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Larger Spade Drills

bluerev06

Plastic
Joined
Jan 23, 2023
I am new to running Spade Drills. The guy training me is...... clueless.

I am running 4" to 6 1/2" spades up to 40" deep, into 4140. In an old and worn out boring mill.

The tool has thru coolant, but in my opinion, not enough. After about 18" deep, chip evacuation becomes an issue. The chips just get ground up. And I suspect cause the spade to get stuck in the bore. It has happened several times.

Do you need a small pilot drill to start? A Center Drill mark? The material is sawcut and fairly square. From time to time, the Drill does seem to bounce when starting. I have been drilling a pilot hole just slightly smaller than the chisel tip on the spade. Usually, 3/16".....ish. I'm starting to wonder about pilot drilling.....

I can't seem to get more than 40 - 45 sfm and 0.004" ipr. Does this sound normal?

Thanx for any info you all can give me.
 
Depends on how stout the machine and setup/work are. Mostly you're not going to run massive feeds unless you have a behemoth of a machine and are drilling near the base of its Y axis travel. And lower feeds yet in tougher steels like 4140. Those external through coolant adapters work, but you need to have good pressure and volume from the coolant pump. The deeper you drill, the more pressure and flow you want. You shouldn't need a pilot but it will help reduce thrust forces on the machine. Definitely keep it smaller than the web/chisel with a long drill.

40-45 SFM is about right for 4140 around Q&T level, and especially as you go deeper you may need to reduce the speed even more without good coolant flow. Also periodically withdrawing the drill and clearing chips is very important when deep drilling without proper coolant pressure and flow. If you don't, what you describe is usually the result: ground up looking chips and a spade that gets stuck when you try to withdraw it.

The feed you just need to judge by the pressure on the machine. You can feel when it's getting difficult to disengage the feed if it's a manual machine. Don't go very far past that point. I once ran a ~6" spade at something like .018" feed per rev but I couldn't disengage the feed. Ended up having to kick the lever out with my foot. There was so much thrust force it had sprung the whole machine. When i finally got the feed disengaged the spindle shot back into the machine like it was fired out of a cannon. While most large machines can handle that level of thrust just fine, that kind of force means that the machine is probably drilling a crooked hole - you don't want that.

To get a proper start on a long spade, start the hole with a stub (short) spade of the same diameter. Switch to the longer one after the short one can't go any farther. A center drill is generally not needed unless you use it to start the pilot. In the case of a long pilot, use the same method: short stub drill first, then switch to the longer pilot drill.
 
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Depends on how stout the machine and setup/work are. Mostly you're not going to run massive feeds unless you have a behemoth of a machine and are drilling near the base of its Y axis travel. And lower feeds yet in tougher steels like 4140. Those external through coolant adapters work, but you need to have good pressure and volume from the coolant pump. The deeper you drill, the more pressure and flow you want. You shouldn't need a pilot but it will help reduce thrust forces on the machine. Definitely keep it smaller than the web/chisel with a long drill.

40-45 SFM is about right for 4140 around Q&T level, and especially as you go deeper you may need to reduce the speed even more without good coolant flow. Also periodically withdrawing the drill and clearing chips is very important when deep drilling without proper coolant pressure and flow. If you don't, what you describe is usually the result: ground up looking chips and a spade that gets stuck when you try to withdraw it.

The feed you just need to judge by the pressure on the machine. You can feel when it's getting difficult to disengage the feed if it's a manual machine. Don't go very far past that point. I once ran a ~6" spade at something like .018" feed per rev but I couldn't disengage the feed. Ended up having to kick the lever out with my foot. There was so much thrust force it had sprung the whole machine. When i finally got the feed disengaged the spindle shot back into the machine like it was fired out of a cannon. While most large machines can handle that level of thrust just fine, that kind of force means that the machine is probably drilling a crooked hole - you don't want that.

To get a proper start on a long spade, start the hole with a stub (short) spade of the same diameter. Switch to the longer one after the short one can't go any farther. A center drill is generally not needed unless you use it to start the pilot. In the case of a long pilot, use the same method: short stub drill first, then switch to the longer pilot drill.
 
I wish we had a shorter spade holder. We only have one.

So you think I should or shouldn't use a pilot hole? I ran a spade today that measured about 0.210" tip, and I drilled a 3/16 pilot about 1 1/4 deep. The drill is bouncing and it severely chipped 2 spades. It occurred to me that it may be acting like a big twist drill with an oversize pilot hole.
 
Shops that can afford the tooling will ejector drill holes with high pressure coolant in the vertical. Most holes that deep are usually done horizontally on a HBM.

