Chinese Whitworth?

I have a Clark CMD1225 mill/drill which is, I believe, a ZX25 clone
made in
Taiwan. Their current version is the CMD1225C which, I'm told, is made
in China.
I'd always assumed that the screw threads were UNC but, when I tried
to fit
new 1/2" UNC nuts to the column clamp bolts, they didn't fit. The
measure 12 TPI, i.e. 1/2" Whit pitch (UNC is 13 TPI); so do the 1/2"
cap screws which bolt the column to the base.
Is it common for Taiwanese/Chinese m/c tool manufacturers to use
Whilst on the subject of Whit and UNC (for diameters where the thread
are the same) I've read lots of dire warnings about mixing male and
female of
different thread forms. I'm quite sure that I've occasionally mixed
them and
not noticed any resultant problem but they haven't been precision
torqued to the eyeballs.
Has anyone had known problems when mixing thread forms?
Reply to
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How do you check the thread form? From having to identify unknown threads at work for either 'homework' jobs to millwrights not knowing what to order as replacements I would suggest your Chinese Whitworth is in fact a M12 x 2 thread? I would think that most Chinese threads would be Metric. Most US threads being UN and European being either Metric or Imperial. There are many different thread forms out there and are not just Whitworth or UN. I use a shadowgraph at work which I know is not the type of kit you would have at home, thread 'combs' are ok but not totally reliable.
As for mixing thread forms, yes you can if you are desperate but I wouldn't, as it's simply not good engineering. Joseph Whitworth (
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) introduced standardisation for a reason, i.e. to make things standard so interchangeability can be achieved.
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Greetings Bob, 1/2-12 is an obsolete thread form that was used in the USA. It is a 60 degree thread form. Taps are still available. I have only seen this thread on old machines and taiwanese machines. Cheers, Eric
Reply to
On or around Wed, 27 Aug 2008 14:28:42 -0700 (PDT), BobKellock enlightened us thusly:
similar machine here has typically-bad metric threads. The cheapo machines often have poorly-sized or poorly-made nuts and bolts.
Reply to
Austin Shackles
I also have a problem with non-standard 'standard' parts on my recently obtained Warco A1S knee mill - not with the nuts'n'bolts, but with the drive belts.
The original belts are clearly numbered B35 & B41, I obtained replacements from the local branch of BSL and the new ones are miles too long.
I've just completed the New enclosure for the VFD from my old mill/ drill - this week I got it fixed to the wall, changed the motor and wired it all up.
I spent a lot of time yesterday packing out the motor mounts with spacers to take up the slack but even with the extra inch or so that I gained the belts are still far too slack and I cannot move the motor back any further due to it fouling the rear of the belt guard - I guess I'm just gonna have to get some more belts.........
Has anyone else had this problem? - if so what is the correct belt size and type.
Thanks and Regards
PS - I hope that this message is not considered to be off topic - if so I apologise to Bob........
Reply to
I had the same problem on my A1S. My local "Belts and Bearings" chap "lent me" a selection of British "B section' belts, after he measured the originals and said they weren't the size printed on them.
By a series of trials and errors, I managed to get two that allowed adjustment, if a little tight to get on the pulleys.
Next size up on either belt and I run out of tension adjustment on the motor "swing". As I have a VFD./3-phase motor set-up, I seldom change the belt unless using a very much larger/smaller end-mill/fly cutter.
My belts sizes are now :- B39 Spindle to Mid. B34 Motor to Mid.
Regards Andy
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Oh. I should also say that, according to the same expert, the pulleys on Taiwanese & Chinese Machine Tools aren't always correct to profile. The (supposedly) "A" section pulley on my lathe motor allowed the belt to sit near flush. He said it was newarer "agricultural profile" than "A". When I replaced the 1-phase motor with a 3-phase/VFD on my Warco 1327 lathe (Taiwanese) I had to get a new pulley to suit the motor spindle size difference. Despite packing the new motor out to give the same spindle position, I had to source two new belts one size up.
BTW. Same expert said his belts are actually measured in metric and labeled to the nearest inch. When I was sourcing a belt for another application, he was able to calculate the belt size for me if I gave him the pulley diameters and centre to centre distance. He converted my imperial sizes to metric first. Even so, the size calculated was one size too small in "Inch belts".
Reply to
Load of rubbish.1/2" x 12 tpi is BSW or British Standard Whitworth and it is 55 degrees. USA have never used 12 tpi preferring 13 tpi x 1/2" for UNC threads.
