Hole Size and Strength

   / Hole Size and Strength #1  

Beltzington

Platinum Member
Joined
Oct 4, 2008
Messages
954
Location
Appling, Georgia
Tractor
JD 3720
This section should be named welding and fabrication so forgive me if I am off topic.

A very smart manager once told me never side track a project trying to achieve perfection which is something I struggle with at all levels. That being said I am not building a satellite and am wondering when talking farm attachments does oversize holes significantly weaken a product. Specifically would drilling a 3/4" hole for a 5/8" bolt even matter once it is securely tightened. The load would only be in one direction so even if it move 1/8" inch it would stay there. Trying to decide if I need to buy a $20 bit, also the extra wiggle room will allow for small fitting errors.
 
   / Hole Size and Strength #2  
On a bridge ,the holes are typically drilled 1/16 oversized.
For an 1/8 oversized hole, we would just use washer on both bolt and nut side of the connection
 
   / Hole Size and Strength #3  
Personally I wouldn't do it. I like to drill 1/32 of an inch over size. But I guess it depends on the application.
 
   / Hole Size and Strength #4  
Personally I wouldn't do it. I like to drill 1/32 of an inch over size. But I guess it depends on the application.

I think we all aspire for this ideal scenario.

Personally I think you'll be fine with the oversize hole. Oftentimes our layout is 'off' and for "some" reason, things just don't fit right. (Molecules move etc)

Heck. Back in the old days (before walking six miles to school in the snow) on some projects I had to torch out the holes and touch 'em up with the die grinder..think I learned that from watching the Flintstones.

Didn't have Jody and YouTube back then......

Terry
 
   / Hole Size and Strength #5  
The size I drill depends on a number of things. Connection type, load directions, overall total load, how well I am able to lay it out, etc.

Sometimes I drill 1/8" over and still needs a little love from the die grinder and carbide. (I dont own a set of threaded transfer punches).

Othertimes, where I can clamp two parts together and get exact, Or drilling a clearance hole that will later thread into something that is not yet drilled and tapped, 1/32" is more than enough. Bolts are clearanced anyway. So simply using the nominal size and cleaning the bur off will clear a bolt without issue.
 
   / Hole Size and Strength #6  
Does depend on the application but if it's as close as you can get, That's as close as you can get. As stated above, I use the torch or plasma to drill holes at times. Just did so on my plow cutting edge. Not too critical.
 
   / Hole Size and Strength #7  
If I am drilling a hole, there is no reason to drill anything larger than 1/16" if you have a complete drill bit set.
As Yomax said, I sometimes use a torch like I did when remounting my driver side step on my RV. The builder used self tapping screws to mount it which sheared off. I torched in new holes and put in 3/8" bolts with double nuts compared to the original 3/16" ST'ing screw. NO WAY was I able to reach up inside the tire well and drill out new holes which still included the sheared off ST screws.
 
   / Hole Size and Strength #8  
Application is key. How much material is there to the edge ? If your 3/4 inch hole leaves 1/16 to the edge... Then no, use the $20 proper bit. If there are 2 inches to the edge ... Sure use the 3/4 drill and washers to adapt.
 
   / Hole Size and Strength #9  
I had a helper like that but someone stole it.
 

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