Starrett Indicator Holder Thread Sizes

[M.B. Naegle]

I was about to use one of our old Starrett indicator holders the other day when I found that not all the parts seem to fit together, so I spent some time tonight trying to hunt down all the bits and pieces that have been scattered between various tool boxes and have come up with the following:

Starrett #196 - Back plunger type indicator basic kit (with clamp holder, tool post holder, rods, etc.)

Starrett #64 - old needle type indicator with tool post holder and rods

Starrett #665 - T-slot Indicator kit

Starrett #196G - Indicator clamp and rod (only)


The specific issue I'm having is that the tool post holder bars (6" x 1" type) from #64 and #196 have threaded holes too small for the rods to thread into. The rods will thread into the clamp type holders, just not the tool post holders. Is there a missing adapter that I'm not seeing in pictures, or could these tool post holders be from some other kit entirely?

Even though most of these seem to use the same pieces, did Starrett change threads for different kits to maybe keep from mixing them? Starrett thankfully has PDF prints available for most of these but they don't all have the thread sizes.

In the end, I could just make a couple adapters. Stuff like this is why I've grown fond of keeping sets like these together in their fitted cases as opposed to having the parts rolling around in the back of a drawer.

 

[4GSR]

There's been a few threads started on this very subject. Have no clue where or how to search for them. PM's search function is not very good looking for stuff like this. I have several sets of the 196 and I have found two different thread sizes, too. Without going out and do some measuring, seem like one set is 8-32 or 10-32, don't remember which. The other thread was something like 12-28 or .250-28 OR the old 14-28 thread. It is an odd balled thread. The rest of them, I have no clue about them.
Ken

 

[M.B. Naegle]

The holder's thread looks like a proprietary thread that looks like a #8 or #10, but the rods look closer to a #12 or 1/4" thread. I need tor break out the thread gauges an get some real numbers.

 

[Conrad Hoffman]

Starrett loves their weird thread sizes. I just went to make a little Delrin pad for the end of the screw on a V-block clamp. Looked like #8-32. Nope, just a bit larger. Nope, not quite #10-32. I said to heck with it, drilled it and pressed it on.

 

[old_dave]

I can only talk about the Starrett No. 196. I bought my set new about 1977-1978. The threaded holes in the clamp and the tool post holder are the same size. Measuring the o.d. of the threads on the rods I get .219-.220 inches, 28 threads per inch. Starter's website has a nice dimensioned PDF set for the No. 196. It describes this thread as ".231-28-UNS". I have a 7/32-28 die that makes a thread that works with the clamp and the tool post holders' threaded holes.

I have one example of how Starrett has changed a product that has spanned many decades. I have my father's Yankee Spring Dividers that are probably almost 80 years old. The adjusting screw is .143 inches in diameter and 36 threads per inch. A couple of years ago I bought the same model new. Its adjusting screw is .120 inches in diameter and 40 threads per inch, maybe it in fact is a 5-40.

David

 

[repair]

Starrett and Brown and Sharpe all make threads that we don't have taps for so you have to order or use only there parts.

 

[M.B. Naegle]

Fixed one set this afternoon.

I started with the Starrett #64 since replacement parts are likely obsolete (even for Starrett). The post had been re-threaded to be a 1/4-24. The bar it threads into I wasn't able to completely determine what it was. It may have been a #9-32, but my thread gauge was a little too big to get an accurate reading of the pitch, and I gave-up trying to figure out the major/minor diameters.

I used a 10-32 carbide tap to chase the threads out, which did a clean job with no crossed threads, and then I re-cut the post's threads to match. The holder may have been case-hardened as a file dug in slightly but a HSS tap would jam. It's one with the rainbow gun-blue finish.

This set's an antique for sure, but other than the thread issues, it's in great shape. I see it as a "splash-proof" .001 indicator, so no reason it couldn't be put to work.