pdm
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 posted on 1/12/09 at 03:01 PM |
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Stuck with micrometer
Afternoon
Not having a good time at the moment with my micrometers !!
For my 25-50mm one, when I measure the standard blocks, it is coming back as 0.02 off.
Now I could just subtract this from measurements which is ok but I tried to adjust them with no joy.
I have a rachet which came with the set and also a set of jewellers screwdrivers to do this with.
As far as I know I need to turn the main collar with the rachet so that the "0"s line up so it measures bang on 25mm and 50mm.
Do I need to undo the grub screw before I use the supplied rachet to turn the collar ?
If so I can't generate enough twist with the precision screwdrivers - they are admittedly a bit cheap and just have a metal knurled handle - is
there some "trick" to using these ? What's the loose nut on the end of them for ?
Thanks in advance - this is driving me nuts and I don't want to break them !! My missus is now doubting my mechanical ability - I need to
re-assert my man know-how urgently !!
M
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coozer
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| posted on 1/12/09 at 03:05 PM |
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Are you sure you haven't dropped them? This can bend the spindle making the difficult to read properly.
They should rotate easily with the ratchet and click click when they touch the parts.
1972 V8 Jago
1980 Z750
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tegwin
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| posted on 1/12/09 at 03:12 PM |
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They tend to locktite the grub screws in...
Use a pair of pliers or pipe grips on the screwdriver and carefully loosen the grub screw... Then it should adjust as you describe...
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Would the last person who leaves the country please switch off the lights and close the door!
www.verticalhorizonsmedia.tv
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pdm
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| posted on 1/12/09 at 03:25 PM |
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Hi
Thanks for responding.
I checked them over for damage when I got them, both the spindles and the winding action so they weren't damaged in transit and I haven't
dropped them since.
The spindle and rachet work really nicely and smoothly and there is no perceptible snagging/roughness in the action of either so I don't think
they are bent.
I'll try some pliers on it and see if that works - I'm terrified of damaging the grub screw thread so I'll go careful.
Do I need to loctite the grub screw back in or can I leave it ?
Thanks again.
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The Shootist
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| posted on 1/12/09 at 04:06 PM |
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Cleaning?
Not to seem rude, but if you don't know how to adjust them, have you cleaned the contact points?
Gently tighten on a piece of card stock and drag it through the points to clean. Repeat as needed.
Adjustments should only be made after a thorough cleaning.
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pdm
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| posted on 1/12/09 at 04:38 PM |
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Yes - I cleaned them with a piece of paper clamped with the rachet to correct tension then dragged for about 1 inch without going to end of paper.
Wasn't too sure if the temperature was an issue so I've been checking them against the standard block in a cold garage...
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Mike S
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| posted on 1/12/09 at 05:00 PM |
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Hi
The temperature might be part of your problem if the garage is really cold as it is at the moment.
Most measurement instruments are calibrated at a nominal 20 deg C. This includes good quality steel rules micrometers, vernier calipers etc.
Try taking it indoors, allow to warm up to room temperature and try it again.
The loose nut on the top of the screwdriver is for putting your forefinger on as a steady when when turning the driver between thumb and next finger
and acts like a swivel. Also known as watchmakers screwdrivers, they are used this way as it gives better control with very delicate tiny screws.
Cheers
Mike
There are more horses' asses in this world than there are horses
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dave r
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| posted on 1/12/09 at 06:27 PM |
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reading you decription, i am not sure you are trying to adjust the right part
read this!
http://its.fvtc.edu/machshop1/Inspection/AdjustMic.htm
dave
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pdm
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| posted on 1/12/09 at 08:29 PM |
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I'll try inside and see if it helps.
I was actually reading the posted link about adjustments but when I tried the rachet spanner, the collar doesn't want to move at all which is
why I thought the grub screw needed loosening.
On the link, in Fig4, mine have a grub screw, screwed into the collar on the opposite side to where the rachet fits...
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dave r
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| posted on 1/12/09 at 09:55 PM |
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never seen one where you need to loosen a grub screw.... all the ones i hae are old school moore and wright or similar
got a photo ?
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pdm
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| posted on 1/12/09 at 10:23 PM |
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Hi
Yep - here's a couple of photos - dont know how to do a proper link yet and my photo archive doesnt seem to work so have put them up at flicker
here:
http://www.flickr.com/photos/41418507@N08/4150724225/
http://www.flickr.com/photos/41418507@N08/4150723811/
(Which on my preview at least has made a link !!)
First one is from bottom showing the hole on the collar where the rachet fits
Second one is from the top showing the grub screw.
Thanks for looking.
[Edited on 1/12/09 by pdm]
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dave r
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| posted on 2/12/09 at 07:01 AM |
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never seen one like that before.. sorry i cant be more help
dave
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pdm
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| posted on 2/12/09 at 08:38 AM |
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Thanks to everyone who responded.
Managed to get this sorted out last night.
No need to undo the grub screw in the end.
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