EDIT: There is tooling out there for drilling large holes which doesn't take a massive amount of force to drill with. Rather it can be adapted to a worn-out boring mill is another question I can't answer. Where are you located?
 
Yeah that's another option, they have those drills with the HSS center and carbide outside cutters, they can run at higher speeds and generally take a good bit less thrust. Trepanning is good for that too but you've gotta have a through hole really to use that.

Anyway, yes I'd use the pilot unless you're having trouble with it, but be certain it's smaller than the chisel/web or you could find yourself with incurable chatter. You might try enlarging the pilot diameter just for a short distance to see if it causes any chatter or reduces the thrust a significant amount. I don't think you'll find a huge difference with only a small increase in pilot diameter. It's still a lot of drill cutting at once. Some spades don't like any pilot at all or they'll start chattering like mad. Sometimes that can be cured by increasing the feed per rev, but only if the machine/setup can take it. You're going to have to do a little trial and error to find the sweet spot. If it keeps bouncing, ditch the pilot.

If you don't have the stub spade, you can also start the long drill easier by drilling and boring a short, full diameter bore that's the same size as the drill, deep enough to get the spade insert fully inside the hole.
 
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A spade that large might require something like 25 gpm of coolant flow and perhaps 30hp or more. Not sure what brand of spade you’re running Allied has a chart somewhere that states the recommended HP, coolant flow, and psi.
The manufacture should have that info published.
How long does it take your machines coolant line or lines to fill a five gallon bucket?
One problem if you’re running a slower than recommended feed is the chips will not break and curl properly, .004 seems slow. Your tool was designed to have a certain chip shape so it can be ejected from the hole. A lower then recommended feed and lack of coolant might be causing your 18” deep problem zone.
Pilot hole is a non starter IMO, spades are designed to cut from solid.

ekretz, I’ve had a column tip back loudly towards the work and have also had the spindle jump back with a big dull twist drill. I’m certain everyone That’s run an old manual had experienced an overloaded tool. My boss threatened to ban me from the power feed if was to hear that happen again.
 
So you think I should or shouldn't use a pilot hole?
I've only used the Acme spade drills, and they are happier without a pilot hole. They like the point to be engaged. I have read about, but not experienced, chipping the insert at the edges of a pilot hole. Rather than drill a pilot, then drill a bigger hole with a spade, I'd drill the pilot, then use the largest boring bar I could fit in the pilot hole. Or drill a really small diameter pilot, but those are hard to make deep and straight.
The thrust eKretz talks about is not exaggerated. On a so-so 16" 7.5HP manual machine, a 1" spade drill is tough going, and a 1.5" spade drill is really pushing it. Problem is tailstock thrust, not spindle HP. If you are running 4" to 6.5" spade drills, you are in a whole 'nother category of work.
 
Yes, that thrust pressure is what mostly limits the feed you can run. The "kick" I mentioned earlier was actually more like 10 or 12 kicks, as hard as I damn well could. Thought sure I was going to break the feed engagement levers off. This was on a 6" spindle G&L floor-travelling HBM, not a toy. And they are known as pretty easy machines to kick the feed out on. HP is generally not an issue at all since these machines are geared way down in RPM to run a large HSS spade.
 
I would definitely use a center drill. The biggest you can find.
And see about getting more coolant pressure. That deep you need quite a bit.
How often are you backing the drill out of the hole to remove chips?
 
Depends on how stout the machine and setup/work are. Mostly you're not going to run massive feeds unless you have a behemoth of a machine and are drilling near the base of its Y axis travel. And lower feeds yet in tougher steels like 4140. Those external through coolant adapters work, but you need to have good pressure and volume from the coolant pump. The deeper you drill, the more pressure and flow you want. You shouldn't need a pilot but it will help reduce thrust forces on the machine. Definitely keep it smaller than the web/chisel with a long drill.

40-45 SFM is about right for 4140 around Q&T level, and especially as you go deeper you may need to reduce the speed even more without good coolant flow. Also periodically withdrawing the drill and clearing chips is very important when deep drilling without proper coolant pressure and flow. If you don't, what you describe is usually the result: ground up looking chips and a spade that gets stuck when you try to withdraw it.

The feed you just need to judge by the pressure on the machine. You can feel when it's getting difficult to disengage the feed if it's a manual machine. Don't go very far past that point. I once ran a ~6" spade at something like .018" feed per rev but I couldn't disengage the feed. Ended up having to kick the lever out with my foot. There was so much thrust force it had sprung the whole machine. When i finally got the feed disengaged the spindle shot back into the machine like it was fired out of a cannon. While most large machines can handle that level of thrust just fine, that kind of force means that the machine is probably drilling a crooked hole - you don't want that.

