## Stress Calculation Small Washer Sitting in Square Hole

## Stress Calculation Small Washer Sitting in Square Hole

(OP)

Hi,

I am trying to prove that a small washer will not yield and bend into a square hole that is close to the same size as the washer.

The washer is 316 stainless steel, 13/16" OD, .405 ID. The square cutout is .563"x.563". The bolt diameter is .375". The max tightening torque is 400 in-lbs, which I converted to 5333 lbs. The washer thickness is .06". It's a carriage bolt with a lock washer and a nut.

Does anyone know how to calculate the stress?

I am trying to prove that a small washer will not yield and bend into a square hole that is close to the same size as the washer.

The washer is 316 stainless steel, 13/16" OD, .405 ID. The square cutout is .563"x.563". The bolt diameter is .375". The max tightening torque is 400 in-lbs, which I converted to 5333 lbs. The washer thickness is .06". It's a carriage bolt with a lock washer and a nut.

Does anyone know how to calculate the stress?

## RE: Stress Calculation Small Washer Sitting in Square Hole

## RE: Stress Calculation Small Washer Sitting in Square Hole

For a more exact treatment, possibly a Roarkes would help.

Regards,

Mike

The problem with sloppy work is that the supply FAR EXCEEDS the demand

## RE: Stress Calculation Small Washer Sitting in Square Hole

## RE: Stress Calculation Small Washer Sitting in Square Hole

STF

## RE: Stress Calculation Small Washer Sitting in Square Hole

## RE: Stress Calculation Small Washer Sitting in Square Hole

What are you trying to break?

I think the facets under the head will spin, before you get that torque on it, too.

My understanding of a carriage bolt installation is the the head's facets must be engaged directly in a square hole that fits snugly with no washer under the bolt head.

The hole in the mating part should be round, to allow engagement of the bolt.

The intended use of Carriage bolts is in very lightly loaded applications, especially where things are placed on the surface of the part that would be scratched by bolt-head hexagons.

Use of a lock washer under the nut restricts turning of the nut but that's not proven to be effective in many cases, but it is the "common" thing that people expect.

For this reason, I do not understand your original question about "a small washer will not yield and bend into a square hole" because the washer should not be in contact with the square hole.

Also for this reason, I cannot understand the torqueing of the carriage bolt, since that will be difficult to accomplish, and hints at an application that is not suitable for these bolts.

Are these bolts even heat treated? I've snapped a few in my time.

STF

## RE: Stress Calculation Small Washer Sitting in Square Hole

John R. Baker, P.E.(ret)EX-Product 'Evangelist'

Irvine, CA

Siemens PLM:

UG/NX Museum:

The secret of life is not finding someone to live withIt's finding someone you can't live without

## RE: Stress Calculation Small Washer Sitting in Square Hole

## RE: Stress Calculation Small Washer Sitting in Square Hole

## RE: Stress Calculation Small Washer Sitting in Square Hole

A few dumb questions... may have missed something...

What is the BOLT specification? Head-style/dimensions, thread-type [coarse/fine/rolled/cut] tension-strength and/or alloy/temper are important.

What is the WASHER specification? The exact alloy/temper of the washer are important.

What is the NUT specification? Washer-flange dimensions, thread-type [coarse/fine], thread-depth and alloy/temper are important.

An aerospace grade tension-bolt 160-KSI steel BOLT MS20006 with an aerospace grade tension NUT [Typ NAS1804-6] can withstand ~400-inch# torque-up... but not advisable [usually 310--330-in#]. Usually this bolt/nut combo is paired with a high strength steel washer such as MS20002-6.

What guide did You use for torque-tension calculations? MIL-HDBK-60? other?

How does the 0.375-dia bolt remain perfectly centered in the 0.563 X 0.563 square hole? What IF the bolt shank slides into a corner, hence the stack is asymmetrical to the Square hole?

Regards, Wil Taylor

o Trust - But Verify!

o We believe to be true what we prefer to be true. [Unknown]

o For those who believe, no proof is required; for those who cannot believe, no proof is possible. [variation,Stuart Chase]

o Unfortunately, in science what You 'believe' is irrelevant. ["Orion", Homebuiltairplanes.com forum]

## RE: Stress Calculation Small Washer Sitting in Square Hole

For the cost of your time, build a model (square hole in a flat plate can be done with a broach and a hand press, or a hand drill and a file). Then squish the washer to the force you claim to expect into the square hole. Takes 1/2 hour.

Hint: You're also apparently thinking of a "force" being loaded on the washer by the bolt. But that force (when tightening) comes from a torque on the nut on the (usually very coarse or very smooth or lubricated or rusted or easily turned or jammed nut). Assuming a force by tightening a nut is an assumption with a lot of assumptions behind it.

## RE: Stress Calculation Small Washer Sitting in Square Hole

Regards,

Mike

The problem with sloppy work is that the supply FAR EXCEEDS the demand

## RE: Stress Calculation Small Washer Sitting in Square Hole

## RE: Stress Calculation Small Washer Sitting in Square Hole

http://www.teslafile.co/wp-content/uploads/2017/09...

http://thelocksmithers.ca/images/donjo.JPG

I'm less sure the bolt body will end up centered in the round through hole. Then there is the .68" Ø lockwasher, which being centered on the bolt, will give the flat washer a noogie in the unsupported region.

https://uproxx.files.wordpress.com/2015/06/brock-l...

## RE: Stress Calculation Small Washer Sitting in Square Hole

John R. Baker, P.E.(ret)EX-Product 'Evangelist'

Irvine, CA

Siemens PLM:

UG/NX Museum:

The secret of life is not finding someone to live withIt's finding someone you can't live without

## RE: Stress Calculation Small Washer Sitting in Square Hole

## RE: Stress Calculation Small Washer Sitting in Square Hole

## RE: Stress Calculation Small Washer Sitting in Square Hole

## RE: Stress Calculation Small Washer Sitting in Square Hole

1) the diameter of the head of the 3/8" bolt is greater than 0.563" then the head will bear against the square hole and the washer isn't doing much and the issue becomes will the head of the bolt fail (as it has only a partial contact with the clamped flanges), assuming the washer isn't effective at distributing the bolt clamp-up force. or

2) if the head of the bolt fits within the square hole (first bad design, no?) then the washer is the loadpath to the clamped flanges. I can easily see that the thickness of the washer is relevant, the diameter less so (as the washer should lift-off around the hole). You can "easily" model this in FEM and spend a month of sundays analyzing it, or you can go to the shop and torque for bolts, carefully.

another day in paradise, or is paradise one day closer ?