Instructables

Increase the precision of a Dremel press drill

This is probably going to be the shortest instructable ever but, hey, I'm new to this :)!

I used to drill my PCBs using a normal, heavy driller (I guess that's why the mm tick bits usually didnt last too long ;)). I had a Dremel but I didn't use it for that, because I was used to the heavier driller.

Then one day I saw this "Dremel Work Station" on sale, which is basically a drill press with a few extra features. Dremel's ads are always mentioning the excelent precision of their tools, and I thought that would be handy for PCB drilling. So I bought one.

Well, I must say that it was rather disappointing, at least for the price (~60euros). The press has a lag of maybe 1-2 mm, which seems little but is enough for you to drill completely out of the spot. When the rotating bit starts touching the PCB, the rotation makes the Dremel deviate 1-2mm (the lag) to one side, and you drill in the wrong place.

I wanted to return it to the store, but I still needed a simpler way of drilling... then an idea came to my mind. If the press always deviates to the side, then let's make the deviation permanent! The fix was easy; just attach a rubber-band! It pushes the Dremel body against the press's arm, completely removing the lag. You should attach a strong one or several of the "normal", weaker ones (as I did).
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lee3219873 years ago
I'm getting excellent holes with the Dremel 4000 + Dremel Work Station part# 220-01 (both brand new).
Here's a video (really just an image) of my results with a 0.5mm drill bit held by Dremel collet part# 4485:
http://www.youtube.com/watch?v=1NClF35nd3s

NOTE: I didn't tighten any extra screws - just put it together as normal.
Nuno (author) 3 years ago
Well, I think I've never used the 90º thing :)

Anyways, forget the rubber band and just tighten the screws to the bare limit as amarquez originally suggested; this will remove the lag. I have mine so tighten that I can ear them scratching on the guide rods and it basically doesn't return to original position on itself.
atomlabs3 years ago
i have one also, and it has the same problem. the solution i found to drill pcb's was to lower as little possible so the lag wont be noticed, it works but if i have to get the handle all the way down it shifts. The rubber band ideia is very wise! but one question i ask to Nuno is; does it affect the 90º angle on the drill?
brianf254 years ago
I picked up one of these at lowes the other day. I had a gift card and was looking to finally spend it. It has the same problem. I was really surprised how cheaply made this thing is. I'd return it but it didn't cost me anything anyways. Will keep the rubber band idea in mind next time I use it.
Nuno (author) 4 years ago
More recently I've also taken the tighten every screw on the damn thing, to the point just short of tightening it so much that it refused to return up path and I also agree that it helps a lot.
amarquez4 years ago
I have been drilling some PCB's with my Dremel Press drill, which is older than the one on this Instructable. I had to tighten every screw on the damn thing, to the point just short of tightening it so much that it refused to return up... it helped somewhat. Dremel rotary tools aren´t so badly made, but their accesories are plain crap. I invite you to try to build a simple but excellent router table for the Dremel by using their 566 Tile cutting kit or 565 Multipurpose Cutting Kit as an attachment to hold the rotary tool, and a piece of 1/2" thick plexiglass rectangle of about 10"X6"" or so, and route a narrow circular cut centered on a one inch hole so that the attachment can be strongly glued to the underside of the plexiglass "table". It will be tremendously better than the absolutely crappy "231 Shaper/Router Table" or the equally flimsy "335-01 Plunge Router Attachment"... Generally speaking, most of the Dremel attachments are not worth their price (even halved!). Now, making a solid stable and precise drill stand is not easy, so we are stuck with the dremel brand one. One worthwhile reccomendation is to use Carbide numbered drill bits, because hi speed steel or even cobalt ones are not up to the task or drilling the phenolic or glass epoxi PCB material. Use the slowest speed possible ("1" on the Dremel) and place the drill bit quite close to the PCB so that you only have to lower the drill a fraction of an inch, so that you minimize the lateral movement of this poorly designed stand. Good Luck.
notstarman7 years ago
Have you noticed the little rubber pads in bottom of the cup. They are about 1-2mm thick. I think your tool is compressing the pads and alowing the tool to wonder. I am using the B&D - RTX in this tool which does not touch the pads and I get no deflextion. Leave it to dremel to make an acessory that that works better with their compeditors tools.
Very good point. Any rubber connecting the Dremel is going to be a problem. I am thinking the best solution is to replace the rubber with solid metal and add an arm to the other end of the tool which holds it firmly in place. Then again, $50 for a good used drill press isn't a bad idea either!
Nuno (author)  notstarman7 years ago
Rubber pads? I can't see none.... at least without disassemble the press, which I don't want to do now (have better things to do ;)). Everything is plastic or metal. Even without the Dremel in the press, the lag is there. The second metal pipe, where the drill attaches (and that holds the drill support, which is what I think you called "cup", the black round piece of plastic), has this lag and rotates around itself.
if you check the plastic body around the areas where the press slides on the steel guide rods you will find tiny brass screws adjust these to remove all play in every direction.keep checking the press slides up and down freely as you can overtighten to the point it wont return back up after pressing down,hope this helps look all around as there are quite a few and the are tiny,dont know why dremel dont put this in their instruction manual and suuply the screwdriver if they cant set em up before shipping them out.lazy i guess. regards,coolmechanic
corradini6 years ago
This is actually more a technique problem -- and easily solvable. You need to "center-punch" your holes first.

