Custom Machined Shafts & Pins

What does each type of shaft or pin need on the print?

Each part in the table starts as round bar and is made by CNC turning.

A sleeve or bushing that a shaft runs in is on bushings, and a sleeve that fits over a pump shaft is covered under pumps and fluid handling. A coupling that joins two shafts is on shaft couplers, and the other round part types are on the machined parts index. A rebuild shop reordering pump shafts and motor stub shafts can start on repair-shop wear parts.

Keyseats, splines, grooves and cross holes

A key fits a slot in the shaft and a matching slot in the hub, and stops the two turning against each other so the torque passes through (source 5). ASME B17.1 sets the size, type and tolerances of parallel and taper keys and keyseats and relates them to shaft and bore diameters (source 6), so a print can name the key size and the standard rather than dimension the slot from scratch.

A spline is a set of ridges on a shaft that mesh with grooves in the mating part, carrying torque and keeping the two at the same angle (source 7). Parallel-key and involute splines are two of its forms, and an external spline can be broached, shaped, milled or hobbed (source 7).

A retaining ring on a shaft sits in a groove, and the ring maker publishes the groove diameter and width for each of its standard rings (source 8). Dimension the groove to the ring you use, or put the ring part number on the print. A cross hole for a cotter or roll pin goes on the print with its size and position. A threaded end takes its thread callout on the drawing, and a part that is more screw or stud than shaft belongs on custom fasteners. A shoulder bolt or stripper bolt, which pairs a smooth shoulder with a threaded end, is on custom shoulder bolts.

What fit does a pin or bearing journal need?

ISO fits name the hole in capitals and the shaft in lower case: in H7/h6, H7 is the hole’s tolerance range and h6 the shaft’s (source 9). Among the common hole-basis fits, H7/g6 is a sliding fit that assembles easily and turns and slides freely, H7/h6 is a location fit that assembles without force, H7/k6 and H7/n6 are transition fits, and H7/p6 is a light press fit that goes together by cold pressing (source 9).

Precision catalog dowels are ground for a slip fit or a press fit, and oversize dowels run 0.001 in over standard (source 1). Custom ground pins and bearing journals take their diameter and fit from your print; how a diameter is ground, and which grinding suits which feature, is on precision grinding.

The tighter a tolerance, the more a part costs to machine (source 10), so put a fit class or limits only on the journals and pin diameters that mate with something; the quote goes to what the print says. The design review that comes back with the quote flags a callout tighter than the part needs.

Runout and straightness on long shafts

Total runout limits how much a surface can vary relative to a datum axis as the part turns a full revolution, and it controls that surface’s straightness, circularity and taper along with it (source 11). A runout callout referenced to the bearing journals tells the quote which surfaces have to run true to them. Position, perpendicularity and runout callouts are quoted from the print. A straightness callout is quoted the same way.

Length makes both harder. Cutting tools push a long workpiece away from its supports, so long work often needs support in the middle (source 12). Long, slender pins suit Swiss screw machining: the tools cut next to a guide bushing, where the stock is more rigid (source 12).

Which material should a shaft or pin be?

Cold-drawn 1018 bar gives closer dimensional control, straighter stock and a better surface for machining, and shafts, axles and pins are among its common uses (source 13). 4140 is a chromium-molybdenum low alloy steel with high fatigue and torsional strength (source 14), the step up for a steel shaft that carries torque.

303 stainless carries sulfur for machining, which lowers its corrosion resistance below that of 304, and shafts and bushings are among its typical uses (source 15); 304 is the choice when corrosion matters more than cutting time. 17-4 PH is used where strength, hardness and corrosion resistance are needed together, and its corrosion resistance is comparable to 304 (source 16).

Brass is used where corrosion resistance and low friction are both needed, in bearings, hinges and valves, and in equipment that must not spark (source 17); brass covers the machining grade. Ti-6Al-4V (Grade 5), one of the most commonly used titanium alloys, has high specific strength and excellent corrosion resistance (source 18). A titanium dowel pin is quoted like any other pin, and titanium covers the grades.

Where the print calls for tool steel, Hudson Tool Steel lists dowel pins and gages among the uses of A2, alongside punches and dies (source 19); that end of the work is on punches. Pins in 420 or 440C stainless are quoted to the print as well. Other alloys and plastics quoted on request. Name the grade on the print.

What to send, and what comes back

The drawing is what the quote reads: each fit, the key or spline data, the ring grooves, the threads and the material. A finish called out on the print is quoted with the part. A STEP file with no drawing is quoted to a ±0.005 in general tolerance, or the one its notes name, so a diameter that has to hold a fit needs its callout on a drawing or in the notes. Ask for more than one quantity, such as 1, 25 and 100, and the quote shows each.

Lead time starts at order approval. Put your need date in the part description and the quote answers it. 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. If a part doesn’t match the print, it’s remade or credited.

Sources

All accessed 27 September 2026. Where a figure here differs from your print, the print governs.

