A. To cut spices with a knife:
Spices other than salt:  It is forbidden to cut pepper with a knife [into small pieces] even in order to eat immediately. The above law applies for all spices which are commonly only eaten when mixed [with other foods]. [See Q&A]
Cutting salt with a knife: It is forbidden to cut salt very small with a knife.
The reason for this is:  (because since [salt] is only fit to be eaten when mixed into other foods it therefore has the same laws as do spices and is not comparable to meat and cheese even though it too does not derive from growing on the ground just like they.) 
Thick pieces of cooked salt:  This [prohibition to cut salt to small pieces] only applies with salt that was initially thick. However salt which was initially thin and was then cooked and became [thick] pieces is permitted to be cut very thin with a knife just as it is permitted to do so by bread being that there is no [prohibition to] grind a previously ground [food].
Summary of cutting foods that are only used to season foods:
Spices and salt may not be cut to very small pieces even in order to eat right away.
May one cut fresh jalapeño peppers to small pieces in order to eat right away?
Is a cinnamon stick considered a spice or a food?
Seemingly it is considered a spice and thus may not be cut small even in order to eat right away.
May one grate horse radish, or cut it very small?
No. It is forbidden to do so even in order to eat right away. One may not even grate it using a knife. Thus it is only permitted to cut it to large pieces.
Are onions and garlic considered spices?
Onions: No, as stated explicitly by Admur below in Halacha C-See there for their ruling!
Garlic: No, as at times it is eaten plain. They thus have the same law as all foods which grow on the ground, as explained in Halacha C below- See there!
May one cut sugar cubes into small pieces [i.e. Is sugar considered a spice]?
One may cut sugar cubes into small pieces even for non-immediate use so long as one plans to eat it on Shabbos. Nevertheless some Poskim rule that sugar cubes do contain a grinding prohibition, and therefore in their opinion it is best to be stringent and only do so for right away use, in which case it is allowed according to all.
B. Cutting into small pieces foods that do not grow from the ground:
Any food which is fit to be eaten in its current form [without needing to be mixed with other foods] and does not grow on the ground, of which its species does not contain the concept of grinding at all, such as cooked or roasted meat or cheese and the like, then it is permitted to cut it very thin even [when done] not in order to eat right away, being that there is no grinding [prohibition] by [these] foods.
Hard Cheese: [Furthermore] even very hard cheese is allowed [to be cut small] being that it is [still] possible to be chewed, albeit with difficulty, and [thus] has a status of [a readily edible] food upon it.
If a person cannot chew: [Furthermore] it is allowed to be cut even by a person who cannot chew.
Raw Meat: However [soft] raw meat, since it is only fit for the strong minded which are willing to chew it in an irregular way [meaning while still raw], [therefore] it does not have the status of food on it for this matter and [the] grinding [prohibition] is applicable to it. Therefore it is forbidden to cut [Kosher] raw meat very thin to [feed] the birds [unless one does so to feed them right away. It is however permitted to cut Treif meat into very small pieces to feed the birds even later on Shabbos.]
The reason that it being fit for dog does not render it the status of food:  Now, although it is fit for dogs [nevertheless] it does not receive the status of food due to this being it is not designated [to be given] to dogs but rather for people or for birds due to its value, and for them [the meat] is not fit [to be chewed] without this cutting. [Thus the food is not yet considered to be food at this stage.]
Foods that do not grow on the ground which are edible in their current state: Do not have the grinding prohibition and may be cut even small.
Foods that do not grow on the ground which are inedible in their current state: Such as raw meat contains the grinding prohibition and thus is forbidden to be cut very small.
- The above is only with regard to using a regular knife and vessels of the like which are not designated for cutting small. Regarding vessels which are designated for cutting small-See Halacha D!
C. Cutting into small pieces foods that grow from the ground:
All the above refers to food that does not grow from the ground, however any food that grows from the ground, even if it is food that can be readily eaten has [the] grinding [prohibition] apply to it.
The reason for this is: because amongst these species [of foods are] foods that are ground, such as grains and legumes.
Vegetables and Fruits: Therefore it is forbidden to cut a vegetable very small in order to eat it, and so too [it is forbidden to cut very small] dried dates and carobs for old people, and if one does cut them very small then he is liable for grinding.
Crumbling bread: It is permitted to crumble bread very small for chickens and doing so does not involve the grinding prohibition.
The reason for this is: because the grain from which the bread was made had already been previously ground and there is no [prohibition to] grind a previously ground [food].
Cutting small with intent to eat right away: [However] all this refers to when one cuts [the food] and leaves it [there] not planning to eat it right away but rather to eat later on. However it is permitted to [even initially] cut [food] very small in order to eat it right away or for others to eat right away or for chickens to eat right away.
