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#587717 - 02/27/15 5:10 pm Dial IndicatorThread  
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Tridentman Online content
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A bit of a question off beam from the normal--but--here goes!
I have an old Mercer dial indicator gage and wish to make an attachment which is U shaped to better measure rim concentricity on a rim I am currently lacing.
The tips of these indicators screw into the indicator spindle and I want to know the thread standard of the female thread in the spindle.
I have an alternative tip which is a roller and I have measured the male thread on that which screws into the spindle.
I have measured 0.109" OD and 48 tpi.
Looking at thread tables gives me the following options:
a) #4 UNF 0.112" OD 48 tpi
b) 6BA 0.110" OD 47.9 tpi
I guess that it is 6BA as the BA threads were used by the Brits for instrument type applications.
But--does anyone actually know?
Thanks in advance for any info.

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#587757 - 02/27/15 9:57 pm Re: Dial IndicatorThread [Re: Tridentman]  
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I have done some further research. It seems that modern "contact points" (proper name for the tips) are either 4-48 threads or 2.5mm threads. And in these thread forms the end shape I need is available as a standard part.
However I still do not know if the Mercer I have has one of these threads (it must be the 4-48 if one of the current standards)or possibly a 6BA thread.
So any info still gratefully received.

#587766 - 02/28/15 12:02 am Re: Dial IndicatorThread [Re: Tridentman]  
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Originally Posted By Tridentman
I have an old Mercer dial indicator gagea) #4 UNF 0.112" OD 48 tpi
b) 6BA 0.110" OD 47.9 tpi
I guess that it is 6BA as the BA threads were used by the Brits for instrument type applications.
But--does anyone actually know?
I don't know the answer to your question, but do know that the "standard" thread for this application used by Starrett, Brown & Sharpe, etc. in the U.S. is 4-48. Whether gages made in the UK were made to the U.S. standard in order to be sold over here, or not, I don't know.

Beyond the above, since the length of the threads on attachments on any of my DTIs is less than 0.2", the difference between 48 tpi and 47.9 tpi would amount to a difference of only ~1/5 x 0.1 = 0.02 of a turn. That is, even if the wrong fastener was used it fit fine. Only if the threaded portion were much longer would binding be detectable.

#587768 - 02/28/15 12:22 am Re: Dial IndicatorThread [Re: Magnetoman]  
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Originally Posted By Magnetoman

Beyond the above, since the length of the threads on attachments on any of my DTIs is less than 0.2", the difference between 48 tpi and 47.9 tpi would amount to a difference of only ~1/5 x 0.1 = 0.02 of a turn. That is, even if the wrong fastener was used it fit fine. Only if the threaded portion were much longer would binding be detectable.


BA threads have a 47.5 angle, UNF threads are, of course, 60. I suppose a 6BA male might fit a #4 UNF female, or the other way around, but it's bad craftsmanship to do so.

Eric


1971 T120RV (R.I.P.)
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#587771 - 02/28/15 12:47 am Re: Dial IndicatorThread [Re: BikeVice]  
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Originally Posted By BikeVice
BA threads have a 47.5° angle, UNF threads are, of course, 60°.
That's certainly what's in the books, but if you examine the threads of small fasteners under a microscope you'll be surprised at how much variation there is in practice.

#587777 - 02/28/15 2:12 am Re: Dial IndicatorThread [Re: Tridentman]  
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T-man,

I may be misunderstanding what you want to make, but there may be an attachment readily available that would do the job for you. I have an old Mitutoyo indicator that came with an attachment that clamps around the indicator stem and then pivots against the contact point. Here's one of them:



The little knurled thumbscrew comes out and allows the 90° pivot lever to be replaced by a 180° (straight across) pivot lever, if you can picture what I'm saying.

Maybe something like this would avoid the thread issue altogether.

Ray


'64 TR6R Plus some Twins from other countries (U.S., Germany, Japan)
#587812 - 02/28/15 10:32 am Re: Dial IndicatorThread [Re: Tridentman]  
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"But--does anyone actually know?
Thanks in advance for any info."


No, I don't I am afraid.

Anything is possible, but as a veteran of the UK scene I would put a large bet on it being a BA thread.

Few industries ever considered using Unified threads and they were normally confined to larger fabricated, export structures like...motorbikes, and of course aircraft. Even there the smaller bits tended to retain BA threads.

#587813 - 02/28/15 10:52 am Re: Dial IndicatorThread [Re: Tridentman]  
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I have some dial indicators, I made a extension for one of them and if I remember correctly, the make was a BATY and the thread was 3/32 x 48 TPI Whitworth.

