Which steel for studs?

[John McCullaParticipant @johnmcculla]

I’m hoping to make some 9/16″ studs, 4″ long, UNF on one end, UNC on the other. They hold the hydraulic pump in place on a Ferguson 35 tractor. My question is this, what steel should I use for this? I only have EN1A round bar ATM, and I assume something a bit stronger is needed.

Any advice is much appreciated!

[Brian WoodParticipant @brianwood45127]

Hello John,

What you have will probably do, but I would be tempted to improve the spec a bit and use some EN8

Regards   Brian

[AStroudParticipant @astroud]

If the pump flange has no rotational location on the mounting housing the studs need to provide the necessary friction grip when tightened to react the pump shaft torque and in my opinion EN1A should be fine to allow the necessary stud tightening torque. Going to a higher spec material will allow a greater tightening torque but with the risk of pulling the studs out of their threads though at 9/16″ you would need to go some on the torque wrench to cause such damage.

[SillyOldDufferModerator @sillyoldduffer]

Any answer will be guesswork unless someone knows what stress the stud was designed to take.

So, consider what happens if a stud breaks?

• If nothing expensive, dangerous or horribly inconvenient can occur, and EN1A is to hand, then use it.  Not because EN1A is the right answer, but because it’s easy!
• If a stud breaking might cause havoc, then play it safe and use the stronger material, which is EN8.

EN1A’s advantage is it’s a delight to machine.   EN8 isn’t so nice but it’s cheap and nearly twice the strength of EN1A.

Seems unlikely here, but beware: if the stud is safety critical, then EN8 with cut threads is unlikely to be ‘good enough’ and an alloy steel with rolled threads might be needed.

Dave

[duncan webster 1Participant @duncanwebster1]

You can’t specify a material unless you know the stress it will be subjected to. ‘Studs have to be strong’ is a knee jerk reaction. Assuming it screws into a cast iron gearbox , most of the load will be taken on the top couple of threads, so there is no point having the stud stronger than the cast iron. I’d use your EN1, a lot easier to machine to  a decent surface finish.

If you look up typical uses of EN1, then studs is in the list.

[densleighParticipant @densleigh]

Why not try Sparex.com  – they supply parts and pieces fro your tractor.

 

No Connection except as a customer

[old martParticipant @oldmart]

You could dangle the whole tractor from one 9/16″ stud, so simply holding on a hydraulic pump would be within the capabilties of any steel alloy.

[Neil LickfoldParticipant @neillickfold44316]

Buy the UNC long capscrews that will have the rolled thread for attaching to the cast iron part. You can screw cut the UNF thread for the nut side of the part. If you use a full form UNF insert, you will have the correct root radius on the thread form. The most common failure of fasteners I have seen, is too small a root radius being used on the thread form. The 12.9 capscrews are not difficult to turn and cut a thread on the plain shank end. You can create the long run out with the end of the thread form as well,(Wind out at a constant rate and then stop)or use a generous R2mm tool to create the thread end undercut.

Neil

[old mart]

On old mart Said:

You could dangle the whole tractor from one 9/16″ stud, so simply holding on a hydraulic pump would be within the capabilties of any steel alloy.

I thought that as well, but didn’t want to say it. 🙂

Tony

[noel shelleyParticipant @noelshelley55608]

As Neil has said, buy long bolts in unc and cut down, 8.8 will be fine, 12.9 is a bit over the top. Noel

[FulmenParticipant @fulmen]

Underestimate the strength of modern machine bolts at your own peril!

A tractor engine is hostile territory. High loads, thermal cycling, vibrations and heavy handed mechanics subject all components to constant punishment. You should always follow (or exceed) OEM ratings when possible.

I would start with partially threaded machine bolts in a UN grade equivalent to 10.9 or 12.9 (‘m clueless when it comes to UN fasteners, but I’m sure you’ll figure it out). These grades are though as heck but still machinable (with carbide tools at least) and should be on par with commercial bolts downgraded one level.

 

[David George 1Participant @davidgeorge1]

The original studs were threaded diferent threads on each end for a reason. You should use a course thread into cast iron housing for thread streangth and the other end should have a fine thread which should has a fine shallower thread with a High tensile nut which will resist vibration causing it to unscrew. You could always use EN16 T  steel which is slightly stronger than EN8 steel.

David

[Tony Pratt 1]

On Tony Pratt 1 Said:

On old mart Said:

You could dangle the whole tractor from one 9/16″ stud, so simply holding on a hydraulic pump would be within the capabilties of any steel alloy.

I thought that as well, but didn’t want to say it. 🙂

Tony

I’m dreadful at sums, but I think a 9/16″ EN1A rod passes the yield point at about 3 tons, after which it’s permanently deformed.

