Custom Studs: Double-End and Tap-End, to Your Print

What does a custom stud change from the catalog part?

A stud is “threaded at both ends with an unthreaded shank in between,” and usually one end goes into a tapped hole while the other takes a nut (source 1). ASME B18.31.2 sorts the inch double-end stud into two types: the clamping type, with the same thread on each end and a nut on each, and the tap end type, made to be installed in a tapped hole (source 2). Either type can be changed in the ways the table lists, and the print carries each change as its own callout.

How is the length of a stud measured?

Length needs care on a stud order, because the conventions differ. An inch tap end or double-end stud is measured overall (source 1). Metric double end studs, source 1 says, “are NOT called out by their overall length”: the overall length is the nominal length plus the metal end length, and that end is a multiple of the diameter that depends on the standard (source 1). Metric & Multistandard Components makes the same point, noting that “the thread of the tap end is not included in the nominal length of the stud,” and gives a DIN 835 M10 x 40 stud as an example with an overall length of 60 mm (source 3).

So the same word, length, can mean 40 on one drawing and 60 on another. Put the overall length on the print, then the length of each threaded end, and say how the length is measured if the callout follows a standard. The quote asks for any of the three that are missing.

What is the tap end threaded to, and how long is it?

The tap end is the one secured in the tapped hole (source 1). For metric studs, source 1 says: “Generally this end has a thread tolerance which results in thread interference. If normal thread is required at this end, it shall be specified in purchase order.” It describes the inch tap end as threaded to a Class NC5 or Class UNRC-3A fit, with the nut end at Class UNRC-2A (source 1), and ASME B18.31.2 covers both regular unified and interference-fit threads at the tap end (source 2). Put the tap-end fit on the print as its own callout, separate from the nut end. An interference-fit tap end is quoted to the class on the print.

How long the tap end should be depends on what it goes into, and the published conventions differ. The table sets three of them side by side as reference; the tap-end length on your print is what is quoted. One of the three, Nord-Lock, adds that for a tapped hole in a softer material or a special alloy, “these values are not sufficient,” and that its formulas “give only an estimation” (source 4).

Double end studs and tap end studs: plain body or reduced body?

Catalogs use the two names differently: ASME B18.31.2 files the tap end stud under double-end studs (source 2), while Wikipedia sets them apart by equal or unequal thread lengths (source 5). On a print, name the ends by what they do, tap end and nut end, each with its own thread and length.

ASME B18.31.2 also covers double-end studs in two body forms, a reduced diameter body and a full body (source 2). Wikipedia describes the difference: a full-bodied stud has a shank equal to the major diameter of the thread, and an undercut stud has a shank equal to the pitch diameter and is designed to better distribute axial stresses (source 5). It adds that undercut studs are only required where the stud is exposed to fatigue (source 5). A reduced body goes on the print as a diameter and a length, and it is quoted from the print.

Fully threaded studs are quoted to the print. Plain lengths are often cheaper as catalog threaded rod; special materials, lengths and ends are quoted.

Right-hand on one end, left-hand on the other, and a hex in the middle

McMaster-Carr’s catalog page describes right-hand/left-hand threaded rods, “Similar to turnbuckles,” with “a hex-shaped body so you can adjust them with a wrench,” and says the end with the left-hand threads “is marked with a groove” (source 6).

A custom stud can follow that pattern with the thread pair on your print. Say on the print which end is left-hand, give the thread for each end, and give the width across flats and the length of the hex or flats. A groove at the left-hand end goes on the print like any other turned groove. A hex body with a thread on each end is close to a threaded standoff, which is quoted on standoffs and spacers, and a stud that threads into a fitting welded to a machined part pairs with weld-in bungs.

Flange and pressure-joint studs

Certified pressure-bolting studs aren’t quoted: flange bolting studs and stud bolts for pressure joints. ASME B18.31.2 lists the flange stud (stud bolt) as its own configuration, apart from the double-end stud, and describes it as “threaded studs used primarily in applications with flanges” (source 2). The quote does not state a pressure rating. This page covers double-end and tap-end studs for frames, fixtures, housings and mounts.

Which material goes on the print?

Studs are quoted in titanium, 304 and 316 stainless, brass, bronze, and hardened, heat-treated steel. A steel stud can be quoted heat treated to the hardness on the print. Other alloys and plastics quoted on request. Name the grade on the print.

Material also decides how the stud behaves against its nut. Wikipedia’s article on galling says a material with high stacking-fault energy, “such as aluminium or titanium,” will be far more susceptible to galling than one with low stacking-fault energy, “such as copper, bronze, or gold” (source 7). Name the nut material in the part description, especially for a titanium stud. A matching nut can go on the same quote, and nuts are quoted to the print.

The other half of the pair matters too. Wikipedia’s article on galvanic corrosion gives the electrochemical potential difference between stainless steel and aluminium as 0.5 to 1.0 V, depending on the alloys, and says it “can cause considerable corrosion within months under unfavorable conditions” (source 8). Put the mating material in the part description.

Plating, black oxide and hydrogen embrittlement

Zinc plating, black oxide and heat treat are quoted with the part. A coating adds thickness to a thread, so the print should say whether the thread size applies before or after plating. A stud maker’s technical note says tap end studs can be plated or coated “if allowances are made for coating thickness and thread fit” (source 9).

