hand feeding a drill on the mill

[TRX]

I have some deep holes to drill. I'll be using a collet in the milling machine, a spotting drill, a carbide stub drill, and then finally swapping to a long HSS drill to finish up. I'm a bit paranoid since the holes will be many hours into a lengthy project. Hole diameter is 17/64" (1/64 larger than 1/4), depth is 3 inches. Material is 1144 steel, supposed to be about 35Rc. Diameter and finish aren't greatly important, but it needs to be within .005 T.I.R. at the bottom, and preferably .003".

Quill travel on the mill is 3.5". I'll have to set an indicator and move the table to change to the long drill. I'm not expecting any problem there.

Since it's a mill I'll be feeding the drill in by hand. For deepish holes on the lathe I'm used to "pecking" a bit at a time, withdrawing the drill when the flutes get clogged, cleaning it, and resuming.

Question 1: I've just assumed that clogged flutes are a fact of life, and that drills have to be withdrawn periodically to be cleaned. Is this right, or am I doing something wrong?

Question 2: As long as chips are still coming out of the hole, do I assume everything is fine down there and keep on going, or do I still need to pull out and clean and give a chance for some fresh coolant to get in there and cool things down? Again, finish isn't as important as staying on-center.

Question 3: drilling in the mill, if I withdraw the drill it's likely that some chips will remain in the hole, even if I cover the hole while cleaning the drill. In my experience, drilling on chips was Not Good. Again, am I doing something wrong? Is there some practical way to get chips out of a hole that small? Or just ignore them?


Sorry for the excessive detail, but I just had one of those moments where I realized I wasn't as sure about what I was doing as I thought...

 

[brucer]

for less than .005 run out I would probably drill and ream...

3" depth shouldnt be a problem, 35rc isnt that hard and should actually help you, the chips will break better than hot roll or cold roll, they shouldnt string out on you which is good, but they couldfall back in the hole causing the drill tip to walk.. i would also use cobalt, hss drill will work, but a cobalt drill will be stiffer..


you are correct in assuming if chips are still coming out while drilling your fine.... I would probably use a cobalt drill just long enough to drill to depth and keep an air hose handy and also a bottle of coolant, keep the hole blown and out during the process.. just retract often and keep the hole blown out and apply coolant..



if your hand sharpening the drills at any time you'll get more than .005 runout..

 

[TRX]

Okay. But what causes chips to *not* come out? Feeding too much? Too little? Turning too fast or too slow? Alignment of heavenly bodies?

I was planning to just buy a 10-pack of drills, on the thought that Cleveland Twist Drill probably knows a lot more about grinding drills than I do.

I'm kind of paranoid about drilling those holes; $25 worth of steel, a full day of machining, then preheat, weld, and anneal before I get to the "drill" part.

PPPPPP - "Proper Prior Preparation Prevents ****-Poor Performance." Hopefully.

 

[brucer]

Okay. But what causes chips to *not* come out? Feeding too much? Too little? Turning too fast or too slow? Alignment of heavenly bodies?

I was planning to just buy a 10-pack of drills, on the thought that Cleveland Twist Drill probably knows a lot more about grinding drills than I do.

I'm kind of paranoid about drilling those holes; $25 worth of steel, a full day of machining, then preheat, weld, and anneal before I get to the "drill" part.

PPPPPP - "Proper Prior Preparation Prevents ****-Poor Performance." Hopefully.

generally chips wont come out because the drill point will dull, then start to rub, then work harden the work piece. running too fast can cause it, heat build up then the piece will work harden on you..

 

[george wilson]

Before you use or even BUY a drill(if possible),run it back and forth across the counter with your finger on it. Notice if the ends of the drill wobble as the bit is rolled. This way you can spot a bent drill,and ANY brand can be bent. Some a lot. You don't want to use a bent drill on a hole of any depth.

If you notice spiral scratches in a hole,it is because the drill is bent,enabling the nibs to scratch the hole.

 

[November X-ray]

I have some deep holes to drill. I'll be using a collet in the milling machine, a spotting drill, a carbide stub drill, and then finally swapping to a long HSS drill to finish up. I'm a bit paranoid since the holes will be many hours into a lengthy project. Hole diameter is 17/64" (1/64 larger than 1/4), depth is 3 inches. Material is 1144 steel, supposed to be about 35Rc. Diameter and finish aren't greatly important, but it needs to be within .005 T.I.R. at the bottom, and preferably .003".

Quill travel on the mill is 3.5". I'll have to set an indicator and move the table to change to the long drill. I'm not expecting any problem there.

I would check what the T.I.R is with the drill bit in the collet beforehand? I would not think 3 inches of depth with a 1/4" bit is impractical, then perhaps two or even three steps of chuck reamers to final out with. I would think you would want reamers with at least 3" of sharpened surface if not even a little longer, of course you would need proper size of collets for the reamers.

Please let us know what you do and how it turned out.

Good Luck!

 

[TRX]

The reason I said surface finish wasn't particularly important was because the finished size of the hole will be 9/32; I'll run a reamer though to bring it to finished size.

None of the tool catalogs I've looked at show a reamer with flutes much more than an inch long.

 

[Tony Wells]

I just checked MSC. They offer 3 different 0.2812 chucking reamers with 1.5000 flute length. I don't think you'll find anything that small with 3" of flute.

 

[Metalmann]

I have some deep holes to drill. I'll be using a collet in the milling machine, a spotting drill, a carbide stub drill, and then finally swapping to a long HSS drill to finish up. I'm a bit paranoid since the holes will be many hours into a lengthy project. Hole diameter is 17/64" (1/64 larger than 1/4), depth is 3 inches. Material is 1144 steel, supposed to be about 35Rc. Diameter and finish aren't greatly important, but it needs to be within .005 T.I.R. at the bottom, and preferably .003".

Quill travel on the mill is 3.5". I'll have to set an indicator and move the table to change to the long drill. I'm not expecting any problem there.

Since it's a mill I'll be feeding the drill in by hand. For deepish holes on the lathe I'm used to "pecking" a bit at a time, withdrawing the drill when the flutes get clogged, cleaning it, and resuming.

Question 1: I've just assumed that clogged flutes are a fact of life, and that drills have to be withdrawn periodically to be cleaned. Is this right, or am I doing something wrong?

Question 2: As long as chips are still coming out of the hole, do I assume everything is fine down there and keep on going, or do I still need to pull out and clean and give a chance for some fresh coolant to get in there and cool things down? Again, finish isn't as important as staying on-center.

Question 3: drilling in the mill, if I withdraw the drill it's likely that some chips will remain in the hole, even if I cover the hole while cleaning the drill. In my experience, drilling on chips was Not Good. Again, am I doing something wrong? Is there some practical way to get chips out of a hole that small? Or just ignore them?


Sorry for the excessive detail, but I just had one of those moments where I realized I wasn't as sure about what I was doing as I thought...

#1. Yeah, make sure the flutes stay cleaned out, use a small hard wire to dig them out if necessary.

#2. Some will spiral out, but chips may clog down in the bottom, better to keep that hole cleaned out.

#3. On deep holes, I always used that hard wire with a small hook on the end, then blow the hole out. Can't be too careful, if they have to be that accurately located. I've done some deep holes where .003 tolerance was like a half mile.

As far as reaming holes that deep, can you get someone to set you up with a shop made floating reamer? That way, you won't need so much flute length.