Thread depth for Hot Dip Galv 1

[bpeirson]

We may be threading A36 bar, 5/8", 3/4" and 1" diameter which will then be hot dip galvanized.

How much extra thread depth do I need for the galvanizing? We will be using a "Rigid 532" pipe threader with UNC dies.

Is there a standard for this?

Brad

 

[mrainey]

For threads with a sixty-degree included angle, the pitch diameter measurement over wires increases by .0040 with each .0010 of coating buildup.

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[CoryPad]

Are you referring to tapping the nuts to be oversized to accomodate the thick coating? If so, refer to A 563 Standard Specification for Carbons and Alloy Steel Nuts, section 7.4 and Table 5.

 

[KENAT]

ASME B1.1 has relevant information also I believe.

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[CoryPad]

I just noticed my post did not include the beginning of the standard designation. It should read ASTM A 563.

 

[HgTX]

A 563 says for HDG you tap the threads for the nut afterward, but for mechanically galvanized you tap them oversized (they don't say by how much, though) and then galvanize.

But you're not talking nuts, you're talking rod, which is playing the role of bolt.

The dimensional requirements of A 325 (assumed to fit A 563 nuts) ought to be relevant. There they say use standard Class 2A threads before galvanizing, and then give a table for how far beyond Class 2A your pitch and major diameter can get after galvanizing. Using that table does mean making sure you're using HDG nuts as well to match your HDG rod, not mechanically galvanized nuts.

Hg

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[bpeirson]

Thanks Hg.

For the others, I don't have copies of ASTM A563 nor B1.1 hence the posting. This is an unusual case for our company so there will be no added value in buying the relevant standards.

Brad

 

[lawayosh]

How long are the finished rods? If possible, it is recommended that threaded items have excess zinc spun off as they come out of the zinc kettle. Some galvanizers are equipped to do this.

Spinning helps to provide a more uniform accumulation of zinc in/on the threads enabling easier nut installation, including those tapped over-size.

Yosh