Upright size
75 mm rack uprights: not the same as 3x3 in
A 75 mm upright is 1.2 mm smaller per side than a 3x3 in upright. A 2020-era REP FAQ describes 75 x 75 mm REP racks; REP's rack guide says 3x3 in.
Also listed as 75 x 75 mm
Short answer
A 75 mm upright is 1.2 mm smaller per side than a 3x3 in upright, which calculates to 76.2 mm, so the two labels are not the same size. A 2020-era REP ISO arm FAQ describes 75 x 75 mm REP racks, while REP's rack guide lists its 4000 and 5000 Series as 3x3 in; the FAQ is generation-specific. See the 3x3 in page.
Key facts
- Nominal size
- 75 x 75 mm[1]
- Calculated other unit
- About 2.953 in (calculated from 25.4 mm per inch)[2]A calculation, never a tolerance.
- Often confused with
- 3 x 3 in (76.2 mm): 1.2 mm larger per side by label[2]The difference is between labels; it is not a fit tolerance.
- Hole diameters makers list
- REP ISO arm FAQ: the PR-4000 version fits an 18 mm hole; the PR-5000 V2 version fits a 27 mm hole[1]Undated REP FAQ from about 2020.
- Pin sizes makers list
- Not confirmed
- Spacing makers list
- Not confirmed
- Rack systems with this upright
- REP racks described as 75 x 75 mm in REP's 2020-era ISO arm FAQ[1][3]REP's rack guide lists the PR-4000 and PR-5000 as 3x3 in.
- Attachments sold for this size
- REP ISO arms (per REP's FAQ)[1]REP's FAQ also says it cannot guarantee cross-company compatibility.
- How to check yours
- Measure the outside of the tube in millimeters. A 75 mm and a 3x3 in tube differ by 1.2 mm per side by label.[2]
- Not confirmed
- Not confirmedWhether current REP racks match the 2020-era FAQ, pin sizes, spacing, and any other maker using 75 mm tubing.
Watch out for
- 75 mm is not 3x3 in. Do not treat a 75 mm part as a 3x3 in part, or the reverse.
- REP's 75 x 75 mm figure comes from a 2020-era ISO arm FAQ; do not assume the current PR-4000 or PR-5000 is identical.
Questions
Is 75 mm the same as 3x3 in?
No. Calculated from 25.4 mm per inch, 3 in is 76.2 mm, so a 75 mm tube is 1.2 mm smaller per side by label. That difference is not a fit tolerance.[2]