The Rolex Datejust epit­o­mizes the clas­sic wrist­watch. We tested the lat­est stain­less-steel model with the new man­u­fac­ture Cal­iber 3235 move­ment un­der con­di­tions that sim­u­late an or­di­nary day in the Datejust’s life.

WatchTime - - Table Of Contents - By Martina Richter

| e Rolex Datejust epit­o­mizes the clas­sic wrist­watch. We tested the lat­est stain­less-steel model with the new man­u­fac­ture Cal­iber 3235 move­ment un­der con­di­tions that sim­u­late daily life.

— When it pre­miered in 1945, the Rolex Datejust was the first au­to­matic, wa­ter­tight wrist­watch with chronome­ter-wor­thy rate qual­ity. It em­bod­ied all of the in­no­va­tions Rolex had de­vel­oped for wrist­watches up to that time, in­clud­ing a date dis­play in a win­dow at 3 o’clock, where the date switched au­to­mat­i­cally at mid­night. To achieve this feat, in­ter­me­di­ate wheels in the move­ment tight­ened a spring mech­a­nism that ad­vanced the date disk. The Datejust is named for this in­stan­ta­neous “just-in-time” date switch­ing.

Thanks to a mov­able fin­ger in Rolex’s new au­to­matic Cal­iber 3235, which pow­ers the Oys­ter Per­pet­ual Datejust 41 we tested, the date can be reset man­u­ally, quickly, when­ever de­sired. Sim­ply pull the crown out to its mid­dle po­si­tion, turn it coun­ter­clock­wise, and the date ad­vances smoothly and ac­cu­rately. The er­gonomic im­prove­ments that Rolex made to this cal­iber, in the in­ter­face for mak­ing man­ual ad­just­ments, are very no­tice­able in prac­tice. The wind­ing stem en­gages se­curely in each po­si­tion so the time can be reset pre­cisely. The crown turns with but­tery smooth­ness. The hands move with no play what­so­ever, so the min­utes hand can be po­si­tioned with its tip per­fectly tan­gent to the de­sired in­dex. The sec­onds hand can be stopped at the full minute easily be­cause the screw-down crown’s stem is in­serted into a long tube and the un­screwed crown is easy to grasp. Screw­ing the crown shut again is very se­cure, with a no­tice­able spring re­sis­tance. This is char­ac­ter­is­tic of the Twin­lock sys­tem, which Rolex in­vented in 1953.

The Twin­lock sys­tem’s in­ter­play with the Oys­ter case guar­an­tees that the Datejust can re­sist pres­sure up to 10 bar, which cor­re­sponds to the con­di­tions at a depth of 100 me­ters be­low the wa­ter’s sur­face. Two in­su­la­tors help en­sure wa­ter­tight­ness: one is lo­cated in the wind­ing crown while the other is sit­u­ated inside the tube. A line un­der the Rolex logo on the wind­ing crown of our steel Datejust shows that our test watch has the Twin­lock sys­tem. Gold Oys­ter cases have two dots on the crown to in­di­cate the pres­ence of the Twin­lock sys­tem, while plat­inum cases have one dot.

Our Datejust’s newly de­signed Oys­ter case has a mid­dle piece milled from a sin­gle block of 904L stain­less steel. A smooth, pol­ished stain­less-steel bezel sur­round­ing a flat pane of sap­phire seals the case from above. The Cy­clops mag­ni­fy­ing lens above the date win­dow wasn’t added to the Datejust un­til 1954. It per­forms its prac­ti­cal pur­pose thanks to its mag­ni­fy­ing ef­fect and the anti-re­flec­tive treat­ment on both its sur­faces.

The back of the case isn’t very ex­cit­ing: it pro­vides no in­for­ma­tion about any of the Datejust’s char­ac­ter­is­tics, like its wa­ter re­sis­tance, its ma­te­ri­als or its ref­er­ence num­ber. Fur­ther­more, the back can only be re­moved us­ing a spe­cial wrench, which Rolex’s au­tho­rized watch­mak­ers slip over the knurl­ing along the edge of the case­back. Un­for­tu­nately, Cal­iber 3235 re­mains in­vis­i­ble to would-be ad­mir­ers who don’t have ac­cess to this tool. That’s a pity, be­cause this move­ment has noth­ing to hide. It boasts all the fine char­ac­ter­is­tics of a Rolex cal­iber: dis­tinc­tively shaped and ar­ranged bridges, gold-plated cov­ers, red re­vers­ing wheels in the au­to­matic-wind­ing mech­a­nism, and hand­some fin­ish­ing such as sun­burst pat­terns, brushed matte parts, a few beveled edges and pol­ished heads on the screws.

