Forming: Tap Drill Sizes

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Jarflo Pipe Taps

Jarflo roll form pipe taps (NPT & NPS) have significant advantages over cutting taps in many applications. These benefits include improved thread finish, stronger threads, longer tap life, faster tapping speeds and no chips. It is not practical to thread form NPTF & NPSF threads because 100% thread is required, and the crests need to be fully formed.

There are two choices in the hole preparation for a Jarflo tapered pipe tap:

  • Tapered Hole – A pre-tapped tapered hole will result in a consistent percent of thread height the entire depth of thread in the piece part. Tapered hole may be drilled, reamed or cored. Tapered holes require the most torque and HP for tapping.
  • Straight Hole – many applications for tapered pipe threads may use a straight hole. The Jarflo tap will ultimately produce the proper tapered thread by forming the material from the top to the bottom of the hole. The straight hole method will result in a full, sharp-crested threads at the top of the hole. The bottom of the hole may have partially formed crests with open “RABBIT EARS”. The benefits of burnished, high quality threads at the top of the hole provide excellent sealing capability for the part. Straight hole procedure will reduce tapping torque and improve tool life.
  • Straight pipe threads can be form tapped using only a high quality drilled hole. Reaming helps control hole size but is not required.

 Standard

NPT Jarflo

  Taper Hole

     Size “T”

  Straight Hole

      Size “S”
1/16-27  .281” – .284”    .272” – .275”
1/8-27  .374” – .377”    .365” – .368”
1/4-18  .490” – .494”    .476” – .480”
3/8-18  .640” – .644”    .626” – .630”
1/2-14  .779” – .784”    .761” – .766”
3/4-14  .990” – .995”    .971” – .976”
1 – 11 ½ 1.240”- 1.245” 1.220” – 1.230”

 

Standard Jarflo

NPS, NPSM, NPSC & NPSI

Straight Hole Size

  for 75% Thread

1/16-27    .282” – .284”
1/8-27    .379” – .381”
1/4-18    .499” – .501”
3/8-18    .639” – .641”
1/2-14    .788” – .791”
3/4-14    .998” – 1.001”
1 – 11 ½ 1.245” – 1.250”
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Forming Tap Drill Sizes

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