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Fine. Whatever you say. I guess my antique lathes were threaded Whitworth but the idiot doing the threading thought that Whitworth threads were 60 degree thread form. Just for kicks try looking at Machinery's Handbook for the thread info. My 1918 edition has 1/2-12 listed as do my 1980s and 1990s editions. And taps are still available. Try
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. I guess J&L are making Whitworth threads with 60 degree thread form too. ERS
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You need to re-apraise the way you read Machiery's handbook then. My 1923 Edition lists only 1/2" x 13 in the "United States Standard Thread" but it does list 1/2" x 12 in the non-standard 'Sharp 'V'' form.
The latest edition still makes a reference to the Sharp V form but it amounts to only 6 lines and comments upon the form being non-standard.
The Unified form in both Course and Fine series is what one would take as the reference when discussing Screw Thread Series today and under that standard 1/2" has always been 13 tpi - from 1/8" upward it is the only one in the series that differs from BSW and that's the reason it stands out.
The form of the thread essentially has no connection with the diameter/pitch relationship of any thread series so it is fatuous to refer to a 60° 'Whitworth' form.
Just because J&L offer 1/2" x 12 taps does not mean that they are 'Standard'.
Machinery's Handbook also lists the elements of the 'fixed pitch' series which includes 12 tpi bu oddly enough it starts at 9/16" - so 1/2" x 12 doesn't even qualify there.
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Of course 1/2" x 12 tpi are listed.It`s a standard thread.Not preferred anymore but a standard just the same.If you look at a British built machine,made pre 1970 it will be all BSW with a bit of BSF. As for finding BSW with 60 degree threads,no chance because if they`re not 55 deg. there not BSW.
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Where does it say on the description that they are 60 degrees?
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It doesn't. But I bought one of these a while back to make some nuts for a Taiwanese grinder. ERS
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My 1920s Lorch-Schmidt lathe has a mandrel thread which has OD 0.995" and using one of those thread gauges (not a projector) appears to be about 10tpi. It's not BSF (as for some reason I have a 1" BSF tap) and it looks like the included angle of the thread is 60 degrees rather than 55. I've never managed to find a standard thread of this form (UNC is 8tpi and UNF 12tpi). The rest of the lathe is metric with right handed 1.5mm pitch screws on tailstock and slides.
Is this likely to be a Lorch-Schmidt special?
Reply to
Alan Bain
I think 1"-10 is a fairly common lathe spindle thread, especially for wood lathes. All these odd thread discussions are interesting to me. You have to understand that most of the "standards" seem to be for fasteners such as nuts and bolts but a lot of other things are threaded also. I personally think that threads range all the way from "only one example known" or "does not come out to any known common dimension or pitch" to "only known to be used by one manufacturer on one product" all the way to "billions and billions sold".
I think it would be cool to thread a rod .864"-17 1/5 tpi with a 23 degree thread angle on one side and 38 degree angle on the other. (Now that I think about I believe one of my first threads was something like that :>).)
I have quite a few taps and dies that do not conform to the current recommended standards but I am sure that they were used somewhere at some time.
Don Young (USA)
Reply to
Don Young
On or around Fri, 29 Aug 2008 21:05:43 -0500, "Don Young" enlightened us thusly:
You presumably all know that Whitworth, which is one of the earlier thread standards, was arrived at by Whitworth collecting together all the examples of threads he could find and taking an average.
Prior to the adoption of widespread standards, people just cut whatever thread they had the tool to make.
Then you get funny things like the cycle threads, which are (almost) all 26 tpi, regardless of size.
I've got a big table somewhere with all the threads in (well, most of 'em)
Reply to
Austin Shackles
On or around 29 Aug 2008 21:59:43 +0100 (BST), Alan Bain enlightened us thusly:
It's probably some sort of special if it's not BSF - the only 1"x10tpi in my list of threads is BSF.
.995" is not 25mm though, so I doubt it's metric.
Mind, you get silly threads. I know something with M30x1.0 on it, and AFAIK I could if I wanted to spend enough money get a tap for it.
I've also seen M10.5x1.0 on cycle hubs.
Reply to
Austin Shackles
How true! I just spent a while cutting 100's of M79.50 x 1.5 pitch on some brass spinnings.
Reply to
Wayne Weedon
...and I've had to make some replacement parts with 10mm x 26 tpi threads. Mixed standard threads like that do crop up from time to time, just to confuse us.
Reply to
Tim Leech

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