Removing snapped stud from small split dies

[Cheshire Steve]

I now have two split BA dies in which I have managed to snap off short stubs of thread, which do not protrude, one brass another steel. These are both good quality dies so I want to extract the stubs. One is 6BA, another 8BA. I was wondering if I can sneak a slitting saw in through the split in the split-die and remove enough metal to collapse the core a little. I wonder if anyone else has any tips.

As regards not doing it again - I am thinking of making a small hand threading jig, that will allow me to use the hold-anything capabilty of my lathes ER25 chuck, but will allow me to turn the die/tap by hand in a bored holder held on the top slide. The same jig should facilitate tapping too, as it will give me the accurate alignment I want plus exposing the squared end of the tap.

 

[metaltrades01]

Maybe grind the side off of a hacksaw blade, until it'll fit through the split in the die...hacksaw blades are cheaper than slitting saws
As for your second question, I have a heavy engineering background and wouldn't have a clue, I'll leave it up to the experienced fella's here.

 

[lensman57]

Hi,
If you have drill press or a even bench mounted mini drill , center the die under thr drill and just drill the bits off using small drills, 1/16" would do for 8 BA.

Regards,

A.G

 

[gus]

Tail stock die holder will be very handy and eliminate broken bolts or badly formed thread.
I made my own thread dies holders from M3----------M10. See attached.
The ratchet wrench is reversible.
The tapping and thread die tools good for shallow holes.
Threading on the lathe is now so quick and easy. Commercial tapping oil
will make threading less tedious and form good threads.

Tapping and die threading on the lathe w/o these tools is pain in the side.

 

[Cheshire Steve]

I already have a tailstock die holder - its fine for larger work >3mm - but for smaller work that is how I snapped the studs. My lathe is an old 3.5" precision lathe, even gently turning by hand the inertial mass in my headstock and pulleys means it is very hard to judge the cutting load on something as small as 8BA, which is especially important when trying to thread up to a shoulder. (Would have been better if I had disengaged the belt drive - duh !).

I was thinking that if I fix the headstock and make a hand turning tool instead of using the tailstock die holder then I might be able to feel the threading process for very small items.

I have been wondering about getting an old watchmakers lathe setup for this small stuff. That might be an option.

 

[GailInNM]

To remove small broken thread sections from a die I use a jeweler's saw. The blades fit through a relief hole in the die and with the die clamped in a vice it is fairly easy to saw lengthwise to the center of the thread. Then saw out to another relief hole or remove the saw and repeat from another relief hole. I have done this a number of times with 0-80 threads (0.060 diameter) out of hard brass that really liked to snap. I had to make several thousand studs and probably broke 10 or so.
Gail in NM

 

[rhitee93]

I have used a simple drill before. If you drill in the broken stud from the finished end of the die, the drill will tend to back the partially threaded piece out the start end of the die.

 

[Cheshire Steve]

Thanks for the jewelers saw idea, sounds like something useful to add to my tool collection, and I can see that three relief cuts would be better than one using the split in the die.

As for drilling the centre, I am not too sure about being able to pilot a really small drill down the centre of an 8BA stud without it touching one of the teeth of the die. I think I'll try the saw first.

 

[rhitee93]

As for drilling the centre, I am not too sure about being able to pilot a really small drill down the centre of an 8BA stud without it touching one of the teeth of the die. I think I'll try the saw first.

I can understand that, but it more doable than you might think. I just had to do it with a 3-48 screw which is about the same size. Don't be too put off by this approach if the saw doesn't work out.

Good Luck!

 

[Cheshire Steve]

Thanks Brian, I have managed to get a slim saw in and then fold the studs in on themselves and extract. Hopefully I managed to miss all the vital cutting edges on the dies, but as I only came in on one side, then at worst I have only touched one of three sets of cutting edges. I think half of the problem is tired eyes ! Get a big enough magnifying glass and things don't look so daunting !

I have also sorted out a chunk of cast iron to make up a hand tapping and die holder guide to go in my top slide. The intention being to turn the tap or die by hand in a bushed bearing so that I can feel it working. Its just for the small stuff.

 

[rhitee93]

I'm glad you got it Steve The die holder sounds like a good idea. These tiny threads are hard to feel if you have to turn a lot of machinery mass.

