Drilling Very Accurate Holes In Metal
Hello Everyone
I am currently taking a break from drilling holes on my new project, and I thought I might try to impart a little knowledge and a few techniques. Over the course of the last three years, I would estimate that I have drilled at least three thousand holes on various projects. Of course my holes have not always been that accurate, and many times it was necessary to elongate my holes with some type of file, just to make everything fit properly. Elongating holes is just not my style and I always hated the appearance, because it shows poor craftsmanship. In an attempt to make accurate holes, I have tried various techniques, and at the very beginning of this new project, I decided to try something new. This new technique is working very well, and I am highly impressed with the accuracy of all my holes. It may not be the fastest process in the world, but it sure beats elongating my holes.
My technique involves the use of several different pieces of equipment and various miscellaneous supplies. From this point on, we will assume that everyone has cut and shaped their blanks to the appropriate size.
I hope you find this helpful.
Bruce
I am currently taking a break from drilling holes on my new project, and I thought I might try to impart a little knowledge and a few techniques. Over the course of the last three years, I would estimate that I have drilled at least three thousand holes on various projects. Of course my holes have not always been that accurate, and many times it was necessary to elongate my holes with some type of file, just to make everything fit properly. Elongating holes is just not my style and I always hated the appearance, because it shows poor craftsmanship. In an attempt to make accurate holes, I have tried various techniques, and at the very beginning of this new project, I decided to try something new. This new technique is working very well, and I am highly impressed with the accuracy of all my holes. It may not be the fastest process in the world, but it sure beats elongating my holes.
My technique involves the use of several different pieces of equipment and various miscellaneous supplies. From this point on, we will assume that everyone has cut and shaped their blanks to the appropriate size.
Computer Aided Design Software:
This software is utilized to design your project. Once the project has been designed, duplicates are made of each part for making drilling templates. Considering that printers will not accurately size the drawings for you, the templates must be stretched to the appropiate size. Several print outs on a laser printer and a very accurate ruler will help you achieve nice templates. Additionally, template lines should be at the finest possible setting.
Laser Printer:
A laser printer is utilized for printing drilling templates.
Sharp Pair Of Scissors:
Scissors are utilized for accurately cutting out the drilling templates.
Spray Glue:
Blank metal parts are sprayed with an even medium coating of glue for adhering the drilling templates. When applying glue to the metal parts, be sure there is enough glue to allow the templates to slide around easily for template alignment.
Drill Press:
Irregardless of the make or model, the drill press must be properly aligned for drilling accurate holes. Please refer to the owners manual for instructions pertaining to alignment.
Milling Vise:
The milling vise provides a means for securely clamping the part to be drilled, and it also allows quick and easy alignment of the holes in respect to the spindle. Additionally, providing you have a few mills and/or rotary files, the milling vise can be used to remove unwanted metal. It is truly an indispensable tool for the DIYer on a limited budget. This is the one I use, http://www.harborfreight.com/5-inch-drill-press-milling-vise-94276.html.
Drill Bits:
Sharp drill bits are an absolute necessity for drilling accurate holes.
Starrett 828A Wiggler/Center Finder:
After clamping a metal blank into the milling vise and chucking the wiggler/center finder, the X and Y axises of the milling vise are adjusted to position the desired hole under the drill press spindle. Using a feeler guage, adjust the tip of the wiggler so that it has 0.027 inches of clearance from the metal surface. With the wiggler pointed toward and perpendicular to the metal surface, start the drill press and center the wiggler with a fingernail, but be careful, because it can bite you 
You will know when the wiggler has found it's center, because it will stop wiggling. Utilizing a flashlight, being parallel to the desired axis and perpendicular to the drill press spindle, adjust the milling vise until the center of the hole is under the point of the wiggler. Once the spindle is aligned with the desired drill location, shut off the drill press and remove the wiggler. Here is a link to the indispensable Wiggler, http://www.starrett.com/metrology/product-detail?k=828A.
You will know when the wiggler has found it's center, because it will stop wiggling. Utilizing a flashlight, being parallel to the desired axis and perpendicular to the drill press spindle, adjust the milling vise until the center of the hole is under the point of the wiggler. Once the spindle is aligned with the desired drill location, shut off the drill press and remove the wiggler. Here is a link to the indispensable Wiggler, http://www.starrett.com/metrology/product-detail?k=828A.
