Deeep 1/2-20

MaxPrairie · Aug 10, 2021

Been a while since I have posted but, I have a request for a job that requires a 1/2-20 thread tapped 14" deep. It is a thru hole but hoping someone has been in this situation before. Any solutions other than buying a long reach tap and making a custom tap extension or welding a 3/8 round to the tap?

gatz · Aug 10, 2021

Does the hole need to be fully threaded ? (That's kind of an unusual request)

If not, just relieve one end and use a standard tap to reach as far as you can/want.

Otherwise, make an extension and silver solder it onto a tap.

Milland · Aug 10, 2021

Simples - tap it from both ends.

More helpfully, it's almost certainly a bad design, and should be relieved where thread's not truly needed. If nothing else, there's a lot of friction along that length, risk of galling, and pitch errors for male and female threads can increase problems the longer the mate it.

michiganbuck · Aug 10, 2021

Whatever the customer wants, and is willing to pay for. Thread class will/may make it difficult or less difficult
I guess one might consider running a reamer through to assure hole size and straightness, the material charismatics, and type of tap.

A custom tap extension may prove better than welding a drive because of stresses made by the heat of welding.

Gordon Heaton · Aug 10, 2021

Curious, is that in steel? I suppose if you used a spiral point tap and could latch onto the chip and pull it through real-time it might not be too bad.

Bobw · Aug 10, 2021

MaxPrairie said:
hoping someone has been in this situation before.

j

Yep.. Been there.

My solution to the problem.. I typed "NO QUOTE" and sent it back..

WizardOfBoz · Aug 10, 2021

Ok, as an engineer, I have to ask if the piece with ID threads is the same material as the bolt. Because if it is, it's like 20 to 28 times more threading than necessary.

And if the theads are being cut in, for example, Manchego cheese, I'm not sure that 14" of 1/2" thread gives you the strenght desired.

Sometimes, the problem isn't doing difficult stuff. Sometimes its a design that requires you to do stupid stuff.

I'd definitely ask if you could drill most of that 14" out. Not only for mfg, but for assembly.

Remember the Kansas city walkway collapse? There was an inapt field mod to avoid having to thread 1.25" rods from the ceiing to the the 2nd floor walkway. The redesign proved fatal for 114 and another 200+ were injured. A better initial design would have saved lives.

Not saying that's the case here, but 14 inches of 1/2 inch thread sounds suspiciously poorly thought-out.

michiganbuck · Aug 10, 2021

You might call Special Drill and Reamer in Madison Heights Michigan.
Tell them Buck recommend them.
likely they have made the same and can recommend what is best for the material of the part.
likely they will make the tool you need.

Very sharp cutter guys in my time.
Yes HSS Carbide Exotics all old hat to them.
*Just slapping on a long shank there are better ways to do that, and better taps for the deeeep.

Special Drill and Reamer Corporation - Madison Heights , MI - Company Data

let me know if anyone remembers Buck.

52 Ford · Aug 10, 2021

bosleyjr said:
And if the theads are being cut in, for example, Manchego cheese, I'm not sure that 14" of 1/2" thread gives you the strenght.

Depends on the climate. If you need it to work in high temperatures, cheese would be a bad choice. Tends to loose it's hardness pretty fast as the temp goes up. Lot's of yield before it breaks, though. I guess if it HAS to be cheese, Parmesan or a similar hard cheese might be the ticket. I have very limited experience cutting threads in cheese, so take my advice with a grain of salt. I imagine extra virgin Olive oil would be a sufficient cutting oil.

Sent from my SAMSUNG-SM-G891A using Tapatalk

michiganbuck · Aug 10, 2021

52 Ford said:
Depends on the climate. If you need it to work in high temperatures, cheese would be a bad choice. Tends to loose it's hardness pretty fast as the temp goes up. Lot's of yield before it breaks, though. I guess if it HAS to be cheese, Parmesan or a similar hard cheese might be the ticket. I have very limited experience cutting threads in cheese, so take my advice with a grain of salt. I imagine extra virgin Olive oil would be a sufficient cutting oil.

Sent from my SAMSUNG-SM-G891A using Tapatalk

OT: (other topic)
I think you are referring to cutting the cheese..we need info about tapping the cheese.

and not about global warming and cow farts being like cutting the cheese.

