I have no idea why this gets NPE's all the time

src/main/java/com/cricketcraft/chisel/block/tileentity/TileEntityAutoChisel.java

@@ -2,6 +2,8 @@ package com.cricketcraft.chisel.block.tileentity;
 
 import java.util.List;
 
+import com.cricketcraft.chisel.api.carving.CarvingUtils;
+import net.minecraft.block.Block;
 import net.minecraft.entity.item.EntityItem;
 import net.minecraft.entity.player.EntityPlayer;
 import net.minecraft.inventory.ISidedInventory;
@@ -29,7 +31,7 @@ import cpw.mods.fml.relauncher.SideOnly;
 public class TileEntityAutoChisel extends TileEntity implements ISidedInventory {
 
 	public enum Upgrade {
-		SPEED, AUTOMATION, STACK;
+		SPEED, AUTOMATION, STACK, REVERSION;
 
 		public String getUnlocalizedName() {
 			return ChiselItems.upgrade.getUnlocalizedName() + "_" + this.name().toLowerCase();
@@ -47,7 +49,7 @@ public class TileEntityAutoChisel extends TileEntity implements ISidedInventory
 
 	private static EntityItem ghostItem;
 	boolean equal = false;
-	private ItemStack[] inventory = new ItemStack[7];
+	private ItemStack[] inventory = new ItemStack[8];
 	private String name = "autoChisel";
 
 	// client animation fields
@@ -114,7 +116,6 @@ public class TileEntityAutoChisel extends TileEntity implements ISidedInventory
 
 		if (!worldObj.isRemote && hasChisel() && base != null && target != null) {
 			if (canBeMadeFrom(base, target)) {
-
 				if (progress >= (hasUpgrade(Upgrade.SPEED) ? FAST_SPEED : SLOW_SPEED)) {
 
 					// reset progress
@@ -141,6 +142,65 @@ public class TileEntityAutoChisel extends TileEntity implements ISidedInventory
 					// if we have the stack upgrade, boost the stack size to the max possible, otherwise just one
 					chiseled.stackSize = hasUpgrade(Upgrade.STACK) ? canBeMade : 1;
 
+					if (canChisel(chiseled)) {
+						// if our output is empty, just use the current result
+						if (output == null) {
+							setInventorySlotContents(OUTPUT, chiseled);
+						} else {
+							// otherwise just add our result to the existing stack
+							inventory[OUTPUT].stackSize += chiseled.stackSize;
+							slotChanged(OUTPUT);
+						}
+
+						chiselItem(chiseled.stackSize);
+
+						// remove what we made from the stack
+						base.stackSize -= chiseled.stackSize;
+						if (base.stackSize <= 0) {
+							setInventorySlotContents(BASE, null); // clear out 0 size itemstacks
+						}
+					}
+				} else if (worldObj.getTotalWorldTime() % 10 == 0) {
+					progress++;
+				}
+			}
+		} else if(!worldObj.isRemote && hasChisel() && base != null && hasUpgrade(Upgrade.REVERSION)){
+			if(Carving.chisel.getItemsForChiseling(base) != null){
+				if (progress >= (hasUpgrade(Upgrade.SPEED) ? FAST_SPEED : SLOW_SPEED)) {
+
+					// reset progress
+					progress = 0;
+
+					// the max possible for this craft
+					int canBeMade = base.getMaxStackSize();
+
+					// if there are items in the output, they count towards the max we can make
+					if (output != null) {
+						canBeMade -= output.stackSize;
+					}
+
+					// can't make more than we have
+					canBeMade = Math.min(base.stackSize, canBeMade);
+
+					// if we can't make any, forget it
+					if (canBeMade <= 0) {
+						return;
+					}
+					ItemStack chiseled;
+					if(Carving.chisel.getItemsForChiseling(inventory[TARGET]).get(0) != null){
+
+						// result will always be a copy of the target, of course
+						chiseled = inventory[TARGET].copy();
+						// if we have the stack upgrade, boost the stack size to the max possible, otherwise just one
+						chiseled.stackSize = hasUpgrade(Upgrade.STACK) ? canBeMade : 1;
+					} else {
+						// result will always be a copy of the target, of course
+						chiseled = base.copy();
+						// if we have the stack upgrade, boost the stack size to the max possible, otherwise just one
+						chiseled.stackSize = hasUpgrade(Upgrade.STACK) ? canBeMade : 1;
+					}
+
+
 					if (canChisel(chiseled)) {
 						// if our output is empty, just use the current result
 						if (output == null) {
@@ -197,7 +257,11 @@ public class TileEntityAutoChisel extends TileEntity implements ISidedInventory
 			return !toMerge.getHasSubtypes() || toMerge.getItemDamage() == inventory[OUTPUT].getItemDamage();
 		}
 
