I understood that the main problem of mixing dairy and meat occurs when there is heat. I'm not saying that one can eat a cold pastrami and swiss cheese sandwich. Rather, that this rule applies to utensils.

So, if the deli and cheese are always cold, couldn't the store clean the slicer well after slicing deli and use the same slicer for cheese?

  • Why would you think they can't? If you Kasher a pot between chicken soup and cream of wheat, isn't that also not going to Treif anything? That's basically the definition of Kashering.
    – Double AA
    Nov 23, 2016 at 15:41
  • Theoretically yes. There is a special way to kasher a knife, assuming this device needs it. Practically there will be too many nooks and crannies that will still have residue. Especially considering who is hired to clean it.
    – user6591
    Nov 23, 2016 at 15:49

1 Answer 1


See Shulchan Aruch YD 89:4

שולחן ערוך יורה דעה פט סעיף ד'‏

..... אסור לחתוך גבינה אפילו צוננת בסכין שרגילין לחתוך בשר ....‏

הגה: וכן להפך נמי אסור מיהו על ידי נעיצה בקרקע קשה שרי (ב"י בשם א"ח וכל בו) אבל כבר נהגו כל ישראל להיות להם שני סכינים ולרשום אחד מהם שיהא לו היכר ונהגו לרשום של חלב ואין לשנות מנהג ישראל:‏

Rabbi Karo says that one may not cut cheese, even cold, with a knife that one uses to cut meat.

The Remo comments that the same applies the other way round (cut meat after cheese).

After pushing the knife into hard ground (and cleaning it, I assume), it (the cutting) should be allowed, but the custom amongst all Israel is to have two knives (one for meat and one for milk) and to mark one of them so it should not be mistaken – and the custom is to mark the milky knife and one should not change from the Jewish custom.

So it seems that you cannot use the same slicer for cheese and meat.

  • It seems, actually, that the Rama says the custom is not to. Others may not have this custom (and anyway the custom he proscribes changing may just be the choice to mark the milky knife instead of the meaty one).
    – Double AA
    Nov 23, 2016 at 17:05
  • @DoubleAA Yes. I was not sure what the Remo meant by the "kol" in אבל כבר נהגו כל ישראל. Nov 23, 2016 at 17:25

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