ANY rotating tool, particularly a drill bit, is almost guaranteed to "walk" slightly. The spinning tip hits the workpiece and, unless it's perfectly symmetrical (an impossibility), one side will dig in slightly more, and the bit will flex slightly. In wood or softer materials, or with fat bits, you don't notice this -- but with thin Dremel bits, going into metals, you've got the worst of all worlds -- a thin (flexible) bit, and a situation where 1-2mm is a full hole diameter or so! It'd be like drilling a finger-sized hole nearly 1/2"/1cm away from your mark!

SOLUTION: center-punch your mark! That is: make a dimple where you want your hole. Twist drill bits will self-center in that dimple, even if you're a little off. (In this case, the drill bit will flex the way you WANT it to!)

In wood/soft materials, just use an awl, nail, etc. In soft metals (brass, aluminum) a nail is fine (always wear eye protection when hitting metal into metal, though!). In iron/steel, use a prick-punch and then a center-punch - every hardware/home store carries them, and they're cheap.

A nice cheapo alternative is a masonry nail - they're made of good (very hard) steel. (You can even make decent tools from them! You have to heat them to cherry-red with a propane torch and let cool slowly - this 'converts' the steel to a more workable form. Grind it in a drill press with a file, or on a bench grinder, or even a belt/disk sander; hacksaw it, file it, even heat it and pound it flat on an anvil and sharpen it, etc. When you're done, heat it red-hot again and quench in oil -- it'll convert back to a very hard state. Do some Google research on "masonry nails" + "tempering" + "quenching" first - you'll find a lot!)
This is completely unrelated to the OP's problem, though. Also, I don't know anyone who centerpunches the PCB boards they are about to drill. I think this would increase the time taken by several orders of magnitude, as well as vastly increasing the danger of splitting the board in half along a row of holes. And if you did all the centerpunching at the start, you would find your drill snapping as it self-centered on the wrong hole from the row of 0.1" (or tighter!) spaced chip mounts, etc. The whole point of using a bench drill for your PCB holes is that they are fast, and precise. Either one alone is useless. Centerpunching, here, would only serve to snap your drill bits, as the tip hits, bites slightly into the hole, then shifts as downwards pressure is brought onto the bit, and the entire drill pivots, shifting the rather fine drill bit sideways. As for the solution here, OP, not a bad idea. All you are doing, and all that needs to be done, is taking out the play (backlash) in the drill system. What happens as the handle is pulled down, is the drill, which is pulled upwards by the spring against gravity, and is driven on one side only, is pushed down on that side too, which creates a torque. This tends to distort the press, and, if not rigid enough, it will warp, and the tip will wander. This shouldn't be an issue with a well-made press. The other effect is that the play in the gears and bearing/slide, from the drill passively being pulled downward (by the force of gravity) to pushing the drill bit downwards (drilling into a thing which pushes the drill itself up), will allow the entire drill to rotate slightly, around the pivot point of the slack bearings, and this is what you are removing, by pre-loading it with the elastic band. Nice trick! :-)
Soapy - you're absolutely correct (on several points). Serves me right for reading hastily.

Centerpunching PCB material is, of course, a dumb idea. (I'm a metal guy, myself, and managed to skip ahead too quickly. (Wandering drill bits in the metals world IS almost always solved by centerpunching and having nice sharp drill bits.)

You're dead-on about the backlash issue as well as the side-loading bias and rotation/flexion. Dremels aren't exactly known for being precision Swiss tooling.

I would, however, suggest investing in very good, sharp drill bits. (I recently had a major problem with broken taps in 304 stainless. Went to this local machine shop with one of those brilliant, WWII old-school machinists -- he laughed at the taps I was using (Irwin, from the big Orange home shop). Sold me a German tap that cost nearly 3x as much -- but the thing cuts through stainless like a chainsaw through butter. Similarly, finally bought a fairly expensive saw blade for my table saw -- it's night-and-day, in terms of how easy it is to cut, and the quality of the finished surface.

I will NEVER try to save money on cutting tools again.)
Thanks for taking my comment the right way. A lot of people would have thrown a fit. I agree with the tip on good blades, etc. The way I see it, I spend the least I can on the drill, and spend a bit more on the bits it drives. I can correct everything about the drill, and, at the end of the day, the hole is what really matters. A sharp cobalt bit will make a neat fast hole through nearly anything, and so the cheap drill doesn't strain, and the battery lasts longer, etc. Also, if I drop the tool and it breaks, or it gets stolen, I can replace it, and I've still saved over the guy buying Dewalt.
Nuno (author)  corradini6 years ago
Actually, I used to "center punch" my homemade PCB boards before I got this drill press. But I used to do it in a more gentle way; I found out by experience that it would be enough to make a small mark with a sewing needle. I would mark all holes first then drill by hand. It worked quite nicely, but of course, it was a little bit more work and, specially, more work on my shoulders to do all of that drilling by hand. As for the rubber band, I could have returned the press but then I would be without a solution anyway, and I had no other options. So I went for the trick. And posted here because it worked so nicely and I just love KISS stuff ;) Thanks to all of you guys for the comments.
theRIAA7 years ago
seems like you should tighten something. try removing/adding spacers where it is loose
Nuno (author)  theRIAA7 years ago
Well, just wanted something that worked, so I didn't even bother to try to open the thing and see where it had the lag... I just kept it because the rubber-band did the fix. There isn't much choice here, I only find Dremmel drill presses on sale.