I have an old Starret 196 indicator set (circa.1960). One of the internal threads in the clamp and the external threads on one of the rods needs chasing. The threads on the rod that works measures 0.222-28tpi . The threads on the rod that needs chasing measures 0.224-28tpi. Does anyone know of a tap & die pair to chase these internal & external threads?
Largest Manufacturing Technology Community on the Web
Stay Connected:
Old Starret Threads
- Thread starter 4thTool
- Start date
- Replies 14
- Views 632
FamilyTradition
Aluminum
- Joined
- Feb 24, 2018
- Location
- Greenfield, Mass
Sounds awfully close to being a #12-28.
I am assuming your .224/.222 measurements are the major diameters of the thread.
Edit: Taps and dies for this size thread are relatively inexpensive and available from McMaster
I am assuming your .224/.222 measurements are the major diameters of the thread.
Edit: Taps and dies for this size thread are relatively inexpensive and available from McMaster
Yes, the 0.224/0.222 thread measurement are the major diameters of the two rods. The 0.222” thread screws into all but one of the internal threads in the clamp. The 0.224” thread starts in the clamp but soon binds.
I contacted Starrett and they acknowledged the use of odd size threads in old tools and they don’t offer taps or dies for them.
My Machinery’s Handbook places the 0.224/0.222 thread between #12 and 1/4”. I looked at McMaster-Carr and didn’t see anything in this size. All I saw were number and fractional sizes and none of them match my size. I must have missed it. Would you please post their part number for the tap.
The die would be nice but if it’s not available, I can cut the 0.224 thread off and turn new 0.222 threads. Seems extreme, but without a die that’s my only option.
Thank you.
I contacted Starrett and they acknowledged the use of odd size threads in old tools and they don’t offer taps or dies for them.
My Machinery’s Handbook places the 0.224/0.222 thread between #12 and 1/4”. I looked at McMaster-Carr and didn’t see anything in this size. All I saw were number and fractional sizes and none of them match my size. I must have missed it. Would you please post their part number for the tap.
The die would be nice but if it’s not available, I can cut the 0.224 thread off and turn new 0.222 threads. Seems extreme, but without a die that’s my only option.
Thank you.
FamilyTradition
Aluminum
- Joined
- Feb 24, 2018
- Location
- Greenfield, Mass
Oops... when I was referring to "this size thread", I was talking the #12-28. Please excuse the error in communication.
If it were my indicator set, I would try the 12-28 tap/die to clean things up and make it "good enough" to function. Unless you are intent on restoring to original condition, why not make it into something that is a common size?
If it were my indicator set, I would try the 12-28 tap/die to clean things up and make it "good enough" to function. Unless you are intent on restoring to original condition, why not make it into something that is a common size?
old_dave
Stainless
- Joined
- Apr 15, 2002
- Location
- Central Mother Lode, California
If you go here: https://www.starrett.com/metrology/product-detail/196A5Z#Downloads you can download a pdf of dimensioned drawings and you will see Starrett describes the thread on the rods as ".231-28". I have the Starrett No. 196 set, bought new circa 1977-1978, it has low hours of use in my home shop. I measured the thread O.D. at 0.219-0.220, that seems a bit undersize for a thread with a nominal diameter of 0.231 inches.
I was able to find both a 7/32-28 tap and a 7/32-28 die; 7/32 = 0.219 while a number 12 would be 0.216.
Anyway the die gives a thread that will screw in to the (original) clamp and that piece that's intended to be held in a lantern-style tool post. On the other hand the tap gave a thread that the No. 196 rod would only screw in to 1-2 turns. My main goal was to tap holes that the No. 196 rods would screw in to so I'm a bit out of luck.
David
I was able to find both a 7/32-28 tap and a 7/32-28 die; 7/32 = 0.219 while a number 12 would be 0.216.
Anyway the die gives a thread that will screw in to the (original) clamp and that piece that's intended to be held in a lantern-style tool post. On the other hand the tap gave a thread that the No. 196 rod would only screw in to 1-2 turns. My main goal was to tap holes that the No. 196 rods would screw in to so I'm a bit out of luck.
David
EPAIII
Diamond
- Joined
- Nov 23, 2003
- Location
- Beaumont, TX, USA
The problem with that approach is it may not be 28 TPI. It could be 27 or 29 TPI. When Starrett says they DID use non-standard threads, THEY MEAN IT.
I would be very careful in measuring the pitch before running a 28 TPI tap or die over the existing threads.
I would be very careful in measuring the pitch before running a 28 TPI tap or die over the existing threads.
jim rozen
Diamond
- Joined
- Feb 26, 2004
- Location
- peekskill, NY
If it's the thread on the end of the C shaped clamp, that goes into a knurled bushing with slotted sides, so it's supposed to be tight fit. Or some other thread?
M.B. Naegle
Diamond
- Joined
- Feb 7, 2011
- Location
- Conroe, TX USA
The only issue I see going to a more common size is that it will become more of a bastard tool than it already is. IOW, however odd the old Starrett threads are, they are at least cross compatible with other Starretts. I have some Starrett indicator attachments, depth mics, and I think some ID mics that someone chased or drilled and re-tapped various attachment points for standard threads, then whatever piece was in the hole was lost. Now instead of borrowing parts from another tool or finding good used pieces on eBay to fill the hole, making custom pieces is my only option to making them functional tools again.
Not saying don't modify it. Whatever you can do to make it work. That is one aspect of measuring tools that I think too many people miss however. The tool isn't complete without all the bits and pieces that are around it in the case, and those little bits and pieces are not always easy to find when they get lost.
