I recently obtained a hand crank drill press from Australia which has a shaft 1/2 inch diameter with 26 threads per inch. I can’t find a chuck that will fit. I called the Jacobs company and they don’t make one that fits those threads. What can I do?
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Replies
You could have a machine shop make an adapter or better yet have them cut off the threaded part and drill and tap the shaft to fit the Jacobs chuck threads then connect it with a threaded stud. Shorter and less things between the chuck and the shaft will make it less liable to have run-out. Keep it simple! I find it very handy to have a good a good machine shop nearby as they can often come up with better ideas. A lot has to do with what they have for machines. Like woodworking there are more than one way to accomplish something. I've even run a different tap or die over existing threads to change them to something else. Depends on the budget and accuracy needed. A good machine that understands your needs and budget is priceless. Finding a retired old timer can often be the best thing. Some shops aren't too helpful. It's like finding a good car mechanic.
Edited 3/7/2004 10:48:21 AM ET by rick3ddd
Australia??? Before you go cutting, chopping or adapting, check to see if the thread is a metric size. Also check the tread size against an OLD Stanley hand drill. Sorry, I don't have one handy to verify the thread size / count.
SawdustSteve
Ditto what Steve said. The first thing I thought when I read 1/2" x 26, even before I got to Australia, what that it may very likely be 12 or 13 mm by 1mm pitch. That would be 0.472 or 0.512 inches by 25.4 TPI.
Edited 3/7/2004 12:07:01 PM ET by Uncle Dunc
Good point about the metric Steve. That crossed my mind after I posted. I'm puzzled by the hand crank drill press reference. I wonder if it's not the old timber framing type drill press similar to the ones made here in the old days which if from Australia might be a british thread standard as well. 1/2-20 is a common thread size for chucks. If metric it could be 12 mm by 1.0, 1.25,1.5, or 1.75. All my catalogs and thread measuring tools are at work so I'm limited here.
Metric 12 x 1.0 pitch (closest to 26 tpi) would easily be mistaken for 1/2-26 by most unused to the metrics of the rest of the world. Unless you can find a metric chuck with those threads modifying or an adapter would be an option. I'd bring it to a couple of machine shops for options and other possible ideas. Can you post a pic? I'd like to se what kind of tool it is out of curiousity.
I just checked my library, and the only 1/2" threads referenced in a fairly exhaustive selection of material are 12, 13, 14, 16, 18, 20, 24, 27, 28, 32, and 40 TPI. The Tool and Manufacturing Engineers' Handbook has extensive tables for thread depth, and they don't mention 26 TPI for any diameter. If you can't find a metric chuck to fit, you can either cut off the threaded portion and thread the remaining shank 1/2 x 20 TPI, or if the shank isn't long enough , turn it down to 3/8" and thread 3/8x24TPI or braze on a steel bushing and thread 1/2 x 20.
I had a look in my tables and found 1/2"-26 called: bicycle thread. So it is an existing thread but not very usual.
Ruud Joling The Netherlands
Where did these bicycle threads originate? I've got whitworth and a number of others in the Machinery Handbook but no mention on that one.
I don't know where it originates: I have here a thick book that only handles screwthread ("schroefdraad" in dutch) and 26 tpi is mentioned in 1/4", 17/64", 5/16", 3/8", 7/16", 1/2", 3/4".
In this book there are astonishing kinds of screwthead: what about sewingmachine thread or : stahlpantzerrohrgewinde (tigertank WII) or Löwenherz thread.
