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Allied Spade Drill

Rogue_Machinist

Hot Rolled
Joined
Jul 26, 2011
Location
Oregon, USA
So my shop took a job where we need to blind drill a hole 10" deep in 304SS. So they wanted me to manually drill each one but didnt wanna spend 45+ minutes a part clearing chips. So they ended up purchasing an Allied Spade Drill 1.25" diameter spade insert super cobalt material. Now onto my question. With the drill being so long 11" of flute length do I have to drill a starting hole say 2" or so deep or can I just let the drill eat and deal with the vibration. Yes the manufacturer recommends drilling a starting hole but that would require me to put all of 200 piece into a manual lathe first and start a "pilot" hole first. Any info would be greatly appreciated. I have used spade drills previously but was only in 4140 and not nearly this deep.

Thank You
 
So my shop took a job where we need to blind drill a hole 10" deep in 304SS. So they wanted me to manually drill each one but didnt wanna spend 45+ minutes a part clearing chips. So they ended up purchasing an Allied Spade Drill 1.25" diameter spade insert super cobalt material. Now onto my question. With the drill being so long 11" of flute length do I have to drill a starting hole say 2" or so deep or can I just let the drill eat and deal with the vibration. Yes the manufacturer recommends drilling a starting hole but that would require me to put all of 200 piece into a manual lathe first and start a "pilot" hole first. Any info would be greatly appreciated. I have used spade drills previously but was only in 4140 and not nearly this deep.

Thank You
What kind of machine? Thru spindle coolant?
 
A starter hole will really help. You dont need much, just enough to locate the drill on entry. Id probably go about 5/8 or so deep on that size drill. The allied drills dance all over the place on start without it.

I use a small insert drill to drill, bore and chamfer the hole, then come on with the allied drill at normal feedrate starting from the outside. Bore your hole at or slightly below the spade drill size and it will cut perfectly on center then.

10" is pretty deep. Still might have issues with chips. I still get stringy chips with allied drills sometimes but I havent gone deep enough to really matter. Good luck with it.
 
Its on a lathe and has thru tool coolant, good pressure!
But im worried about the vibration can I just turn the RPM down or do I really need that starting hole (allied recommends 3x dia depth)
I've used a bunch of Allied drills and usually follow their recommendations (but not always). Sometimes it will go fine without a pilot but other times a pilot is a must. A 10x drill is pushing it, but I'd probably give it a try without the pilot but be prepared to switch you process to include the pilot.
 
A starter hole will really help. You dont need much, just enough to locate the drill on entry. Id probably go about 5/8 or so deep on that size drill. The allied drills dance all over the place on start without it.

I use a small insert drill to drill, bore and chamfer the hole, then come on with the allied drill at normal feedrate starting from the outside. Bore your hole at or slightly below the spade drill size and it will cut perfectly on center then.

10" is pretty deep. Still might have issues with chips. I still get stringy chips with allied drills sometimes but I havent gone deep enough to really matter. Good luck with it.
Yeah like I said, Ive used them before. But never this deep and usually in materials that arent as gummy as 304. Ok I will likely so what you suggested. Or have one of the lower guys do the drill maybe an inch deep and just go from there. These parts were making are dumb and we think the only reason they were dropped on us is because the previous manufacturer didnt wanna deal with them anymore. LOL.
 
I've used a bunch of Allied drills and usually follow their recommendations (but not always). Sometimes it will go fine without a pilot but other times a pilot is a must. A 10x drill is pushing it, but I'd probably give it a try without the pilot but be prepared to switch you process to include the pilot.
Yeah thats what im likely going to have to do. But figured there are people in our trade that just go full send NO F***S given. LOL
 
I'm actually using one (spade drill) for the first time right now. And it happens to be Allied with probably the same cobalt insert (I know its cobalt for sure).
In 303, 1" drill, 8" long, but im only going 4" deep (through). I'm super impressed! I'm starting right on the flate face, no pre hole or spot, 380rpm, .008" per rev, no peck or chip break. I did dial it in to center within a couple tenths. It goes right in, and plows through quiet as a church mouse. Untill breaking through, then it makes some noise, naturally. Only experience I have to share. Only shared because its fresh in my brain, LOL.
 
I use a lot of AMEC and similar drills, a pre drill helps, but depending on a few factors isn't always necessary. I do start in feeding slow until the tip stabilizes if no pre drill is used.
 
