This is a timely post for me. I have ancient experience using a drill press, but the projects I have drilled at home have all been with a hand drill, even one panel with over a hundred holes. But it's been years since I've made anything at home that requires drilling, and for my current project I realized my skills with a hand drill would not be sufficient to get my holes to line up, and for this I have little room for error. I have a drill press on order, as I've mentioned in another thread, and I've been reading all the metalworking advice I can find online or get from the library -- books such as Metalworking Tools and Techniques by Stan Bray, Crowood Press, 2003.
My question is about the need for center punching when using a drill press (rather than a hand drill) for making holes in aluminum. My thinking is that with the work and the drill shaft fixed in position, the center punched hole will exert an undesirable lateral force on the bit, however small, because the center punched hole will never be perfectly aligned with the bit. Better, I believe, to use a spotting bit directly without center punching. So far this is theoretical. What do people think?
Then there is the question what type of spotting bit to use! Should the diameter of the spotting bit be the diameter of the finished hole or smaller? What angle to use? Should the angle of the spotting bit be greater than, less than, or equal to the angle of the drill bit? I'd say greater than or equal to, not less than.
Then for aluminum what should be the best angle for the drill bit itself? Some say the softer the metal the more acute should be the angle. What material and coating (if any) is best for the spotting bit and primary bit? Should cutting fluid be used, and if so, what kind?
If a spotting bit of the proper size and type has been used, is there any reason to drill a succession of hole sizes rather than one hole of the final size?
I still have a long wait until my drill press arrives.
My question is about the need for center punching when using a drill press (rather than a hand drill) for making holes in aluminum. My thinking is that with the work and the drill shaft fixed in position, the center punched hole will exert an undesirable lateral force on the bit, however small, because the center punched hole will never be perfectly aligned with the bit. Better, I believe, to use a spotting bit directly without center punching. So far this is theoretical. What do people think?
Then there is the question what type of spotting bit to use! Should the diameter of the spotting bit be the diameter of the finished hole or smaller? What angle to use? Should the angle of the spotting bit be greater than, less than, or equal to the angle of the drill bit? I'd say greater than or equal to, not less than.
Then for aluminum what should be the best angle for the drill bit itself? Some say the softer the metal the more acute should be the angle. What material and coating (if any) is best for the spotting bit and primary bit? Should cutting fluid be used, and if so, what kind?
If a spotting bit of the proper size and type has been used, is there any reason to drill a succession of hole sizes rather than one hole of the final size?
I still have a long wait until my drill press arrives.
If by a spotting bit you mean a center drill designed to make a shallow pilot hole to lead the actual drill truely that is a good technique, but as you observe you will not be able to line up that drill to perfectly hit the target if it is just marked. The purpose of using a center punch is to force the drill point to hit the precise target. Like you noted, the drill will actually be pulled sideways into the divot left by the punch. If you have lined up closely just continue drilling. If there is considerable bend in the bit you should reposition to align the drill once the hole is started. Either way if a precise outcome is desired then you should scribe crossmarks for each hole and center punch by walking the punch tip to the intersection of the crossmarks.
By spotting bit I mean something like this:
Item # 09960635, 120 Futura Coated Cobalt NC Spotting Drills on Hassay Savage Company
Once I get the work properly fixed in position and an origin established, I should be able to move to each hole's coordinates in turn and drill. I should not have to scribe anything. Fixing the work accurately on the table will be a project in and of itself, of course.
Again, I agree with Conrad Hoffman's procedure if I were tying to use a hand drill for this.
For some of what I'm doing I will need 3/8 inch holes, as a pilot for an 15/16 inch chassis punch. For a hole that large (3/8 inch) I am wondering if it would be better to use a 3/8 inch step drill or a regular 3/8 inch twist drill?
The only time you dispense with the center punch is if using a milling machine and can set X and Y exactly. For all other purposes you center punch. For all purposes, including the milling machine, you use the combined center drill and countersink. On the drill press you still center punch and use the combined center drill and countersink. These do not bend or deflect.
The work has to slide on the table so it will locate itself to the center drill. Use something like Boeshield or Bostik waxes on the table to prevent rust and keep 'em slippery. If the part is small you have to have it in a vise or clamp it for safety, but you'd still start the center drill to locate the part before clamping it. Drills must never drill at an angle due to misalignment between the punch mark and the chuck.
