Whitworth thread form.......55 degrees.........supposedly.
ET: Engine (Twin) Black Shadow Crankcase Threads
- Thread starter RayF
- Start date
There was an awnser by mr trever clever about this.
I dont know the top angle 55 or 60 degr.
But understood it was slightly bigger as the mentioned normal diameter.
But why PEI did that i don't have a clue.....
I looked some spindles up under the microscope. But the threads are very different when looking up 10.
So i ordered a tap 0.006 bigger 55 degree.
That fits in a standard hole.
Have a andy molnar cases and at first the rods did not fit, but they do now.
Might have been easyer to skim them threads on the spindles....
Cheers on a beautifull Norfolk Sunday morning.
I dont know the top angle 55 or 60 degr.
But understood it was slightly bigger as the mentioned normal diameter.
But why PEI did that i don't have a clue.....
I looked some spindles up under the microscope. But the threads are very different when looking up 10.
So i ordered a tap 0.006 bigger 55 degree.
That fits in a standard hole.
Have a andy molnar cases and at first the rods did not fit, but they do now.
Might have been easyer to skim them threads on the spindles....
Cheers on a beautifull Norfolk Sunday morning.
I notice that Andy Davenport has a constant Ebay listing for ET55/2 High Tensile Stainless Steel Head Bolt Sets, CNC Machined.
I would assume that he would know the exact specification, thread form and diameter.
I would also assume that Andy Molnar would have this information.
That is if it has not been definitively ascertained already.
I would assume that he would know the exact specification, thread form and diameter.
I would also assume that Andy Molnar would have this information.
That is if it has not been definitively ascertained already.
i'd suggest to stop and think about suitability of 5/8" BSF or any custom larger thread. given the scenario where the head joint needs to be lapped in. That larger thread needs to pass through the muff to enable lapping, unless you have two piece cyl' / head stud. Or , should the muff liner be firmly fixed in the crankcase halves. A relatively simple job becomes a split case job just for access.
Also with regard heli coil repair, how's that going to work on the rear pot rear right stud.
Also with regard heli coil repair, how's that going to work on the rear pot rear right stud.
Looking at options for repair I´d suggest having an adapter in the engine case with any thread oversize according diameters available from the stripped thread in engine case metric or not. I don´t remember if I had to tap some new threads in the case but made adapters from alu 7075 to go with M 10 x1.5mm standard studs at bottom and M 10x1 mm for top nuts. So then once you repaired the case you can do more options:
Either get available studs when you tapped your adapter for standard studs - BSF likely - or any other thread. Those who run big bore Vincents reportedly got 10 mm studs as not a lot of space available with big bore cylinders too close to old through holes with their enlarged diameters for positioning components from top to bottom. 10 mm seems quite up to the job obviously.
I did not like that idea of positioning and slipping components all the way down or up in the through holes over the long stepped studs. Japs have never done this but had short hollow dowels for positioning, cylinders, heads, engine cases, all of this. You can do this as well with 10 mm studs, just make some short hollow dowels and loctite one half in one component. So the 10 mm stud will just slip through, no positioning from it, this is the dowels´ job - and easy to assemble. So the original stepped studs look a bit nonsense and a nuisance in real life.
Another way is to loctite hollow dowels onto 10mm studs in strategic places copied from originals if you want to keep the slipping top end components over the lot like before. So no turning operation for special stepped studs necessary.
I did all 10mm studs with thread rolling heads on stainless, some titanium in some places too. But actually , when not rolling threads I have gone from die cutting to lathe cutting tool when having stainless or titanium external threads to do. Threads come out a lot cleaner than trying same with used dies.
Again amusing for me reading once more discussions about identifying obsolete threads when repairs are the subject. Would not care at all about original as you have to do a repair anyway, so you better choose the economic option. And don´t worry about a large repair thread in the engine case, it will be a lot stronger , even when close to edges in some places. The adapter will hold then pull of the smaller stud easily - and don´t overdo the top nuts: The ht steel studs will get even more loads when the engine and all alu cylinder and head heat up !! I will try extra low torque on top nuts, by hand feel certainly , no torque wrench ever used on bikes !
Vic
Either get available studs when you tapped your adapter for standard studs - BSF likely - or any other thread. Those who run big bore Vincents reportedly got 10 mm studs as not a lot of space available with big bore cylinders too close to old through holes with their enlarged diameters for positioning components from top to bottom. 10 mm seems quite up to the job obviously.
I did not like that idea of positioning and slipping components all the way down or up in the through holes over the long stepped studs. Japs have never done this but had short hollow dowels for positioning, cylinders, heads, engine cases, all of this. You can do this as well with 10 mm studs, just make some short hollow dowels and loctite one half in one component. So the 10 mm stud will just slip through, no positioning from it, this is the dowels´ job - and easy to assemble. So the original stepped studs look a bit nonsense and a nuisance in real life.
Another way is to loctite hollow dowels onto 10mm studs in strategic places copied from originals if you want to keep the slipping top end components over the lot like before. So no turning operation for special stepped studs necessary.
I did all 10mm studs with thread rolling heads on stainless, some titanium in some places too. But actually , when not rolling threads I have gone from die cutting to lathe cutting tool when having stainless or titanium external threads to do. Threads come out a lot cleaner than trying same with used dies.
Again amusing for me reading once more discussions about identifying obsolete threads when repairs are the subject. Would not care at all about original as you have to do a repair anyway, so you better choose the economic option. And don´t worry about a large repair thread in the engine case, it will be a lot stronger , even when close to edges in some places. The adapter will hold then pull of the smaller stud easily - and don´t overdo the top nuts: The ht steel studs will get even more loads when the engine and all alu cylinder and head heat up !! I will try extra low torque on top nuts, by hand feel certainly , no torque wrench ever used on bikes !
Vic
I think that I have misunderstood some of what Brian wrote above in #15. There is no need to take either the heads or muffs over the lower threads in the ET55/2 or to take those out of the crank cases with the heads and barrels still in place.
if you wished to slide the barrels up and over the in situ studs because for what ever reason the barrels cannot be parted from the cases, the recourse would be a jamb nut on the exposed thread of the stud and unscrew.
To precis my original post: does the stud hole in the barrel have sufficient clearance for a 5/8" BSF threaded stud to be withdrawn.
Sorry Simon, Cycle Threads are all 60 deg. There is a BSB (Brass) thread that is 55 deg. Whitworth form but they are not really compatible but will fit.
I made my Titanium cylinder studs to the same dimensions as the originals which have very long threaded portions with an oil groove in the middle. I turned them on a friends lathe because his better lathe had a thread cutting gearbox and finished them with a hand chaser. A brand new Tracy tools HSS die just broke up when I tried to just finally size the threads, hence the hand chaser. Stupidly, I did not complain or send the die back as I should have done.
I just torque my aluminium head nuts to 30 ft,lbs and have never had any problems on my highly tuned Racer.
I made my Titanium cylinder studs to the same dimensions as the originals which have very long threaded portions with an oil groove in the middle. I turned them on a friends lathe because his better lathe had a thread cutting gearbox and finished them with a hand chaser. A brand new Tracy tools HSS die just broke up when I tried to just finally size the threads, hence the hand chaser. Stupidly, I did not complain or send the die back as I should have done.
I just torque my aluminium head nuts to 30 ft,lbs and have never had any problems on my highly tuned Racer.