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spkrman15
07-03-2008, 10:08 PM
I have 500 holes to drill in 0.125" thick Stainless steel tubing. I have no coolant set up on my milling machine. The holes are to recieve 1/2" Stainless steel tubing. On a 1/3 of the holes i have to drill right through the tubing which is 1-1/2" in diameter.

What drill bit do you recomend?

The tubing has to have a loose fit. I thought a 14mm end mill would do the trick. If so how many flutes? Coating? Recomended speed?

Would an endmill with carbide inserts be good?

An annular cutter?

Rob :)

tattoomike68
07-03-2008, 10:23 PM
I would just use a good HSS drill bit and run it slow, lots of feed and shoot oil on it with an oil can the same stuff you would use to cut threads.

Some good cutting oil, heavy feed and slow RPM will give you longer tool life. if its 304 dont run a dull bit just stop and touch it up sharp again.

I dont think you need any fancy tooling but if you have to drill 10,000 holes I would invest in a high dollar drill setup and coolent system like a simple kool -mister.

wierdscience
07-03-2008, 11:24 PM
Cutting oil in a squirt can will get you by,but coolant even primative coolant would be better.

If it's nothing but a five gallon bucket hanging from a rafter dripping through a short piece of copper tubing.Or even a cheap parts washer pump from HF.

118* cobalt screw machine drills work good for that kinda job,the shorter length means a more rdgid drill,less chance of walking.

Like Mike said lots of feed,but go slow breaking through,the more pressure on break through the bigger the burr,hot ss burrs are hard to get rid of.

spkrman15
07-04-2008, 06:55 AM
i can set up an air system to help cool the bit as it is drilling. Would that be good?

Evan
07-04-2008, 07:04 AM
I recently needed to drill some 1/8" holes in work hardened SS. The best solution was to plunge cut them with a .125" 4 flute carbide end mill. It worked perfectly. I would use a carbide drill bit for your job.

Swarf&Sparks
07-04-2008, 07:40 AM
I've worked a lotta stainless, there aint no in-between.
Use sharp carbide dry, even a (sharpened) masonry drill, or use HSS with flood suds.
It work-hardens in milliseconds.

Evan
07-04-2008, 08:09 AM
Use sharp carbide dry, even a (sharpened) masonry drill,

I tried the masonry drill first. It seemed like a good idea. I guess they don't make them like they used to...

http://vts.bc.ca/pics4/drillbent.jpg

Swarf&Sparks
07-04-2008, 08:12 AM
If it won't last in a hammer-drill, it aint gonna work in the mill either, Evan :D

Quality tooling don't cost much more than cr@p.

Evan
07-04-2008, 08:20 AM
It came "free" with a cheap battery drill. I did a thread on an easy mod for cheap chargers a couple of years ago. It just cuts the charge current to a safe level that won't overheat the batteries. The mod only applies to the really cheap chargers though.

http://bbs.homeshopmachinist.net/showthread.php?t=15733

Swarf&Sparks
07-04-2008, 08:29 AM
"It came "free" with a cheap battery drill"

Was that the carbide drill, or the charger? :rolleyes:

airsmith282
07-04-2008, 08:41 AM
i drill more stainless then i want to remeber all the time i use 300 RPM max and i feed is slow and use cutting oil and keep the bit clear of swarf , the SS i use moist are 303 316l , i also use HSS and colbalt drills depending on the size iam drilling and how deep in i have to go..

slow or fast that ss is going to heat up... go to fast and kiss the drill but good by it will dull up really fast, been there done that a few times now i drill it slow and feed it slow...

Rustybolt
07-04-2008, 09:41 AM
i drill more stainless then i want to remeber all the time i use 300 RPM max and i feed is slow and use cutting oil and keep the bit clear of swarf , the SS i use moist are 303 316l , i also use HSS and colbalt drills depending on the size iam drilling and how deep in i have to go..

slow or fast that ss is going to heat up... go to fast and kiss the drill but good by it will dull up really fast, been there done that a few times now i drill it slow and feed it slow...


