Thread: Metric threading on Hercus 9A

Originally Posted by RossA

...the part requires ~10mm at each end of a 70mm rod to have 12x1.5 and 13x1...

Pardon me if I'm throwing up a red herring, but from my thread tables, those threads are not standard threads. Are you sure that is what they are?

Michael

Hi Michael,

If they are cylinder head studs that could be correct, though 13 X 1 is almost a gas thread size.

It's just a thought John. The reason I raise it is that the threaded ends will have to go into either a nut or a tapped hole, but if they are non-standard, then how was that matching thread created as taps would not be readily available either?
The item could be a cylinder stud, but typically threads into a casting have a coarser pitch, so I would have expected something like a (more common) M12x1.75. I would also expect a longer length of thread than 10mm either end. While tinkering away in the shed I did find a thread a few weeks back that was x/32"; I think it turned out to be a little used BSF size. 12mm is close to 15/32" and 13mm is close to 1/2" so that set me thinking...
It would be really annoying for Ross to get all set up to cut these threads and then discover that the part he has made does not quite fit. Better to check now.


Michael

12x1.5 is by absolutely no means an uncommon thread in my experience, got plenty of bolts and other bits around here which are that thread, along with taps to suit. Googling "12x1.5 tap" gives pages of results, the first from Sutton.

Many of the common thread tables only list metric 'coarse' threads, and omit other quite common threads in what is sometimes referred to as metric 'fine' (a constant source of headache to me). Even when they DO list a fine pitch, they only list one, and my experience suggests that there is often an even finer pitch in common use than 'fine'. If you play with European vehicles, (definitely Italian ones), you'll very quickly learn of the existence of 8x1.0, 10x1.0, 10x1.25, 12x1.25, 12x1.5, as a LOT of bolts are these threads - and sometimes go into aluminium castings to boot. I've wasted hours of my life trying to remove a stud from Alfa 156/147 gearboxes in order to remove the gearbox and replace the clutch - from memory the thread on that bastard of a thing was 18x1.25, or possibly by 1.5. Up the back of the motor, getting an eighth of a turn at a time at best, and the thread was always thoroughly grown to the aluminium. No matter how much Inox and back and forth you did, it was luck of the draw whether the thread in the casting would come out with it or not. Not uncommon for it to take over an hour to get that one stud out.

The banjo bolts for turbo oil supply pipes can be any of 10x1.0, 10x1.25 or 10x1.5 - all common on various late model vehicles.

You also come across some truly oddball stuff - Alfetta GTV6 lower sump bolts are 7x1.0 from memory, for some absolutely unknown reason given the abundance of both 8x1.25 and 8x1.0 bolts elsewhere on the vehicles. Think I've encountered both 9mm and 11mm fine pitch bolts before too. So while 13x1.0 I would definitely personally class as pretty uncommon, I'm sure it exists and has been used somewhere. Indeed a quick google for 13x1.0 taps does return a couple of results...

All depends on the machine/equipment, the particular location of the thread and its country of origin. Generally continental European and Asian stuff I'd be pretty confident it is metric, but for older British, American and Australia I'd be looking more for a suitable imperial thread. Newer British or Australian, most likely metric again. Anything to do with hydraulics or possible pipe threads - could be anything under the sun.

Around here, 12x1.5 normally wouldn't raise an eyebrow unless I found it on some of the ancient Australian or British crap I have laying around here. (It's happened before, usually someones stripped a bolt and rethreaded, but not always). 13x1.0, highly dependent on where exactly I found it as to whether I'd believe it to be metric or be rather suspect of it being some form of imperial thread.

Originally Posted by Jekyll and Hyde

12x1.5 is by absolutely no means an uncommon thread in my experience, got plenty of bolts and other bits around here which are that thread, along with taps to suit.
.
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Indeed a quick google for 13x1.0 taps does return a couple of results...

This is the solution IMO. Dies are available in both sizes. Gotta be easier than trying to get an imperial lathe to turn metric threads when you don't have the appropriate change gears.

M12x1.5 die (select from drop-down menu):
https://sydneytools.com.au/product/d...BoCprsQAvD_BwE

M13x1 die:
https://www.ebay.com.au/itm/32450881...BoCcJUQAvD_BwE

Originally Posted by Michael G

Pardon me if I'm throwing up a red herring, but from my thread tables, those threads are not standard threads. Are you sure that is what they are?

Michael

Thank you Michael you have pointed out an error in my original post.

The smaller thread is actually M12x1.25 and this has been confirmed with a standard nut.

The larger thread has been confirmed as M13x1.0 by an ex machinist who now sells engineering hardware. He did say that thread was not very common but definitely part of a "standard". An engineer once said to me "The good thing about standards is there are so many to choose from"

To put this into a better picture for you the part I am making is to replace a stand off for the trucks on a pair of roller skates. The original was made of aluminium and he kept breaking it so we agreed to try it in BMS. The large end screws into the sole plate on the base of the skate.

I will look at your links Jack620 and consider the options.

The second part of my journey is to be able to cut metric threads in the future too. So, while I could buy the dies, if I don't invest in the change gears I am limiting my ability in that respect. I already have a reasonable set of metric taps and dies but if I can use the lathe the world is my oyster.

We have a Myford at work with a full set of metric change gears which have never been used so I am looking at using that for this job and will look at Mal's offerings for my lathe.

Cheers,

Hi Ross, Guys,

I too have an Imperial Myford lathe, a S7LB with a quick change gearbox, I don't have any metric gears as such ! But by changing one gear I can cut most metric and BA threads along with some quite strange threads if you get the gearbox settings wrong.

The only gear that is changed is the one immediately following the tumbler gears. I don't recall what number of teeth without going and looking but there is also a couple of charts giving the gear and gearbox settings on the
The home of Model Engineer and Model Engineers' Workshop Magazines web site.

I'm not at home right now, so not able to go and look at mine.

Look forward to that information BaronJ

Cheers,

Originally Posted by RossA

Look forward to that information BaronJ

Cheers,

Have a read of this thread

https://www.model-engineer.co.uk/for...?th=140427&p=1

I have both the 33 & 34 tooth gears, I also printed out the gearbox setting charts.

The weather in Scarborough, East Yorkshire, UK was very nice this last week

Very interesting BaronJ but the Myford gear set is a different beast to the Hercus one so not sure that solution would work straight up.

Have asked a friend to 3D print a set for me so waiting on that as a possible option.

Cheers,

Hi Ross,

I'm sure that I have seen something similar for the "Southbend" and "Hercus" lathes where a gear was changed and the gearbox was adjusted to get various threads. But yes it would depend upon the gear ratios.

Well I finally did figure out what that gear set was intended to be used for. They are the gears for the gear hobber which goes in the mill attachment.

To add to the original list I also have 80, 30 and one or two others as well.

I cannot imagine how many ratio options that many gears selections would give but if I ever need to cut a gear at least I know I can.

Cheers,
Gear Hobber.jpg

Originally Posted by Michael G

While tinkering away in the shed I did find a thread a few weeks back that was x/32";
Michael

Hi Michael,

FWIW 5/32x32TPI, (5/32W) was a very common thread until quite recently. It was frequently used on drawer pull knobs, and, I think, in some 240V fittings. If my memory is correct (it's been a long time), but I think it was also the thread in the spoke nipples on early twenties Austin 7 wheel spokes.

Frank.

There are lots of combinations of gears that will let you cut reasonable threads.
These are the two Hercus used for cutting metric threads, that can be used on a 9A lathe with a standard imperial gearbox.
imp-met.jpg

this may help
............bob