Need Help!- drill and tap 304 SS

[Shop junkie]

I'm having a problem with a very simple dill and tap operation. I feel like a dork, but I haven't done and drilling and tapping in stainless since I got this machine so I'm kind of in the dark. So far I've broke a center drill and rounded off a drill. So if someone could take a look at my program and tell me what I'm doing wrong I would appreciate it.

Oh and my mill is a HAAS TM1

%
O7809 (shift plate for guys next door.)
T1 M06 D01 (#2 CEN DRILL)
G00 G54 G90 X-1.0 Y1.0
S1200 M03
G43 H01
X.375 Y-.250 Z.1
M08
G83 Z-.250 Q.020 R.1 F5.0
X1.0
X1.625
M09
G80 G00 Z1.0

T2 M06 (.242 DRILL)
S1000 M03
G00 G54 G90 X.375 Y-.250
G43 H2
Z.1
M08
G83 Z-1.100 Q.025 R0.1 F5.0
X1.0
X1.625
M09
G80 G00 Z1.0

T3 M06 (G DRILL FOR 5/16-18)
S1000 M03
G00 G54 G90 X.375 Y-.250
G43 H3
Z.1
M08
G81 Z-1.050 R.1 F8.0
X1.0
X1.625
M09
G80 G00 Z1.0

T4 M06 (5/16-18 TAP)
G00 G54 G90 X.375 Y-.250
S288
G43 H4 Z.1
G84 G98 Z-.500 R.100 F16.0
X1.0
X1.625
G80 G00 Z1.0
G00 X.375
G84 G98 Z-.850 R.100 F16.0
X1.0
X1.625
G80 G00 Z1.0


T5 M06 (.500 c-sink)
G00 G54 G90 X.375 Y-.250
S1400 M03
G43 H5
Z.1
M08
G81 Z-.210 R.1 F20.0
X1.0
X1.625
M09
G80 G00 Z1.0

T1 M06
M05
M30
%

( .500 thick 2.0 wide 304 stainless, XY0 left upper corner)

[AMCTony]

I would cut the RPM on all drilling down about 50% and take much larger pecks. If possible do not peck with 304. T1 = no peck, T2 = 0.250 peck. Pecking and dwelling in 304 is a sure fire way to ruin tools. Peck little or not at all if possible. Flood coolant!!!!

[behindpropeller]

How come you are not countersinking before tapping?

[Shop junkie]

I mostly work in plastics so with plastic I don't. Should I with stainless?

[billystein]

Hi,
I have had the best luck drilling 304 by holding the sfm at 48.

#2 c'drill rpm looks ok I would probably start at 1000 rpm feed 1 ipm
use g83. use good quality c'drill

.242 drill rpm = 757 feedrate start at 1 ipm maybe you can go 1.5 or 2
peck .03 - .04

.261 drill rpm = 702 feed start 1-2 ipm peck = .1
I know guys that can drill faster but I have found that the tools will actually last a while keeping close to these parameters
use the best cobalt drills you can find use proper coolant mix.
if you want to try to speed up job then increase feed instead of trying to increase rpm.
good luck

[Shop junkie]

Thanks for the help guys.

I'm not to worried about how long it takes, I just need to get the parts done with out killing my tools. I would have ordered some nice tools for the job but it's a last minute deal I took to help some guys out. So, nom I'm under the gun using a HSS c-drill and non coated drills.

So, I need all the help I can get.

[billystein]

c'drill should be ok.
decrease rpm about 20 % to start. the feeds should be ok
just keep the chips coming and dont let the drills turn red and you should be fine. Also please show anyone how we do this or we will have to kill them.

billy

[Shop junkie]

Well with the hepl from you guys I got 1 good part so far. Here's what the porgram looks like now. What'cha think.

%
O7809 (shift plate for guys next door.)
T1 M06 D01 (#2 CEN DRILL)
G00 G54 G90 X-1.0 Y1.0
S400 M03
G43 H01
X.375 Y-.250 Z.1
M08
G81 Z-.250 R.1 F2.0
X1.0
X1.625
M09
G80 G00 Z1.0

T2 M06 (.242 DRILL)
S400M03
G00 G54 G90 X.375 Y-.250
G43 H2
Z.250
M08
G83 Z-1.100 Q.250 R0.250 F2.0
X1.0
X1.625
M09
G80 G00 Z1.0

T3 M06 (G DRILL FOR 5/16-18)
S400 M03
G00 G54 G90 X.375 Y-.250
G43 H3
Z.225
M08
G81 Z-1.050 R.225 F2.5
X1.0
X1.625
M09
G80 G00 Z1.0

T4 M06 (5/16-18 TAP)
G00 G54 G90 X.375 Y-.250
S288
G43 H4 Z.1
G84 G98 Z-.500 R.100 F16.0
M00
X1.0
M00
X1.625
M00
G80 G00 Z.1
G00 X.375
G84 G98 Z-.700 R.100 F16.0
M00
X1.0
M00
X1.625
M00
G80 G00 Z.1
G00 X.375
G84 G98 Z-.850 R.100 F16.0
M00
X1.0
M00
X1.625
M00
G80 G00 Z1.0

T5 M06 (.500 c-sink)
G00 G54 G90 X.375 Y-.250
S1400 M03
G43 H5
Z.1
M08
G81 Z-.180 R.1 F20.0
X1.0
X1.625
M09
G80 G00 Z1.0

T1 M06
M05
M30
%

( .500 thick 2.0 wide 304 stainless, XY0 left upper corner)

[davereagan]

Why center drill, drill .242 and then drill .261? Drill right to .261 Real oil on the tap and the new speeds are much better.

[Shop junkie]

I center dill out of habbit mostly and not wanting the holes to be off. As far as the other I don't think I have the HP to pull a .262 in SS, 1" dp, it's only a TM1.

[beege]

Sure you do! If you can't cut 1/2" I'd be very surprised/disappointed.

[Shop junkie]

Really..?I guess I've just been a puss...