when it fails. It is up to people who do post ideas on here to make sure no one can come to any harm if they follow your actions.

BTW, I used to build custom Rolls Royces, and I would have a Ford any day, well not really a Ford, almost anything else, but you get the point.


Bogs

[dsquire]

Hi All

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

Cheers 

Don

code
16982

[snoopdog]

I never did understand it for threading, is you want to slam the lathe in reverse why can you back off the cross slide too? I can thread normal at a fast rate.

Its kind of pointless in my eyes, I see nothing to be gained but some tool flopping in the wind. Bye bye rigidity. it might work for a watch maker but I dont do tiny parts, no way would it be of help on the big stuff I do.

[No1_sonuk]

I never did understand it for threading, is you want to slam the lathe in reverse why can you back off the cross slide too? I can thread normal at a fast rate.

Its kind of pointless in my eyes, I see nothing to be gained but some tool flopping in the wind. Bye bye rigidity. it might work for a watch maker but I dont do tiny parts, no way would it be of help on the big stuff I do.

Did you read the thread, including watching Bogs' videos?  In one he makes a quite hefty thread.
"Slam the lathe in reverse" isn't the way to do it either.  Stop, then reverse is.

[John Stevenson]

no way would it be of help on the big stuff I do.

I only do big stuff and it works for me, in fact I no longer thread any other way.

John S.

[Ned Ludd]

Please define "big stuff".

It may only be small in your eyes but today I was cutting several M12 by 1.5 threads in mild steel at
about 200 RPM in about a dozen or so passes. Yes, I know I could have turned the speed up but my
 reactions ain't what they used to be.    I could have taken less passes, by increasing the first
few passes, but I wasn't in any hurry. If it can work on that it will work on anything!
As an old saying goes "don't knock it, till you try it", they really are a very useful tool and if built to a reasonable standard are quite rigid.
Ned

[No1_sonuk]

I've done up to M10 x 1.5 - not needed to  go higher yet.

[DaveH]

Hi,

Now lets be nice

 

My problem is I don't have a brake on my lathe

So stopping in the same place is a little hit and miss.

Any thoughts

 

DaveH

[John Stevenson]

Biggest so far this week is 4" gas thread, that's 4.450" OD x 11 tpi

Smallest was M16 x 1.5

John S.

[AdeV]

My problem is I don't have a brake on my lathe

So stopping in the same place is a little hit and miss.

I have the same problem - although the lathe does have a brake, it barely works, so - like you - stopping in the same place required a degree of co-ordination and reaction times that I simply don't posess. Not to mention the fact that all the bits of my lathe have so much inertia, that it's probably quicker for me to cut threads in the "traditional" way.

If I ever get a lathe like John Bogs's (which stops stone dead the instant you hit the footbrake), then for sure I will build one of these threading tools.

[DaveH]

Ade,

Thanks for the reply.

Even the normal way is a bit tricky if I only have a mm or two to play with.

Strange you should mention John's lathe, mine is the same, only a much earlier model 1990 ish.

No brake though. I can and do cut threads just a bit slow.

I was just wonder how others get on without a brake.

Also does anyone use a "swing up" or simular tool without a brake.


DaveH

[wheeltapper]

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.

when I tried this tool out I cut a 1.5 thread on a lump of 1" mystery steel and using the forward and reverse buttons it made a reasonable job at 200 rpm and my reactions aren't as sharp as they were. I say reasonable because it was a grunchy bit of metal and I didn't use any lube.

I couldn't see any deflection or wobble either.
I like it.

Roy

[AdeV]

100 rpm.

   

I thread at either 35rpm or 59rpm, and I reckon the latter one is a bit swift!

I must admit, I don't cut myself a relief at the end of the thread; I just watch it & wind the cross slide out at the end of the last groove, simultaneously disengaging the drive. It usually works out OK...

[DaveH]

Roy,

There is not a chance I could accurately stop my lathe within 1 mm. I have even tried to (measure) how far it will run after the stop switch at different speeds. Even thats not constant (depends on the depth of cut / type of metal).

Cutting a 1/2" thread up to a shoulder (1mm) can be a bit tricky.

Really not good for "m'nerves"

I can do it but what a pain.

A brake and this type of holder seems a good way to go.

Any more thoughts.

DaveH

[DaveH]

Ade.

I have 60   90   200rpm

If it is a bit tricky I use 90 rpm otherwise 200rpm.  The 60 means I have to change pullies - danm I'm lazy

And if it is really really tricky I turn the chuck by hand - that's slow

and it makes my arm ache

DaveH