He was born in Wöhrd, Nuremberg,[1] but moved to Amsterdam, where he worked for Izaak van der Putte and Hermanus Uytwerff before opening his own type foundry in 1735.

After Rudolf died in 1742, his son Hendrik Joris Wetstein sold the company in 1743 to Izaak Enschedé of Haarlem, forming the nucleus of the type-founding business of Joh.

His "Courant-Letter" face used by the Haerlemse Courant was one of the first marketed specifically for the use of newspapers;[1] historian Harry Carter praised him as "a superb cutter of small types, and in refinement of design and execution his news fonts are unsurpassed".

[2] During the 1760s he contributed to a planned book on the technology of typefounding and punchcutting intended to be published by the brothers Ploos van Amstel as a Dutch response to Pierre-Simon Fournier's Manuel Typographique, which was never finished.

Lane, who has prepared an edition and commentary on it, notes that "Enschedé scrupulously saved Fleischman's own account book and other documents, including even his passports, so that his career can be reconstructed in remarkable detail.

[17] Flesichman's typefaces have a high x-height (large lower-case letters, following the "Dutch taste" style of the preceding century) and strong appearance on the page, and have not always been well-reviewed aesthetically.

[19][4] Lane comments that "his romans lack the staid majesty and subtle curves"[1] of Baskerville's delicate typefaces of the same period, and James Mosley wrote that "Fleischman was undoubtedly a virtuoso punchcutter, even though there is something rather arid about his hard, angular types.