Our drill line uses those bits mostly. No pilot usually needed. Use bit to make “center punch” like a spotting drill size or smaller. This is at higher rpm/less ipr- just enough really to focus the wondering of tip to center. Then allied recommendations plus/minus.
 
I have a bunch of long allied type spade drills and I only use them for big deep holes. It's really the only thing they're good for (compared to other options).

So you have the right tool for the job.

10" deep at 1.25" diameter is not very deep for one of these. If you can spot it it'll likely be ok, just a lot of noise when it starts. Since you're in a lathe and presumably in a turret, make sure the centre alignment of the drill is as close to perfect as you're able. Remember to account for indicator droop when you're checking this. If you can't get it right then you'll need a starter hole, do as mmurray suggests above. Keep the coolant concentration up. Keep the feedrate as close to the recommended as your machine is able to manage - proper cutting data with a spade drill requires a lot of thrust, especially in something like 304. Don't be afraid of feed when starting the hole - too light a chipload really amplifies the chatter and jumping around at the start. Don't push the surface speed too much or you'll burn the corners of the insert. Do change the insert as soon as the corners start to show wear, failure will come rapidly after that.
 
he manufacturer recommends drilling a starting hole but that would require me to put all of 200 piece into a manual lathe first and start a "pilot" hole first
Why do you have to put them in a separate machine for the pilot? Do it all in one setup. I'd try a #6 center drill as the starter hole.
 
Why do you have to put them in a separate machine for the pilot? Do it all in one setup. I'd try a #6 center drill as the starter hole.
Unfortunately my shop doesnt believe in purchasing tooling but in this case the parts were making are balanced and the drill needs to be within .010" of the print dimension. I dont have enough spots in my turret to start a pilot in the machine except maybe a tapered shank 1.25" HSS drill.
 
Unfortunately my shop doesnt believe in purchasing tooling but in this case the parts were making are balanced and the drill needs to be within .010" of the print dimension. I dont have enough spots in my turret to start a pilot in the machine except maybe a tapered shank 1.25" HSS drill.

You're going to want to find a way.

Doing the start hole in a different machine/setup defeats the purpose of it, unless you are going to indicate every piece back in again...
 
I like using Allied drills. Can't speak for the pilot drilling, I have never gone that deep. There is a "TC" (tiny chip) geometry that can help with stringy chips. Might need to try that geometry if chips are becoming an issue. Good luck!
 
As others have said, if you go to the deep hole drilling guide on the allied machine tool website, there is steps and speeds and feeds to start with for operations just like this. They recommend a pilot hole, thru coolont if possible also.
 
I drilled a few long deep holes once in stainless with an allied spade drill. From my experience a cobalt tip is good. I started with carbide and it chipped quickly. The other thing is that ideally you’ll find a feed/speed that will break chips. In practice in my case at least i had to peck drill it to break the chips. And through coolant isn’t optional.
 
Unfortunately my shop doesnt believe in purchasing tooling but in this case the parts were making are balanced and the drill needs to be within .010" of the print dimension. I dont have enough spots in my turret to start a pilot in the machine except maybe a tapered shank 1.25" HSS drill.
You don't need a same size pilot hole. A good rule of thumb is to measure the web thickness of your drill, the thickness of the spade bit in this instance, and select a drill bit a little smaller for your pilot. I was told this keeps the drill engaged but guided enough to keep it from wandering and I have had good success with this method. The pilot only needs to be a maximum of your spade bits length because once the whole insert is in the part you are at all the support it's ever going to get.

An allied spade bit of that size should be 3/16" thick so I'd drill a 5/32" hole about a half inch deep for a pilot.
 
I do 1.5" and 2" 10" through 4140 all the time. No stainless, but I hit 'er with a center drill and let 'er buck. I didn't find any pre-drill instructions, I just figured out how to prevent the chatter by trial and limited error.
 
I drill 4140 CDHT often but very little stainless, when I use my 1/2" x 9" deep AMEC (cobalt, tiny chip insert) I start with a stub drill for starting no center drill, and switch to the long drill to finish. High pressure coolant (mineral oil) never had any trouble.

But then the OP hasn't given hole tolerance either, if he's looking for +/- .001" straight and +/- .0005 bore diameter with no bell mouth at entrance that could (very likely) become a problem depending on many factors including his machine rigidity especially at 10" deep.
 








 
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