A Problem with my Starrett mics.

[Catshooter]

I have had a problem with two different Starrett mics.

I purchased both off ebay. I like a clean tool, so I allways disassemble and clean thourghly. Then, when I go to re-asessemble as the mic face enters the lock ring I can feel a big jump in resistance. In fact, the friction thimble doesn't have enough friction to continue screwing it in. The lock still functions just like it did before I took it apart, it'll lock and un-lock just fine.

I tried adjusting the little ring at the end of the barrel that is designed to apply resistance or not, I even removed the adjustment ring, makes no difference.

What have I done wrong?


Cat

 

[hickstick_10]

theres crap in the thread, a very tiny amount.

If everythings took apart, (I dont usually condone this) but lightly puff some compressed air through the female threads. A little gun oil helps alot as well after you clean up.

Dont take apart micrometers unless necessary, you wouldn't take apart a dial indicator to clean it now would you?

You can totally clean the barrel and frame of a mike without dissasembly

 

[John Garner]

Catshooter --

I'll presume you're talking about Starrett's "heritage" knurled-ring lock that fits into a slot cut into the micrometer frame.

1. The only thing retaining the knurled ring is the micrometer spindle. Take the spindle out of the frame, and the knurled ring will almost certainly move laterally if it doesn't fall out. If you wiggle the ring around as you try to poke the end of the spindle back through it, you should be able to feel the hole line up with the spindle . . . unless the lock ring has been tightened without the spindle in place.

2. If the lock ring has been tightened without the spindle in place, simply loosening it will not open the hole enough for the spindle to enter freely. Slide the lock ring out of the frame, disasemble it, use a razor-knife blade to wedge the slots in the collet open a bit, and reassemble. (It's been several years since I've done this job, and I don't positively remember the details, but I do have a hazy memory of needing a wee drop of oil as stuckum to hold the slotted collet, rollers, and the knurled ring together while taking it off the bench and sliding it into the micrometer frame.)

John

 

[PeteM]

Just to add to John's comments - the ring may have been bent slightly closed. As John suggests, an X-acto knife etc. can open it up. Alternately, it may not be seated quite centrally (too deep or too shallow) in its guide.

Be sure not to lose the little roller the lock ring uses while disassembling and reassembling the ring. Easy to lose, hard to find.

You can check if the lock ring is actually the problem by assembling the mic without the lock. If it still binds, it's likely the thread take up adjustment is slightly buggered.

 

[dfw5914]

Like the others say, it's most likely the lock ring, if turned too far with the spindle removed it will deform (soft iron and very delicate when not supported by the spindle) and make for a very difficult to turn spindle when reassembled.

Slide the lock out of the frame and rework as required. (3/8ic insert for ref)

 

[SouthBendModel34]

More, please about cleaning w/o disassembly

HickStick_10,

"You can totally clean the barrel and frame of a mike without dissasembly "

Alright, I'll bite - how are you doing this? Do you literally mean total cleanliness, as in confidence that there's nothing lurking inside ?

Does your method work with J.T.Slocomb mics as well as Starrett and B&S ?
(There's another thread somewhere on PM about the ins and outs of dismantling a J.T.Slocomb. Slocomb put a severely-worded warning in their manual cautioning against disassembly. That was dealt with in the other thread.)

Just amazing how much one can learn on PM.

JRR

 

[hickstick_10]

HickStick_10,

"You can totally clean the barrel and frame of a mike without dissasembly "

Alright, I'll bite - how are you doing this? Do you literally mean total cleanliness, as in confidence that there's nothing lurking inside ?

Does your method work with J.T.Slocomb mics as well as Starrett and B&S ?
(There's another thread somewhere on PM about the ins and outs of dismantling a J.T.Slocomb. Slocomb put a severely-worded warning in their manual cautioning against disassembly. That was dealt with in the other thread.)

Just amazing how much one can learn on PM.

JRR

Badly worded I'l admit.