In this case I think on my fathers hand drilling machine: the chuck was an integral part of the machine: not interchangeable, 3 jaws and a conical outside (excuse my english)
Ruud Joling The Netherlands
That book sounds like a wonderful book. What is its name? About 25 years ago I was in New York and went to a place called the American Screw Threads Institute. They had a one-room library, and all 4 walls were covered with books on screw threads. The next time I went back, they had disappeared. Does your book cover threads for clocks and watches also? I don't know any Hollandische, but I could write in German or French if it is easier for you to read. Rob
Edited 3/8/2004 2:27:50 AM ET by rob
The name of the book is: schroefdraad (dutch for screwtread) Indeed there is a lot of very fine and tiny stuff in it for clocks, microscopes etc. It starts at 0,25mm (0,0098") 25 BA. Where are you looking for? are you a clockmaker? I own a screwcutting lathe but the smallest thread I cutted with it was 6mm x 1mm.
Sometimes I make or repair jewelry where I have to make or replace tiny screws or bolts. I have a set of taps and dies (15 sizes) which runs from 1.7 mm diameter x 0.34 mm pitch to 0.4mm diameter x 0.10 mm pitch. The set is 25 years old and I don't remember where I got it. Some of the taps are broken now, and I can't get replacements. None of the books I have even reference these small sizes, which is why I was interested in the title of your book. Thanks for the help. Rob
I just noticed an adverticement here in the Netherlands: offered is a set of new taps and dies from 1 till 2.5mm (in small) increments for €50 interested?
I might be interested. How many taps/dies are there in the set, and what sizes and pitches are they? The set I have now came with 2 taps for each die, since they knew I was going to break taps, which I did.
When you work in soft metals like silver or gold, even alloys like sterling Ag or 14K Au which will work-harden when they are drawn into wire will change size when they are threaded. For instance, if you start with a 1mm (.039") sterling wire, to get a well threaded bolt you have to use a 1.2mm die, and when you are finished you have a 1.1mm threaded wire. To use the bolt, you file it lightly to remove the burrs, drill a .038" hole (U.S. #62 drill bit) and tap it with a 1.1 mm tap.
As you can see, this process only works if you have a group of taps and dies which are close together in size and have the same pitches. In my set, the 1.2, 1.1, and 1.0 mm sizes have an identical pitch of 0.25 mm, and other groups are similar in sharing the same pitch.
I really appreciate your help. Thanks again. Rob
If you give me your e-mail adress I send you the link to: "Marktplaats" (Marketplace) I think it is Russian stuff (not bad at all!)
[email protected]
my website: http://www.ruudenmieke.nl (it is only dutch!)
Edited 3/12/2004 6:45 pm ET by Dutchy
Toolmakers and tool builders are smart people. You can get any pitch in any diameter, you want.
A lot of manufacturers used to use "special" threads to protect their product lines.
A wonderful combination of threads is 26 pitch left hand on one end and 25 pitch right hand on the other end.
George, if I had a source of rods like that, and taps to match, I could make handscrews in which one jaw closed slightly faster than the other, which would truly be the answer to a question no one ever asked. And just think of the application in the field of turnbuckles. I think we're on to something here!
Incidentally, since you speak of combining 25 and 26, If you look up "stick" in the Oxford English Dictionary, in the middle ages it was a measure of a quantity of small eels, either 25 or 26. I'm not sure if we don't know which it was, or if they didn't care. Or maybe they lacked our hypothetical rod.
Rob
Edited 3/8/2004 9:43 pm ET by rob
With a screw cutting lathe and an assortment of change gears, you can cut about any thread pitch you can imagine and never need a tap or die. My little Taiwan lathe has a 16 tpi leadscrew and 12 gears, from 25 to 80 teeth. These gears will make 95,040 different combinations. In real life not all of them are useful, because some of them won't physically fit on the lathe and some are duplicates. I can actually make threads from about 5 tpi to about 160 (both numbers very vaguely retrieved from memory).
Just one example, I needed to cut some 27 tpi threads to adapt a couple of microphone stands to a different use. (27 tpi is a US standard pipe thread, but the threads on the mic stands weren't tapered.) I didn't have the right gears to cut exactly 27 tpi, but I did have a combination that would cut 26.898. (Or something like that. Again remembering from a long time ago.) Anyway, it was close enough that both pieces screwed onto the 27 tpi mic stands for about 12 turns before binding.