To get a proper start on a long spade, start the hole with a stub (short) spade of the same diameter. Switch to the longer one after the short one can't go any farther. A center drill is generally not needed unless you use it to start the pilot. In the case of a long pilot, use the same method: short stub drill first, then switch to the longer pilot drill.
That is part of my problem as well. At 0.005 feed, disengaging the feed lever is extremely difficult.
 
The chips seem to curl nicely. No long.chips at all.
A spade that large might require something like 25 gpm of coolant flow and perhaps 30hp or more. Not sure what brand of spade you’re running Allied has a chart somewhere that states the recommended HP, coolant flow, and psi.
The manufacture should have that info published.
How long does it take your machines coolant line or lines to fill a five gallon bucket?
One problem if you’re running a slower than recommended feed is the chips will not break and curl properly, .004 seems slow. Your tool was designed to have a certain chip shape so it can be ejected from the hole. A lower then recommended feed and lack of coolant might be causing your 18” deep problem zone.
Pilot hole is a non starter IMO, spades are designed to cut from solid.

ekretz, I’ve had a column tip back loudly towards the work and have also had the spindle jump back with a big dull twist drill. I’m certain everyone That’s run an old manual had experienced an overloaded tool. My boss threatened to ban me from the power feed if was to hear that happen again.
 
M
I've only used the Acme spade drills, and they are happier without a pilot hole. They like the point to be engaged. I have read about, but not experienced, chipping the insert at the edges of a pilot hole. Rather than drill a pilot, then drill a bigger hole with a spade, I'd drill the pilot, then use the largest boring bar I could fit in the pilot hole. Or drill a really small diameter pilot, but those are hard to make deep and straight.
The thrust eKretz talks about is not exaggerated. On a so-so 16" 7.5HP manual machine, a 1" spade drill is tough going, and a 1.5" spade drill is really pushing it. Problem is tailstock thrust, not spindle HP. If you are running 4" to 6.5" spade drills, you are in a whole 'nother category of work.
My Spades are Acme.....
 
A cent
I would definitely use a center drill. The biggest you can find.
And see about getting more coolant pressure. That deep you need quite a bit.
How often are you backing the drill out of the hole to remove chips?
A Center Drill was what I was thinking about changing to. Some of the coolant piping is a bit restricted. I'm going to try and correct that.
 
I doubt I have 10 gpm.

That's going to be part of the problem with the spades getting stuck. You also want to have hundreds of psi according to official recommendations. You can get by with less but you'll need to stop the drill more frequently and clear the chips and ground up gunk stuck in the hole. Piping changes aren't going to do much for you without a good coolant pump. I made up a tool I used for clearing deep spade holes - a small half-circle of steel welded onto a long ¼" square rod. Retracted the drill and used it to " sweep" out the chips and that every so often. Used to have to drill very deep holes to collapse long keys from steel mill drive rolls. No other way to get them out.

There are also different spade geometries. Try calling Allied and asking for the geometry that requires the least thrust pressure. You can also regrind them yourself to get better cutting action if your shop has a T&C grinder. Used to be that the spade makers would give you resharpening geometry to info, don't know if they still do that. I've got a handful of sheets spec'ing that geometry in my reference file if you want a copy.

Also, I would not use a center drill. I have definitely had that cause cratering at the point where it intersects with the spade cutting edge on larger spades like these. Instead, use a small stub drill ground to the same point angle as the spade.
 
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The biggest spade I have used was 3”. Was...
Feed locked and took beam with plate on a spin until the bit became a stub. Scarey moment- I swear it took minutes for the drill spindle to stop after hitting the switch.

I have pilot holes to be bad with inserts, mostly just get bouncing if you use them. Putting a very lite center drill mark at higher rpms with the same bit changes for the better your hole a good amount. I stay under 2 inch thicknesses most of the time, no sample size at 40.
Peck and patience. Steel ain’t gonna get antsy and run away.
 
If you will look at page 368 of their master catalog 1674578987615.png
They have what they call "High Performance" spade drills. Unfortunatly, they only go up to 5". I bet they do these much larger if you were to inquiry. I've used these in my past in smaller sizes and they out perform standard spades nearly 10 times faster! Leaving a very nice surface finish in the hole. These people have other drilling systems to look at also.

Edit: I also agree about not using a center drill to start a spade with. Just peck at the surface until you get a decent drill point started to diameter or near full diameter before kicking in the feed. IMO.
 
I once ran a ~6" spade at something like .018" feed per rev but I couldn't disengage the feed. Ended up having to kick the lever out with my foot. There was so much thrust force it had sprung the whole machine. When i finally got the feed disengaged the spindle shot back into the machine like it was fired out of a cannon.

I've found that stopping the machine and running the table out helps.
 








 
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