9/16 nut help!

Hello again everyone,

So the continuing saga (farce!) with fitting a QCTP to my lathe continues.

I sourced a stud from Little Machine Shop in the US and it fits right over my standard stud - it has a M8 tapped internal thread which works perfectly. So I fit it, and slide on the QCTP and try on the locking flange nut at the top - and guess what!?!? Yep / it doesn’t fit!!!

The one supplied in the arceuro QCTP is 14mm (9/16 UNF) and the LMS stud needs a 9/16-18 flange nut - seriously- you could not make this up!

Can anyone help me please with a 9/16-18 flanged nut? To buy one from the US is circa $25 plus about the same post. I cannot justify that.

Any suggestions most gratefully accepted. Fed up doesn’t come close!

Many thanks

m

Dear Margaret,

I will have 9/16th dia FULL nuts but I think that they will be BSF. I may also have a 9/16th UNF tap. I will check what I have got later this afternoon or tomorrow morning. Don't despair!

John

Dear John

Thank you so much. I am not sure what 9/16-18 (UNF or whatnot) means but it’s what the LMS stud is threaded with.

Best wishes

M

9/16 inch outside diameter of the thread, 18 threads per inch; UNF stands for Unified National Fine and is one of the American "UN" series industrial standards for screw-threads.

UN-series threads were fitted to a lot of motor-vehicles and military equipment in the UK at one time and the fastenings are available here; though perhaps not flanged nut. You might even be able to obtain one from a garage! It does not need be flanged though - use an ordinary full nut and a thick washer.

9/16 BSF has 16 threads per inch and a 55° thread form

9/16 UNF has 18 threads per inch and a 60° thread form

I suggest you need to use the correct nut

MichaelG.

.

Post crossed with Nigel’s

Edited By Michael Gilligan on 24/09/2023 13:09:34

9/16 UNF nuts are readily available in the UK.

Tony

What size are H-D cylinder base / head stud nuts?

I'm not sure how important it is to have a flanged nut, you could turn up a thick washer and use that in place of the flange with a plain nut on top, not too expensive

There are loads of 9/16 UNF nuts on ebay.co.uk

With or without flanges, and a few interesting ‘specials’

list them with cheapest with p&p first …and take your pick

[ some are ‘stiff-nuts’ … which may, or may not, be useful ]

MichaelG.

Margaret, I think you're getting your threads a a bit mixed up.
The ArcEuro tool holder looks to be this one which on the spec sheet says the thread is M14x1.5mm
Yes, the 14mm diameter is about 9/16" but it's not an imperial size.

The LMS version on sale, I assume is this one; it specifies 9/16" x18 tpi, which is a UNF thread.

The actual toolposts are probably the same, it's just that the fixing post is a different thread.
Traditionally the UK used Whitworth/BSF threads on machine tools etc, whereas the USA uses Unified.
The diameters may be the same size, but the thread forms are different.

Most of the rest of the world uses Metric, which is why many of the far eastern tooling imports feature metric threads; hence the same QC toolpost marketed in the US uses a 9/16" x 18UNF thread, and our version often uses the M14 stud as it's cheaper than having BSF ones made specially for us, as almost no-one uses it any more.

Your local car spares will likely have a 9/16" x18 UNF plain nut, which you can use with a thick washer for the time being; You could even use a Nyloc nut and turn off the plastic locking ring.

Your local Landrover spares counter will almost certainly have the Nyloc ones, as they are used for leaf spring shackle bolts; N.B. make sure you specify the thread to them, as they may also stock BSF (& metric).

Longer term let me have your address and I'll knock one up, but I'm not using the workshop at the moment, as I await new specs following a cataract operation; I'm not safe using machine tools at the moment.

Bill

From what I've seen of industrial machines common practice with Dickson QCTP is to use a plain nut, a thick washer and a thick wall spacer loosely spigoted into the toolpost bore. The spacer being needed to lift the nut above the tool clamp screws.

I do know of folk whose opinion I have reason to respect advocating a second, standard thickness, washer under the nut in addition to the aforementioned thick one. I have never seen a flange nut used. My instructors said that the sole use for flange nuts in a machine shop was with mill table clamping kits.

I imagine the reasoning behind the use of a thick washer on top of the spacer was to spread any twisting loads as the nut was pulled down tight so the post itself doesn't try to turn. Observation of the Dickson set-up on my big Pratt & Whitney lathe seems to support this idea as both washer and spacer turn slightly with the nut on final tightening but lag. So the top washer turns less than the nut and the spacer less than the washer whilst the post says still. The turn angles are small, little more than barely enough to see and probably wouldn't be visible on smaller machine where the tightening torque is proportionally less.

I don't use a locating pin or underneath ratchet on my tool posts but I do require that the post sides stay in alignment with lathe cross slide and bed.

Whether the distribution of frictional forces to reduce the chance of a toolpost turning actually matters in practice I know not. I don't recall any such post twisting effects when using a simple standard washer under the nut of the tool post stud on my SouthBend lathes. Simple hand holding worked just fine.

Clive

Hi, they are also available from Spalding Fasteners. If it was me choosing one, I'd go for the yellow one. A thick washer can easily be made from a piece of flat steel, cutting it out with a suitable size hole saw, and then drilling the hole for 9/16" clearance, and then just tidy it up with a file.

Regards Nick.

