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View Full Version : Swing threading - The Final Cut



John Stevenson
12-30-2009, 03:17 PM
Camera

Lights

Action.

The first post on this tool was here http://bbs.homeshopmachinist.net/showthread.php?t=38585but i want to start a new one as that one ran on a bit.

I do a lot of my threading using inserts from Coventry Die holders, these come in numbered sets of four and if any are chipped or missing the set is scrap but you only need one for threading and you only need the pitch you are doing, diameter doesn't matter.

The result is you can get these surplus for pennies, so a new tool holder was called for.

http://www.stevenson-engineers.co.uk/files/swingfinal1.jpg

easy to make as i cheated and put the old tool in the mill vise, located on existing hole and slot in turn then changed to holders over.

http://www.stevenson-engineers.co.uk/files/swingfinal2.jpg

Shot from underneath showing the slot and an insert fitted.

The old tests were done in brass for two reasons [1] easier and more forgiving but [2] if it had wanted to dig in it would have done so in the softer brass than say steel.

This time I decided to find the horriblist steel I could, a while ago I bought some 16mm rolled black steel for some safety bars, this stuff is horrible and is very close to rebar.

http://www.stevenson-engineers.co.uk/files/swingfinal3.jpg

Anyone who has used this stiff knows how horrible it is to machine.

Job setup and test begun. I ran at 80 rpm to take a video but I could have gone faster because the quality wasn't great and it took 7 minutes to do the thread when it should have taken about 3, point was though that it shows it swinging clear to try the thread whilst the cut is still on and when it was done, that was it, no chasers, dies or thread files.

Video here :-
http://www.youtube.com/watch?v=6TR0ssQrmI8

Final shot of the finished thread.

http://www.stevenson-engineers.co.uk/files/swingfinal4.jpg

This is the worst angle and a couple of flanks have torn but believe me it's 100% better than anything that could have come off a die using this sht.

Well that's me done then as this tool will do all my external threads.
for the record 80 rpm, 16mm dia x 2mm pitch [ about 12 /13 tpi ] on rolled black bar.

.

Alistair Hosie
12-30-2009, 03:37 PM
Wow well done young sir I applaud your intellect as always merry Christmas.Alistair

shadoof
12-30-2009, 03:44 PM
John,

I made up some holders for the Coventry dies, didn't work too good so went back to single pointing,

Do you alter the die in any way? do you feed these in until they don't take any more off ?

Thanks

Lee.

Robo
12-30-2009, 04:04 PM
Looks great but for some reason I can't watch your video. Trying to figure that out.

DFMiller
12-30-2009, 04:50 PM
John,
That looks great. I was hoping for audio also. :-)
Looks like you have demonstrated several great ways of making threads.
I guess I had better get off my duff and make a holder for my dickson quick change!

John Stevenson
12-30-2009, 05:29 PM
Dave, sorry it's a nice little Panasonic digtal that takes decent stills but it's limited on video and fully enough it doesn't do audio which I find unusual.

As I don't do many it isn't a problem but something to look at when it comes up for replacement.

.

Doggie
12-30-2009, 10:39 PM
Very well done Sir John. Honestly I have wondered if and had thought about using a thread chaser die to cut threads. However my method was to use a chaser and thread the usual, ordinary way. Like you would if you single-point with a threading tool. But to me, your flip-up threader tool / machine reverseal is the masterpiece of your operation. With that setup you would never have to disengage the half-nuts.......COOL :cool:

I am now going out to my shop and start the building of one of those "flip up style" tool holders. And seriously John, that may be a patent-able design you have. The flip up tool holder that is. You may want to look into that idea.

I suppose you do all the cutting with the first few threads on the chaser,HUH? I wonder if you could grind off the back half of the thread chaser in order to allow for clearance for a lathe center. Like when you are doing a long piece and need to have a center on the workpiece?

Like I said, that is a masterpiece....Your friend, Doggie :cool:

motorworks
12-30-2009, 10:50 PM
Nice John
I picked up an 8 TPI and an 11 1/2 TPI at a local industrial shop
new, but one in the set was missing :)
On my to do list as I have to thread lots of pipe.
Have you tried threading the pipe from China
what a fu3king mess :(
No wonder the women have sideways vaginas :)

J Tiers
12-31-2009, 09:01 AM
Don't those have back relief for the size they were intended to do? Does that cause any trouble? Might not as the size is likely to be related to the pitch, but if you went UP on the diameter they might start to drag. or that might not happen for any practical sizes.




