kind of thread is this

can somebody tell what kind of thread is this? http://www.signaturehardware.com/product8636
it is for an old fashined door knob spindle,the thicknes is 9/32 square
stock, and 20TPI,is there a nut or bolt made for this thing? Thanx
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On Thu, 13 Oct 2011 15:56:00 -0400, Jimmy Suarez wrote:

Old enough to be its own standard, for one -- the house that my maternal grandmother lived in was built in 1905 and had that style of hardware in it. 1905 wasn't quite Before Standardization, but it was certainly at a time when standards weren't terribly prevalent.
Now I'm kinda curious -- and I don't know the answer!
--
www.wescottdesign.com

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Jimmy Suarez wrote:

I've seen those before on many occasions in the UK. If your stock is 9/32 AF then that would give 0.398" across the corners if perfect but they're usually rounded, I would hazard a guess and look at 3/8" BSF which is 20 tpi. I understand Whitworth was used in the US for a while but BSF only came about in the early years of the 20th century, BSW having become a standard around the mid 19th century.
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That's what lathes are for. Had a couple like that on the French doors at my parents' house, most of the rest in the place were a little smaller and segmented diagonally so that the knob setscrew would expand them in the latchset's square hole. Never had any trouble with knobs pulling off with that sort, the French doors' knobs were always loosening up. I think those spindles were hard and the setscrews wouldn't bite in. Glad to know there's replacement parts now, the place was built in the mid-20s and regular hardware stores had nothing when we went looking, knobs or spindles.
Stan
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I don't know what the thread is, but those things are so soft it usually doesn't even matter. They'll mush in anything.
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I can't believe this Jimmy, nobody can give you an answer,I thought some great machinists are posting here.I heve seen this type of door knobs in many houses built from the 1900s to 1940s.
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wrote:

The thread in question is 3/8-20 UN. This is an obsolete thread that probably is found only on door spindles and in door knobs today. It may show up on other door hardware but AFAIK it is not used on anything else. Taps are available to repair door knobs and levers. You could make your own nut. I have made much door hardware for various customers and all upper end hardware seems to use obsolete threads or metric threads. You may be able to get away with an M10x1.25 nut or bolt. 10 mm is nearly .014" larger than 3/8" (.375") but the pitch m1.25 is less than .001" different than 20 TPI. I'm sure the M10x1.25 nut would thread onto the spindle but it would be a loose fit. Cheers, Eric
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"Suga Moto Soy" wrote in message wrote:

Well, mine was built in 1924, but assuming it was a long-time standard, the thread is 18 tpi (0.072" pitch) (Starrett thread gage) and the major diameter of the threads is around 0.375" (Starrett mike). The spindle is a little worn from old age and use, so I'll let you guess at what nut might fit. It looks to me like a 3/8 x 18. I don't believe that's a standard; UNC is 3.8 x 16 and UNF is 3/8 x 24.
I'd double-check that 20 tpi; it's close, but no cigar on the spindles on my doorknobs.
--
Ed Huntress


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Ed Huntress wrote:

I suggested 3/8" BSF which is 20 TPI but the OP doesn't seem to have responded to any poster regarding their comments. If the OP is in the US then BSF won't be that common unless they're next to gunner's motorbike but for me my neighbour has quite a selection of BA, BSF, BSW, BSP, and more recently UNF and UNC, and staggeringly a few metric, I also know a guy that would have many such spindles from various periods so could measure if required.
The period of manufacture would be of some use in pinning down standards or not. I recently repaired a ceiling light, most likely of Dutch manufacture in the 19th century, and the main thread holding it together appeared to be M10.7 x 1.5. From the design with solid arms no provision had been made for gas or electric so candles were the original light and I reckon it dated from the first half of the 19th century. The 1.5 mm thread pitch would be 17 TPI, which I have never seen anywhere , but 1.5mm pitch might make sense. IIRC at that date no real standards existed, BSW coming in around the mid 19th century in the UK, so I expect the threads were produced to suit in the factory which certainly seems to be supported by the other mish-mash of threads else where in the items. In the end I single point cut the main suspension rod thread at one end to suit the female piece it mated with and the non-visible end I fitted with a M10 helicoil.
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"David Billington" wrote in message wrote:

I suggested 3/8" BSF which is 20 TPI but the OP doesn't seem to have responded to any poster regarding their comments. If the OP is in the US then BSF won't be that common unless they're next to gunner's motorbike but for me my neighbour has quite a selection of BA, BSF, BSW, BSP, and more recently UNF and UNC, and staggeringly a few metric, I also know a guy that would have many such spindles from various periods so could measure if required.
The period of manufacture would be of some use in pinning down standards or not. I recently repaired a ceiling light, most likely of Dutch manufacture in the 19th century, and the main thread holding it together appeared to be M10.7 x 1.5. From the design with solid arms no provision had been made for gas or electric so candles were the original light and I reckon it dated from the first half of the 19th century. The 1.5 mm thread pitch would be 17 TPI, which I have never seen anywhere , but 1.5mm pitch might make sense. IIRC at that date no real standards existed, BSW coming in around the mid 19th century in the UK, so I expect the threads were produced to suit in the factory which certainly seems to be supported by the other mish-mash of threads else where in the items. In the end I single point cut the main suspension rod thread at one end to suit the female piece it mated with and the non-visible end I fitted with a M10 helicoil.
=============================================================When I hear stories like that, I always wish I could be there when the next handyman tries to repair the custom thread. <g>
My ancient plumbing contains a few brass parts that I've had to custom-thread, but I don't think it will all last before I have to replace the whole works. I've already succumbed to plastic pipe in place of oakum and lead on my cast-iron waste pipes. so the end is near.
The spindle on one of my tub faucets is a piece I turned from the bronze propeller shaft of a 50' commercial fishing boat, with the splines cut by cranking the feed handle on my lathe, with a lathe bit clamped in my milling attachment.
That's why my wife calls me a cheapskate.
--
Ed Huntress


