Machining Speeds & Feeds Card
One page. Speeds, chip load and drill feed, imperial and metric.
$3.99
BuyNPT Pipe Thread Calculator
ANSI/ASME B1.20.1 tap drill, TPI, diameters, and makeup depth
Select a standard NPT size from 1/8" to 4". Get threads per inch, major and minor diameter, the shop tap-drill size, hand-tight engagement (L1), and wrench-makeup / total useful engagement (L2).
Machining
Complete Machining Speeds & Feeds Guide
27 pages. Milling, drilling, tapping, turning and CNC routing.
$12.99
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Machining Job Estimator
Quote shop work and check operations against your spindle's top speed.
Excel or Google Sheets. Best on a computer.
$29.00
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Machining Complete Bundle
Card, 27-page guide and the estimator workbook. All six files.
Excel or Google Sheets. Best on a computer.
$34.99
$45.98 if bought separately — save $10.99
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Pipe Thread Tools From the Shop List
Only products that already exist in TestTalkHQ's affiliate catalog — sealant, tap fluid, drill index, and a leak check. Dedicated NPT tap sets, PTFE tape, pipe wrenches, and NPT thread gauges are not in the current CSV, so they are not invented here.
RectorSeal T Plus 2 Pipe Thread Sealant
Soft-set PTFE-filled pipe dope for NPT joints. Brush it on the male threads after you confirm size and engagement — it is not a substitute for correct makeup length.
View on Amazon →RectorSeal Tru-Blu Pipe Thread Compound
Thicker blue compound that stays put on vertical fittings. Use when T Plus 2 slumps, and still stop at the wrench-makeup length from the calculator — extra turns crack fittings.
View on Amazon →Hi-Spec 39-Piece SAE & Metric Tap and Die Set
Machine-thread tap/die coverage for UN and metric holes on the same bench. It is not an NPT pipe-tap set — use a dedicated NPT tap for tapered pipe threads.
View on Amazon →Tap Magic EP-Xtra Cutting Fluid
Flood the tap when you cut NPT in steel or stainless. Dry taps glaze, undersize the minor, and leave a loose joint that sealant cannot save.
View on Amazon →IRWIN 29-Piece Black Oxide Drill Index
Fractional sizes covering the common NPT tap drills from 7/16" through the larger pipe sizes you can still hand-drill. Verify the letter-R hole for 1/8" NPT with a numbered bit if you have one.
View on Amazon →RectorSeal Better Bubble Leak Detector
Brush on after wrench makeup and pressurize. Bubbles at the last engaged thread mean you are short of L2 or the threads are the wrong form (BSPT/parallel mix-up).
View on Amazon →As an Amazon Associate, TestTalkHQ earns from qualifying purchases.
How to Use This NPT Calculator
Pick the nominal pipe size stamped on the fitting (1/8" through 4"), then choose a mode. Tap-drill mode puts the shop drill front and center. Engagement mode puts ASME hand-tight (L1) and wrench-makeup / total useful thread (L2) first. Both modes still report TPI, major OD, approximate minor diameter, pitch diameter at the pipe end (E0), vanish thread, and overall thread length.
NPT is a 60° thread cut on a 3/4" per foot taper (1° 47'). Nominal size is not the measured OD — 1/2" NPT pipe is 0.840" outside. That is why a 1/2" UNC tap-drill chart will wreck an NPT hole. Use the Tap Drill Size Calculator for UNC/UNF/metric, and this tool for tapered pipe.
Read the full callout walkthrough in the NPT Pipe Thread Sizing Guide. If a joint still leaks after correct L2 makeup, go to NPT Pipe Thread Problems and Solutions. If the threads look like NPT but the gauge will not start, you may be holding BSPT or a parallel thread — see NPT vs BSPT vs Straight Thread.