#587818 - 02/28/15 11:17 am Re: Dial IndicatorThread [Re: Tridentman]  
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Many thanks for your inputs.
Thinking back I must have had this dial gage for about 45 years.
Mercer are now made in Switzerland but in those days they were "Made in England".
All small threads like that in those days were BA and I strongly suspect that this thread is 6BA.
My sets of taps and dies finishes at 4BA so I have ordered a set of 6BA taps and a die.
I am also going to order a flat contact point with a 4-48 thread and a 4-48 to 2.5mm converter.
So, armed with all these I think I can equip myself to do the job.
Having said that I don't really want to wait for these parts to arrive so will probably turn up a piece of aluminum rod with a hole in it to give a light push fit over the dial indicator stem. This will get me going with the "proper" kit OK for the next wheel.
Ray--what I am trying to do is true up a wheel with two dial indicators giving me the lateral run out and the concentricity simultaneously.
The process of setting offset, lateral run out and concentricity one by one on an iterative basis doesn't turn me on so I like to adjust one aspect whilst seeing by a turn of the wheel the effect on the other parameters (as they are all interdependent to an extent).
The indicator on the side of the rim to give lateral run out is OK as a standard point contact point as are normally fitted as standard to a dial indicator gage.
However the indicator on the circumference measuring concentricity (or lack of it) if it has a point contact point tends to show false readings if the lateral run out is not spot on.
So I want to replace this contact point with a flat pad so that lateral run out does not give false concentricity readings.
I hope this makes some sense!
Thanks again for all your input.

#587896 - 02/28/15 8:20 pm Re: Dial IndicatorThread [Re: Tridentman]  
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Rummaging through my box of miscellaneous taps I came across a 3/32" X 48 tpi taper tap.
I tried it in the female thread of the dial indicator and it went in easily. In fact the thread depth in the spindle was much longer than I expected it to be so the tap went in about 1/4".
It felt sloppy in terms of diameter but OK in terms of pitch so I think another pointer towards 6BA.
Hope this isn't boring everybody ---but I guess it may help someone else in the future.

#587916 - 02/28/15 11:54 pm Re: Dial IndicatorThread [Re: Tridentman]  
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Originally Posted by Tridentman
. . . Having said that I don't really want to wait for these parts to arrive so will probably turn up a piece of aluminum rod with a hole in it to give a light push fit over the dial indicator stem. This will get me going with the "proper" kit OK for the next wheel.

I'm still not sure I understand the U shape or the aluminum rod with a hole in it, but you have made me curious. I have to do some wheel truing in the near future and would be curious to see your setup if you can post a picture.

I would just be using a flat contact point like this one on the left:

[Linked Image]

[Linked Image]


'64 TR6R Plus some Twins from other countries (U.S., Germany, Japan)
#587971 - 03/01/15 1:11 pm Re: Dial IndicatorThread [Re: Tridentman]  
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Ray--thanks for your input and photos.
I am trying to get to the configuration as shown by the flat contact point on the left of your photo (please forget the U shape--I was not thinking straight when I said that).
I need the flat point so that when placed at the edge of the rim measuring radial run out I do not get misleading readings if there is lateral run out present.
I have found a very useful web site--- www.longislandindicator.com and will be ordering tomorrow one of their "Mitutoyo Flat Point--Disc Shaped" contact points (their part # MTC 48-01 which is 1/2" diameter. I think I will also order a converter part # MTC 13-02 so that I can fit points into another newer gage I have.
I am hoping that I can fit the 4-48 thread into the stem of the spindle on the Mercer gage--which I am convinced is 6BA. I also have a 6BA die and tap on order so between the whole lotr I think I will be able to get myself kitted out OK.

#587973 - 03/01/15 1:14 pm Re: Dial IndicatorThread [Re: Tridentman]  
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Sorry--I forgot the aluminum rod.
Until I get the items mentioned above I may make a flat contact point by taking a piece of 1/2" dia aluminum rod, face off one end in the lathe and at the other end bore a small diameter hole of a size which will be a light push fit over the stem of the dial indicator spindle.
Hope this makes sense!

#587991 - 03/01/15 2:43 pm Re: Dial IndicatorThread [Re: Tridentman]  
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Originally Posted By Tridentman
I need the flat point so that when placed at the edge of the rim measuring radial run out I do not get misleading readings if there is lateral run out present.
I was about to take a photo to upload but realized it's easier to ask you to google "Starrett 25R". That will show you a set of indicator tips of various shapes including at least four flat ones (one of which has a very low profile so is easy to miss when looking at the photos). That should help you decide which one(s) seem most appropriate for your plans.

#587999 - 03/01/15 3:14 pm Re: Dial IndicatorThread [Re: Tridentman]  
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Many thanks, MMan, in fact broadly similar to the range of contact points on the site I referenced above.
Much clearer now in my own mind about how to go forwards.
Many thanks for all your inputs.

#588006 - 03/01/15 4:08 pm Re: Dial IndicatorThread [Re: Tridentman]  
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Originally Posted by Tridentman
Much clearer now in my own mind about how to go forwards.
Many thanks for all your inputs.

And I am now clear on what you were saying -- thanks for the further explanation. I was wrong earlier when I said Mitutoyo. My old indicator is actually by LS Starrett. That flat button contact point used to work well in the days before CNC when I needed to move a lathe tool a few thousandths.

