7/8 UNF

[lostsheep]

7 thread Vs 9 thread is the spec, but most combi valves are only 5 threads. That would be 0.35" or just over 3/8". That was calculated based on 5/8-14 BSP (parallel).

If it’s two turns then it is:

1/14 = .071

.071 x 2 = .142

I was ASSuming 2.5 turns when I came up with it .178”

Also, 3/8 is .375” so just under if you were aiming for .350

 

[The Chairman]

Also, 3/8 is .375” so just under if you were aiming for .350

Dayum, I haven't made that mistake in a coon's age. Good catch. I divided 1 by 14 and multiplied by 5 to get 0.35". Traditionally, 3 threads will give any fastener about 85% strength and that's usually "gudenuf". At least, that's what we assumed when I was an apprentice machinist. There are actually nice formulas you can use for each diameter, pitch, and composition, but why be safe when you can wing it, right?

 

[Tracy]

Anybody know what the actual difference in thread depth is between 200 bar and 300 bar?

I can measure when I get back to my shop but seems like good info to post here if someone knows.

Edit: if I recall correctly it’s 14 TPI, so ~.178” between 300 bar and 200 bar, that sound right?

About this much.

 

[The Chairman]

About this much.View attachment 809293

Less the kerf.

 

[Gone for diving]

Traditionally, 3 threads will give any fastener about 85% strength and that's usually "gudenuf"

as a mechanic rule of thumb is diameter of the bolt, is minimum the length the nut or threads should be,
Fairly good rule when bolting in to a threaded housing, and your grabbing bolts from the bin.

 

[Gone for diving]

What's this jig / clamp thing?

 

[The Chairman]

as a mechanic rule of thumb is diameter of the bolt, is minimum the length the nut or threads should be,
Fairly good rule when bolting in to a threaded housing, and your grabbing bolts from the bin.

Much of what mechanics bolt into are of cast iron or aluminum, so this is true. That doesn't apply to threads cut in solid stock. However, more threads are almost always better. Especially to the psyche.

 

[Gone for diving]

Yeah there some very interesting things,
Where I worked, before I was there,
They had a machine, the bolts that held on the drainage plow, would blow the heads of the bolts off after a while, so course they got higher grade bolts etc... still did it.
So from CAT they got same size studs, with their nuts which are a bit longer then normal nuts, don't know what grade, but they never had any problems after that,

moral of the story,
threads /studs are stronger than a bolt

 

[The Chairman]

Heads popping off of bolts could be over torqued or sheared off. Putting in a softer, yet longer nut might allow for a reduced torque on the bolt. I would lose bolts on my zero turn and going to grade 8 bolts solved that issue. I still used a SS nylon lock nut. All the pressure was in shear on the bolts. Most bolts are used for shear strength. Not Din. The pressure on those threads is compressive. As long as you compress the o-ring by seating the metal to metal, you don't need much torque. Well, unless you drop the tank on its valve with a reg in place. Plenty of shear forces then.

 

[Gone for diving]

Heads popping off of bolts could be over torqued or sheared off. Putting in a softer, yet longer nut might allow for a reduced torque on the bolt. I would lose bolts on my zero turn and going to grade 8 bolts solved that issue. I still used a SS nylon lock nut. All the pressure was in shear on the bolts. Most bolts are used for shear strength. Not Din. The pressure on those threads is compressive. As long as you compress the o-ring by seating the metal to metal, you don't need much torque. Well, unless you drop the tank on its valve with a reg in place. Plenty of shear forces then.

Oh they tried higher grade bolts, and wasn't from over torque,

The theads never broke always where the bolt head meets the shank, always the corner.

I don't remember clearly the specifics but
Think it was 6pc 7/8 bolts,
Think it had 5 inch grosser bars on a really long tracks, and occasionally they would give it a tug with a small excavator, in tough stuff,

Similar idea of the machine

But totally off topic