Automotive & Motorsport

Which material for which part

Most parts on this page start in aluminum, and two alloys cover most of it. 6061 is described as “one of the most common alloys of aluminium for general-purpose use”, with automotive parts among its listed uses (source 1). 7075 is one of the 7000 series alloys that Wikipedia says are “often used in transport applications due to their high specific strength, including marine, automotive and aviation” (source 2). Brackets, adapters and spacers are usually drawn in one of them: billet aluminum parts covers what billet means and which parts suit it, and 6061 versus 7075 sets the two side by side.

Titanium is the step up when strength for its weight matters. Wikipedia puts it at 60% denser than aluminium but more than twice as strong as 6061-T6, and says titanium is used in automotive applications, “particularly in automobile and motorcycle racing where low weight and high strength and rigidity are critical” (source 3). Steel and 17-4 PH stainless take over where the load or the temperature is past what an aluminum part is drawn for. 4140 sits in the 41xx chromium-molybdenum family, which Wikipedia calls considerably stronger and harder than standard 1020 steel, though without enough chromium to match stainless for corrosion resistance (source 4). 17-4 PH is listed for applications that need high strength and corrosion resistance up to 600 °F (source 6).

The table gives published figures for one material in each group, from the source named in its last column. They are typical or minimum values for the condition shown (for 17-4 PH, the highest strength the source gives), not a measurement of any part, and sources differ: a supplier datasheet republished by AZoM lists a typical 1,000 MPa tensile strength and 910 MPa proof stress for Ti-6Al-4V (source 8), against the 900-950 and 880-920 MPa ranges below. 4140 and the other alloy steels are left out on purpose, because Wikipedia’s figures for them change with the condition and the section size (source 4). Other alloys and plastics quoted on request. Name the grade on the print.

Fits, bearing bores and press fits on the print

A fit is the clearance or interference between two mating parts, and ISO and ANSI both sort fits into clearance, location and interference categories (source 9). On a drawing a fit can be written as a code: in H7/h6, “a commonly used fit”, the upper-case letter gives the tolerance range of the hole and the lower-case letter that of the shaft, and the code sets the upper and lower size limits of each (source 9). Wikipedia lists a bearing bush as an example of an interference fit, and adds that press fits are “more often used for bearing-housing or bearing-shaft assembly” (sources 9 and 10).

On a drawing, put the fit code or the size limits on the bearing seat, pressed-in bushing or locating pin itself; with a STEP file and no drawing, write them in the notes. Typical tolerance is ±0.005 in, and bearing and press fits are held tighter where the print calls for it. Every part is inspected against your print before it ships. A hub or pulley with a bore and a keyway is quoted from the same print, and the bushing that presses into it can go on the same quote.

Corrosion, and the finish that goes on the print

Bare aluminum, steel and stainless behave differently, which is why the finish belongs on the print. 6061 “remains resistant to corrosion even when the surface is abraded” (source 1). The 41xx steels do not carry enough chromium to match stainless (source 4). Anodizing on aluminum “increases resistance to corrosion and wear”, but it does not increase the strength of the part (source 11). A finish called out on the print is quoted with the part, and anodizing, powder coating and passivation each have a page of their own.

Where the detail for each part lives

Each common part has its own page: custom brackets, bushings, spacers and standoffs, weld-in bungs, flanges and custom fittings. This page covers the buyer and the material; those cover the part.

Sources

All accessed 30 September 2026. Where a figure here differs from your print, the print governs.

1. Wikipedia, "6061 aluminium alloy": en.wikipedia.org/wiki/6061_aluminium_alloy (T6 tensile and yield strength, typical and minimum; density; general-purpose use, automotive parts among the listed uses; corrosion resistance when abraded).

2. Wikipedia, "7075 aluminium alloy": en.wikipedia.org/wiki/7075_aluminium_alloy (T6 tensile and yield strength; density; transport applications including automotive; vulnerability to stress corrosion cracking).

3. Wikipedia, "Titanium": en.wikipedia.org/wiki/Titanium (60% denser than aluminium and more than twice as strong as 6061-T6; use in automobile and motorcycle racing).

4. Wikipedia, "41xx steel": en.wikipedia.org/wiki/41xx_steel (4140 in the chromium-molybdenum family; stronger and harder than 1020 steel; chromium content short of stainless corrosion resistance; property tables by condition and section size).

5. Wikipedia, "Ti-6Al-4V": en.wikipedia.org/wiki/Ti-6Al-4V (density, tensile ultimate and yield ranges).

6. Wikipedia, "17-4 stainless steel": en.wikipedia.org/wiki/17-4_stainless_steel (tensile strength up to 190,000 psi; density; applications needing strength and corrosion resistance up to 600 °F).

7. Wikipedia, "A36 steel": en.wikipedia.org/wiki/A36_steel (minimum yield 36 ksi and ultimate 58-80 ksi under 8 in thick; density 7,800 kg/m³).

8. AZoM, "Titanium Alloys - Ti6Al4V Grade 5", supplied by U.S. Titanium Industry Inc., 30 July 2002: azom.com/article.aspx?ArticleID=1547 (typical tensile strength 1,000 MPa, 0.2% proof stress 910 MPa).

9. Wikipedia, "Engineering fit": en.wikipedia.org/wiki/Engineering_fit (ISO and ANSI fit categories; fit codes such as H7/h6; bearing bush as an interference example).

10. Wikipedia, "Interference fit": en.wikipedia.org/wiki/Interference_fit (press fits used for bearing-housing and bearing-shaft assembly).

11. Wikipedia, "Anodizing": en.wikipedia.org/wiki/Anodizing (corrosion and wear resistance, no added strength; Type II and Type III thickness; growth of half the oxide thickness per surface; the drawing note "dimensions apply after all surface finishes"; small threaded holes).

12. Larry Chesterfield, "Oversized Parts After Anodizing", Products Finishing, 1 August 2001: pfonline.com/articles/oversized-parts-after-anodizing (growth roughly one-third to one-half of the coating thickness per side; the machined dimension has to allow for it).