Mikes (starret, B & S, mitutoyo, no name chinese, moor and wright) are pretty much the same animals. I cant speak for slocomb as I've never seen one (arent they a brand thats no longer made?)

Its would be pretty clear to anyone who's actually used a micrometer if there is anything lurking inside(tight feeling, or it has a crunchy feel perhaps), I should have stated that if the thimble turns fine without a gritty feel to it, and it appears to me well taken care off and reasonably clean, then leave it alone if possible. Wipe off the barrel, and thimble, give everything a light coating of oil and put it back in the box. A mikes a pretty simple tool, and that barrel pretty much covers the thread against any but the most extreme ingress of grit and bad stuff. Il admit if it looks like its been swimming in a barrel of valve grinding compound, you better turn the spindlel out , and clean it more extensively.

Its the same when people completely dissasemble some guns because they think they need to do that to clean it properly, wrong. It usually causes more trouble then it cures.

Plus the OP didn't state (and I assumed, my bad) that the mike was turning stiffly BEFORE he dissasembled, hence it was ok, and probably (me assuming again) only needed a good wipe down.

And when you think about it, MOST measuring tools should not be dissasembled for clean them, as they are well protected to begin with. I'l say right now, do not disassemble dial or electronic vernier calipers, indicators, bore gauges, bore mikes and so forth and so on, unless absolutely necessary.

FWIW: Mitutoyo says not to dissasemble there line of rod inside micrometers as well.

Sorry If I wasn't clear.

edited to add: I just took apart my 6-7 #436 starret to see if i could hit the same problem, and the fellas are right, that little bugger of a ring can screw you up, that ring has a tiny key in it and a tiny key slot facing forward, so the ring must come straight forward, out comes the lock assembly, and open that little slotted ring a bit. Like the gentleman here said.

If you were able to start screwing it in i'd still stick with crap in the thread.

 

[Catshooter]

Very interesting and informative replies gentlemen, thank you.

I allways disasemble and clean tools (and guns ) when I aquire them. Some of them have been old, old enough that the oil inside has turned to varnish. Rarely does it give me trouble on re-asembly, but it does happen I'll admit.

It is amazing how much one can learn on the web and this forum is no exception.

Thanks again.


Cat

 

[locoguy]

Have you attempted to assemble it w/o the lock, simply to see if the ring is the problem?

 

[Catshooter]

Not yet. I deceided to soak it in solvent while I awaited the responses to this thread.


Cat

 

[Frodge]

Like the others say, it's most likely the lock ring, if turned too far with the spindle removed it will deform (soft iron and very delicate when not supported by the spindle) and make for a very difficult to turn spindle when reassembled.

Slide the lock out of the frame and rework as required. (3/8ic insert for ref)

How does this sort of lock ring work? Mine looks exactly like this. How can I make it tighten more.

 

[Thunderjet]

Just to chime in here.

I disassemble and clean ALL my mics regularly. Usually an acetone bath and a a trip thru the vaper degreaser is part of the party.
I have micrometers that are Lufkin, and were probably made in the 40s. Still in use today.

 

[sfriedberg]

How does this sort of lock ring work?

See that little circle inside the roughly-triangular cutout in the ring filler? That's a floating cam. When you turn the ring in the "lock" direction it drives the cam into the narrower portion of the cutout in the filler. See how there's a gap in the ring filler? When the cam gets wedged into the narrower portion of the cutout, between the filler and the ID of the ring, it will deflect that part of the ring filler, making it jam against the spindle (which passes through the center of the ring filler). See the little square sticking up that's part of the ring filler? That little bump engages with a little recess in the body of the micrometer and keeps the ring filler from rotating.
So when the ring filler is jammed against the spindle, and also prevented from rotating, it prevents the spindle from rotating (at least easily).