Dremel 562 Tile Cutting Bit:
Once the spindle is aligned with the desired drill location, this carbide tile cutter is utilized to make a pilot dimple in the metal surface. Chuck this bit into the drill press and turn it on. Bring the spindle down very slowly to make an appropriate size dimple. If you need a large hole, you should start out with smaller drill bits and work your way up to the final size. If you make a dimple with this bit and then try to immediately drill a 3/8 inch hole, odds are that the hole will not be accurately drilled. Additonally, if large holes must be drilled, save them for last to preserve the template. Here is a link to the Dremel 562 Tile Cutting Bit, http://www.dremel.com/en-us/Accessories/Pages/ProductDetail.aspx?pid=562.
MAPP/Propane Gas And Torch:
After all the holes have been drilled, the template must be removed. To help facilitate the easy removal of a drilling template held by spray glue, a torch is utilized to apply heat from the backside, until the glue is pliable enough to allow easy removal of the template.
Acetone/Laquer Thinner:
After the drilling template has been removed, residual glue can be removed with acetone or laquer thinner. Laquer thinner and paper towels work the best for me.
I am sure that many will disagree with my methods, but I can honestly say that this method will provide very accurate holes and leave your metal unscarred.I hope you find this helpful.
Bruce
Comments
Last weekend I busted a 1/16in bit while trying to drill a pilot hole.
Not long after, I fragged a 10-24 tap. It was tough going, a very hard grade aluminium. It hadn't bottomed-out, but the tap was in about 3/4 of its length, which is pretty much where the break happened, and I heard this *pop* and then it was frozen like.
I was using WD-40 for cutting oil, probably a mistake that.
I'd never tried to tap a hole so extensively as that (approx 1/2in) before.
One end of this strut I got great, the other was absolute Hell. It was when I went back to improve, I just knew I could get another 3-4 turns, but No!
Usenet group rec.crafts.metalworking is the best place for this sort of stuff.
If you're drilling clearance holes, would help just to make them somewhat bigger? Clearance hole charts often have a "loose fit" and "tight tolerance" listing.
You might want to have a look at Tap Magic. It works great with aluminum.
PJ,
I'm sure you already know there are "blind hole taps" and "through hole taps". If you're not careful, sometimes these can get switched in your storage box and you'll bottom out a through hole tap on a blind hole and experience that curious snapping effect that hard steels are overly prone to. Also, it helps to back up your tapping process every couple of turns to "break" the chip formation, otherwise you can build up too much stress in the process.
I'll have to look for that "Tap Magic".
Should I drill "dry" though? It seems that using oil would prevent the tip from digging in. A "little" is good, but a lot's bad?
Did somebody say "hijack"?
About one drop of oil on your drill bit should be okay for drilling aluminum. If you're drilling deeper than about 1/4 inch, then you might want to add another drop every 1/4 inch or so after that. If you're drilling a tapping hole for 10-24, the bit will be large (stiff) enough not to wander around from its original target, unless, of course, it's dull.
One thing about tapping: you've got to make sure you start out nice and straight. Use a tapping block to get things started. If you start out a little crooked, then you're gonna snap fer sure.
LOL I have clearance charts stored in about six or seven different places. Yes, clearance is very important! By the way, I never seen one of those tapping blocks before, I wish I would have known about that much sooner
@PJ Allen
Broken taps and drill bits are a nightmare, especially since they are hardened steel and continue to snap or break when trying to remove them. I have alway resorted to milling on the backside of the metal until I just touch the broken culprit. If its a drill bit, I then it out. If it is a tap, then I usually cut a larger hole around the offending piece. When all broken pieces have been removed, refill aluminum alloy tod and remachine.
Center drilling is very important, since drill bits can wander and bend, even when the workpiece is clamped. The conical entry created by the center drill accommodates the tip of a standard bit so that the cutting edges at the end of its flutes can begin to work right away. This avoids the tip having to plunge into the surface first, which is what causes wandering and bending of the bit. Since the center drill itself is very stiff, relative to the diameter of its pilot, it will not bend or wander like a regular bit of the same pilot diameter would.
-Phil
I abandoned the center punch and center drill for my current method, and I am much more satisfied the drilling accuracy. However, even with center punched metal, the wiggler can help establish alignment between the desired hole and the spindle.
Bruce
One More Time! (How 'bout one more "one more"?)
I have a spring-loaded punch [General] that I like a lot (a lot better than one that gets whacked with a hammer.)