The reason for this allowance is: because [the Torah] did not forbid a person to eat his food in big or small pieces and thus [we see that] it is the way of eating to eat also small pieces and anything that is done in a way of eating carries no prohibition as was explained in chapter 319 [Halacha 1] regarding separating food from its waste in order to eat it right away that it does not contain any prohibition since this is the way of eating and it is allowed to even initially do so.
Other Opinions: There are opinions which question this allowance [to cut small when intending to eat it right away].
The Final Ruling: It is proper to suspect for this latter opinion and be careful to cut the vegetable (which is called lettuce) into slightly large pieces as then according to all opinion there is no grinding prohibition involved. However in our provinces it is the custom to cut radish very very small as well as onion and they have upon whom to rely on [Halachicly]. Nevertheless, at the very least they must beware to not begin to cut them until after [the men] leave the Shul being that it may only be done in actual proximity to the meal as was explained in chapter 319 [Halacha 4] regarding separating [food from its waste]. [See Q&A regarding if when cutting large one may do so even much time prior to the meal!]
Summary of cutting foods that grow on the ground
Foods which have never before been grinded small: Such as all fruits and vegetables, is Biblically forbidden to cut small in order to eat later on. Regarding cutting them to eat right away it is disputed if doing so is forbidden, and it is proper to be stringent to cut the pieces slightly large. Nevertheless those communities which are accustomed to be lenient have upon whom to rely, so long as they do so right before the meal. [See “The Laws of Borer” Halacha 4 regarding the exact definition of “right away”]
Foods which have been already ground: Such as bread of which its grains were already grinded to flower, and precooked salt which had dissolved and the reformed a block, is allowed to be cut small even to eat later on.
When cutting the food slightly large may one do so even much time prior to the meal?
Seemingly one may do so whenever he wishes so long as he intends to eat the food on Shabbos. This is unlike the ruling in SSH”K which writes that it is proper to only do so in close proximity to the meal even when cutting large
What is the definition of cutting small?
Some opinions rule cutting small is defined as cutting it to whatever size one usually cuts it to. Thus cutting it slightly larger would mean to cut it larger than one usually would cut it during the week.
Others however rule that there is no known measurement for what is defined as small, and one must thus always be careful to cut the pieces slightly large.
May one cut a fruit/vegetable to very thin slices [long but thin]?
Some Poskim rule that it is forbidden to do so as cutting very thin is equivalent to cutting into very small pieces, even if the slices remain long. Other Poskim however rule that this is permitted to be done.
If one transgressed and cut fruits/vegetables into small pieces not in close proximity to the meal, may the food still be eaten?
Inadvertently: If it was done inadvertently [such as one forgot about the prohibition and the like] it is permitted to eat the food. [See footnote  for reason]
D. What items may be used to cut with? May graters and the like be used?
A knife/chisel/ax: [It is allowed to be cut] whether with a knife or with an ax or a chisel as although these are vessels designated for prohibited use it is allowed to move them in order to use [for a permitted purpose] as explained in chapter 308 [Halacha 12].
A Grater: It is forbidden to grate any food, even one that does not grow on the ground, very thin with a dented grater which has sharp teeth (that is called Riv Eizin [grating iron] in Yiddish) even in order to eat right away.
The reason for this is: as since the vessel is designated for this use, doing so is considered a mundane action, as is crushing spices with a pestle and mortar. [See footnote  with regards to foods that grow from the ground]
Other cutting vessels: This law applies for any other vessel that is designated for this use of cutting small.
Using a grater or other instruments made for cutting items small:
It is forbidden to grate any food very thin with a grater, or with any vessel made to cut items small, even in order to eat right away.
May one use an egg slicer on Shabbos to cut eggs?
May one use a knife which is specifically made for cutting small?
This matter is disputed amongst Poskim. One should therefore avoid using it on Shabbos.
May one use a bread machine to slice bread on Shabbos?
If doing so does not involve electricity it is allowed. One may even adjust the blades to fit the sizes of the slices that he desires.
E. Cutting non food items into very small pieces:
Even if one is not meticulous on the sizes, if he cuts [wood] into very thin pieces in order to light up a fire [with them], then he is liable for [the] grinding [prohibition].
Practical Summary-Cutting foods to small pieces:
Foods may only be cut small if either :
- They have already been previously ground,
- Have never been previously ground but do not grow on the ground, and are edible in their current state, and are not used as a spice.
- In all cases they may only be cut using vessels that are not designated for cutting small.
 Mishneh Berurah 25 and Ketzos Hashulchan 129/2. Vetzaruch Iyun why Admur did not write this.