Edited By Nicholas Farr on 24/09/2023 14:07:09

If you don't have thread gauges then a standard M10 stud or screw will have a 1.5mm pitch. If you have one you can check it against your unknown thread like using a thread gauge to see if it is also a 1.5mm pitch thread. An M10 thread will not match an 18 TPI imperial thread form.

Martin C

Hi all,

thanks for your replies. I agree a non-flanged nut with a thick washer would probably be fine.

can’t remember which chap said 9/16-18 are readily available in the UK - I have not been able to find any. Would you be kind enough to post a link please?

many thanks

m

Nicholas - thanks for the link to Spalding.

are these 9/16-18? Seems to suggest so in the spec if I am reading it corrext. Apologies for the seemingly naieve reponse but I have no engineering knowledge at all.

**LINK**

many thanks

M

.

As recently stated:

There are loads of 9/16 UNF nuts on ebay.co.uk

With or without flanges, and a few interesting ‘specials’

list them with cheapest with p&p first …and take your pick

[ some are ‘stiff-nuts’ … which may, or may not, be useful ]

.

Do you need a link to an ebay search ?

… I think this might do it:

https://www.ebay.co.uk/sch/i.html?_from=R40&_nkw=9%2F16+unf+nut&_sacat=0&_sop=15

MichaelG.

Edited By Michael Gilligan on 24/09/2023 14:23:20

Just Google search 9/16" UNF nuts

Tony

I recommend buying a copy of Tubal Cain's "Model Engineer's Handbook" (Link is to Waterstones' - other suppliers available. Many 'what-nots' are explained!

Margaret has bumped into the 'which standard system' problem, and it's worth thinking about. Briefly:

• British Engineering was originally based on the Inch, and standardised on Whitworth Threads. (aka BSW). Later BSW, which is a coarse thread, was found wanting for many purposes and the system was expanding by adding a fine series (BSF). This too was found unsatisfactory for Instrument and Electrical Work, so a third system, not remotely Whitworth, was added - BA. None of these are interchangeable.
• In the USA, also based on the inch, it was immediately noticed that Whitworth threads are over complicated, so the Americans adopted a different standard - the National Thread. Their system also added finer threads later on. National and Whitworth threads are similar but not compatible.
• The rest of the world went Metric, based on the metre, and produced a third system of threads. These don't match US or British sizes.
• During WW2 considerable trouble was caused when it was found British and American fasteners were incompatible - Margaret's QCTP incompatibility problem on a grand scale, with Tanks, Guns, Aircraft, Ships and machines of all types out of action due to minor technical differences. By agreement, the US and UK both adopted the Unified System, which is mostly the US National System, based on the Canadian Industrial Inch, which was 25.4mm. Almost universal in the US, and for a short time, UNC and UNF became common in the UK.
• After WW2 it became increasingly apparent that the Metric system has many advantages. Thus almost the whole world went metric apart from the USA. The UK chose to metricate slowly, gradually abandoning BSW, BSF, BA, UNC and UNF. Extending the pain badly damaged British industry. Most British engineering was exported because the UK domestic market is quite small. Foreign customers were not impressed by the mix of Whitworth, Unified, and Metric components sold to them by the UK, whilst confused standards reduced productivity and made it difficult to modernise. Today the UK is mostly metric. New design has been metric for about 30 years and it's slowly but surely becoming difficult to source older components.

So British Model engineers setting up a workshop have choices! My view:

• If the work is restoring old British manufactured items, go Imperial.
• If the work is building models from classic plans, go Imperial. This is especially true of steam locomotives and traction engines because so many good designs are pre-metric.
• If you inherit an Imperial or US English workshop, stay with it.
• Everything else, go Metric. Metric is generally cheaper and easier to source, and the trend will continue. US industry is the last bastion of English measure, and even they are slowly but surely metricating. Inches are a disadvantage when selling equipment outside the US. In the UK importing nuts and bolts, or anything else, from the US is extra expensive - avoid!

Pays to standardise if you can. In practice, it's hard not to work with all these systems occasionally. I do experimental work, where Metric is wonderful, and almost everything I own is standard metric. Imperial repairs aren't the end of my world, except I have to recognise what's needed and do the conversions. However, Imperial is a time-waster compared with the same job in Metric, because I often have to buy or make stuff specially. Metric jobs turning up in Imperial workshops are a similar nuisance. Whatever you do, don't get Metric vs Imperial vs US substantially the wrong way round!

Dave

PS Flange Nuts are ordinary nuts with a built in washer, so you don't have to worry about losing the washer.  If a flange nut can't be found, a washer and ordinary nut work just as well.   Also, flange nuts often come with ridged bottoms designed to grip: don't use this type on a QCTP without a washer underneath, or file the ridges smooth first!

Edited By SillyOldDuffer on 24/09/2023 14:38:48

Guys, I’m getting more and more confused (doesn’t take much!)

As mentioned in my opening post - the arceuro 111 QCTP is supplied with (according to their catalogue) a flanged nut specified as 14mm (9/16 UNF).

The toolpost stud from LMS is specified on their website as having a 9/16-18 thread.

to recap - the nut supplied with the 111 QCTP (specified as 14mm (9/16 UNF) WON’T FIT this stud.

So if I buy a 9/16 UNF nut surely it’s going to be the same as the arceuro nut? Or am I missing something?

Thanks all

M