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304 Stainless Drilling Operation

09/16/2011 4:02 PM

I am involved in a project that will require the mass production drilling of 20 holes per part at (4mm) .157" dia.. The holes are located around the circumference of a (48mm) 1.89" dia. with a sectioned wall thickness of 3.8mm (.15"). The part is 304 stainless steel. Does anyone have experience in such. I am planning on using carbide stubby drill bits. The holes also have to be chamfered or at the very least have no burr. Questions: drill speed RPM., feed rate, any special coolants that enhance performance, what tool life to expect?

Also. If you know of any store boughten equipment or suppliers of an automated drill unit to do approx. 180 parts an hr.. Each part having 20 holes. Preferably located in North America.

Greatly appreciated.

Mash

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#1

Re: 304 Stainless drilling operation

09/16/2011 4:08 PM

sounds a LOT like something I wrote a 4 axis CNC program for a few years back. we used a solid carbide bit, fairly aggressive feed rate to prevent work hardening, and used a through hole deburring/chamfer tool after drilling. after machining, we had an adjustable blade type reamer mounted to the end of a piece of PVC pipe with a shaft in the end of the pipe (for flexibility) and chucked the shaft up in a drill bit and ran the reamer through the machined pipe just to make sure all of the burs were removed.

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#2
In reply to #1

Re: 304 Stainless drilling operation

09/16/2011 10:29 PM

I'm glad someone has a better answer. I had to drill 3mm holes, and most brands of steel bits were lucky to do 1 hole 8mm deep.

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#3

Re: 304 Stainless Drilling Operation

09/16/2011 11:04 PM

Stainless is awful about galling, especially when cutting threads. The old formulation of
Rapid Tap, including trichloroethane, and brake fluid (ethylene glycol) were the two recommended coolants in the Steamfitting trade. One chemist claimed that the trichloroethane was the magic ingredient, but it's now banned.

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#10
In reply to #3

Re: 304 Stainless Drilling Operation

09/17/2011 11:33 AM

It's been 10 years since I worked fabrication. We had trichloroethane then, it was nice and had a sweet smell to it. I don't see why they banned it but it's like everything else that works effectively, the EPA has to do away with it.

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#4

Re: 304 Stainless Drilling Operation

09/16/2011 11:05 PM

Don't have a complete answer for you but here a few extremely important points:

Keep your drill speed down, check either a St Stl reference chart/book for preferred drill speed.

Use copious quantities of an appropriate drilling fluid. The more the better. I have had excellent results drilling st stl for many years with a product named "Anchorlube". Lube keeps the heat out and reduces heat from friction among many favorable properties.

Use an aggressive feed rate. Again check your chart for ideal feed rate for the hole size you are drilling.

Don't know if carbide bits are necessary. Use at least a good HSS steel bit. Use a short length bit such as a screw machine length to keep flexing of the bit to a minimum. Make sure bits are sharp.

Overall, the most important factor is using sufficient quantities of lubricant/coolant. When forced to I have drilled 304 with some pretty lousy quality bits which were the only ones available at the time. Success was only due to the lubricant in more than necessary quantities.

Good Luck, Old Salt

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#5

Re: 304 Stainless Drilling Operation

09/16/2011 11:38 PM

CNC Turret Punching machine may be the way to go.

The CNC Turret Punch Press is economical and able to produce variety of component with out re-tooling and suitable for repetitive jobs. The machine can do complex profiles, punch holes etc at one go with amazing productivity.

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#6

Re: 304 Stainless Drilling Operation

09/17/2011 12:04 AM

A concern you havn't mentioned is work-hardening at the drill points. This will lead to cracking and should be addressed.

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#7

Re: 304 Stainless Drilling Operation

09/17/2011 12:14 AM

That works out to 1 second per hole, which seems rather fast for a drilling operation.

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#8

Re: 304 Stainless Drilling Operation

09/17/2011 2:42 AM

We have done jobs like this , the cutting speed is maintained between 50-80 Metres

per minute (150 ft to 250 ft per minute) and feed rate not less than 0.2 mm/rev

(0.008"/rev) and if it is possible then put a few drops of Tri Chloro Ethylene as the

drill starts cutting.

I am sure this will do.

Regards

Kishore K Gupta PYN

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#9

Re: 304 Stainless Drilling Operation

09/17/2011 7:57 AM

I have drilled stainless out in the hot sun and do not burn up drill bits. The only lubricate you need is ice cold water. I have found that the colder you keep stainless the easier it is to drill. Heat is the culprit. If I am where I can keep a small steady stream of ice water on the part then that is what I do. If I am inside where the water wil be a mess I place ice cubes around my drilling point for about 5 minutes and then drill with the ice laying around the drilling point. Speed of the drill is adjusted accordingly. Don't laugh at me until you try this. I know it is too simple. It is just an easy way to keep the heat out of the part and make it easy to drill. You could use a water soluble oil and keep it chilled in your crc machine and it would work even better. More than likely you could increase your drill speed considerably.

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#11

Re: 304 Stainless Drilling Operation

09/17/2011 11:40 AM

You have a lot of good comments to read on here.

Keep your drill bits sharp, the drilling speed low and use lots of cutting oil. I say this because I'm assuming you're not outfitted with a punch press. Even a punch press you have to keep it oiled but the punch press is better for large volume jobs than a drill press. You can use a 4mm punch for anything no thicker than 4mm.

If you can set up with water and soluble oil I'd go that route, however if not, again keep the drill bits sharp, drilling speed low and use lots of cutting oil.

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#12

Re: 304 Stainless Drilling Operation

09/17/2011 3:52 PM

We work exclusively with 304/304l stainless and we find that Kool Tool works best and is environmentally friendly.

Drill speed to be under 500 rpm with .015" per revolution feedrate and a quality drill bit make it all come together. Bit lasts long / great finish/ countersink with single edge at slow rpm.

If material is flexible you may be able to use 303 as it has the same chemistry as 304 but with a trace amount of sulfur to make it free machining.

Hope this helps

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#13

Re: 304 Stainless Drilling Operation

09/19/2011 11:31 AM

Hi Mash, first let me say that I work for a self feed drill manufacturer. We have many similar applications to the one you describe, including munitions. If you want minimum burrs in the ID of the tube use a drill with Air over oil (hydra-check) this will reduce the energy stored in the cylinder as the air is compressed. RPM should be around 800 to 1300 depending on the coolant and type of cutters used. Flood coolant is best but not always practical .It is always a good idea to use drill bushings if possible. The top three manufactures in the US for this size drill are E2, Sugino and ARO If you need more info just say so.

Glenn

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