Extension handle for a Starrett solid-rod inside micrometer set

[Paul Jones]

This is an extension handle for a Starrett solid-rod 2” to 12” inside micrometer set. The micrometer sets usually have a place in the case for storing the handle but it is something extra to buy. It is a simple addition to the set and rather than buying the 6 inch long handle, I made my own with a shorter 3.5" handle (shorter is easier to use).







I used 0.25” diameter 303 stainless steel rod to make the handle. The most challenging part of the machining was the 0.110” X 52 TPI thread that fits into the side of the micrometer. As you probably know, Starrett does not use “off-the-shelf” thread sizes for their tools (e.g., see my HMT article for making clamping screws for Starrett V-Blocks at http://www.homemadetools.net/forum/b...8166#post53090 ).



The 0.110” X 52 TPI by 0.107” long thread does not have very much room for cutting threads and stopping the lathe cutting tool at the shoulder. I used the “upside down” threading tool technique that allows machining away from the headstock by running the spindle in reverse (clockwise) direction and leaving the lead screw in the towards the headstock direction but now the lathe carriage is moving away from the spindle as the spindle runs in reverse. This allows plenty of time to stop the cutting and return to the shoulder of the part for the next cut using a conventional single point threading method.




I used a very small carbide threading insert from NIKCOLE and the 3/8” square NIKCOLE Mini-Systems™ tool holder (ideally for the upside down technique it is best to use a left-hand tool holder to get closer to the shoulder but I only have the right-hand holders). I also used their 0.050” grooving insert in a ½” square tool holder to machine the 0.110” major thread diameter. The same grooving tool also cut the thread relief at the handle thread shoulder. The handle knurls are a cross cut 21 pitch size and this time I did not reduce the rod diameter because the difference in the ideal knurl diameter and the 0.250" diameter was only 0.007".










Thank you for looking,

Paul Jones


P.S. You probably noticed that I use a CNC ER32 collet chuck held in a 6-jaw chuck. The 6-jaw chuck cannot hold the small diameter stainless steel rods and using the CNC ER32 collet chuck is a much faster setup than swapping out the D1-3 mounted 6-jaw tru-adjust chuck. The CNC ER32 chuck has almost no TIR and once you located and mark the optimum position with the least TIR when held in the 6-jaw chuck it is possible to limit the TIR to less than 0.0003" TIR.

[DIYer]

Thanks Paul Jones! We've added your Micrometer Extension Handle to our Measuring and Marking category,
as well as to your builder page: Paul Jones's Homemade Tools. Your receipt:

Micrometer Extension Handle by Paul Jones

tags: handle, micrometer

[Toolmaker51]

Another home engineer conquers proprietary threads!
Paul Jones, you've assembled a first rate setup to accomplish what few can outside 'our' circle. Even less would understand why.

Many products use bastard threads or components, with varied justifications.
Naturally, some were in place before standardization was standard, and continue using original manufacturing equipment. I say that makes sense.
Other products want control of who is getting inside, I like that less.
I'm certain a lower tier exists, thinking their item is so exclusive, special bits will protect it. More likely the design flaws are masked yet easily remedied, they think you'll just buy another of theirs.
That's a challenge if ever there was one!

[Paul Jones]

Thank you Toolmaker51 ,

This time I took advantage of the Starrett website where ironically they published the blueprints to some of their tools and luckily for me they had the simple blueprint to the extension handle for a Starrett solid-rod inside micrometer. Starrett blueprint has the exact thread specification. However, in more cases with adding additions to Starrett tools I had to measure the thread pitches and diameters with the tried and true ways using thread gages and three-wire method of measuring threads. It is not difficult but using the blue print is so much easier.

Regards,

Paul Jones

[Toolmaker51]

Imagine being so highly placed in a specialized market; yet confident enough to publish blueprints.
There are some people not so impressed with Starrett; however those individuals haven't nearly 140 years in business.
Here is offered what I regard as the best metrology house for calibrations and repairs, Long Island Indicator at 027 : Long Island Indicator Service : Sales, Repairs and Spare Parts
Of all the text the site holds, the backdrop is always quality.
And none exhibit this more pointedly than "What has ISO got to do with it?" on page 002 : About Standards and Specifications

Imagine being so highly placed in a specialized market...

[Paul Jones]

Toolmaker51,

Thank you for pointing out the Long Island Indicator Service Inc. This company and website has been my longtime source of information for using an Interapid DTI and avoiding any pitfalls. As you already know, just reading the website continent pages will improve anyone's use of any type of Dial and Test Indicators. It is worth the time doing this.

Regards,

Paul Jones

[Don42]

Sometimes a design that will best meet the intended function will work best with non-standard threads. The makers of products that use them may have best possible performance in mind.

I turned a carrying case for my very expensive hearing aids (thank you, VA) from 3" delryn rod stock. Finished OD is 2.75". The cap is a plug that screws into the body, with an O-ring seal to make it waterproof. The lathe-cut threads are 2.60" x 32 TPI double-start. I made them double-start partly just to see if I could do it, and partly to make it easier to find the point of engagement for closing such fine large-diameter threads. Turn no more than half a turn backwards until it clicks, then screw it shut thus engaging the O-ring seal.

Another home engineer conquers proprietary threads!
Paul Jones, you've assembled a first rate setup to accomplish what few can outside 'our' circle. Even less would understand why.

Many products use bastard threads or components, with varied justifications.
Naturally, some were in place before standardization was standard, and continue using original manufacturing equipment. I say that makes sense.
Other products want control of who is getting inside, I like that less.
I'm certain a lower tier exists, thinking their item is so exclusive, special bits will protect it. More likely the design flaws are masked yet easily remedied, they think you'll just buy another of theirs.
That's a challenge if ever there was one!

[Paul Jones]

Hi Don42,

I agree that the design in many cases will best meet the intended function and will work best with non-standard threads. This is especially true in large diameter part cases. I have done this many times.

However, in the case of Starrett using a 0.110” X 52 TPI seems a little odd when the standard National Fine (NF) No. 4 with a 0.112" X 48 TPI would have work just as well. When looking at the two different threads side by side it is difficult to distinguish one from the other without making the measurements. It could be the Starrett designs predate the established standards considering the L. S. Starrett Company was founded in 1880. Starrett makes very nice tools and we appreciate this.

By the way there is a fantastic YouTube video by John Sanders (NYC CNC) on a tour of the Starrett factory and one on my favorites and a must see episode.

Regards,
Paul Jones

[olderdan]

Thanks for that video link Paul, what a fantastic factory It took me back to my apprentice days at Vickers Armstrong which was as big as a town.
It had every aspect of manufacturing from foundry to polishing, even had its own railway and hospital.
Sadly now a housing estate but at least I was a part of it once.

[Toolmaker51]

Vickers? As in pumps and associated hydraulic controls?
Another reason at least half the world is still speaking language of their choice.
Certainly not exclusive, Rolls Royce and others come to mind...no jokes about Lucas.