Is it possible to enlarge a nut thread by 1mm?

[jeffberk]

I've located a 26Mx1.5 staking nut. Would it be possible to cut 27Mx1.0 threads into it to make a 27Mx1.0 staking nut?

BACKGROUND: I've been working on a manual transmission rebuild (Nissan FS5W71B) and ran into a problem locating a right hand staking nut. My older transmission used a 27Mx1.0 right hand staking nut (no longer available) to hold everything together while the newer transmissions used a left hand staking nut. I've lost access to the community metal shop due to Covid so I cannot turn my own nut. I ordered a 27Mx1.0 tap as a way to make them if the metal shop becomes available but I was wondering...

My other option would be to reuse my old nut with Loctite and maybe a washer so I can restake the nut at a different location.

 

[rlitman]

I think it would be possible, but might be a lot to chew for the tap in one pass.

Before trying to tap it, I would see what the tap drill size is, and run that drill through it to take off as much meat as possible. I would expect it to take off the thread crests while leaving a nice root groove for your tap to follow. That should make it easier going.

 

[vavet]

Are you sure the thread pitch is 1mm?
I checked McMaster. For 27mm nuts, they list 1.5, 2, and 3 mm thread pitches. It doesn't really matter because they don't have any left hand thread nuts in that size anyway, but usually the thread pitches are standardized.

Good luck though...sounds like a fun, but tedious project. Got any pics?

 

[The Cobbler]

I think you'll end up with a mess of threads . 1.5 to 1 thread will not turn out well, (IMO)
I would try a shim washer to relocate the stake point and do that

 

[cvairwerks]

Quick answer is nope....All you will do is wreck the threads.

 

[APEowner]

That's probably not a good solution. The difference between the major and minor diameters are around 2mm to so you'll end up with a significant amount of the original thread weakening the fastener. Frankly I'd reuse that old nut with a washer if needed. The stake is a safety so the whole thing doesn't fall apart if it loosens it doesn't hold it tight.

 

[The Cobbler]

another option might be to grind a new slot on the shaft to create a new stake area

 

[PugetDude]

Could you just drill out a standard 3/4” SAE nut and re-tap the threads to 27x1.0? Use a thin pattern locknut if space is an issue.

 

[txvwnut]

On those old Nissan transmissions I would re-use the staking nut and tack-weld it to the main shaft. I built a lot of Nissan gearboxes in the eighties and even the improved nut would still unscrew its *** off the shaft. Even saw some of the early left hand thread gearboxes do the same thing.

 

[rlitman]

...1.5 to 1 thread will not turn out well...

Ooh, I missed that. Somehow, my brain had me reading 1.0 to 1.0.

 

[BLUE72CAMARO]

In theory yes i believe so, this doesnt make it a good idea though. 26M nut major diameter should be around 26mm (probably slightly larger though) 27Mx1.0 thread minor diameter should be around 26mm minor diameter. Soooo in theory you could bore the 26mmx1.5 threads out and then cut the 27mmx1.0 threads into it. Again this is all in theory and I suspect you would end up with some fairly loose fitting 27mm threads because the minor diameter will end up on the big side from removing the previous threads.

 

[rlitman]

I think it would be easier to start with an M27x1.0 nut, and figure out how to modify it to be staked or can it be drilled for safety wire?

 

[jeffberk]

OK, it sounds like my best bet, short of turning my own after Covid-19, is to reuse the old nut but add a washer so I can stake it in another spot. Adding some Loctite would help. I'm not sure why thread sealant wasn't used in the original build.
No welder so I can't use txvwnut's suggestion.

 

[Monza Harry]

No welder so I can't use txvwnut's suggestion.

In NE Ohio I can't imagine that you could swing a dead cat without hitting someone with a welder that couldn't use a couple of bucks for a quick tack. That is "speed country" as I remember it. I would look for a FB group and try trading some favours, if you have no fear tearing a gearbox apart and reassembling, you will be able to find someone with a welder and/or a lathe to trade with. Just thinking out load. Harry

 

[Mallen]

In theory yes i believe so, this doesnt make it a good idea though. 26M nut major diameter should be around 26mm (probably slightly larger though) 27Mx1.0 thread minor diameter should be around 26mm minor diameter. Soooo in theory you could bore the 26mmx1.5 threads out and then cut the 27mmx1.0 threads into it. Again this is all in theory and I suspect you would end up with some fairly loose fitting 27mm threads because the minor diameter will end up on the big side from removing the previous threads.

It won't work. The minor diameter of a 27mm female thread is under 24mm

 

[dutchgray]

It won't work. The minor diameter of a 27mm female thread is under 24mm

Not if its 1mm pitch, the tapping drill would be 26mm so if you could bore an M26 nut out and end up not much bigger than 26mm it would probably work, depends on how good you want your new threads to be.

 

[Chrisb62]

Metric drill size is diameter minus pitch so a 27mm nut with a pitch of 1mm is indeed 26mm tap drill. As has been stated by others.
26mm minus 1.5mm pitch is bore diameter of 24.5mm ,so would need to be bored or drilled to start the tap if you so choose this method.

 

[Forgottonia]

You get a long enough cheater bar on that wrench and you won't need to change the threads.

