Tiny little pins...how would YOU make them?

Hi All:
I have another tiny turning project.
This one is tricky because there's so little to hang onto.
Here's a picture:

The thread is M1.6 x 0.35 and there is a hex in the end (0.028" across the flats 0.75 mm deep)

So I pondered two options:
The first was to turn the pin and single point the thread, then cut off and flip the part and sinker EDM the hex in.
Burning a little hex like this is a bit of a pain, but it can be done if you are willing to spend enough time on it, making a trode, setting it up and letting it noodle away.

The other was to buy 5 mm long M1.6 setscrews and turn down the non-hexed end to get my pin.

I chose the latter, and I eventually got it to work, but it's a bit of a fiddle.
The length of the threaded bit is 1.2 mm, so hanging onto it without wrecking it was tricky and I couldn't turn it very aggressively so a single pin takes almost an hour to make.
(0.001" DOC and many many passes)
I ended up having to make a hardened collet I could squeeze in the Sherline 4 jaw chuck...the brass one I made first didn't survive a single pin before it let go and took out a tool tip and a pair of underwear.
The successful collet was A-2 at 63 RC and it's holding up well.

These were turned on a manual lathe (One of those who's name we dare not speak here)

If you had the gear to do it either of those ways, which would you pick?
Would you maybe find a third way?
Would you have the balls to try to wobble broach the hex? (material can be 17-4 PH or 4140 HTSR)
The hex is just for an Allen key
There's a total of 8 pins to make in two different lengths.
You have to get the pin diameter (1mm ) within a few tenths...it needs to run nicely in a 1 mm reamed hole in 660 bronze.
I turned them to 0.0398" diameter and then polished them in with a mylar abrasive strip ( for finishing dental white fillings) under the scope.

Cheers

Marcus
www.implant-mechanix.com
www.vancouverwireedm.com

Sub it out to you?

Rob F. said:

Sub it out to you?

Click to expand...

You stole my answer

implmex said:

Would you have the balls to try to wobble broach the hex?

Click to expand...

No...

Marcus, I think you need a Levin lathe. I am very happy to have and use Levin lathes and even happier that I do not need to do those insanity-inducing jobs with them. But the lathe would do it. Could even use the tailstock to support the screw and take heavier cuts, then cut off the support hole, if it is not allowed.

Larry

Swiss part.

Face, turn pin diameter and major of thread, part off / pick up in sub; face/chamfer, spot, drill/bore, rotary broach hex, single point thread.

I would have

zSwiss said:

Swiss part.

Face, turn pin diameter and major of thread, part off / pick up in sub; face/chamfer, spot, drill/bore, rotary broach hex, single point thread.

Click to expand...

What’s your price for 8 parts? Most Swiss guys give me weird looks when I ask for 8 parts. It’s just not in their mindset even when I am willing to pay.

Now Marcus is pretty valuable, so Swiss shop has a chance on these.

What if you threaded the collet, then clamped it down on the stub thread? Seems like that would at least triple your grip.

newtonsapple said:

I would have

What’s your price for 8 parts? Most Swiss guys give me weird looks when I ask for 8 parts. It’s just not in their mindset even when I am willing to pay.

Now Marcus is pretty valuable, so Swiss shop has a chance on these.

Click to expand...

Would be the smallest run that I have done, but it is doable. Repeat customer? Friend of a friend? Off the street? Possible repeat job? Stock, and tooling already on hand? Pin a normal size or do I already have a collet to match?

Looks like a 1-2 hour job, at most.

Next time you need small-run swiss stuff, keep me in mind.

Thread the set screw into a hole in the center of say a 1/2" rod, with a set screw in the hole for it to bottom out on.
Hold the rod in a 4 jaw chuck so you can center the hole.
Grind the threads down to the pin diameter with a tool post grinder.

Hi All:
Gordon Heaton described exactly what I ended up doing but failed to mention...I threaded the blank for the collet and then hardened it and split it on the wire EDM.
I relieved the back end of the collet body a few thou so the tip of the collet would collapse when I squeezed it with the 4 jaw.
If I'd had more to make I would have built a better collet something like a WW watchmaker's collet to eliminate all the screwing around centering the parts.

