When is it necessary to incorporate a tapped hole versus a drilled hole?

[EulersFormula]

If I need bolt holes drilled into a component and I have nuts available, is it ever necessary to have the machinist thread the holes if the system will not be exposed to vacuum conditions?

 

[tygerdawg]

Yes.
If your assembly will be disassembled regularly, I like to have threaded holes, not nuts+washers.
If you wish to reduce the part count of your assembly.
If the amount of material is not sufficient to support threads and bolt pull-out strength.
If the base material is soft (like aluminum) and would be subject to eventual thread damage.
I'm sure there are many other reasons.

 

[rorix_bw]

What significance is the vacuum conditions? Are you threading to create a seal, or is there some reason I do not understand, in how a nut and bolt hold, that requires vacuum?

 

[Sultan of Hel]

If parts are cheap and labor is expensive (as is usually the case), or if the force which the fasteners are withstanding is fairly high, I would suggest a bolt/washer/lockwasher/nut assembly. The washer distributes the force over a wider area on the surface (sparing the part) and the lockwasher keeps the nut from unthreading due to vibrations. There are two advantages to this setup:
1. If the thread strips on either the bolt or the nut, you can change those rather than drilling out the threaded hole and retapping it or resorting to expensive helical inserts.
2. You can use stronger fasteners than the base material, assuming relatively small shear forces or enough distance from the bolt to the next component or the edge of the plate (so that the plate can withstand the shear forces).

Where I work, we usually use threaded holes only where there is only enough space on the other side for a low-profile nut (which, with a threaded hole, can act as a locknut), or not enough space for anything at all.

 

[alphy]

I would say that the decision to incorporate a tapped hole versus a drilled hole depends on the specific requirements and conditions of the system in question. Tapped holes are typically used when a threaded fastener, such as a bolt, is needed to secure two components together. This allows for a stronger and more secure connection compared to simply using a nut on a drilled hole.

In terms of when it is necessary to incorporate a tapped hole, it is important to consider the forces and stresses that will be acting on the system. Tapped holes are generally recommended for applications where there will be significant movement or vibration, as they provide a more secure and reliable fastening method. They are also useful when working with materials that may be prone to stripping, such as softer metals or plastics.

In the scenario described, where nuts are available, it may not be necessary to have the machinist thread the holes. However, it is important to consider the strength and durability of the connection. If the system will be subjected to heavy loads or frequent movement, it may be beneficial to have the holes tapped to ensure a more secure fastening.

Additionally, if the system will be exposed to any harsh or extreme conditions, such as high temperatures or corrosive environments, a tapped hole may be necessary to prevent the fastener from loosening or becoming damaged over time. In this case, the added cost and time of tapping the holes may be worth it in the long run to ensure the integrity of the system.

In conclusion, the decision to incorporate a tapped hole versus a drilled hole should be based on the specific needs and conditions of the system. It is important to consider factors such as forces, materials, and environmental conditions to determine the most appropriate fastening method for optimal performance and durability.