And don't forget sharp, sharp, sharp tools.
Sometimes if the material is thin enough it can be annealed after work hardening. We sometimes have to do this to our vibrating bowls when we add attachments. The bowls are made from 304 SS.

Swarf&Sparks
07-04-2008, 10:09 AM
And if you're dry drilling SS, keep the pressure on!
If it aint cutting, it's rubbing and rubbing leads to work-hardening in milliseconds.
I've got away with it a couple of times, (work hardened holes) annealing with the TIG torch, and re-drilling.
But don't rely on it.

mochinist
07-04-2008, 10:16 AM
A carbide drill with a hard grind would work nice, whether or not the 500 holes or job justifies the expense of the drill is the deciding factor there. Cant really add anymore to what tattoo and weird said except that I would probably regrind the drill point to 140deg or so, instead of the 118 that you probably already have.

Swarf&Sparks
07-04-2008, 10:24 AM
Yup, flatter angle drill works great, as long as you're prepared to spot drill first.

Ries
07-04-2008, 12:18 PM
I do this a lot- and in a 1/2" size, I use roto broaches, or other carbide annular cutters designed for mag drills.

http://www.jancy.com/index.cfm?fuseaction=products.showProducts&cat=27

You can send these out for resharpening- I usually buy 2 or 3 in each size, as my local welding supply store will send em out with about a 5 day turnaround, so I always have a good one, a backup, and one being sharpened.

On smaller holes, I use plain old twist drills- we had a job a few years ago where we drilled over 6000 holes in 3/8" and 3/16" stainless, and I just bought a 12 pack of drill bits, and kept changing em out as they got dull, and resharpening em in batches. They got pretty short by the end, but we would get 50 to 100 holes from each.
We got by fine using Cool Tool, which is a lube/coolant, in a squeeze bottle.

Swarf&Sparks
07-04-2008, 12:21 PM
Looking back at the OP, I'd go for a 1/2" masonry drill.
Put a good edge on it with a green wheel.
How much is it gonna cost you to find out?

Edit to say, back off the drill angle as suggested, spot drill first.

sconisbee
07-04-2008, 04:19 PM
Around about 350 rpm with a 1/2 inch drill (the numbers say 382 rpm) use a good quality sharp TiN coated HSS drill, Dormer Jobber drills with a split point are great for this, center punch and drill, no mystics just keep pressure on the downfeed to keep the drill cutting and ease off a little as you breakthrough to reduce burr formation and chance of grabbing. Just dont let the drill point dwell in one spot and you will be fine. If you have the rigidity to run a carbide drill and the job is worth the expense then go for it, preferably coated carbide rigid setup and bump up the speed and ease up on the feed a little, be aware carbide drills are rarely forgiving and break easily in loose setups.

Swarf&Sparks
07-04-2008, 04:35 PM
"I have 500 holes to drill in 0.125" thick Stainless steel tubing."

forget Tinite, moly, or anything else! It will cost you a fortune!
Sharp HSS is good for a coupla dozen holes, at that dia, drilled in 3 stages. (IE, 3 drills)
What is this job worth to you?

Masonry drills are cheaper than quality HSS.
Put a green wheel on your grinder. That will put a "goodenuf" edge on a carbide drill.
Talking masonry drills here.
Not specialized carbide/moly/TiN.....etc.

spkrman15
07-04-2008, 08:22 PM
Hey guys thanks for all the advice.

Slow and steady then! I was leaning towards a Hss+Cobalt end mill with 4 flutes. Ok i ordered one today. My supplier is also looking into cobalt drill. Short, short short! I will have to build a vice to hold the tubes as not to mark them.

As for coolant, i have a pump system i am setting up. I might get a chance to work on it tonight or tomorrow...or maybe Sunday....

AS for regrinding drill bits to a 140 angle, uhm i am not set up to do that kind of work accurately. Practice, practice, practice but maybe when i have 10 holes to do and not 500.

Rob :)

lane
07-04-2008, 10:35 PM
Here is a trick I use for drilling stainless steel. We work a lot at work and it works better than any thing I have tried in 40 years
Use a center cutting 4 flute BALL end mill For drilling any thing hard are stainless steel works better than any drill bit ever would.