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10 votes
Accepted

Fixing a blind bolt hole when the first 2-3 threads are ruined?

I'm not a machinist, but I've tapped a few holes in my time. In my experience a tapered tap will handle this problem as the taper will reach down to the good threads and self align. Use some oil with ...
Eric S's user avatar
  • 915
9 votes

Fixing a blind bolt hole when the first 2-3 threads are ruined?

The product that you're describing (an 'expanding tap') doesn't exist, unfortunately. I had a similar problem a few years back, and actually built my own out of a Sleeve anchor, like the one pictured ...
Jonathan R Swift's user avatar
9 votes
Accepted

What is the name for a bolt hole with a slot that allows the bolt to be inserted or removed when the nut is loose?

I would call that a 'key hole'.
Aakash Sheth's user avatar
9 votes
Accepted

Are M8 screws double the size of M4 screws?

The ISO metric bolt has its diameter as the numeral part of the name. So M8 has a diameter of 8mm compared to that of the M4 bolt. So far scaling would make sense. However, the pitch of them is not ...
kamran's user avatar
  • 22.4k
7 votes

How to make screws stay tight under high vibration?

There are several ways you might try to fix this, for example. Don't use screws. Put some studs into the screw holes in the motor and fix them permanently (like the studs that hold the wheels onto a ...
alephzero's user avatar
  • 12.5k
5 votes
Accepted

What causes a fastener to lock?

Oxidation, dried lubricant, contaminants, rust - all that acts as a layer of glue binding the elements. As you apply a firm torque, you snap that bond. It takes a considerable time to re-form.
SF.'s user avatar
  • 6,105
5 votes

Fixing a blind bolt hole when the first 2-3 threads are ruined?

You could drill out the hole to remove the munged threads down to the remaining good threads. This should make it easier for the tap to get into the thread grove correctly. Another thought would be ...
Jim's user avatar
  • 51
4 votes

Do bolts become tighter or looser at cryogenic temperature?

The bolt tension could increase, decrease, or stay the same. It depends on the thermal stress distribution in the whole structure, which is likely to be eventually supported by something that remains ...
alephzero's user avatar
  • 12.5k
3 votes

What causes a fastener to lock?

Under high pressure and high heat metal bonds by a process called diffusion. Where the atoms of the two parts intersperse over time. This and oxidation, slow chemical burning of unintentional ...
kamran's user avatar
  • 22.4k
3 votes
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What does P0.35 stand for in a Tech drawing for a Bolt

I would go with Pitch of 0.35mm ie 1 turn advances by 0.35mm A view of the drawing may clarify this.
Solar Mike's user avatar
  • 15.8k
3 votes
Accepted

Correct term for non-countersunk flat hex screw/ bolt?

I would call that a wafer head machine screw.
Chris Johns's user avatar
  • 15.2k
3 votes
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Convert translational stiffness to rotational stiffness of a screw

The translational stiffness is written as $$ k_l = \frac{A\,E}{\ell},$$ where the stiffness $k_l$ is in $\left[\frac{N}{m}\right]$, the area $A$ is in $\left[m^2\right]$, the young's modulus is in $\...
useless-machine's user avatar
3 votes

Fixing a blind bolt hole when the first 2-3 threads are ruined?

The most common way to fix mangled threads, if they're really beyond fixing and if there's enough meat to open the hole a bit larger, is to use something like a heli-coil (aka : threaded insert). For ...
J...'s user avatar
  • 197
3 votes

What is the purpose of drilled washers?

Depending on the size and thickness these could be spacers. One example is their use on cars to increase the track. They can also be designed as flexible drive plates between a motor and gearbox for ...
Solar Mike's user avatar
  • 15.8k
3 votes

Why is retorquing sometimes necessary and other times a mistake?

