Big Barn
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Hole Size and Strength
- Thread starter Beltzington
- Start date
- Views: 5200
MMagis
Veteran Member
As mentioned, application makes difference, but it sounds very unlikely a hole oversized 1/8” is going to hurt anything. If for some reason in the future you decided it was too sloppy, you could just make up a bushing to fix it.
But my guess is, you’ll forget all about it.
But my guess is, you’ll forget all about it.
dragoneggs
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As others and especially Hoss has mentioned the application and loading is key. Edge distance is a consideration for a couple reasons. One is tear out... if your hole is close to the edge of the structure and the load is generally in that direction then you want the hole to have at least 2D edge distance (measured from the center of the hole). Bolt fit (clearance vs. tight or interference fit) generally is only an issue in fatigue situations where the bolt can help create a little compression zone around the hole. Holes and notches are where cracks cracks start. A loose fit bolt not clamped/bolted down tight enough for operating loads will also produce excessive wear and maybe eventual failure of that joint or inadvertently overload somewhere else. Another preventive but probably way overboard step would be to ream your hole so it is smooth. Smooth surfaces wear better and slow corrosion and crack propagation.
So... in the end... it is always a compromise as to the fit of the fastener and the ease of fabrication and install. My :2cents:
So... in the end... it is always a compromise as to the fit of the fastener and the ease of fabrication and install. My :2cents:
CCWKen
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There is a standard for bolt hole clearances. Typically a close fit and a free fit.
Standard Tap Drill / Clearance Holes Table - Engineer's Handbook -
If you are having problems laying out the position of the hole(s), then that's another issue. Buy a set of transfer punches. I use these all the time.
Transfer Punch Set - 28 Piece
Standard Tap Drill / Clearance Holes Table - Engineer's Handbook -
If you are having problems laying out the position of the hole(s), then that's another issue. Buy a set of transfer punches. I use these all the time.
Transfer Punch Set - 28 Piece
Scrambler82
Veteran Member
IMHO... The bolt hole should be as close to the diameter as possible.
Once the bolt is in the properly sized hole and tightened to specifications, it becomes part of the metal piece.
There are applications where movement is needed, a bridge bolted too tight will fail sooner than one that can move in the wind and Chang weight. The same goes for each application, as stated, allowable tolerances are engineered in, not decided on when the holes are being made.
Another way to look at it is, if all the holes are 1/8 to 1/4 oversized, every time I you move the tractor with a load all of the bolts need to move in the hole to hit solid metal, add up all of the movement and the tractor or a piece of equipment is out of alignment and is not pulling properly or is wearing where it shouldn't be wearing.
I go back to the original statement... Make the hole as tight as possible !
Once the bolt is in the properly sized hole and tightened to specifications, it becomes part of the metal piece.
There are applications where movement is needed, a bridge bolted too tight will fail sooner than one that can move in the wind and Chang weight. The same goes for each application, as stated, allowable tolerances are engineered in, not decided on when the holes are being made.
Another way to look at it is, if all the holes are 1/8 to 1/4 oversized, every time I you move the tractor with a load all of the bolts need to move in the hole to hit solid metal, add up all of the movement and the tractor or a piece of equipment is out of alignment and is not pulling properly or is wearing where it shouldn't be wearing.
I go back to the original statement... Make the hole as tight as possible !
dragoneggs
Super Star Member
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I like your tools SA. Im quite disappointed you didn't bring them out when I was over!Another thing, is to get the nut and bolt real tight. These two things are a big help in doing that!
Shield Arc
Super Member
I keep my helpers in the house when I have visitors!:laughing:
Streetcar
Veteran Member
Every structural bolt that I have installed on a bridge is tighten so that there is no movement between plates.
Bolted Bridge connections are designed based on clamping force not shear of the bolt. Riveted structures used the shear strength of the rivet body at the connections
To op , why not use bigger bolt. What exactly are you building.
I looked at snow plows on the job today. They all had slotted holes for adjustment with bolt size 5/8 or larger. They had washers on both nut and bolt side.
Streetcar
Veteran Member
Dragon
Why would you recommend reaming a drilled hole.
I agree that proper location ,(edge distance), spacing and tightening are important for proper performance of the connections
Irregularities (notches, cracks etc) are stress risers and can lead to failure.
Smooth Holes on the other hand are only a problems for the material is not enough section to handle the stress. Drilled holes are a standard method to repair cracks in bridges
Not a bolt but on my tandem disc which is a heavy duty 14' model the hole it the hitch is significantly smaller than the hole in my draw bar. There is maybe 1/2" difference is size maybe more. I have not had any problems or unusual wear with the loose pin bouncing around in there and I have pulled it as deep as it will go over about 80 acres.