I'm no connoisseur of drill angles and use standard metal working bits for everything except large holes in wood. Then it would be a spade or a Forstner. Or a hole saw. If you're not following the right procedure, no magic angled split point fancy pants drill bits will save you.
Combined center drills and countersinks come in numbered sized from tiny to huge. The most useful is probably the #2, and KEO is a good brand. I do a lot of very small stuff and probably use a #1 more, but that's too small for most home projects. It would be rare that I ever grabbed a #3. Somewhere I have one half the size of my fist, but I've no idea when a person would ever need that. I don't own a drill chuck big enough to hold it!
BTW, those spotting drills are good if you have a milling machine, but really aren't suited for what we're talking about here. They're simply a very rigid drill bit with short flutes, but won't necessarily follow a center punch mark accurately. The tip of a center drill is designed to center on a punch mark, and can do so within less than a thousandth of an inch if conditions are right. The short tip pilots the hole, then the countersink section give the subsequent drill a better guide, if you want to go that deep. Something like this. Failure to use these usually leads to tears.
For aluminum, a squirt of WD-40 is as good as anything. Don't drill dry if you want a clean on-size hole. For wood sometimes a bit of paraffin or candle wax is good on the cutting edges and work surfaces, especially with hand planes.
The work has to slide on the table so it will locate itself to the center drill. Use something like Boeshield or Bostik waxes on the table to prevent rust and keep 'em slippery. If the part is small you have to have it in a vise or clamp it for safety, but you'd still start the center drill to locate the part before clamping it. Drills must never drill at an angle due to misalignment between the punch mark and the chuck.
I'm no connoisseur of drill angles and use standard metal working bits for everything except large holes in wood. Then it would be a spade or a Forstner. Or a hole saw. If you're not following the right procedure, no magic angled split point fancy pants drill bits will save you.
Combined center drills and countersinks come in numbered sized from tiny to huge. The most useful is probably the #2, and KEO is a good brand. I do a lot of very small stuff and probably use a #1 more, but that's too small for most home projects. It would be rare that I ever grabbed a #3. Somewhere I have one half the size of my fist, but I've no idea when a person would ever need that. I don't own a drill chuck big enough to hold it!
BTW, those spotting drills are good if you have a milling machine, but really aren't suited for what we're talking about here. They're simply a very rigid drill bit with short flutes, but won't necessarily follow a center punch mark accurately. The tip of a center drill is designed to center on a punch mark, and can do so within less than a thousandth of an inch if conditions are right. The short tip pilots the hole, then the countersink section give the subsequent drill a better guide, if you want to go that deep. Something like this. Failure to use these usually leads to tears.
For aluminum, a squirt of WD-40 is as good as anything. Don't drill dry if you want a clean on-size hole. For wood sometimes a bit of paraffin or candle wax is good on the cutting edges and work surfaces, especially with hand planes.
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i thought you only need lubrication on milling machines or lathes, but thinking about it a drill press is just a milling machine of sorts so that makes sense, i'm still trying to persuade the wife to let me move my workshop to the spare room else i have nowhere to set up a drill press and bench vice, i guess any complicated metalwork i will mark out and entrust to a local engineering firm, once she finds out how much that costs i think she'll let me have my way 
Neil.
Neil.
Conrads advice is right on the money, so it is in addition to the usefull points he makes.
Use a very sharp center punch. A scratching pen is the best I could find for the job. Don't punch too hard, where too hard depends on the material. Alu is really soft, so don't hit too hard. Brass is a lot harder, so it deserves a bit more punishment. The point is that you don't want to create a crater with a caldera, just a little notch to centre the pilot drill. The reason is that the ridges of the caldera might be gripped by your drill, sending it off course. For best precision, don't use pencil or whatever, but scratch with the sharp point of a Stanley knife a cross where the hole has to come (using a steel ruler or straight edge). This allows you to sense where the punch has land. Plus, a cut in a piece of metal is much thinner than anything you can accomplish with a writing material. With some practice you could replace the Stanley knife with point of a caliper, which you slide along the side of your material at the appropriate distance. It is caliper-abuse, but everybody does it, because once you get the hang of it, it is a quick and precise way (if the dimensions of your material are correct).