Because, what would a cow's fart smell like? ... Dairy air.

And you better have a can of spinach and watch out for that sailor man when you talk about virgin Olive Oyl
Just saying tapping with virgin Olive Oyl and you might get your flutes broken.

gbent · Aug 10, 2021

bosleyjr said:
Remember the Kansas city walkway collapse? There was an inapt field mod to avoid having to thread 1.25" rods from the ceiing to the the 2nd floor walkway. The redesign proved fatal for 114 and another 200+ were injured. A better initial design would have saved lives.

Not quite. The full length (40'+) threaded rods weren't the problem, the builder didn't want to thread the the support nuts half way down the rod. It would have been easy if the designer had ever heard of coupling nuts.

Instead, they put one hanger for the top walk way, and put the support rods for the lower walkway a few inches to the outside of the fabricated beam supporting the walkway. Now, instead of the upper beam only supporting the upper walkway, the upper beam support now had to support both walkways.

The design of the beams supporting the walkways was problematic on its own, and doubling the load caused a catastrophic failure.

crazygoat · Aug 10, 2021

Am I assuming a 1/2-20 threaded hole 14" deep in a part and not 14" of thread? Makes a whole of difference in the answers you will get. Please clarify exactly what scenario it is.

pavt · Aug 10, 2021

Bobw said:
j

Yep.. Been there.

My solution to the problem.. I typed "NO QUOTE" and sent it back..

Last time someone wanted me to go that deep I started talking about marriage.

MaxPrairie · Aug 11, 2021

Part is 14” long with 14” of thread.

MaxPrairie · Aug 11, 2021

michiganbuck said:
You might call Special Drill and Reamer in Madison Heights Michigan.
Tell them Buck recommend them.
likely they have made the same and can recommend what is best for the material of the part.
likely they will make the tool you need.

Very sharp cutter guys in my time.
Yes HSS Carbide Exotics all old hat to them.
*Just slapping on a long shank there are better ways to do that, and better taps for the deeeep.

Special Drill and Reamer Corporation - Madison Heights , MI - Company Data

let me know if anyone remembers Buck.

I will let you know what they say if I end up going that route.

MaxPrairie · Aug 11, 2021

Milland said:
Simples - tap it from both ends.

More helpfully, it's almost certainly a bad design, and should be relieved where thread's not truly needed. If nothing else, there's a lot of friction along that length, risk of galling, and pitch errors for male and female threads can increase problems the longer the mate it.

The mating part has an inch of threads and is otherwise relieved 0.375.

crazygoat · Aug 11, 2021

MaxPrairie said:
Part is 14” long with 14” of thread.

I can see all kinds of problems with pitch stretch. I don't have any idea why anyone would think that is good design. Sorry that I can't help.

MaxPrairie · Aug 11, 2021

Bobw said:
j

Yep.. Been there.

My solution to the problem.. I typed "NO QUOTE" and sent it back..

Thought about that. But also figure I can charge for pain and suffering.

pavt · Aug 11, 2021

MaxPrairie said:
Thought about that. But also figure I can charge for pain and suffering.

You had better charge a lot for pain and suffering then. As well as time and materials. If it was me, I would invest in a few spiral-flute taps from a good, major brand name such as Guhring or Emuge. Solder or loctite a shank onto them and go for it (after you figure out how to drill the tap hole) ..... I'm betting the job takes 3 taps. Just back out when it starts to feel dull, and grab the next tap.

Bobw · Aug 11, 2021

gbent said:
Not quite. The full length (40'+) threaded rods weren't the problem, the builder didn't want to thread the the support nuts half way down the rod. It would have been easy if the designer had ever heard of coupling nuts.

Instead, they put one hanger for the top walk way, and put the support rods for the lower walkway a few inches to the outside of the fabricated beam supporting the walkway. Now, instead of the upper beam only supporting the upper walkway, the upper beam support now had to support both walkways.

The design of the beams supporting the walkways was problematic on its own, and doubling the load caused a catastrophic failure.

That was a mess.. Is it common to make a beam by welding C-channel together? And if it is,
is it common for them to come apart? Is it common to drill a hole and put your entire load
through the center of the weld?

Hyatt Regency walkway collapse - Wikipedia

Deeep 1/2-20

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