Starting Procedures For Drilling CJT KOOLCARB Catalog

Self Start
Entry Feed Rate

To properly self start a drill use the following:
•Shortened Projection
•Rigid Part Fixturing
•Enter Machined Surface

startnew1.jpg (16540 bytes)

Tool Material

Up To 100%

Reduce 30 to 50%

Carbide

5.5 x Ć

8.5 x Ć

Carbide Tip

4 x Ć

6 x Ć

HSS, Cobalt

4 x Ć

6 x Ć

Drill Depth

For greater drill depths or better positioning use other starting methods shown.

	Spot / Starting Hole Versus Follower Drill
Tool Groups	Wider + 5° To + 10°	Same	Less
HPS Carbide ( A, B, M )
Carbide Standard
Carbide Tipped
HSS, Cobalt
	Most Appropriate	Occasionally Appropriate	Don't Use

* If you cannot drill first and chamfer the hole afterwards, reducing RPM (up to 60%) and Feed/Rev (up to 40%) while machining out the difference in point angles may help protect the carbide drill.

** Accurate position & size control to within .002" [0.05mm] oversized on the start hole can yield hole accuracy comparable to most busing starts. DO NOT rotate long tools i.e. #172 & #175) outside starting hole or whip-out will occur. Ease the long tool into the starting hole at 200 RPM and .025" [.635 mm] / Rev.

Avoid using a spot drill with a chisel flat. Use CJT Styles 114, 113, 115 for spotting.

Avoid convex spots from indexable drills or non-center cut tools.

Bushing Against

.0002"[ 0.005mm ]
Greater Than
Maximum Drill
Ć Tolerance

Bushing Away

CJT Tool Group Letter(s)	Bushing		Most Appropriate
	Against	Away
			Occasionally Appropriate
A, B, E, M, P, T
D, G, J, Q, R
			Don't Use
F, N

.012"[ 0.3mm ]
Maximum Off Part

	Spot for Carbide	Spot for H.S.S.	Starting Hole** for Carbide
Wider
	ł Follower Drill