So yeah Gordon, you are exactly right in your description of your method and it works well.
The only remaining problem was that I had so little to hang onto, even with that tactic that I was afraid to push it after the screwup with the original brass collet, so I nibbled it in baby cuts.
I had to turn a lot off the length of the setscrews I started with in order to make the shorter ones and getting the diameters right meant that I had to run a few spring passes to get them parallel enough to be able to polish them in the rest of the way.
There were a lot of passes and a lot of polishing to get them accurate enough.
I aimed for 2 tenths under nominal, and that turned out to be just about right.

L Vanice you are correct in your assessment that the Sherline lathe is marginal to do this sort of work, and a Levin would be very nice to have.
But I danced with the girl that brung me and it ended up working OK, so I have no legitimate complaints.

Zswiss, normally I get to plan the jobs better and when it's a Swiss part I have no hesitation farming it out...but for eight parts in two sizes I just didn't think it was worth it.
Besides, the job was sprung on me on Friday evening and needs to be in the customer's hands tomorrow morning.
No time to even get properly organized on this job.
Good thing I happened to have enough M1.6 x 0.35 setscrews left over from another job.
BTW there are no drawings...only models that need liberal interpretation by the prototyper, so they're hard to farm out.

But the customer pretty much pays what I demand...these kinds of jobs have been good for me because nobody else wants to do them especially on short notice.

Cheers

Marcus
www.implant-mechanix.com
www.vancouverwireedm.com

I have never done any that small but have set cone point set screws out end in a female tail stock center and ran them on a grinder by dressing the wheel before the finish tickle to size.. and used that dressing to rough grind the next one to +.001 / +.002

Using a B&S13 grinder

Gordons idea but in a CNC lathe, longer screw, tailstock to support, then wire EDM the false tail. If the threaded collet held well enough, you wouldn't need the false tail. Grinding would be my second choice if turning it was not successful. Never tried rotary broaching that small, but if Slater makes it, I would trust that it would work. We have used their broaches for lots of projects. This is the big brother to what you have. 1op complete with sub spindle. Still pretty small.

They were M2, but I've had to do something a lot like this (though not to Marcus's quality level), and didn't have an emergency collet handy.
Bored a rod to the thread, split it, tried to clamp that in a round collet, and took light cuts to keep it from slipping. Didn't work great. Redid the rod so the screw goes in head first up to a shoulder with a hole just big enough for an allen key, slipped an allen key in from the back to tighten it up to the shoulder. Cuts weren't quite as small on an M2, but I would have been a lot happier if I'd had the ability to rotary grind under coolant.

Pretty sure that I may have used a 60gt white wheel grinding the like..but larger parts. plunge cross-feed straight in to rough, dress and take .oo1 -.oo2 to size.
then use that wheel to rough the next part.

Hi again All:
So last night I got "The Call"
"We need another pin."
This one is quite different...still M1.6 on the threaded end but a lot longer...10 mm overall length and the head is mercifully 2.7 mm long.
So here it is:

I did this one by cutting a setscrew to length and then boring a pocket into it 0.035" diameter and 0.0715" deep with a 1/32 endmill as a boring bar.
I turned down the end of a 1 mm dowel pin with a 0.0005" press fit and pressed and Loctited the little sucker in there.
I then turned the end of the pin to length with a WW collet, pushing the headed pin in from the back with a little bar tapped M1.6 at one end so I could hold the pin.
A lot of screwing about, but it's DONE and it looks like it is supposed to.
This one is going to be pricey...I screwed around for a whole morning to make it.

I'm guessing (hoping, wishing, praying??) they'll bust the Allen key before they budge that little threaded collar.
So I'm going to call it good!

Cheers

Marcus
www.implant-mechanix.com
www.vancouverwireedm.com

I've made a lot of m1.4 x 0.3 pins with a turned down 0.312" dia (+/- .0004) x 0.040 long beveled pin, thread length about 1.5 mm (so overall length about 2.5 mm).