Whatcha' building?

 

[Richard Carlstedt]

After doing this several times years ago, I built a home made EDM machine http://tech.groups.yahoo.com/group/EDMHomeBuilders

You can drill it out, but don't try it freehand--do this
Take a piece of brass stock , say 1.5 inches (40 mm ) in diameter
and chuck it up and face it . Now carefully center drill it ( small ! ) and then drill a hole that is 75 % of the root diameter or 75 % of tap drill size.
Go as deep as you can , doing peck cycles. if you reach .375 ( 10 mm ) --great ! Now Counterbore the face to match the diameter of your die...closely ! go as deep as needed to ensure locating on the die . About .125" ( 3 mm ) should work
You may want to deepen the hole a bit now , but that is up to you.
Now part of the "Jig" about .375 thick so you have about .25 (6mm ) of hole for a guide
I like about .25 ( IF Possible) for guiding . The actual amount should be 1/2 of the twist drill flite pitch to give 360 degree support !
Now before you drill, you need TWO drills to match the hole.
Take one drill and present it to your grinder straight on !
You want a flat bottom drill of sorts !

Now set the jig on the die and use the flat drill first.
Gently !!!.... engage the broken stud. You only want to remove the angled break. The drill will flatten the stud end, but will not drill it effectively. Thats when you then use a sharp drill to drill out the broken piece. just start slowly so it centers itself .
After drilling through, you will easily crush what is left of the stud
If both dies are the same OD, then use the jig on both, and then opren up the larger one.
Rich

 

[Richard Carlstedt]

Oh, the reason for brass or bronze, is they are bearing materials.
That means lower friction in dragging, and resistance to cutting.
That keeps the drill in position longer and will not dull it .
Do not use Aluminum !
Rich

 

[Cheshire Steve]

Thanks Rich for the detailed description, good idea using a guide and a squared off drill to get a surface to drill into. That was always going to be an issue with drilling the centre of a broken stud. As for EDM, I have heard of that being used to loosen a broken off tap in a complex expensive casting (like a large cylinder block), but it is a destructive process for the tap, and I think would be destructive for a die containing a broken off stud too.

 

[Richard Carlstedt]

Steve
I was able to burn out a broken stud in a 0-80 Die ( .060" or 1.5 mm) with my EDM, using a .032 brass wire
It did not hurt the die. Just like drilling the stud, I was able to crush the stud after

For one model, I had to make almost 200 double ended 0-80 studs.

Rich

 

[Cheshire Steve]

I suppose if you are using it as a superfine drill then EDM won't touch the die provided your alignment is perfect, and it will work regardless of the shape of the broken off end. I don't think I would go to the trouble of building an EDM machine just for that purpose though - hopefully I won't be making the same mistakes again.

Making studs is my most common threading operation. I have acquired several old, part finished, or 'rescue' models (give a 'dog' a home - something I often regret), and while restoring them I usually end up replacing screws or bolts which have been used in place of studs on things like valve chest and cylinder covers. Lately I have been diverted by acquiring a c1850 clock movement which I was thinking of mounting in a skeleton clock. Another little project for the winter evenings, and reading about escapements is a diversion away from engines. I have an unusual watch lathe to restore too, which I should probably do first and then learn about while using on the clock movement.

http://www.lathes.co.uk/unknown66/

I currently have in mind to mount it on one of those old Singer sewing machine treadle tables, turned into a little workbench for small items. It count be entertaining to power it from the treadle. Threading small stuff can then hopefully be done on an appropriately delicate lathe.

 

[Richard Carlstedt]

Steve
Yes, I keep the location of the EDM electrode pretty tight
Thanks for your comments !

Here is a photo of some of my studs
The tin is 3 inches in diameter
Rich

 

[gus]

Two hundred pcs of these tiny studs is no joke.

Just a suggestiion. Way back in 1961 while I was doing a two year trade school I found myself forced volunteer to set up a Harrison Turret Lathe for some foreign big guns from Cambodia to view.In our part of the world then,Turret Lathe was high tech.Part of the deal was to put a quick release die head.
In no time I turned out 100 1/2 BSW Hex Bolts during trial runs.

Maybe just for fun of it,one of us could design/build/operate this die head.Or perhaps a thread rolling machine.