In any case, as MMan said earlier, I think any 4-48 point will fit the short length of thread you are dealing with. A good thing that comes from this -- when I was looking around to see who had contact points that you might use, I found out how cheap these dial indicators are now. I think I need another one (or two). It would be nice, as you said, to have two of them on the wheel at once.

Ray


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#588021 - 03/01/15 5:17 pm Re: Dial IndicatorThread [Re: Tridentman]  
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Well-I spent a bit of time this afternoon turning up an aluminum "thimble" about 1/2" in diameter and bored a hole in the end to just slide over the spindle of the dial indicator.
And--even better--it works a treat.
So--tomorrow--after shoveling the 6" of snow that is falling as I write this--it is on with the rim set up.
BTW--Ray--if you are thinking of buying another dial indicator--on the site I referenced above there is a very honest down to earth view from the repairers view point of the different makes of dial indicators. Very much worth a look before you shell out hard earned dollars!
HTH

#588068 - 03/01/15 9:12 pm Re: Dial IndicatorThread [Re: Tridentman]  
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Thanks, T-Man. I'll have a look. I'm glad you got that to work. There's satisfaction in using an old indicator that you have had so long, and finding that it still works well. I've had mine for forty years now.

I know that you know this, but if you shovel your snow, take it slow and easy. I used to say, "Knit one, purl two", as in one scoop followed by two rests. These days, it is "Knit one, purl five or six!"

Be careful and live to ride your Brit bikes.

Ray


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#588138 - 03/02/15 10:49 am Re: Dial IndicatorThread [Re: Tridentman]  
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Thanks for the advice, Ray.
I have just come in after clearing the drive of another 6" of snow--this winter seems to be never ending!
I took your advice and when my wife asked me what I was saying under my breath I told her that I was knitting!
Her suspicions of a rapidly declining brain were I think confirmed!

#588497 - 03/04/15 5:22 pm Re: Dial IndicatorThread [Re: Tridentman]  
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Thought I'd add this observation on using dial indicators on chrome rims.

I use a dial indicator when I true a rim as well. But I've found that although the tips are normally polished nicely, they are still very hard and will leave a scratch line on the chrome if you indicate the outside surface of the rim. For that reason, I made a tip of aluminum so I is soft and will not leave a scratch. I'm sure brass would work as well.

regards,
Rob

#588555 - 03/04/15 11:36 pm Re: Dial IndicatorThread [Re: Tridentman]  
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I agree--the points or small ball ends that are normally "standard" on dial indicators are very hard and I can imagine would easily scratch chrome as Rob indicates (no pun intended!).
However the flat points present a much bigger area to the rim meaning greatly reduced pressure and therefore less chance of scratching.
As mentioned above I turned up a 1/2" diameter aluminum "point" with a hole bored in so that it slides nicely over the dial indicator spindle stem (with no standard point fitted)and this works fine.
I am expecting delivery tomorrow of a pukka flat point and also 6BA taps and dies so that I can answer my initial question--in terms of the thread in the spindle of the old "Made in England" Mercer dial indicators.
Quite an innocent question but it has taken me on a little journey whereby I now know much more about dial indicators and their points.
Such is the attraction of fettling Brit bikes!

#588907 - 03/06/15 4:01 pm Re: Dial IndicatorThread [Re: Tridentman]  
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Well--the parts didn't arrive yesterday--delayed by the snow I guess--but they did arrive today.
What arrived--four things--a 6BA tap, a 6BA die, a flat tipped contact point with a 4-48 thread and a converter with a 2.5mm male thread and a 4-48 female thread.
So --I first tried the 6BA tap in the end of the dial indicator spindle thread. No go--I couldn't get it started at all.
Then I tried the 2.5mm male thread on the converter in the dial indicator spindle thread. Went in just like a stripped thread--like a pea rolling around in a bucket.
Then tried the flat tipped 4-48 point in the dial indicator spindle thread. Success! Felt just right. I then tried the point that came with the dial indicator from new--it felt exactly the same as the 4-48 flat tipped point.
So I am now confident that the spindle thread on the old Merecer dial indicators "Made in England" is 4-48. A bit surprising--but I can't argue with the evidence.
As far as I am concerned this is the end of the story.
Sorry to be so anal but it might help someone else in the future.

#588958 - 03/06/15 7:47 pm Re: Dial IndicatorThread [Re: Tridentman]  
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Quote:
As far as I am concerned this is the end of the story.


Sorry but now we want to know how it turns out- rimwise- ha ha - keep us posted!

is it Spring yet?

cry


1978 Bonneville T140V PX
#589091 - 03/07/15 3:22 pm Re: Dial IndicatorThread [Re: Tridentman]  
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I'm little late to the party, but I have a Mercer dial indicator on my cylinder bore gauge, and I've just verified the contact point thread.

T-man, just like your Mercer, my Mercer (and Mitutoyo and Starrett) has a 4-48 thread ... that must have been an industry standard throughout the imperial world. By way of contrast, my Somet (Czech) indicator has a metric thread.

In my experience, BA threads are mainly found in electrical devices.

.. Gregg


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