If you want a long, enthusiastic disquisition on the joys of computer programming, just ask me, "Dunc, with 95,040 different choices, how do you find the right combination of gears to cut a particular thread pitch?"
The problem with jewelry sized screws is that for the screw you're using silver or gold and the wire won't take the side pressure of a cutting tool--it bends before you can get the threads cut. My dies are about 1/4" in diameter, and I made a die holder sort of like a pin vise. I cut very slowly by hand, no more than what is effectively 15 RPM.
For the screw hole you have to have a tap, since there's no way to get an internal thread cutting tool inside a hole which is less than 1/16" in diameter.
>> The problem with jewelry sized screws ...
I didn't realize you were talking about jewelry. I was reacting to your comment about a handscrew.
>> ... the wire won't take the side pressure of a cutting tool ...
>> For the screw hole you have to have a tap ...
It's true that I was thinking of cutting larger and more robust workpieces. But it's also true that with a thread cutting lathe and a few other tools, you can make your own taps and dies in whatever thread pitch you like.
If you're working in gold and silver, would a steel screw of the right size serve as a tap?
Use a type "F" screw.
Here fishy fishy....
Not really, because there's no flutes for the cuttings to go into. You can take a hardened screw and cut or grind flutes in it but it's cheaper and easier to buy a tap.
>> ... 26 pitch left hand on one end and 25 pitch right hand on the other ...
There is one application in which such a thing could actually be useful, other than for protecting the product line. That's a differential setup for very fine linear movement, such as focusing. If every turn of your focus screw moves the lens forward 1/25" but at the same time pulls it back 1/26", the net forward motion is 0.001538". If you put a knob with 50 divisions on the screw, then each mark on the knob represents about 31 microinches.
That's a great idea. I'll file it away for future use. Rob
Just the type of application I was thinking of.
Change it with a Heila-Coil. Piece of cake.
Here fishy fishy....
What to say about run-out with a helicoil? You better look for someone with a decent lathe.
For a hand cranked press and done right... No way...
Here fishy fishy....
Helicoils only come in standard sizes like sparkplugs, and 1/2 x 26 isn't one of them.
What's/Who's the manufacturer NEWTRVA, and any idea of age.
I've got a ton of spare parts here.
Cheers,
eddie
To second Eddie.
the two key questions are how old is the machine and who is the manufacturer?
If it's older than about the mid 70s then it is very unlikely to be a metric thread unless the tools originated in Europe.
If it pre-WW2 then it's almost certainly one of the British "standard" threads. All I know about these is that some were a bit weird. Whereas Metric and American spanners are sized according to the size of the nut, Dad's got a set of English spanners that are sized by the thread make and diameter – the size of the nut used on a 1/2 bolt varied according to the thread pitch. for example a spanner marked 3/8 W is for the nut on a 3/8 Witworth threaded bolt.
Assuming that you have the actual thread pitch and diameter and not a nearly there match you may find a suitable chuck on a UK web site.
Older Miller Falls had those chucks. Check out flea markets as these 'Egg Beater' hand drills are cheap and still around
Stein
Thanks for all the replies. The drill press was made by Silex Tools. According to information on the web, these tools were made in Australia by Howard F Hudson Pty Ltd. By its looks I would say it is about 40 or 50 years old. I measured the shaft with calipers and it seems to be 1/2 inch. A 1mm thread gayge does not match, but a 13tpi gauge fits perfectly in every other thread, observed under magnification. I will try to work out a solution that does not involve cutting my "antique".
Silex were pre-metric, so it's an imperial thread, probably (potentially ?) an instrument thread as I believe that they were instrument manufacturers during WW2.
This chuck is common - you could substitute one from an eggbeater drill of a similar vintage.
Cheers,
eddie
Just a thought-- have you tried screwing a 1/2 x 13 NC nut on your shaft? If it goes on, you could get or thread a chuck to fit? Keep us informed. Rob
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