Drilling hole in 1-3/8 pipe for fulcrum

In summary, the conversation is discussing the design of a small crane using a 1-3/8" steel pipe as a fulcrum. The person wants to know if there is a formula or table to determine the load strength of the fulcrum, specifically in relation to the size of the hole drilled for the pivot pin. The expert provides information on the pipe's dimensions and material specifications and calculates the maximum force that can be applied to the lever arm based on the allowable bending and bearing stress of the pipe.
  • #1
bnaudie
1
0
Drilling hole in 1-3/8" pipe for fulcrum

I am designing a small crane for a special purpose. I am using a 17 ga. steel 1-3/8" ten-foot pipe as a fulcrum. I am going to drill a hole 2 feet from one end to run the axle through. That will leave 8 feet on the other side.

Is there a table or formula to determine how much load strength this will have? More importantly, what would the strength be depending on what size hole I drill? Is a 1/2" hole acceptable?
 
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  • #2
bnaudie: You have a steel pipe having outside diameter d1 = 34.925 mm, wall thickness t1 = 1.4732 mm, and length L1 = 3050 mm, used as a class 1 lever. Unless you can give us the material specification number of your pipe, we can assume it is steel ASTM A53, grade A. Therefore, we can currently assume the pipe allowable bending stress is Sba = 136.7 MPa, and allowable bearing stress is Sbra = 191 MPa.

Consequently, your fulcrum can withstand a maximum force of P1 = 340 N, not because of your current pivot pin (axle) hole size (d2 = 12.7 mm), but instead because of the bending stress on your given lever. This means the force you can apply to the tip of your 2440 mm lever arm can be a maximum value of 68.0 N.
 

1. How do I know where to drill the hole for the fulcrum?

The location of the hole for the fulcrum is dependent on the specific application and the desired balance point. It is recommended to use a marking tool or measuring device to accurately determine the placement of the hole.

2. Can I use any type of drill bit to drill the hole in the pipe?

The type of drill bit needed will depend on the material of the pipe. For most metals, a standard metal drill bit will suffice. However, for harder materials such as stainless steel, a carbide-tipped or cobalt drill bit may be necessary.

3. What is the ideal size for the hole in the pipe for the fulcrum?

The size of the hole will depend on the size and weight of the object being balanced on the fulcrum. It is recommended to make the hole slightly larger than the diameter of the fulcrum to allow for smooth movement.

4. Should I use lubricant while drilling the hole in the pipe?

Using a lubricant, such as cutting oil, can help reduce friction and heat while drilling the hole. This can help prolong the life of the drill bit and make the drilling process smoother.

5. How do I ensure the hole is drilled straight in the pipe?

Using a drill press or a guide can help ensure the hole is drilled straight in the pipe. It is also important to use steady and consistent pressure while drilling to prevent the drill bit from veering off course.

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