1. MSC Industrial Supply, "Dowel Pins Technical Guide & Diagrams": mscdirect.com/resources/buying-guides/dowel-pins (dowel pins take shear loads while the screws take tension; precision pins ground for a slip or press fit; oversize pins 0.001 in over standard; pull-out dowels with an internal thread for removal and reuse).

2. Carr Lane Manufacturing, "Types of Locating Pins & Their Applications: A Guide": carrlane.com/engineering-resources/technical-information/manual-workholding/locating-devices/locating-pins (locating pins are press fit into the tool body or slipped into a bushing).

3. Wikipedia, "Clevis fastener": en.wikipedia.org/wiki/Clevis_fastener (unthreaded clevis pin with a domed head and a cross hole for a cotter pin; made to carry shear).

4. Jim Fattori, "What You Need to Know About Leader Pins and Bushings", Plastics Technology, 2 May 2022: ptonline.com (leader pins lead one half of a mold into the other and align the halves on closing, in a close sliding fit with bushings in the opposite half).

5. Wikipedia, "Key (engineering)": en.wikipedia.org/wiki/Key_(engineering) (the key sits in slots in the shaft and the mating part, prevents relative rotation and transmits torque).

6. ASME B17.1-1967 (S2023), "Keys and Keyseats": asme.org (size, type and tolerances of parallel and taper keys and keyseats, and their relationship to shaft and bore diameters).

7. Wikipedia, "Spline (mechanical)": en.wikipedia.org/wiki/Spline_(mechanical) (ridges on a shaft that mesh with grooves in the mating piece and keep the angular correspondence; parallel key and involute splines among its types; external splines broached, shaped, milled or hobbed, among other methods).

8. Smalley, "Retaining Ring Types and Selection": smalley.com/blog/retaining-ring-types-and-selection (external rings sit in a shaft groove; standard rings are listed with their groove diameter and width).

9. Wikipedia, "Engineering fit": en.wikipedia.org/wiki/Engineering_fit (upper case for the hole, lower case for the shaft; H7/g6 sliding, H7/h6 location, H7/k6 and H7/n6 transition, H7/p6 press fit).

10. Wikipedia, "Design for manufacturability", section "Tolerances": en.wikipedia.org/wiki/Design_for_manufacturability (the tighter the tolerance, the more expensive the part is to machine).

11. Jason Richter, "Total Runout", GD&T Basics: gdandtbasics.com/total-runout/ (variation relative to a datum axis over a full revolution; controls straightness, circularity and taper of the surface).

12. Wikipedia, "Metal lathe": en.wikipedia.org/wiki/Metal_lathe (cutting tools push long work away from its supports, so it is supported in the middle; Swiss-style tools cut next to the guide bushing, where the stock is more rigid, suiting slender work).

13. Eaton Steel Bar Company, "1018 Cold Drawn & Finished Steel Bar": eatonsteel.com/1018-cold-rolled-steel-bar.html (cold-drawn 1018 gives greater dimensional control, improved straightness and a better surface for machining; shafts, axles and pins among its uses).

14. AZoM, "AISI 4140 Alloy Steel", updated 18 December 2019: azom.com/article.aspx?ArticleID=6769 (chromium, molybdenum and manganese low alloy steel; high fatigue and torsional strength).

15. Dalsteel via AZoM, "Stainless Steel - Grade 303 (UNS S30300)", 22 October 2001: azom.com/article.aspx?ArticleID=964 (the sulfur that aids machining lowers corrosion resistance below Grade 304; shafts and bushings among its uses).

16. Wikipedia, "17-4 stainless steel": en.wikipedia.org/wiki/17-4_stainless_steel (used where high strength, hardness and corrosion resistance are required; corrosion resistance comparable to 304).

17. Wikipedia, "Brass": en.wikipedia.org/wiki/Brass (used where corrosion resistance and low friction are required, such as hinges, bearings and valves; non-sparking fittings and tools).

18. Wikipedia, "Ti-6Al-4V": en.wikipedia.org/wiki/Ti-6Al-4V (ASTM Grade 5, one of the most commonly used titanium alloys; high specific strength and excellent corrosion resistance).

19. Hudson Tool Steel, "A2 Tool Steel": hudsontoolsteel.com/technical-data/steelA2 (punches and dies, dowel pins and gages among the uses of A2).

20. ASME B18.8.2-2020, "Taper Pins, Dowel Pins, Straight Pins, Grooved Pins, and Spring Pins (Inch Series)": asme.org (dimensional data for five pin types; the data does not imply that every size is a stock production size).

21. Wikipedia, "Spring pin": en.wikipedia.org/wiki/Spring_pin (also called a tension or roll pin; rolled from strip, slotted or coiled; body larger than its hole, held by the force against the hole wall).

22. Engineers Edge, "Involute Spline ANSI B92.1 Equations and Design": engineersedge.com (number of teeth, diametral pitch, pressure angles of 30, 37.5 and 45 degrees; side fit and major diameter fit).

23. Meyer Gage via Newman Tools, "The ABC’s of Pin Plug Gages, and the 10 percent gauge rule": newmantools.com/meyer/pluggage_ABC.htm (GO and NO-GO gages check a hole’s lower and upper limits; gage tolerance classes).