 

[Frodge]

See that little circle inside the roughly-triangular cutout in the ring filler? That's a floating cam. When you turn the ring in the "lock" direction it drives the cam into the narrower portion of the cutout in the filler. See how there's a gap in the ring filler? When the cam gets wedged into the narrower portion of the cutout, between the filler and the ID of the ring, it will deflect that part of the ring filler, making it jam against the spindle (which passes through the center of the ring filler). See the little square sticking up that's part of the ring filler? That little bump engages with a little recess in the body of the micrometer and keeps the ring filler from rotating.
So when the ring filler is jammed against the spindle, and also prevented from rotating, it prevents the spindle from rotating (at least easily).

Thanks you for the detailed response. Appreciate it greatly. I have an old 230 Starrett in very nice shape. I cleaned it today. Is there a way to make it lock tighter? Mine won't turn using the ratchet speeder when locked but can turn using some slight force With the thimble.nothing looks worn or broken.
One thing I don't understand is if the inner piece with cam doesn't tünch and irbid independent of the thumb wheels how does the thumbwheel force the cam into the narrow portion of the wheel and inner sleeve are independent of each other?

 

[EPAIII]

Thanks for the description. I always wondered how those things worked. Very clever! I bet there's a patent.

See that little circle inside the roughly-triangular cutout in the ring filler? That's a floating cam. When you turn the ring in the "lock" direction it drives the cam into the narrower portion of the cutout in the filler. See how there's a gap in the ring filler? When the cam gets wedged into the narrower portion of the cutout, between the filler and the ID of the ring, it will deflect that part of the ring filler, making it jam against the spindle (which passes through the center of the ring filler). See the little square sticking up that's part of the ring filler? That little bump engages with a little recess in the body of the micrometer and keeps the ring filler from rotating.
So when the ring filler is jammed against the spindle, and also prevented from rotating, it prevents the spindle from rotating (at least easily).

 

[Frodge]

I would like to increase tension a little on the lock. I still don't understand how the outer ring moves independently of the inner plate, how it forces the cam into the narrow part of the slot.
Is it ok to add a tiny drop on the cam pin and between the outer and inner plate/ring. Mine was very stiff to turn.

 

[eKretz]

The small pin rotates between the inner and outer rings when you spin the outer ring, which forces it to climb the ramp, which squeezes the inner ring tight against the spindle OD... not very mechanically inclined?

Anyway, the spindle doesn't need to be clamped all that tightly, just enough to keep from moving if it gets bumped.

 

[Frodge]

What I'm asking is the outer thumbwheel that you turn goes over the inner plate with the ramp that holds the pin. I understand that the pin moves to the narrow part of the slot and tightens the clamp around the spindle. My question is something needs to be offset I would think to force the inner plate closed as you turn the outer ring. To simplify my question why does the outer ring not just spin around that inner plate with the ramp, at what point, or what forces the pin to go into the smaller part of the ramp by turning the outer ring.

 

[eKretz]

What I'm asking is the outer thumbwheel that you turn goes over the inner plate with the ramp that holds the pin. I understand that the pin moves to the narrow part of the slot and tightens the clamp around the spindle. My question is something needs to be offset I would think to force the inner plate closed as you turn the outer ring. To simplify my question why does the outer ring not just spin around that inner plate with the ramp, at what point, or what forces the pin to go into the smaller part of the ramp by turning the outer ring.

Friction! It works just like when you roll a round item between your fingers. The ramp wedges as the pin climbs. These parts are precisely fitted so that the pin is touching both rings at the same time even when it's unlocked. As has been noted by others, if the outer ring has been tightened without the spindle in and the inner ring gets bent, the lock will rub and the spindle will be tight. Sometimes the pin won't grab right away when locking is attempted either. Don't do that. Best to have the inner ring sprung open a bit.

 

[Frodge]

I have mine where it is working now. With the lock out of the mic, should the pin drop in the notch freely, or should there be some resistance putting the three pieces (lock) together. The lock is a little hard to turn to lock unlock, but the spindle Sturms freely I locked and locks pretty well when locked. There seems to be a sweet spot where the outer and inner wheel need to go together in order for the lock mechanism to lock and unlock.