-		return ((IChiselItem)inventory[CHISEL].getItem()).canChisel(worldObj, inventory[CHISEL], General.getVariation(inventory[TARGET]));
+		if(inventory[TARGET] == null){
+			return ((IChiselItem)inventory[CHISEL].getItem()).canChisel(worldObj, inventory[CHISEL], General.getVariation(inventory[BASE]));
+		} else {
+			return ((IChiselItem)inventory[CHISEL].getItem()).canChisel(worldObj, inventory[CHISEL], General.getVariation(inventory[TARGET]));
+		}
 	}
 
 	private boolean hasChisel() {
@@ -208,14 +272,27 @@ public class TileEntityAutoChisel extends TileEntity implements ISidedInventory
 	private void chiselItem(int chiseled) {
 		if (!worldObj.isRemote) {
 			boolean breakChisel = false;
-			if (((IChiselItem) inventory[CHISEL].getItem()).onChisel(worldObj, inventory[CHISEL], General.getVariation(inventory[TARGET]))) {
-				inventory[CHISEL].setItemDamage(inventory[CHISEL].getItemDamage() + 1);
-				if (inventory[CHISEL].getItemDamage() >= inventory[CHISEL].getMaxDamage()) {
-					setInventorySlotContents(CHISEL, null);
-					breakChisel = true;
+			if(inventory[TARGET] == null){
+				if (((IChiselItem) inventory[CHISEL].getItem()).onChisel(worldObj, inventory[CHISEL], CarvingUtils.getDefaultVariationFor(Block.getBlockFromItem(inventory[TARGET].getItem()), inventory[TARGET].getItemDamage(), General.getVariation(inventory[TARGET]).getOrder()))) {
+					inventory[CHISEL].setItemDamage(inventory[CHISEL].getItemDamage() + 1);
+					if (inventory[CHISEL].getItemDamage() >= inventory[CHISEL].getMaxDamage()) {
+						setInventorySlotContents(CHISEL, null);
+						breakChisel = true;
+					}
 				}
+				PacketHandler.INSTANCE.sendToDimension(new MessageAutoChisel(this, chiseled, true, breakChisel), worldObj.provider.dimensionId);
+			} else {
+				if (((IChiselItem) inventory[CHISEL].getItem()).onChisel(worldObj, inventory[CHISEL], General.getVariation(inventory[TARGET]))) {
+					inventory[CHISEL].setItemDamage(inventory[CHISEL].getItemDamage() + 1);
+					if (inventory[CHISEL].getItemDamage() >= inventory[CHISEL].getMaxDamage()) {
+						setInventorySlotContents(CHISEL, null);
+						breakChisel = true;
+					}
+				}
+				PacketHandler.INSTANCE.sendToDimension(new MessageAutoChisel(this, chiseled, true, breakChisel), worldObj.provider.dimensionId);
 			}
-			PacketHandler.INSTANCE.sendToDimension(new MessageAutoChisel(this, chiseled, true, breakChisel), worldObj.provider.dimensionId);
+
+
 		} else {
 			if (breakChisel) {
 				worldObj.playSound(xCoord + 0.5, yCoord + 0.5, zCoord + 0.5, "random.break", 0.8F, 0.8F + worldObj.rand.nextFloat() * 0.4F, false);

src/main/java/com/cricketcraft/chisel/inventory/ContainerAutoChisel.java

@@ -25,9 +25,10 @@ public class ContainerAutoChisel extends Container {
 		addSlot(tileEntityAutoChisel, 1, 78, 52);
 		addSlot(tileEntityAutoChisel, 2, 103, 15);
 		addSlot(tileEntityAutoChisel, 3, 8, 62);
-		addSlot(tileEntityAutoChisel, 4, 151, 11);
-		addSlot(tileEntityAutoChisel, 5, 151, 31);
-		addSlot(tileEntityAutoChisel, 6, 151, 51);
+		addSlot(tileEntityAutoChisel, 4, 151, 5);
+		addSlot(tileEntityAutoChisel, 5, 151, 25);
+		addSlot(tileEntityAutoChisel, 6, 151, 45);
+		addSlot(tileEntityAutoChisel, 7, 151, 65);
 
 		bindPlayerInventory(player);
 	}

src/main/java/com/cricketcraft/chisel/item/ItemUpgrade.java

@@ -13,7 +13,7 @@ import com.cricketcraft.chisel.block.tileentity.TileEntityAutoChisel.Upgrade;
 
 public class ItemUpgrade extends BaseItem {
 
-	public IIcon[] icons = new IIcon[3];
+	public IIcon[] icons = new IIcon[4];
 
 	public ItemUpgrade(String unlocalizedName) {
 		super();
@@ -40,7 +40,7 @@ public class ItemUpgrade extends BaseItem {
 	@SuppressWarnings({ "unchecked", "rawtypes" })
 	@Override
 	public void getSubItems(Item item, CreativeTabs tab, List list) {
-		for (int i = 0; i < 3; i++) {
+		for (int i = 0; i < Upgrade.values().length; i++) {
 			list.add(new ItemStack(item, 1, i));
 		}
 	}