First, I threaded those on the Hardinge lathe using stainless steel wire, and a collet (a real PITA) had to use a tiny stickout from the collet, and an extremely sharp polished hss threading too. On those:
1)chuck wire in collet with about 2.5mm stickout
2)thread 2+ mm (again, a PITA, several passes and tool must be razor sharp)
3)turn pin on end (several passes with sharp hss tool, check last pass with micrometers)
4)cut off threaded end to length using a Proxon tool mounted in a tool-holder with a wafering cutoff blade with the pin rotating in the lathe (I have an old emco lathe that I use for these tiny grinding and cutoff operations with abrasive/wafering blades. I still had to add a felt-lined "shroud" around the cutoff blade to keep from losing a good percentage of the parts during cutoff.
5)run the threads thru an m1.4 die, to remove pin/thread shoulder burr by holding the "pin" end in a pin-vise.

After I couldn't put up with the tedium of that, I started using m1.4 stainless screws:
a)cut the head off of m1.4 stainless 12mm long screws using the compound-mounted mounted wafering blade (gives you a ~12mm long piece of m1.4 threaded stock.
b)chuck in collet in Hardinge (I have hardened collet that matches the M1.4 stock diameter), with a tiny bit of stickout
c)turn the 0.031 pin down using very sharp hss tool, (3 passes)
d)flip threaded stock around and turn pin on other end of stock
3)cut off pin to length held rotating lathe with compound-mounted wafering blade (I have a small 3-jaw drill chuck with the jaws ground down, which is chucked in the emco 3-jaw to hold the pins. Length is adjusted using the compound-mounted abrasive cuttoff tool (still had to use the felt-enclosed shrouds to minimize part loss)).
4)the abrasive cutoff does't bung up the threads at all, they thread right in; if you need to thread in past the pin, the pin-turning does leave a tiny burr, so they have to be run thru a die to remove that tiny should/pin burr...

The critical things in that manual process were a precision lathe with a very good collet, and an extremely sharp HSS tool, and using the toolpost mounted abrasive wheel for any cutoff operations (and magnifying glasses)...
Thankfully, those are now being easily swiss-machined.
Cheers

implmex said:

Hi All:
I have another tiny turning project.
This one is tricky because there's so little to hang onto.
Here's a picture:
View attachment 384183
The thread is M1.6 x 0.35 and there is a hex in the end (0.028" across the flats 0.75 mm deep)

So I pondered two options:
The first was to turn the pin and single point the thread, then cut off and flip the part and sinker EDM the hex in.
Burning a little hex like this is a bit of a pain, but it can be done if you are willing to spend enough time on it, making a trode, setting it up and letting it noodle away.

The other was to buy 5 mm long M1.6 setscrews and turn down the non-hexed end to get my pin.

I chose the latter, and I eventually got it to work, but it's a bit of a fiddle.
The length of the threaded bit is 1.2 mm, so hanging onto it without wrecking it was tricky and I couldn't turn it very aggressively so a single pin takes almost an hour to make.
(0.001" DOC and many many passes)
I ended up having to make a hardened collet I could squeeze in the Sherline 4 jaw chuck...the brass one I made first didn't survive a single pin before it let go and took out a tool tip and a pair of underwear.
The successful collet was A-2 at 63 RC and it's holding up well.

These were turned on a manual lathe (One of those who's name we dare not speak here)

If you had the gear to do it either of those ways, which would you pick?
Would you maybe find a third way?
Would you have the balls to try to wobble broach the hex? (material can be 17-4 PH or 4140 HTSR)
The hex is just for an Allen key
There's a total of 8 pins to make in two different lengths.
You have to get the pin diameter (1mm ) within a few tenths...it needs to run nicely in a 1 mm reamed hole in 660 bronze.
I turned them to 0.0398" diameter and then polished them in with a mylar abrasive strip ( for finishing dental white fillings) under the scope.

Cheers

Marcus
www.implant-mechanix.com
www.vancouverwireedm.com

Click to expand...

As was mentioned earlier, a watchmaker's lathe such as a Levin would be perfect for this. I love the one I have, but they cost quite a bit for how small they are. Could you not purchase some extra long set screws, put the pin end in the chuck, then turn however much you need and part off?

I would use this: Right in the comfort of your office!



Might take a little longer though.

Funny you guy talking about levin lathes, I just came across this small pile of them being auctioned off in California. Don't know anything about these, in particular, or them, levin lathes in general, never having seen one in person.