Rolex in­au­gu­rated a new gen­er­a­tion of me­chan­i­cal move­ments in 2015 with two pre­cious-me­tal mod­els: the Day-date 40 and the Datejust Pearl­mas­ter 39. This was fol­lowed in 2016 by a bi­color ver­sion of the Datejust 41, and in 2017 by the Datejust 41 in stain­less steel and the new 43-mm Sea-dweller. Four­teen patents pro­tect Cal­iber 3235, which marks a new per­for­mance stan­dard for the brand in terms of rate pre­ci­sion, power re­serve, shock re­sis­tance, re­sis­tance to mag­netic fields, ease of ad­just­ment and reli­a­bil­ity. Com­pared to its pre­de­ces­sor (Cal­iber 3135), 90 per­cent of its com­po­nents have been re­vised and op­ti­mized: from the main­spring and the bar­rel to the au­to­matic-wind­ing mech­a­nism, and from the gear train to the es­cape­ment. The lat­ter bears the Chronergy name and is a patented Rolex in­no­va­tion.

The Chronergy es­cape­ment in­creases the ef­fi­ciency of the Swiss lever es­cape­ment by 15 per­cent. This ac­counts for nearly half the boost in the move­ment’s run­ning au­ton­omy, which now far sur­passes Cal­iber 3135’s 48 hours; Cal­iber 3235 amasses a power re­serve of ap­prox­i­mately 70 hours. The re­main­ing lion’s share of the in­crease was achieved by chang­ing ge­ome­tries. Rather than be­ing ar­ranged in a con­tin­u­ous line, as in the past, the el­e­ments of the es­cape­ment are now set on an an­gle, which re­sults in greater lever­age. The es­cape wheel is skele­tonized to lighten its weight and re­duce its in­er­tia. The ruby pal­let stones have been thinned to 125 mi­crom­e­ters, a 50-per­cent re­duc­tion com­pared to the pre­vi­ous ones. And the con­tact sur­faces of the es­cape wheel teeth have been dou­bled. More­over, fab­ri­ca­tion from a nickel-phos­pho­rous al­loy as­sures that the Chronergy es­cape­ment is in­sen­si­tive to mag­netic in­ter­fer­ences. This is also true of the blue Parachrom hair­spring, which “breathes” inside Cal­iber 3235 and is made from a nio­bium-zir­co­nium-oxy­gen

al­loy. This lit­tle spring, which has been proven to re­main sta­ble de­spite tem­per­a­ture fluc­tu­a­tions and shocks, ends in an op­ti­mized Rolex over­coil and is mounted on a large bal­ance with vari­able mo­ment of in­er­tia. The bal­ance can be finely ad­justed by turn­ing four gold Mi­crostella nuts along its rim. Highly pre­cise me­chan­i­cal pro­cess­ing has im­proved the ad­just­ment of the bal­ance by a fac­tor of three.

The bal­ance os­cil­lates on a staff with a new geom­e­try, of­fer­ing greater re­sis­tance to mag­netic fields, and is pro­tected by Rolex’s Paraflex anti-shock sys­tem. The os­cil­la­tions oc­cur un­der a sta­ble bridge with greater im­pact re­sis­tance, an op­ti­mized height-ad­just­ment sys­tem and new in­te­grated pro­tec­tion for the bal­ance wheel.

