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How to select Mold Polishing Stones for finishing various types of metal surfaces.  

To determine what type of BORIDE Stones can and/or should be used for most efficient stock removal and finish, the polisher must evaluate the following criteria's:

a) What type of material needs to be polished (Steel, Brass or Aluminum) and how hard is it? 

1. Is it in the 22 to 38 RC range?
2. Or is it more in the 39 to 55 RC range and more?

b) What type of machined surface does it have?

1. The machined surface is an EDM surface finish.
2. Milling machine surface finish.
3. Copy milling machined surface finish

c) How will the stones be used?  

1. By hand (use more the softer stone types)
2. By reciprocating machine (DieProfiler, AirLappers, etc.)  use harder type stones. 
3. By ultrasonic polishing machine (use very hard stones: AM-8 or ceramic stones)  

First Choice and/or Options:

1. EDM finish with steel type of 22 to 38 RC hardness, try first AS-9. If not available, try AM-8, AO or AM-K.
2. EDM finish on 38 to 62 RC type steel, try first CS-HD. If not available try AS-9,   AM-8, AO or AM-K.
3. Milling machined finish with steel type of 22 to 38 RC hardness, try first AO. If not available, try AM-2, Die Stone or CS-M.  
4. Milling machined finish with steel type of 38 to 62 RC hardness, try first CS-HD. If not available use AO, CS-M, AM-2, Die Stone. 
5. For Stainless Steel, your first choice should be T-2.  If not availble use AB, AS-9, AM-8, CS-M.
6. For Aluminum use first T-4.  If not avalable use AM-K or AS-H (start with 400 grit, as this is a fast cutting stone)
7. For Steel Casting use: CS-M, CS-HD and/or AB

Sequence of Grit and the type of stone recommended for polishing P20 or H13

EDM Surface finish is:                                Fine                 Medium              Coarse

Start with AS-9, AM-8 or CS-HD           320 or 400 Grit        220 Grit          150/180 Grit

Proceed to AS-9                                        600 Grit              400 Grit         320 & 400 Grit

Finish with AM-2                                        600 Grit              600 Grit            600 Grit         

"Mill" Machined Surface is:                        Fine                  Medium             Coarse

Start with AO, AM-2, CS-M or AM-K            320 Grit                220 Grit          100  Grit

Finish with AM-2                                      400 & 600            320 &  600      220 & 320        

                                                                                                                   400 & 600

Last Stones/Grit before Diamond Finish:                                                       

Use AM-2                                                    900 Grit               900 Grit          900 Grit

Next use Diamond compound:             15 or 9 micron            15 or 9           15 or  9   

Notes: The stone types that are listed provide the most effective sequence of finishing.

For example, if the AS-9 type stones is listed first it means that the AS-9 type stone is "most suited" for the specific application. However, if the AS-9 stone is not available then use the next stone type that is listed as an option (AM-8, AO and so.... on....)!

1. NOTE: You may have developed your own polishing steps and/or procedure. Naturally, if this is the case the above information may not apply to you.
2. For experienced polishers going on to a 900 stone finish may be considered as  "time consuming". Usually, a "good" 600 stone finish may suffice prior to diamond polishing.