The problem is we’re all guessing.  I agree EN1A should be OK for this purpose but I guess we’re all assuming the stud doesn’t need to be strong, perhaps because we expect this to a restoration project and the tractor isn’t going to be worked hard. Might think different if we knew how the stud related to the pump and tractor.  For example, did Massey Ferguson specify strong studs because the hydraulic pump subjects them to a powerful pulsating load that causes fatique cracking?

John didn’t say why the old studs have to be replaced.  I assumed rust, but what if they broke in service…

Dave

[FulmenParticipant @fulmen]

@Dave: I think that “the weakest link” rule will apply here (unless the friction coefficient of the coarse threads are  higher). EN16 sounds like a decent material, closer to what I would expect from something like 10.9 or 12.9 bolts. Again, I know nothing about UK steels so while I can look them up I don’t know enough to recommend any.

[DiogenesParticipant @diogenes]

Which studs are these?

Isn’t the pump secured by a couple of dowels / pins?

[David George 1Participant @davidgeorge1]

Have a look on here.

https://borderagriparts.co.uk/product/pto-stud-kit-716-unf?gad_source=1&gclid=Cj0KCQiAoae5BhCNARIsADVLzZcy3SoRM8VJgv1vWrNk8RE8qU3TVmMBLam1E6e-HlDxuQbzEeis1roaAniCEALw_wcB

David

[noel shelleyParticipant @noelshelley55608]

Many cars in the 60s had coarse and fine threads on the head studs eg, BMC B series engines. The fine thread will give a higher tensile load on the stud at a lower torque on the nut. I’ll check the Ferguson manual later. Noel.

[duncan webster 1Participant @duncanwebster1]

Surprisingly it doesn’t make much difference within sensible limits. Most of the torque is absorbed in friction under the nut and in the threads. I have a very erudite paper about it, too techy to reproduce here, but the conclusion is that thread pitch doesn’t make much difference to the relationship between torque and tension.

[ChrisLHParticipant @chrislh]

Duncan’s point explains why it is such hard (and inefficient) work raising your car using the usually supplied screw jack.

[noel shelleyParticipant @noelshelley55608]

Hi John, are you sure the studs are 9/16″ and not 9/16″ AF nuts/heads ? 3/8″ dia ?  I have read the manual and the pump is a floating assembly carried or restrained from rotation by dowels. 9/16 dia, certainly nothing that big in there that I can see. Noel.

[John McCullaParticipant @johnmcculla]

Hi everyone, thanks for all your replies and helpful advice.

Firstly my apologies, I accidentally typed hydraulic pump (I don’t know why), but what I should have typed was hydraulic cylinder. This hangs on the underside of the top lid and moves a piston, which in turn is what lifts the link arms on the back of the tractor. I imagine it experiences a reasonable amount of force in normal use, however this one broke the aforementioned studs because the relief valve failed. When this happens they can even break the top lid in two, so breaking the studs was probably the better option.

As to why I can’t just buy them from Sparex or someone else is because they don’t seem to be available. Agriline do supply the studs (https://agrilineproducts.com/massey-ferguson-hydraulic-cylinder-stud-9-16-4-unf-4026), but they’re a different thread and only work with the cylinder they supply, meaning you have to buy both. They are still available from Massey Ferguson dealers, however they are a truly astronomical price (approx £180 for the four studs).

A friend asked me about making some because he needed the tractor repaired in a hurry. I wasn’t able to do it time, so he had them made at a local precision engineering business, but I was curious as to what would be the best approach to take, hence my post.

[bernard towersParticipant @bernardtowers37738]

If the PRV is a common problem then EN1A studs are the way to go if its going to save more expensive bits.

[duncan webster 1Participant @duncanwebster1]

As its a cylinder, working out the stress is easy if you know the cylinder bore and working pressure. Then you can decide on a material.

[noel shelleyParticipant @noelshelley55608]

For your own idle curiosity using 1 ton/square inch and Pi R squared to give the piston area you can get some idea of the normal max working load, may well be about 10 tons. More important is why did the relief valve not open ? Muck or rust ? The internal pump is quite small and it’s delivery is 2.8 gals/min, to small to operate external power at a reasonable speed. Good Luck. Noel.

[Howard LewisParticipant @howardlewis46836]

The loads imposed on the mounting bolt of a hydrulic cylinder for a three point linkage can be quite high.

What weight do you expect to lift?

What is the mechanical advantage of the linkage?

Load x M A will tell the magnitude of the load on the fixing.  Then build in a safety factor!

Essentialy, as a pivot, the stud will be loaded in shear, so the grade of steel needs to have a high shear strength, (Greater than plain mild steel, I suspect) although 9/16″ diameter will take a lot to shear, but I still wouldn’t use mild stee).

If it is any help, a 1/2 UNF bolt made from W range steel will take a tensile load of 7 tons to put into yield and take a permanent extension. Probably that would be my starting point

Better to be too strong than too weak with the dire consequences of that!

You might even be able to find a suiutable stud, already used on a tractor somewhere (Spares for vintage tractors? Lots of dealers at tractor shows).

Howard

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