Not saying don't modify it. Whatever you can do to make it work. That is one aspect of measuring tools that I think too many people miss however. The tool isn't complete without all the bits and pieces that are around it in the case, and those little bits and pieces are not always easy to find when they get lost.
Thank you for everyone’s suggestions and comments! They’re valuable and very helpful.
My assessment of 28 TPI was based on measurement with my thread gauge. That blade was the best fit but I suppose that could be off as well, but it’s close.
My preferences are more in line with M.B. Naegle. I can certainly rethread everything to a common Unified National thread size; that’s easy. However, in my experience, non-standard modifications have a tendency of blind-siding me at a later date. Like when you want to expand/replace components. They can be modified too but you just keep getting deeper and deeper into it.
I was unable to locate 7/32-28 taps & dies in McMaster-Carr. However I do find them on the internet. Since my needs are to merely chase threads, perhaps a ginger application of that tap will remove enough of the “burr” that the rod (with cutting oil) can finish the job. Doubtful but worth a try. I believe the clamp is cast iron and the rod is steel. As for the external thread, I’ll experiment with a scrap of steel rod and the die. I’ll see how things fit and make some decisions at that point.
Thank you again to all!
My assessment of 28 TPI was based on measurement with my thread gauge. That blade was the best fit but I suppose that could be off as well, but it’s close.
My preferences are more in line with M.B. Naegle. I can certainly rethread everything to a common Unified National thread size; that’s easy. However, in my experience, non-standard modifications have a tendency of blind-siding me at a later date. Like when you want to expand/replace components. They can be modified too but you just keep getting deeper and deeper into it.
I was unable to locate 7/32-28 taps & dies in McMaster-Carr. However I do find them on the internet. Since my needs are to merely chase threads, perhaps a ginger application of that tap will remove enough of the “burr” that the rod (with cutting oil) can finish the job. Doubtful but worth a try. I believe the clamp is cast iron and the rod is steel. As for the external thread, I’ll experiment with a scrap of steel rod and the die. I’ll see how things fit and make some decisions at that point.
Thank you again to all!
I would probably try making a .224-28 thread out of 4140PH and grind a gnash on it for cleaning out the threaded holes and use a thread file or triangular needle file to clean up the male threads.
While you are at it you could make a slightly undersized .224-28 thread to verify the pitch is correct.
While you are at it you could make a slightly undersized .224-28 thread to verify the pitch is correct.
old_dave
Stainless
- Joined
- Apr 15, 2002
- Location
- Central Mother Lode, California
Looking back at my notes, my endeavors here took place over the span of a year, 2017-2018. Finding a 7/32-28 die was easier, ordered one from KBC. They also showed a 7/32-28 tap, but when it arrived it turned out to be for a double start screw! Eventually got a Greenfield Tap & Die branded 7/32-28 tap from an outfit called Opentip.com.
Starrett must use taps and dies for their ".231-28" threading on the 196 set. Wonder if they make their own.
I think there's a dodge where you stick a sliver of wood, maybe like a round toothpick, in one flute of a tap to make it cut oversize. I've never tried this.
David
4GSR
Diamond
- Joined
- Jan 25, 2005
- Location
- Victoria, Texas, USA
Want to be careful here. Starrett used two different size threads on the 196 sets over the years. I had examples of this in my collection of 196s I have. I took a piece of 3/8" or was that 5/16", drill rod and made my own posts. Took and single pointed the threads. Easy pezy. Yes, it is a 28-pitch thread from what I remember. Remember, the bar and clamp that is in the set is case hardened! Don't try to run a tap in the threads!!! It will be bad!!
4GSR,
Knowing that Starrett used two different threads in 196 kits may explain a few things. I have one complete kit and parts from another; both circa 1960 though. The thread in my C-clamp is different than the thread in my 3/4” lantern post bar. It seemed odd Starrett would use two different threads in a kit where parts should be interchangeable.
I’ve considering making my own tap but I’m beginning to think the smart thing to do is throw the who mess out and start over.
Which ever the case may be, my great thanks to everyone for their advice and suggestions; all very helpful!
Knowing that Starrett used two different threads in 196 kits may explain a few things. I have one complete kit and parts from another; both circa 1960 though. The thread in my C-clamp is different than the thread in my 3/4” lantern post bar. It seemed odd Starrett would use two different threads in a kit where parts should be interchangeable.
I’ve considering making my own tap but I’m beginning to think the smart thing to do is throw the who mess out and start over.
Which ever the case may be, my great thanks to everyone for their advice and suggestions; all very helpful!
Conrad Hoffman
Diamond
- Joined
- May 10, 2009
- Location
- Canandaigua, NY, USA
Not hard to make taps, good old thread here- https://www.practicalmachinist.com/forum/threads/making-taps.187694/
I've also made dies, but they're more of a pita, especially if you have to make the mating tap first.
One thing I know for sure about old "funny" threads- no CNC back then so the pitch has to be something you can achieve with change gears.
I've also made dies, but they're more of a pita, especially if you have to make the mating tap first.
One thing I know for sure about old "funny" threads- no CNC back then so the pitch has to be something you can achieve with change gears.
Conrad,
Thank you for the link to the old thread to make your own tap. Great stuff; empowering! I already ordered a 7/32-28 tap, I’ll see how it does. I’m expecting it to be a little loose but if nothing else I think I should be able to at least verify 28 TPI. If it doesn’t work, I have some O1, I’m eager to try making my first tap.
Thank you for the link to the old thread to make your own tap. Great stuff; empowering! I already ordered a 7/32-28 tap, I’ll see how it does. I’m expecting it to be a little loose but if nothing else I think I should be able to at least verify 28 TPI. If it doesn’t work, I have some O1, I’m eager to try making my first tap.