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Ed Huntress wrote:

It might be amusing but I doubt it will happen in my lifetime. If they know something about the history of threads and the date of the piece then they might realise why the threads are oddball to modern eyes. The one that got helicoiled was only visible when the piece was dismantled and the wrought iron suspension rod had rusted in and had to be machined out so the thread insert was a good option. The one where I kept the odd thread had a good female thread in a brass casting and would have been visible on close inspection but not seen in the normal way as it was in the top suspension eye . As the female thread was good and the casting somewhat asymmetric it was easier to cut the thread to the odd specification. Many of the other threads at the ends of the arms which coupled the candle holders and drip trays to the arms looked more like a deep Edison screws thread rather than a normal V form.
I don't know much about old screw forming techniques but the oddball thread was larger than the rod it was on, like it was rolled rather than cut, but I didn't think they did that in the early 19th century. Any thoughts.
BTW the reason for the repair was that the light had fallen from the ceiling. It seems a water leak had allowed water to collect in the hollow brass ball at the bottom of the light unknown to the owners and about 6 years after the leak the central suspension rod had rusted to the point it gave up and the brass 2 tiered 12 light assembly fell to the floor bending and breaking many of the arms. The bulk of the repair was the work to straighten and repair the breaks. This is a similar light http://www.lassco.co.uk/?idX&tx_evlasscoproductdetail_pi1%5Buid%5D 747

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wrote:

The spindles are usually 20 pitch, Ed must have some oddballs. The thread form doesn't matter much because so little of is left on the corner of the spindle.
Paul K. Dickman
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"Paul K. Dickman" wrote in message wrote:

It appears that 3/8 x 18 was one of the old standards:
http://www.robertbrooke.com/door/locksets_lockwood.html
I checked mine with a loupe; it's definitely 18 tpi.
--
Ed Huntress

>Paul K. Dickman
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Yours may be 18 tpi, but the standard is 20 tpi.
http://houseofantiquehardware.com/s.nl/it.A/id.3517/.f
Dan
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wrote in message wrote:

Why did you clip out the reference to 3/8 x 18s, Dan?
Besides the Lockwoods, here are some other manufacturers who used 18 tpi threads:
http://www.robertbrooke.com/door/locksets_corbin_russwin.html
http://www.robertbrooke.com/door/locksets_marks.html
If you look around, you'll see that there appear to have been three standards for 3/8" threaded door knob spindles: 16 tpi, 18 tpi, and 20 tpi.
--
Ed Huntress





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I did that because it did not seem pertinent to what I was replying to. I was saying that 20 tpi seems to be the most prevalent thread. Not that there are not other sizes, just that 20 tpi seems to be the most common.
I looked at the specifications for door spindles at both Home Depot and Lowes. You would think that they would include the TPI in the specs, but they do not.
Dan
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wrote:

To be fair, the original poster specifically stated that the spindle he was looking at was 20tpi.
There are indeed three standards: "Standard spindle thread is 20 TPI. Also available in 16 TPI ,#2600S (Sargent) &18TPI, #2600L (Lockwood)."
I repair, refinish, rework about a dozen vintage mortise locksets each year.
It may be a regional thing, but here in Chicago, I have never seen anything but the 20s.
I can say with certainty, however, that these threaded spindles suck. The average homeowner performs less maintenance on his doorknobs than he does on his roof. This, combined with the small area of thread engagement and the fact that most of these things are made out of some metallic colored hard cheese, means that it is only a matter of time before they fall apart.
Go get yourself some knobs with square holes and some threaded hole spindles.
Paul K. Dickman
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Sorry about the delay,computer crashed,I measured all the spindles(6) that I've found in my house(built the 1930s)and it looks to me that they are all 20tpi,now I have to find some 3/8x30 bolts or nuts.I found on a site 9/32x20 british threads-9/32 square stock is the size of the spindle.My next question is how do you thread a square rod without breaking the die?
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Jimmy Suarez wrote:

A couple of replies gave sources for the ready made spindles such as
http://houseofantiquehardware.com/s.nl/it.A/id.3517/.f
Who list 20tpi items and other pitches. Also you're not looking at a 9/32"x 20tpi thread but a 3/8" x 20tpi because 9/32 is the AF size of the spindle and you want the diameter which will be the distance across the points of the square shaft.
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    [ ... ]

    How many?          For one or two -- single point it on a lathe?
    I guess that someone could make dies with spiral flutes but I would not want to pay for them. :-)
    Enjoy,         DoN.
--
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Email: < snipped-for-privacy@d-and-d.com> | Voice (all times): (703) 938-4564
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