 However in the Sharreiy Tziyon he permits even cutting it small when done to eat right away. The Peri Megadim and Elyah Raba leave this with a Tzaruch Iyun!
 In other words: Although salt does not grow on the ground, nevertheless it contains a grinding prohibition being that it is used as a spice. [See Ketzos Hashulchan 129 footnote 12]
 Ketzos Hashulchan 129 footnote 12
 As since today many people eat them while still fresh, prior to them drying up and becoming very spicy, they therefore do not have the status of a spice and rather have the same status as foods that grow on the ground, of which there is a dispute as to whether they may be cut small for immediate use. [ibid]
 As they are never usually eaten plain and thus have the status of a spice. [ibid]
 Ketzos Hashulchan 129 footnote 13
 It used to be that cinnamon sticks were eaten plain, and it is for this reason that Admur rules in the laws of blessings [Seder Birchas Hanehnin 6/19] that its blessing is “Hadama”. However today since eating the sticks are unheard of, perhaps it has lost its food status and is only considered a spice and thus today may not be cut small even if one will eat them right away. [ibid]
 Ketzos Hashulchan 129 footnote 13
 As it is never eaten plain and is thus considered a spice. [ibid]
 Ketzos Hashulchan 129 footnote 14-regarding garlic
 Ketzos Hashulchan 129/4 footnote 16
 Sugar cubes do not contain the grinding prohibition as there is no grinding after grinding. It is similar to pieces of salt which have been cooked and turned into solid pieces which do not contain the grinding restrictions. [Ketzos Hashulchan 129 footnote 16, M”B and Peri Megadim 321 M”Z 10.]
 Shevisas Shabbos Tochein 16
 His reasoning is because this rule that grinding does not apply by previously ground items was only said by bread since it is a soft food, however by other items which become hard like sugar the grinding prohibition remains. His proof is from the fact all agree grinding applies by earthenware even though it was previously ground.
The Ketzos Hashulchan 129/3 sides like the Peri Megadim that there is no grinding prohibition by sugar. He negates the source of the Shevisas Shabbos saying the above law by earthenware does not apply by items that have grown on the ground.
 Aside for the Ketzos Hashulchan’s argument that sugar does not contain the grinding prohibition, he further argues that even if it does using a knife to cut it is considered a great irregularity and hence allowed. Thus in his opinion there is no need to be stringent at all to cut it for right away use, even under the basis that it contains the grinding prohibition.
 Sugar is not considered a spice as it is edible on its own and hence may be cut for right away use. [Ketzos Hashulchan ibid]
 Lit. well. Meaning that the thought does not disgust them.
 Ketzos Hashulchan 131/3
 As concludes Admur in next Halacha 321/10 [brought in C]. So rules Ketzos Hashulchan 131/3
 Ketzos Hashulchan 131 footnote 12
 Lit. importance
 Halacha 8
 Halacha 9
 Lit. complete food
 See Ketzos Hashulchan 129 footnote 3 which learns that the same laws which apply to allow one to do Borer apply here as well, as by both cases the permission is based on that it is done in the way of eating. Thus to grate vegetables using a designated vessel for grating would contain a Biblical prohibition according to all, just as is the law by Borer.
 321/10 and 12
 Az Nidbaru 12/22
 Biur Halacha 321 “Hamichateich”
 Ketzos Hashulchan 129 footnote 2
 So rules Tzemach Tzedek in Mishnayis Shabbos
 Igros Moshe 4/74-Tochein 3; Minchas Shlomo 91/13; and so rules plainly Piskeiy Teshuvos 321/4
 Ketzos Hashulchan 129 footnote 5
 This means one did so despite having knowledge of the prohibition.
 Just as is the rule with all Shabbos transgressions which are done intentionally. [See “Laws of Cooking” Chapter 2].
 The reason for this is because a) there are opinions [Rambam] which hold that the Biblical grinding prohibition only applies if one plans to cook the grinded food. And b) Since here one is allowed to cut thinly prior to the meal, there is no worry that if we allow the inadvertent sinner to eat the food then people will do it advertently and say that it was inadvertent, as they could simply do it near the meal. [Ketzos Hashulchan 129 footnote 5]
However the M”B, based on the Chayeh Adam rules that it is forbidden.
 The Ketzos Hashulchan adds that regarding foods which have a grinding prohibition, using any grinding designated vessel is Biblically forbidden even if done to eat right away, as using such vessels is not the way of eating but rather the way of working. [See there 129 footnote 3 and 4] Thus it is not just forbidden due to being a mundane act.
 Halacha 8
 SSH”K 6/3
 Aruch Hashulchan rules its permitted while the M”B  rules that it is forbidden. SSH”K rules like the M”B.
 SHH”K 6/11