And seriously John, that may be a patent-able design you have. The flip up tool holder that is. You may want to look into that idea.



It WAS... now it's free for all.

John Stevenson
12-31-2009, 09:18 AM
And seriously John, that may be a patent-able design you have. The flip up tool holder that is. You may want to look into that idea.

Your friend, Doggie :cool:

No way, for a start you need to get world wide patents to make it worth while, a British patent won't do anything in the US plus even if I had US patents the way the US Patent system works they would still grant another and leave me to fight it out.

World wide sales will be capped at $x.xx dollars which will be less than applying for patents and defending them.

.

JoeFin
12-31-2009, 09:52 AM
I was never able to get those kind of results with them.

I still have 5 or 6 of the dies setting around here. Most of them the grade for SS pipe, in 2 different thread pitches.

Had too much deflection of the work piece, and then the die would try to go under the work piece. Then I realized the ones I had were made to go in machines that ran at 12 or 36 RPM with extremely high torque.

But I never tried making a dedicated holder as you have done

Boucher
12-31-2009, 10:01 AM
Several years ago I met a guy that was a EE and a Lawyer. He was doing research for a Houston law firm that specilazed in Patten Law. His take on things was that if you got a Patten it was worthless unless you had $10 Million to defend it.

Boucher
12-31-2009, 10:22 AM
John:
This thread is obviously very valuable to this group. You have credited others with the original idea but your rendition, implemention, and post is sincerely appreciated.

I have been sort of handicapped by a problem disengaging the half nuts under cutting load. This makes threading up to a sholder a pucker factor 10 operation. This lathe has the brake that allows me to simply reverse direction.

I consider this the best post of the year.

THANK YOU!

Black_Moons
12-31-2009, 02:26 PM
Boucher: By time you are in the landing grove, should'nt there be no cutting load? Infact if your lathe refuses to disengage untill cutting load ceases, Could'nt you just lean on your half nut lever lightly and it will pop out once it hits the grove?

My lathe has a similar problem I noticed with the carriage feed if im silly and leave my hand on the carriage hand feed wheel and apply to much resistance. Scared the hell outta me once when i could'nt figure out why it would'nt disengage as that shoulder was getting closer and closer!

Alternatively you could try REALLY hard to fix it.. might be worth it. Especialy if anyone else ever uses your lathe someday (IE a friend in your shop, Not just the next guy you sell it too) Could be as simple as cleaning some slideing parts.


JoeFin: If you mean those pipe dies that look like a 10 point threading tools, While I havent used them iv seen in the catalogs, I think that those are designed to be used in 'die heads' that hold like 4 of them, I presume all offset slightly, or you buy 'sets' of dies.. anyway, its basicly a box tool that prevents the pipe from escapeing :P As you mention the torque required is INSANE
Id expect to need like a good 6 jaw chuck or a 3 jaw with custom softjaws to just hold the work, and yea, 10~30rpm is probley just about right for the machines that do it.. Iv seen electric pipe tappers that run about that speed and are 2'+ long. Might not be something you'd want to try in your lathe considering the kinda torque it would put on your tailstock and gearbox, Even if 2hp at 60rpms would likey do it. (Assumeing a 12x36)
Maybe 3/8" NPT and smaller could be done but I would'nt wanna push it.
(Pipe threading can also be done on the lathe by turning beween centers and by use of a taper attachment)

form_change
12-31-2009, 03:11 PM
Nice idea - I'll have to try that.
I've also been told that patents aren't worth anything if you can't defend them. Worse, there are countries in the world where they are ignored anyway if they can (China is one that has issues like this).
A better thing to do may be talk to someone like Hemmingway or Warco and see if they are interested in making/ distributing them - you might get some cash out of it.

Michael

dieselphil
08-23-2016, 09:01 AM
Hello Sir, new member here - I stumbled across your post and decided I should join up just so I could reply. I know it was a long time ago now that you wrote it, but thought I'd add my congrats on an excellent bit of work. I'm relatively new to owning my own machines, having worked in engineering all my working life and approaching retirement age now.... I had come up with a similar scheme, but was planning to have my tool swing down and out of the cut - probably released by electrical means (limit switch and solenoid). Have you thought about/tried this approach? that way one does not need the full undercut on the part nor have to have a lathe with "instant" brake and reverse capability. I also wasn't sure about the key and slot - why not just use the side faces of the tool as the guide surfaces? what does the keyway buy you? Once again, gongrats on a good job, Phil