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How To Grind D2 Tool Steel On A Manual Surface Grinder

surface grindingD2 tool steel is a lot like bad tasting medicine that is good for you: you hate it, but you need it. So, how can you grind D2 tool steel on a manual surface grinder, with precision and economy?

How to grind D-2 tool steel without flood coolant

Suppose you are using a typical surface grinder, such as a Mitsui, Brown and Sharpe, Okamoto or Harig 6x12 or 6x18.

Your grinder has no flood coolant, and you prefer not to use some kind of spray mist coolant; you are going to be dry grinding the steel.

Do not try to dry grind large workpieces on a manual surface grinder, it will not work. Unless you have absolutely no other option, don't even consider trying to dry grind a large workpiece. Smaller workpieces will work fine, just be patient.

A typical injection mold or stamping die component could be 2x4 x1/4 in, and you might have 4 of them to grind together. They can certainly be ground dry on a manual surface grinder, though flood coolant is obviously preferred.

Mill off excess grinding stock first, if possible

If there is too much stock left for grinding, which seems to often happen, you could try hard milling the excess material off in a manual milling machine, such as a Bridgeport or Deckel, using a solid coated carbide end mill.

Usually there are plenty of good used carbide cutters left over from CNC precision milling jobs in the shop. If you find one with a radius on the corners, it will hold up much longer. A bull nose cutter, with a .010 in. radius will last longer and leave a better finish that a square cornered cutter.

Norton suggests using a 5SG-46 grit grinding wheel

Once you get to the point where you are ready to grind, use a Norton 5SG-46 grit wheel. This is a blue, gel seeded ceramic grinding wheel that is made especially for tough materials, such as D2 and H-13. For the cost, you will get more than your money's worth. These ceramic grinding wheels work much better than your common aluminum oxide gray wheel.

Some toolmakers have good results with a hard wheel, such as an H or I from Norton. The softer wheels seem to break down too quickly and waste a lot of your time with constant dressing.

Try relieving the center of the grinding wheel

One trick is to take a dressing stick, such as a Norbide or carborundum stick, and carve out a groove in the center of the wheel, in order to reduce the heat build-up. This can also be done with a typical single point diamond. The idea is to minimize heat buildup.

CBN or Diamond wheels work best, if applicable

If you have a lot of grinding of these tough tool steels, A2, D2, H-13, or DC53, you might consider investing in a CBN grinding wheel. These super abrasive grinding wheels work wonders on the toughest hardened tool steels, but cost much more, of course! You will, however, quickly recoup your investment just by saving time dressing the wheel every few passes.

Let the D2 workpiece settle before taking finish passes

D2 also has a tendency to expand and twist after a lot of grinding has been done. It is advisable to let it settle down overnight before taking your finish passes. Once you do get this stubborn material finished, it will be like that nasty tasting medicine and work well in your injection mold or stamping die.


How to grind D2 tool steel on an automatic wet surface grinder

mitsui automatic wet grindingGrinding D2 tool steel on an automatic wet grinder is a different story than using a manual surface grinder with no coolant. For larger workpieces, such as injection mold cores and cavities, or stamping die plates, wet grinding is the only good option.

Using an aluminum oxide wheel

If you are using a typical aluminum oxide grinding wheel in a CNC grinder with flood coolant you will have to be patient and persistent. It certainly can be done, but the process is quite time consuming.

From personal experience, the best process is to dress the wheel open by feeding the cluster diamond quickly across the wheel. Take care to ensure that the wheel will provide a good finish and not leave a rough surface, however.

Supposing that you have .008 in to remove from a 10x12 piece of D2 steel, set the control to remove .0002 per pass, use flood coolant and an average cross feed.

You will find it necessary to redress the wheel after every ..001 in removed. In reality, you will only remove approximately .0008 in, so it will take some time to finish the process.

Allow the workpiece to stabilize

Once the piece is semi-finished with .0005-.001 remaining, remove it from the machine and let it warm to room temperature and stabilize. Once it is to room temperature you can make an accurate measurement and begin the finishing process following the same procedure.

Norton recommends SG wheels

If you have an SG wheel your grinding process is essentially the same, but more efficient. The SG wheel can remove stock much more quickly than a standard aluminum oxide wheel and is the preferred wheel for grinding D2 steel.

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