At the other end of the en­ergy chain, highly ac­cu­rate me­chan­i­cal pro­cess­ing en­abled Rolex to achieve a 50-per­cent re­duc­tion in the thick­ness of the bar­rel’s wall. The greater vol­ume of space inside the bar­rel can ac­com­mo­date a longer main­spring, which re­sults in an ad­di­tional gain of 10 hours of run­ning au­ton­omy. Far­ther along the power train, new lubri­cants im­prove the ef­fi­ciency of the gear train. In­ci­den­tally, Rolex de­vel­ops and syn­the­sizes these lubri­cants it­self. Last but not least, the new Per­pet­ual ro­tor more quickly re­plen­ishes the reser­voir of en­ergy in the bar­rel. The os­cil­lat­ing weight is cut out to ab­sorb shocks: it’s now made from a monobloc and is fit­ted on a ball bear­ing. The weight is held at its cen­ter by a sin­gle screw, thereby fa­cil­i­tat­ing assem­bly.

Like all Rolex mod­els, our tested watch is cer­ti­fied as a “Su­perla­tive Chronome­ter,” ac­cord­ing to Rolex’s own pre­ci­sion stan­dard, which was re­de­fined in 2015. This norm is more rig­or­ous than any of the gen­er­ally valid stan­dards in the watch in­dus­try. For ex­am­ple, Rolex in­sists that the rate tol­er­ance of the move­ment af­ter in­stal­la­tion inside the case must not stray be­yond ±2 sec­onds per day. We tested this on our tim­ing ma­chine and then on equipment that simulates the con­di­tions of daily wear on a wrist. None of our mea­sured val­ues ex­ceeded 1 sec­ond per day. The per­for­mance also re­mained within these nar­row lim­its more than two days af­ter the ex­haus­tion of the spec­i­fied power re­serve and af­ter ex­po­sure to a mag­netic field of 1,000 gauss. The rate fluc­tu­ated slightly while un­der the

direct in­flu­ence of mag­netic fields, but it im­me­di­ately nor­mal­ized af­ter­ward and with­out de­mag­ne­ti­za­tion. Com­pared to Zenith’s Defy El Primero 21, which we sub­jected to the same tests, Rolex’s Datejust was much less dis­turbed by mag­ne­ti­za­tion.

The ad­jec­tive “Su­perla­tive” on our Datejust’s an­thracite-col­ored rhodium dial aptly de­scribes the ex­cep­tional abil­i­ties of Cal­iber 3235. The sun­burst pat­tern on the watch’s face plays with the light, as do the shiny frames around the ap­plied hour in­dexes and the facets on the hands. This ex­erts only a mi­nor in­flu­ence on the watch’s leg­i­bil­ity be­cause ev­ery­thing is suf­fi­ciently large, well pro­por­tioned and neatly ar­ranged. When the lights go out, the Chro­ma­light in­lays in the in­dexes and hands shine with such an in­tense blue glow that it hardly both­ers the ob­server that two in­di­ca­tors have no lu­mi­nous ma­te­rial: the date at 3 o’clock and the Rolex crown at 12.

The Oys­ter bracelet at­taches to the case where the Rolex logo crowns the dial. The wrist­band fits seam­lessly in the newly de­signed con­nect­ing pieces that are firmly an­chored be­tween the lugs. The three-row bracelet con­sists of solid, partly pol­ished and partly satin-fin­ished el­e­ments made of 904L stain­less steel. Sev­eral of these parts are screwed to­gether near the clasp so the bracelet’s length can be easily ad­justed.

The Oys­ter­clasp fold­ing clasp is equipped with the Ea­sylink ex­ten­sion sys­tem, a sys­tem patented by Rolex that al­lows the bracelet’s length to be var­ied easily by as much as 6 mm. All in all, the Datejust 41 unites the lat­est de­vel­op­ments from the Rolex brand, just as its pre­de­ces­sor did when it was in­tro­duced more than 70 years ago. This isn’t no­tice­able at first glance, and the un­der­state­ment is ex­actly what makes this model so ap­peal­ing. —

The Cy­clops mag­ni­fy­ing lens, which was added to the Datejust in 1954, is a dis­tin­guish­ing fea­ture of Rolex watches and very prac­ti­cal in daily use.

The Datejust 41 has a smooth bezel and an easy-to-use Twin­lock crown.

The Ea­sylink ex­ten­sion sys­tem is con­cealed inside the Oys­ter­clasp fold­ing clasp.

Chro­ma­light in­lays in the in­dexes and hands shine with an in­tense blue glow in the dark.

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