Plated, hardened studs need one more line on the print. Wikipedia’s article on hydrogen embrittlement lists electroplating among the electrochemical sources of hydrogen, says higher-strength steels are more susceptible than mid-strength steels, and notes that baking after electroplating is commonly used but “not always fully effective” (source 10). Baking is quoted when the print calls for it.

What to send: a print, or a new sample stud

Start with a print that calls out each end: for the tap end and the nut end, the thread size, pitch, series or class and thread length; then the overall length and how it is measured, the body diameter, the points, any hex or flats, the material, the hardness and the finish. The same stud maker’s note asks for this too: “Prints should be furnished on Double end or Tap End studs whenever possible” (source 9). A 2D PDF with every dimension on it needs no CAD line in the quote. Files: Any file type; STEP + PDF ideal.

No print yet? A hand sketch with the two thread callouts and the lengths works, and so does a new sample stud or an unused spare. Send a new part, not the worn one. Wear changes the sizes that matter. Reverse engineering measures a sample and makes the drawing. The sample ships back with the parts. The drawing made from a sketch or a sample is quoted as its own line on the first order, and reorders come off the same drawing. Parts are supplied as replacements by fit and dimensions. No OEM logos, part numbers or markings are copied.

What tolerances go on a stud?

On a stud, the callouts that matter most are the two thread classes and the lengths, and each thread is quoted to the class on its callout. The rest follows the general bands: Typical machined tolerance is ±0.005 in, ±0.001 in on critical turned diameters, and down to ±0.0002 in on wire-EDM and other finished features; ground features are quoted to ±0.0001 in. If the two threads must run true to each other or to the body, put the runout callout on the print. Position, perpendicularity and runout callouts are quoted from the print. A body diameter that has to be ground is quoted with precision grinding, and the general bands for turned work are covered on CNC turning.

Quantities, reorders and blanket orders

One stud is a normal order. 25 pieces is a good start. At 200, the price per part drops a lot. Ask for more than one quantity, such as 1, 25 and 100, and the quote shows each. For how quantity works on a small lot, see small-batch CNC machining, and for a single replacement, one-off CNC machining.

Reorders at the same revision: send the last quote or PO number and it’s requoted. Studs you replace on a schedule can go on a blanket order covering a year’s usage, shipped in releases. Price, release schedule and lead time per release are set in the quote.

How long do custom studs take?

A stud quote comes back in 24-48 hours. Rush: 1-2 weeks. Standard: 4-6 weeks (typical). Extended: 6-8 weeks, for jobs that aren't time-sensitive. On a stud, plating counts as a secondary operation. Rush 1-2 weeks applies to machined parts with no secondary operations. Heat treat, grinding, EDM and finishing add time, and the quote gives the real date. When a machine is down, start with rush CNC parts.

What comes with the studs

Screws and bolts with heads are on custom screws, bolts and studs; shoulder screws are on custom shoulder bolts, and studs in threads no longer made are on obsolete thread fasteners. Every part is inspected against your print before it ships. If a part doesn’t match the print, it’s remade or credited.

Sources

Quoted passages on this page come from the following, all accessed 29 September 2026. Where anything here differs from your print, the print governs.

1. K P Shah, “Studs (Article-17),” Practical Maintenance, 1 February 2009: practicalmaintenance.wordpress.com/2009/02/01/studs-article-17 (stud, tap end and nut end; interference at the metric tap end; metric and inch length rules; IS 1862 types; DIN metal end multipliers; points).

2. ASME B18.31.2-2014 (R2019), “Continuous Thread Stud, Double-End Stud, and Flange Bolting Stud (Stud Bolt) (Inch Series),” ASME, 2014: asme.org/codes-standards/find-codes-standards/b18-31-2-continuous-thread-stud-double-end-stud-flange-bolting-stud (clamping and tap end types; interference-fit tap end threads; reduced and full body; the flange stud as its own configuration).

3. Metric & Multistandard Components Corp., “Double End Stud 835 | Tap End Stud | Metric Threaded Studs,” undated, metricmcc.com/double-end-stud-835 (tap end not in the nominal length of a metric stud; DIN 835 M10 x 40 example).

4. Nord-Lock Group, “The Experts: Thread engagement in a tapped hole,” Bolting Tips, 2015, nord-lock.com/learnings/bolting-tips/2015/the-experts-thread-engagement-in-a-tapped-hole (recommended engagement in steel and aluminum; softer materials).

5. Wikipedia, “Threaded rod”: en.wikipedia.org/wiki/Threaded_rod (tap-end and double-end studs; full-bodied and undercut studs).

6. McMaster-Carr, “Right-Hand/Left-Hand Threaded Rods,” undated, mcmaster.com/products/threaded-rods/thread-direction~right-hand-and-left-hand (turnbuckle-style rods; hex body; groove marking the left-hand end).

7. Wikipedia, “Galling”: en.wikipedia.org/wiki/Galling (stacking-fault energy and susceptibility to galling).

8. Wikipedia, “Galvanic corrosion”: en.wikipedia.org/wiki/Galvanic_corrosion (stainless steel against aluminium).

9. Sigma Fasteners, “Tap End Stud - AWHEM Recommendation,” 21 December 2016, sigmafasteners.com/tap-end-stud-awhem-recommendation.html (plating and coating allowances; prints for double end and tap end studs).

10. Wikipedia, “Hydrogen embrittlement”: en.wikipedia.org/wiki/Hydrogen_embrittlement (electroplating as a source of hydrogen; higher-strength steels more susceptible; baking).