This is not something engineers learn, it's something mechanics/millwrights learn. Because static friction is higher than dynamic friction, bolts should be torqued once and while the bolt/nut is still ...
Tiger Guy's user avatar
  • 6,901
2 votes
Accepted

Maximum shear force of metric steel bolt

The Guide to Design Criteria for Bolted and Riveted Joints 1974 by Fisher and Struik, you can use the approximation: $$S_{Ult-Shear}\sim 0.62\cdot S_{Ult}$$ and from the Distortion Energy Theory: $...
DLS3141's user avatar
  • 2,145
2 votes

Maximum shear force of metric steel bolt

For metric bolts the tensile strength can be calculated from the grade of the bolt expressed as A.B (eg 8.8). The first number is the ultimate tensile stress in 100s of Mega Pascals and the number ...
Chris Johns's user avatar
  • 15.2k
2 votes

How to make screws stay tight under high vibration?

"split lock" spring washers are nearly worthless for serious torque or vibration. Belleville type lock washers are better, especially if serrated. The best by far, amazing actually, at least ...
Pete W's user avatar
  • 1,561
2 votes

How to make screws stay tight under high vibration?

The loctite is only good for one kind of rootcause. Please try the loctite + spring washer combo. If it is still loose, use 2 pcs spring washer. These should do the job. Or worst case use mechanical ...
Peter Bende's user avatar
2 votes

What bolts should I specify with Weathering Steel?

Re-iterating some of above as manufacturer I can advise that Weathering Steel TCBs are generally available in M24 diameter only, with the following lengths: 70, 80, 90, 100, 105, 110, 120, 125, 130, ...
Arnie Glausiusz's user avatar
2 votes

Correct term for non-countersunk flat hex screw/ bolt?

"Low-profile cap head bolt" would describe it also. Googling that returns images like but the accepted answer is technically correct.
Criggie's user avatar
  • 430
2 votes
Accepted

Flanged connection studbolt length calculation

In small bolts, threads is 1D but in larger size is less than 1D. Free threads in best practice is 2-3 threads. Don't forget to take gasket thickness (SPWD or RTJ?) in calc. Additional free threads ...
RainerJ's user avatar
  • 21
2 votes

Is there a rule of thumb to construe a screw

In a handbook of mechanical engineering facts you will find tables containing maximum load ratings for different diameters and types of screw fasteners, and required torque values to hold those loads. ...
niels nielsen's user avatar
2 votes

What causes a fastener to lock?

A standard bolt will stretch when tightened. This stretching increases force on the threads of both the bolt and hole and thus increases the force required to overcome static friction and loosen the ...
UseitorLoseit's user avatar
2 votes
Accepted

How to find the diameter of bolts in a flanged joint?

Your calculation for the maximum forces to the bolt appears flawed. The forces resisted by the bolts in tension is equal to the total force of the area on either side of the tube. You have the tube ...
ShadowMan's user avatar
  • 480
2 votes

Can I use a wooden flat screw head with a washer to mimick a pan head screw?

I assume that the 'leg' is tubular steel with pre-drilled holes. The problem with using countersunk screws is twofold, firstly that countersunk they will only make contact with the very edge of ...
Chris Johns's user avatar
  • 15.2k
2 votes

Can I use a wooden flat screw head with a washer to mimick a pan head screw?

If you use a washer under the head of the flat head wood screw, get you a cup washer. these are intended to let you use flat head screws as if they were pan heads. They hold the wedge profile of the ...
niels nielsen's user avatar
2 votes

Can I use a wooden flat screw head with a washer to mimick a pan head screw?

It seems reasonable to believe that the flat head (countersunk) screw would apply enough force to split the wood, hence the restriction. If you use a flat head screw and the washer prevents the ...
fred_dot_u's user avatar
  • 7,132
2 votes
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Determining when bolt will bend

Assuming that nothing else will give out first, what metric would I use to estimate how much weight it can support before flexing the bolts? Is it "bending stiffness" rather than "shear strength"? ...
Drew_J's user avatar
  • 593
2 votes
Accepted

What is the best way to fasten securely a load onto a hollow brick?

I'd recommend first making a hole to fill the channels in the brick with mortar/concrete locally. This way you will effectively have a solid brick which allows for a much stronger fastening and a much ...
ingenørd's user avatar
  • 1,288

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