Is one allowed to use can openers on shabbos or chag?

Question

Is one allowed to use a can opener on Shabbos or Chag to open things like canned veggies etc?

Also on Shabbos or Chag may one open canned food that has the pull tab and doesn't require a can opener?

Answer 1

We need to define what can be the problems.

1. To use a special utensil, which is not a problem at all.
2. to create an utensil.

The OP does not regard the problem of creation or repair of an utensil.

Mishna Shabbat 22, 3:

שׁוֹבֵר אָדָם אֶת הֶחָבִית לֶאֱכֹל הֵימֶנָּה גְרוֹגָרוֹת, וּבִלְבַד שֶׁלֹּא יִתְכַּוֵּן לַעֲשׂוֹת כְּלִי. ‏

We are allowed to break a barrel with a view to eat the content, e.g. dried figs.

וְאֵין נוֹקְבִים מְגוּפָה שֶׁל חָבִית, דִּבְרֵי רַבִּי יְהוּדָה. וַחֲכָמִים מַתִּירִין. ‏

We can not to pierce the cap of the barrel, according to Rabbi Yehuda, and Chachamim allow. {Obviously the hole is made with a spin, which is similar halachically to opener}

וְלֹא יִקְּבֶנָּה מִצִּדָּהּ. ‏

We can not drill it on the side.

Gemara 146a:

בעו מיניה מרב ששת: מהו למיברז חביתא בבורטיא בשבתא? ‏

R`Shesheth was asked: What about piercing a cask with a spit (a tip) on the Sabbath?

לפיתחא קמיכוין - ואסיר, או דילמא: לעין יפה קמיכוין, ושרי - אמר להו: לפיתחא קא מכוין - ואסיר. ‏

does he intend [making] an opening, so it is forbidden, or perhaps his intention is to be generous and it is permitted? - He intends [making] an opening, replied he, and it is forbidden. {we see again that the problem is not linked to the use of an opener-like utensile}

מיתיבי, רבן שמעון בן גמליאל אומר: מביא אדם חבית של יין ומתיז ראשה בסייף - התם ודאי לעין יפה קמיכוין. הכא, אם איתא דלעין יפה קמיכוין - לפתוחי מיפתח. ‏

An objection is raised: Rabban Simeon Ben Gamaliel said: One may bring a cask of wine and strike off its head with a sword? - There his intention is certainly to be generous: but here, if he really means to be generous - let him open it.

In Gemara 48b is discussed also if the separated piece is an integral part of the barrel.

In this Mishna and Gemara we see two problems, to make a precise hole which is an amelioration of the barrel, to use an instrument in way to drill well the barrel. A gzera Derabanan when the hole is to output only.

The use of an opener is not on itself a problem.

אמר רבה: דבר תורה - כל פתח שאינו עשוי להכניס ולהוציא - אינו פתח, ורבנן הוא דגזור משום לול של תרנגולין, דעביד לעיולי אוירא ולאפוקי הבלא. ‏

Said Rabbah: By the words of the Torah every opening which is not made for putting in and taking out is not an opening, and it was the Rabbis who forbade it on account of [the ventilation of] a hen-coop, which is made to permit the fresh air to enter and the fumes to pass out.

In a tin can, the aim of the opening is not to putting in and taking out, but to taking out the food only (Nowaday nobody open a tin can to reuse it). So there is no problem MideOrayta.

Mekalkel is Patur Aval assur, but only for big container greater than 40 Sea.

The use of a tool is not a problem because it make an allowed work. It isn't Keli Shemelachto leIssur.

The problem is apparently not linked to the can opener. (You can see in Shemirat Shabbat Kehilcheta 9, 3. He reports several Acharonim for allowance with a can that everybody leaves.)

But may be that is we make a very imperfect whole it is allowed because this is no similarly to a hole made for putting in and taking out.

Concerning the OP, no doubt that when poskim talk about tin can, they assume that people cut it with a can opener. OPENER IS ALLOWED

There is a question about Keli Shemelachto Leissur Ul'heter. The opener can open a can which have a hole in the bottom and can not be a Keli. So the Melachto is not specifically leIssur.

Answer 2

In general it seems like the question you are really asking is whether or not one creates a new vessel by opening a can (which would therefore make it prohibited). The answer is, if you are Ashkenazi, then a lot of poskim consider it forbidden as they view it as creating a new vessel, this is the opinion of Rav Shlomo Zalman. However, many Sephardic poskim disagree with this, such as Ovadia Yosef. Here is his opinion regarding opening bottle caps:

Rav Ovadia Yosef disagrees with both points of Rav Shlomo Zalman. He thinks that even while the cap is attached to the bottle it is considered a kli since it is covering the bottle (Yechave Daat 2:42). Also, if you would be able to take it off without breaking the ring, even though it wouldn’t fit over a bottle of the same size, it would technically still be usable to cover (albeit not via screwing) a smaller bottle. (Response to Rav Shlomo Zalman quoted in Yalkut Yosef Shabbos Krach Bet 314:18:20) Additionally, the Magid Mishnah (Hil’ Shabbos 12:2) holds that metakein kli is completely permitted if you don’t have intent. Combining his above reasoning with the Magid Mishnah’s leniency, Rav Ovadia paskins that it is permitted to open bottle caps for the first time on Shabbos. Rav Shlomo Zalman disagrees with Rav Ovadia's application of the Magid Mishnah. He explains that even though your main intent is for the drinking, it’s also on your mind to make a cap that would be usable in the future. Nonetheless, Rav Ovadia paskins that it is permitted, and does not differentiate between metal and plastic bottle caps.

Source: http://www.halachipedia.com/index.php?title=Opening_bottles_and_cans#cite_note-25