Curta Repairs

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Written by Jack Christensen

If you need your Curta cleaned or repaired, contact one of the people below. And if you repair Curtas, or know someone who does, please select Edit Text (see below) and add the appropriate contact information.

                        Photo courtesy of RickFurr


Do not submerge your Curta in a mixture of "white gas" (a clean burning fuel for camping stoves) and oil in an attempt to simultaneously clean and lubricate it. You will wash away molybdenum grease that is needed to lubricate a couple locations deep within the Curta. In addition, you will deposit oil at locations that must not have any lubrication (the "ten carry mechanism" (levers, blocks and transmission gears) and the "anti-reversing disc teeth"). Many Curtas have been inadvertently ruined when this procedure was performed.

Also, when cleaning the grey paint of a Type II, use only a mild cleaner. Strong cleaners have been known to soften or even dissolve the grey crackle paint. On occasion, the paint has come off in sheets when a solvent was used to clean dirt and oil from the paint.

Important Information Regarding Curta Repair Parts

Replacement parts needed in repairs generally cost between $10 and $600 (w/o installation labor). Even the simplest lever or gear can cost $40. Some Curtas that look nearly perfect on the outside can incur major expenses to replace broken parts inside.

Most broken or damaged Curta parts can be replaced with NOS (New, Old Stock) parts. But some NOS parts are very rare. One such part is the central "tens unit" on a Type II. As of 12/8/04, there is only one NOS "tens unit" known to exist. Of course, such a part could be obtained by disassembling a Type II "parts unit".

Similarly, the metal clearing lever for the Type I is in short supply. Unfortunately, many clearing levers have been damaged when placing the instrument into its cannister. If the clearing lever is not moved to its storage position before replacing the cannister top, the extended ring portion of the clearing lever will catch the edge of the cannister, resulting in a bent or broken part. There are few "uncommitted" NOS metal clearing levers remaining. (That is, clearing levers that have not been put aside for installation on a Curta "just in case".) The remaining metal clearing levers will most likely be installed only on very, very old Type I Curtas. An "everyday" Type I with a broken metal clearing lever can be repaired, but the broken metal clearing lever will be replaced with the more robust style plastic clearing lever used on all later manufactured Curtas.

Another rare item is the bottom foam cushion for a Type II canister. There are only a few NOS Type II cushions remaining.

There are no NOS metal cannisters for the Type I or Type II. As far as "used" metal canisters are concerned, there may be a few. But these extra canisters are often retained as a back-up part by the owner of a Curta (i.e., used canisters are rarely available as a stand-alone spare part). There are a few NOS plastic canisters for the Type I, but none for the Type II. If a Curta is purchased without a canister, it is going to be very difficult and costly to obtain a replacement canister for that machine.

NOS clearing plates, body shells, and knurled hand grips are also very rare. There is only one NOS Type II grey painted body shell and upper collar available. There are no new bottom nameplates for a Type II.

On some early Type II Curtas the "tens carry springs" are very weak and brittle. There are 21 of these parts in each Type II, and it is not uncommon to find many broken springs in these Curtas. Unfortunately, so many replacement springs had been used to repair only a few Curtas that there is now a serious shortage of this critical part. An early Curta Type II in need of several tens carry levers, although perfect in every other regard, may be impossible to repair.

Curtas in need of parts no longer available are usable only as a "parts unit" for another broken Curta.. Such "non-repairable" Curtas can be perfect in every other regard, but be of little value to anyone who wants a complete and functioning machine. Unless you are willing to locate and buy another Curta to disassemble, the value of a Curta in need of an unobtainable NOS part is very low, no matter how perfect it looks in other regards.

Some Curtas in need of many repair parts, even when the parts are available, may nevertheless be useful only as a "parts units". This is simply because the cost to replace many broken parts may exceed the price of a fully functioning unit.

If you haven't done so already, please read about the Curta2000 modifications done by George Heath ( This excellent article will describe a procedure you can follow that will require extensive repairs. Any of the gentlemen below will gladly accept your modified Curta as a parts unit following the Curta2000 conversion.

Here are some recognized service locations for the Curta

JackChristensen repairs Curtas using original Contina factory tools and parts. You can reach Jack at:

Or visit the Timewise Curta Calculator Cleaning and Repair Service page. Simply click on any one of the following:

HansRudolfRoshard repairs Curtas using original Contina factory tools and parts. His workmanship and detailed knowledge of the Curta mechanism is amazing. You can reach Hans at:

Or visit his web site at:

GregSaville repairs Curtas. You can reach Greg at:

Or visit his web site at:

BerndSchroeder repairs Curtas. You can reach Bernd at:

Or visit his web site at:

RomanoManaresi repairs Curtas in Italy.

You can reach Romano at:

Or visit his web site at: - English/Italiano

Edit Text of this page (last edited December 21, 2015 by
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