For wood, don't use metal drills, but the spiral ones with a little guiding point escpecially for wood. Predrill a guiding hole somewhat smaller than this guiding point, and presto.
vac
Use a very sharp center punch. A scratching pen is the best I could find for the job. Don't punch too hard, where too hard depends on the material. Alu is really soft, so don't hit too hard. Brass is a lot harder, so it deserves a bit more punishment. The point is that you don't want to create a crater with a caldera, just a little notch to centre the pilot drill. The reason is that the ridges of the caldera might be gripped by your drill, sending it off course. For best precision, don't use pencil or whatever, but scratch with the sharp point of a Stanley knife a cross where the hole has to come (using a steel ruler or straight edge). This allows you to sense where the punch has land. Plus, a cut in a piece of metal is much thinner than anything you can accomplish with a writing material. With some practice you could replace the Stanley knife with point of a caliper, which you slide along the side of your material at the appropriate distance. It is caliper-abuse, but everybody does it, because once you get the hang of it, it is a quick and precise way (if the dimensions of your material are correct).
For wood, don't use metal drills, but the spiral ones with a little guiding point escpecially for wood. Predrill a guiding hole somewhat smaller than this guiding point, and presto.
vac
I plan to use a machinist's vice bolted to this table:
PROXXON - KT 150
I don't want the work to slide at all on the table, as that messes up the coordinates.
I've used a center drill on a lathe many many years ago in school. I don't think I've ever used a center drill on a drill press. Some authorities say to use a center drill when starting a hole on a drill press. Other authorities say this is common but wrong practice and that a spotting drill is the proper tool to use. Still other sources say that if you are using a carbide bit you should neither use a center drill nor use a spotting drill. I am still trying to figure out what is best practice.
Edit: What would be wrong with using a spotting drill to drill the entire hole in one step?
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But if using a hand drill, how can you be certain that you are drilling at precisely right angles to the surface?
Will a deep centre punch assist?
I found when drilling a pilot hole through a to-be-detachable panel into the cabinet, because the pilot hole wasnt at a precise 90 degrees, when drilling out the cabinet hole, it wasnt directly under the panel hole... At least... I can only assume it was because I drilled at other than 90 degrees - since the panel was clamped perfectly square to the cabinet when drilling the pilot.
Will a deep centre punch assist?
I found when drilling a pilot hole through a to-be-detachable panel into the cabinet, because the pilot hole wasnt at a precise 90 degrees, when drilling out the cabinet hole, it wasnt directly under the panel hole... At least... I can only assume it was because I drilled at other than 90 degrees - since the panel was clamped perfectly square to the cabinet when drilling the pilot.
Lavcat, you're essentially converting your drill press to a milling machine. Admittedly a bad one, but often good enough for the purpose at hand. Thus, no center punch, just X-Y coordinates. Use whichever type of spotting or center drill suits your fancy, but never ever skip that step if you want your holes located accurately. I'm not sure if spotting drills have clearance or taper, so they might be OK for thin material. Obviously they'll drill a hole! They tend to be expensive and nobody has a full set of different sizes. They are not the tool to use on the drill press when dealing with center punched marks, no matter what "authorities" say! There's a reason the catalogs list them as "NC spotting drills".
Trivia- vacuphile is absolutely right. Old time machinists used nothing more than a steel machinists ruler and a sharp pointed scribe mounted to a post and base for the surface plate. They set the height of the scribe against the ruler, then scribed the (blue/inked) part. With skill and practice it was possible to locate everything to a few thou. A serious user of punches will want what's known as a "bright grind" on the point. That means the grind marks are parallel to the axis of the punch, not around in a circle the way most are done. Yes, I abuse my vernier calipers now and then, but they make hermaphrodite calipers for a reason you know!
I've never managed to drill a hole at 90 degrees to anything using a hand drill. Best I can do is hold a square next to it while drilling, but the results are never perfect. Most people seem to do better at this.