 

[RPH]

Friction weld!

 

[larry_g]

OK, it sounds like my best bet, short of turning my own after Covid-19, is to reuse the old nut but add a washer so I can stake it in another spot. Adding some Loctite would help. I'm not sure why thread sealant wasn't used in the original build.
No welder so I can't use txvwnut's suggestion.

If the washer presents a problem then grinding a bit off the mating surface will allow the the nut to turn on further. Big problem with this is getting the mating surface flat and perpendicular to the center-line of the bore.

lg
no neat sig line

 

[Mallen]

Actually, when you put it back its going to align to a random spot. It may or may not just work out on its own.

 

[Mallen]

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[Jagmandave]

Why do you suppose they back off? Seems like some Locktite red would do the trick if applied properly?

OTOH, $45 for a new one as Mallen posted seems reasonably for a custom made part that's unobtainable otherwise.

I would reuse it, and see if torquing it to the right value would give me a spot that I could stake down - plus I would use some Locktite red on it for good measure

 

[Mallen]

These guys claim to have a part that seems to cross in a UAE warehouse. I'd use a virtual credit card number though. Never heard of them. There's a few references that say they are legit when googled. According to the first link, it's supposed to cross to 32354-a7400. The second link claims to have one.

https://datnissparts.com/x-main-sha...54-a7400-32354-e9800-32354-e9802-32354-e9804/

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[OhioRandy]

Not a good idea. Messed up threads. No strength left. Get a machine shop to turn you a nut.

 

[Mallen]

Not a good idea. Messed up threads. No strength left. Get a machine shop to turn you a nut.

On a regular nut it might work if the dimensions worked out, but the lip on the stake nut would likely be to thin.

Hopefully one of those options I posted will work out.

 

[txvwnut]

Why do you suppose they back off? Seems like some Locktite red would do the trick if applied properly?

OTOH, $45 for a new one as Mallen posted seems reasonably for a custom made part that's unobtainable otherwise.

I would reuse it, and see if torquing it to the right value would give me a spot that I could stake down - plus I would use some Locktite red on it for good measure

They back off as the groove on the shaft doesn't extend past the nut enough so the stake doesn't have much to hold onto. Red Loctite won't work due to the heat and vibration and I think gear oil will break its bond down. When I was doing those boxes on the regular we tried everything we knew of. The welder turned out to be the best option as the heat in the box isn't enough to flow the weld metal.

 

[Jagmandave]

Isn't Locktite red good to 400*? Seems like that should hold it, but I'm not the one who rebuilt one, so not my area of expertise. If the trans is getting hot enough to melt 400* locktite, something's wrong....

I still don't understand why they back off....what is it about this particular transmission that causes this> Is it vibration? I mean, I've taken apart Sprite transmissions where the main nut had backed off completely - different trans I know, and in my case it was always one that had been "worked" on before I got it. I've never had one come loose when properly torqued and lock-tabbed.

 

[Mallen]

Think about it this way. The engineers didn't switch to a left handed nut on the newer models for no reason. It was done to fix a problem. Think about how that works. There is something with considerable mass on a shaft, retained by the nut. Those parts can move a tiny fraction of a degree due to the inertia of the parts and any slop in the keyway. Suppose the shaft rotates clockwise (which makes sense since the switched to a left handed nut) When the shaft starts rotating, the parts on the shaft want to stay where they are, so they exert a counter clockwise torque on the nut. On top of that, the engines power isn't smooth. It's tends to be evened out by the flywheel and the mass of the crankshaft, but it's actually a series of pulses of power. Those pulses will travel down the power train as torsion waves. The shaft will actually ring like a bell twisting clockwise the counterclockwise then clockwise again as they die out. The clockwise twist of course will always be more than the counterclockwise twist. It's going to be almost like an impact wrench. Decelerating you see a torque in the opposite direction, but hard acceleration is probably far more common than than hard deceleration and you don't see as much of a pulse in the opposite direction. So the net effect will tend to loosen a right handed nut.

But yea, they must have thought the right handed threads were ok to begin with. It's probably just the peculiarities if that particular transmission and maybe the vibrating of the engine it's attached to that makes that part less reliably stay put. But it seems pretty clear to me that they knew something wasn't working as well as the original engineers had intended as they had to change to that left handed nut.

 

[htmdude57]

In NE Ohio I can't imagine that you could swing a dead cat without hitting someone with a welder

I agree. Cleveland is the home of Lincoln Electric. You could probably look on CL, or post your own request looking for a hobbyist.

 

[matt_i]

Is the staking nut deformed so that part of the threads "metal-flow" into a keyway?

If you are worried about the rotation of where the stake(s) will align, an easy idea is to either grind the existing washer or create a custom thickness. For the 1.0mm pitch, taking .25mm off the thickness will result in a quarter-turn of additional rotation. Maybe that's too thin and you need to make a washer of (nominal + 0.25mm) to do the same thing just opposite side. If the flats are in play then you might need 1/6mm to get the next flat or about .0065".

Having a surface grinder would make this a fair bit easier.

 

[jptbay]

Room for a Nord-lock washer under the old nut?