Even with accurate alignment, a drill bit can wander, and a small one can bend. The very tip of a large drill, unless it's a small pilot tip, cannot be expected to guide the bit into the surface of the workpiece with any precision. At least that's been my experience.
-Phil
I agree with you completely, center drilling or at least dimpling is an absolute necessity. Most of the stuff I drill through is no thicker than 1/4", with most diameters being smaller than 1/4", so my method is sufficient for that. If there is any doubt, I usually go a little deeper with the tile cutting bit, instead of just making a dimple. The tile cutting bit does not drill, instead it grinds a straight 1/8" hole, thus for bits larger than 1/8", it provides a straight path for drill bits to follow. For large holes, I usually climb 1/16" in size until the desired size has been reached.
Bruce
http://www.cottandco.com/lots/societe-genevoise-mp-3k-jig-boring-machine
It was kept in an air-conditioned room.
That must be the ultimate hole maker. The company doesn't seem to be around any more.
-Phil
The oil is to help prevent heat build up (excessive heat destroys drill bits). Especially were the sides of the drill bit are contacting the side of the hole. As far as cutting goes, I think that there is no such thing as too much, it would make a mess though. I use enough just to keep the bit wet. When it starts smoking, then there is not enough.
The tile cutting bit is certainly better than nothing, but the center drill is exactly the right tool for the job.
Center punch - actually center "press" because aluminum is soft enough to not require a hammer to make a mark.
Use a hand drill that has a chuck that is easily turned by hand. Using a ~ 1/8" bit gently start the hole by turning the chuck with your hand, air drills work really well for this. Once the divot is made, drill normally.
This method works really well in thin stock, faster than using a drill press. As the material gets thicker there will be a point where you cannot keep the holes uniformly straight and should then resort to the drill press if possible.
I've been tapping holes using WD-40 for a long, long time, too, and this was the first time I've ever broken a bit > a #80 - or a tap. But, up till now it's always been sheet metal, < 1/8in, and this was nearly 3/4. Well, 'nuff said on that account.
[I remembered while I started, like a flash-back, one of the old guys, "Bob C.", getting on me about not using that "cutting oil" over there, some chartreuse liquid in a glass jar with a masking tape label, and how I'd feel dumb "when that freezes up in there."]
It drills and taps like greased lightening.
BTW, for milling aluminum, I just use WD-40, since my CNC mill's electronics aren't protected against flood cooling.
-Phil
You're correct, Phil, as it turns out aluminuminum is not called out on the label (ferrous metals and copper.) I sure do have a lot left over.
I'll try and find yours or EA's.. somewhere.. out there.. on the Internet.
--> amazon.com carries them both!
Also on Amazon. I guess it does come in liquid form too.
With my new method, all holes appear to be dead center. Considering that all holes have been drilled for a loose fit, I should have no problems bolting my new machine together.
With the exception of smaller bits (#43) bouncing around at the start, the tile cutter and wiggler do a very nice job.
Just for clarification purposes, I believe a centering bit would be ideal, but they are pretty darn expensive. However, from this point on, I will only center punch metal blanks that cannot be safely mounted to the drill press. I believe the ideal setup would be to align the spindle with a wiggler, dimple the metal with the tile cutter, and then start the actual hole with a center drill, especially for larger holes.
Additionally, I should have been a little more specific with the title. I should have titled this thread: "Drilling Very Accurate Holes In Metal With A Common Drill Press".
What is it that people say? Oh yeah, "This isn't my first day to the rodeo".
Bruce,
Have you measured dimentions on the paper before and after gluing the paper to the metal?
I know from my model airplane building, paper can change size depending on how humid it is. I wonder is the solvents in the spray glue could affect the paper's size.
Do you have a particular brand of spray glue you like best?
For those headed to Cuba,
I read in one of my hobby magazines a few years back an article about cutting threads with a tap. The artcle mentioned three different taps should be used with each thread cut. The first tap used just cuts a partial thread in the metal. The second tap cuts the threads a bit deeper and the final tap cuts the finished threads.
I don't think I've ever seen these sets of three taps sold. It sure seems like using three different taps is a good idea, I wonder why I've only seen it mentioned in one magazine article?
Using a series of taps like that is standard practise; they are know as 1st, 2nd and 3rd cut taps. They are generally available:
http://www.ukdrills.com/product.php?catid=293&gclid=CPinpI3P7q8CFUdItAodwSlLzQ