Trivia- vacuphile is absolutely right. Old time machinists used nothing more than a steel machinists ruler and a sharp pointed scribe mounted to a post and base for the surface plate. They set the height of the scribe against the ruler, then scribed the (blue/inked) part. With skill and practice it was possible to locate everything to a few thou. A serious user of punches will want what's known as a "bright grind" on the point. That means the grind marks are parallel to the axis of the punch, not around in a circle the way most are done. Yes, I abuse my vernier calipers now and then, but they make hermaphrodite calipers for a reason you know!
I've never managed to drill a hole at 90 degrees to anything using a hand drill. Best I can do is hold a square next to it while drilling, but the results are never perfect. Most people seem to do better at this.
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Considering I don't plan on making a lot of holes, at least for right now, frontpanelexpress would probably have been a good solution. But I really want to do this myself. Also some folks have said frontpanelexpress had scratched their panels.
For a few years I was president of a corporation that made computer peripherals. We contracted with a very good and very patient and kind machinist. I could have practically anything made I could dream up. But what fun is that?
Thanks. Although I don't plan to do milling, just drilling.
Any thought about my question whether to use a 3/8 inch step drill or regular 3/8 inch twist drill for drilling a 3/8 inch hole? And if a step drill, how to start the hole?
The one thing not mentioned (often implied though, mainly by Conrad H) is: patience, and lots of it.
I allways centre punch and, if I need accuracy, I use an optical centre punch.
For labelling a panel I use Letraset after the mechanicals of the panel is finished. Finishing often takes lots of sanding and polishing. A fine coat of laquer is applied, cured for 2days, than the letters are applied. Several thin coats of laquer over top, (curing in between) will give you a factory-made look.
Living in a condo now I had to make space in the utility room for a foldable wood/metal workbench (I miss my 600ft2 garage) and a permanently set-up small drill press (I to cannot drill a 90 deg. hole by hand). E
I allways centre punch and, if I need accuracy, I use an optical centre punch.
For labelling a panel I use Letraset after the mechanicals of the panel is finished. Finishing often takes lots of sanding and polishing. A fine coat of laquer is applied, cured for 2days, than the letters are applied. Several thin coats of laquer over top, (curing in between) will give you a factory-made look.
Living in a condo now I had to make space in the utility room for a foldable wood/metal workbench (I miss my 600ft2 garage) and a permanently set-up small drill press (I to cannot drill a 90 deg. hole by hand). E
For center punching, use an automatic one. You'll never be sorry you bought it.
automatic center punch - Google Search
automatic center punch - Google Search
It is the nature of becoming longer in tooth and shorter in vision, layout of complex back panels always ended up with accumulated error. What solved it was to do the layout on computer then transfer with a center punch and use Conrad's drill techniques'. That combined with patience has resulted in panels worth anodizing and silkscreening letters on. For aluminum automatic punch "priceless".
Bill
Bill
Sorry, I've never used a step drill. Probably a good choice if the material is very thin. Start with a hole near the bottom step I'd guess- so you don't have to use a conventional larger drill on thin material where it can grab. For rack panel thickness, 1/8"?, I just use regular good quality twist drills, what you see listed as Jobber, bright finish. Avoid any of the cheap gold coated drills from Harbor Fright and buy a brand name you've heard of.
Patience is certainly an asset, along with a good magnifying lens. My eyesight isn't what it was when I was 20. Or 40. I use a magnifier for all layout tasks. +1 on the automatic center punch!
Patience is certainly an asset, along with a good magnifying lens. My eyesight isn't what it was when I was 20. Or 40. I use a magnifier for all layout tasks. +1 on the automatic center punch!
I've never used a step drill either. This is the step drill I was thinking of:
Amazon.com: Irwin 10312 Unibit12 3/8-Inch 1/4-Inch Shank Step Drill Bit: Home Improvement
The panal is 1/8 inch aluminum. Do I understand correctly that this would be thick enough to use a twist drill for a hole this large? I probably have an ordinary 3/8 inch twist drill of some flavor. The cosmetics of the hole are not too important as long as it is the right size in the right place. The hole is for the bolt of a Greenlee punch that will make the final hole, which is for a female XLR.
My eyesight isn't what it was when I was sixty, which is one reason I decided to get a drill with an xy table. Patience I have. I am still patiently waiting for the drill to get here from Deutschland.
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