Punching steel

Date 11-14-2008 15:55 Edited 11-15-2008 00:53

Hello Giovanni, I could be wrong in my interpretation of the meaning of his question, but I believe he may be asking about the process of making holes in steel by using an ironworker or other mechanized/hydraulic hole making device. In this case "punching" the steel might be referring to using a punch and die combination in one of these machines to make holes in the steel. One other thing that comes to mind is a term that was used in my locality when we had an aluminum smelter in operation. In this case they would refer to "punching" pots. This was essentially a reference to how they would tap the pot of aluminum in order to drain it into the crucible and move the molten aluminum after it had been melted. I wonder if there is possibly a similar term used to describe a part of a steel making process, but I don't know the answer to that. Best regards, Allan

P.S. I have included a pdf. file from Cleveland Tool Steel that gives an example of the type of tooling that an ironworker might use to punch holes in steel. Hope this makes sense with regard to your associates question.

Attachment: Mubea.pdf (159k)

By Jim12

Date 11-14-2008 23:36

I would be temped to agree with aevald post of punching with an ironworker.

By DaveBoyer (*****)

Date 11-15-2008 06:08 Edited 11-15-2008 06:10

   I too agree with the punching holes definition, the machine being any of: an ironworker, a punch press, or a specific machine called a punch. The slugs from the holes are sometimes refered to as "punchings"

   Metal stamping would include this operation and any others done on a punch press.

   If He was refering to a particular type of steel, and arived at "punching" by translating to English, He may be asking about "deep drawing steel" which is extremely malleable & ductile, fully annealed steel with a really low carbon content. An example of this would be the material used in drawn steel beverage cans [when they were made of steel].

By welderbrent (*****)

Date 11-19-2008 23:56

When you first wrote this I thought Allan had probably given to most likely answer. But as I happened to click here and re-read today I was wondering if perhaps you might be talking about an actual type of steel, not a process. Hard to tell when your going through language translations. But it is possible that you are looking for either a 'tool steel' or maybe 'pin stock' as in for equipment parts or other alloy applications.

Just a thought. Have a Great Day, Brent

By 803056

Date 11-30-2008 02:15

I believe Allen has it with his reference to "punching holes" in steel using a punch and die set (male punch and female die).

The fact that he mentioned a civil engineer asking the initial question makes Allen's reply all the more meaningful if the question was asked in relation to bolted structural connections. A related question that comes up frequently is how holes that have "ragged" (rough or torn) edge conditions and a pronounced burr around holes made with worn punch and die sets affects the load capacity of the bolted connection.

With that in mind, I believe this question is in regards to holes that are punched through structural steel using punch and die sets rather than holes that are drilled with twist drills. So the link to the website included in Allen's reply is "spot on" the mark.

Best regards and Happy Thanksgiving (OK so I'm a little late).

Al

By DaveBoyer (*****)

Date 11-30-2008 04:07

Al: Do they still ream holes that take bolts or rivets in shear so that they line up and are a uniform diameter through the hole, or has this gone by the wayside?

By 803056

Date 11-30-2008 04:34

It has been my experience that drilling/punching holes undersized and then reaming them to the proper size is not the standard practice for buildings.

Burrs and rough edges are typical and not addressed unless the engineer makes it a specific requirement. Burrs 1/16 inch or less in height are acceptable per the Specification for Structural Joints Using A325 or A490 Bolts (June 2004). Over-sized holes and slotted holes are acceptable for certain connections defined by the document listed.

Snug tight connections and pretensioned connection loaded in bearing do not depend on the clamping forces to develop their strength. Therefore, the presence of burrs isn't an issue. The direction of a slot is of concern and over-sized holes aren't permitted for snug tight connections in bearing.

I remember one project that required all the holes to be drilled undersized (no punched holes) and reamed to size. The bolts were 1 inch A490's. My elbows have been shot to hell ever since. There are winter mornings when I can't even pick up a cup of tea as a result of the abuse my elbows took. I should have stuck with welding, but noooo, I wanted to get away from the smoke and heat for a while. Dummy, dummy, dummy! :)

Best regards - Al

By aevald

Date 12-01-2008 05:35

Hello Al, it was my understanding that bridge work still required under-size/reaming of connecting plate holes and such, do you know if that is still the case? I have never done reaming for structural on buildings, but I have also not done bridge work so I don't know about holes related to that application. Best regards, Allan

By 803056

Date 12-01-2008 13:55 Edited 12-01-2008 14:06

Again, in general the answer is no.

There were one or two bridge projects I've worked on where the holes were drilled undersized and reamed to insure good fits, but splices on bridge girders, diaphragms, etc. are simply drilled (not punched) to size. The connections are considered to be slip-critical, so high strength bolts, fully tensioned, etc. are the norm. The general practice is to assemble the joint with several "barrel" pins to properly align all the holes, bolt and tighten several open holes, remove the pins and complete the bolting process. The pins are not removed until the connection is made fast so there is no slippage when the pins are removed.

Match drilling the splice plates and the girders (at the same time) by the fabricator minimizes misalignment of holes as would be the case in the fabrication of structural steel for building where the members are not fitted together in the shop. The bridges I've worked on are assembled in sections by the fabricator to make sure everything fits properly. Then it is disassembled and shipped to the site. It is pretty impressive to see huge sections of a basquel bridge assembled in the shop, disassembled and shipped to the site for erection. As a matter of fact, that was the last job I worked on that required the holes to be sub-drilled and reamed, but only the main girders that were attached to the drive mechanism where perfect alignment was required. If I recollect the details, body interfering bolts were required in specific connections.

You have to keep in mind that different states may impose their own requirements that are more stringent than neighboring states. So, where one project may require undersized holes and reamed to size, the next project slated for a different state may not.

Best regards - Al

By G.S.Crisi (****)

Date 12-12-2008 14:36

Gentlemen,
Professor Simon Priszkulnik, of the Civil Engineering Department of Mackenzie Presbyterian University in Sao Paulo, thanks you for the valuable help you provided him and wishes all of you a Merry Christmas and a Happy New Year.
Giovanni S. Crisi