HK SERIES - THE GRAPHITE WORLD HAS SELECTED

Recommended Tool Shape

There are commercially available graphite-use end mills with long length of cut, long shank, and air hole to facilitate dust disposal

Recommended Tool Materials

Cutting-edge life tests have shown that sintered diamond is the best tool material followed by cemented carbide, high-speed steel, CBN, and ceramics. Cemented oarbide (K10 and K05) are used most frequently because the are available and easy to work with

Recommended Feed Speed

Rough milling 0.15-0.25mm/tooth

final milling 0.05-0.15mm/tooth

Recommended Cutting Direction

Adopt down-cuts for end milling since up-cuts may results in chipping along the working edge of the graphite

Recommended Cut Depth

A jet of air gushing from the end mill tip will facilitate the removal of machining dust, allowing cut depths five times as deep as the end mill's diameter.However, you may find that milling at a small cut depth under a high feed rate will be more efficient

PRECAUTIONS WHEN USING THE HK SERIES EDM'ing Surface Area Vs Surface Finish

The size of EDMing surface affects how the surface is finished. Note that greater electrode surface area results in rougher surface finish regardless of the grade graphite used

EDMing Surface Area (mm)	VDI	Ra(µm)	Rmax(µm)
50-99	16-21	0.631.12	5-9
100-150	21-23	1.12-1.40	9-11
151-200	23-26	1.40-2.00	11-14
201-300	26-29	2.00-2.80	14-21
301-400	29-32	2.80-4.0	21-30
401-500	32-35	4.00-5.60	30-40
501-	35-	5.60-	40-

If EDM is unstable, refer to the following table to adjust your  

EDMing conditions.

Problem	Solutions
EDMing speed is too slow	Increase IP, optimize the on time
Too much electrode wear	Increase IP, optimize the on time
Surface finish is too rough	Decrease IP, optimize the on time
Unstable electric discharge	Decrease IP(especially at the start of EDM) Optimize the on time 200µm sec or more for HK-0 to HK-75 100µm sec or more for HK-3
Gap Contamination	Increase jump height, set higher jump frequency Increase jump speed, check dialectric fluid

Surface Roughness Conversion Table (Rmax values are for reference only)

VDI	Ra(um)	Ra(µ inch)	Rmax(µm)
14	0.50	20	4
15	0.56	22	-
16	0.63	25	5
17	0.70	28	-
18	0.80	32	-
19	0.90	36	-
20	1.00	40	8
21	1.12	45	9
22	1.26	50	-
23	1.40	56	11
24	1.60	63	12
25	1.80	72	-
26	2.00	80	14
27	2.20	88	16
28	2.50	100	-
29	2.80	112	21
30	3.20	125	23
31	3.50	140	-
32	4.00	160	30
33	4.50	180	-
34	5.00	200	-
35	5.60	224	40
36	6.30	250	45