need help drilling technique

[sonnybiker]

hello all, can anyone help me here?
i had problem with drilling condition...
my workpiece is 31,5 thick, and i need to drilling a 330 holes with 1 mm drill for 6 mm in depth.
the drilling starting at 24,5 mm depth (the workpiece is step in geometry)
im using 4900 rpm in spindle speed and 47 mm/m in plunge rate.
overall lenght for the tool are 41mm and the flute lenght are 22 mm.
the safety clearence of the tool are 35mm. im using the peck drill method for 0,25 mm in depth for every hole.
when i'm starting to drill, the drill are vibrate (of course i'm using centre drill for start).
can any one help me with the problem for the rite drilling condition?

note: im using white hss drill (straight shank) from nachi and its the only tool that available in here... and im attach the file for drilling

thanks for the help....

[fuzzyracing1967]

Sounds like your center drill point is a smaller degree angle then your drill,should be the other way around.

[sonnybiker]

i'm using 2 mm center drill with standart angle, the shank diameter of center drill is 6 mm (2 x 60 degree) and using 1 mm drill with 118 degree angle. still confuse with this drilling, coz i have broke 4 drill

[neilw20]

I notice that the holes are closely spaced. Are you using coolant or air.
Could it be swarf getting captured by the tip of the drill?

[sonnybiker]

@neilw20, im using pure cutting oil for cooling.
at firts im drilling with centre drill for 1,5 mm depth, after that im using special drill to make a chamfer for 3,5 mm depth (the drill angle is 60 degree angle and it has sharp tip like pencil) after that im drilling with ordinary HSS drill with 1 mm dia.
the 1 mm drill dont even drilling the hole, its only vibrate when it touch the material.
please note that i only can hold the tool for 5 mm ( the tool overall lenght is 41 mm)
by the way, im using DECKEL MAHO DMC63V with siemen 840d as controller, the software im using rite now is mastercam X2 with SP1

[fuzzyracing1967]

assuming you allready tried differant speeds and feeds,the only thing I can think of would be how ridgid everything is,(the part itself,does it vibrate?,or how little of the drill you are holding),just a thought.

[sonnybiker]

Originally Posted by fuzzyracing1967 assuming you allready tried differant speeds and feeds,the only thing I can think of would be how ridgid everything is,(the part itself,does it vibrate?,or how little of the drill you are holding),just a thought.

i do have tried diffrent speed and plunge rate, everything is rigid (the holder, the drill too), im holding drill fo 5 mm ( the length is 41 mm)

[neilw20]

If the feed rate on the pre-drilling is too low, or there is dwell at the bottom the bottom of the hole may be getting work hardened.
If the drill is vibrating it sounds like it is hitting hard area and not starting to cut. What grade of steel is being drilled?

Edit:
Yes. Carbide bit will usually overcome this problem.

[Ch_Irawan]

Hi Sonny,

I am not a machinist can't help you on the drilling technique, but if you are interested to try Solid Carbide Drill Bits for your case then i can tell you where to buy them in Jakarta. The bits ussually used for PCB or Jewelry making, 1/8" shank and 1.5" total length is the most common.

Regards, Ichan.

[sonnybiker]

Originally Posted by neilw20 If the feed rate on the pre-drilling is too low, or there is dwell at the bottom the bottom of the hole may be getting work hardened. If the drill is vibrating it sounds like it is hitting hard area and not starting to cut. What grade of steel is being drilled? Edit: Yes. Carbide bit will usually overcome this problem.

the drill condition is fine, there is no hardened material, i can know if there is one...coz i can drill it on manual machine.

im using pure cutting oil for coolant. the material grade is S45C. i think i have to use carbide solid drill or super hard HSS drill... but from the info i collected...the carbide tool is too low on plunge speed... i have solid carbide drill, from the salesman info, the plunge rate can only go for 1.7 mm/m...
the time is so important here coz im drilling for 330 holes...

[sonnybiker]

Originally Posted by Ch_Irawan Hi Sonny, I am not a machinist can't help you on the drilling technique, but if you are interested to try Solid Carbide Drill Bits for your case then i can tell you where to buy them in Jakarta. The bits ussually used for PCB or Jewelry making, 1/8" shank and 1.5" total length is the most common. Regards, Ichan.

hello ichan... i live in jakarta too, but im working in kerawang... can i call u?
please send me ur phone to my email
sonny_ahi@telkom.net

regards

[Ch_Irawan]

Just send my number to your e-mail, nice to meet you here.

Regards, Ichan.