Drilling pcbs

[mikeb]

Ok, finally I've had enough - is it just me, or do other people find that when you use one of the mini-drillbit chucks (that let you utilise 0.8mm, 1mm etc drill bits in a larger drill) that there is *always* 'wobble' of the bit? To me, the way the mini chuck tightens means that even if the drill bit being used in in correctly, it can never be completely straght, but rather there is a little 'yaw' involved (i.e. the drill bit traces out a small circle around the centre of whether you would like to drill the hole).

Do I need to draw a picture to illustrate this?

Mike

[Gilles C]

No problem with my Dremel.

But I always use a center punch to mark the holes before I drill them...

[mikeb]

No, I'm not talking about the bit wandering when it's applied to the material - it 'wanders' already due to the stupid way the chucks I have tighten up.

(looks around for a picture)

Mike

[black mariah]

Get a smaller drill.  :lol: You could be experiencing some flex in the bit, especially with smaller ones. There's nothing you can do about that. Find a picture and we'll see exactly what you're talking about.

[mikeb]

Ok ... look here....



There is a thread on the main part (the part that is clamped inside the drill); this thread is what the silver section travels up and down on, and tightens and loosens about the the desired drill bit.  What this means is that the chuck 'head' is not at 90 degrees to the main shaft; more like 89 or 91 degrees. Hence, even with the main shaft inserted and clamped firmly in the drill, and the drill bit inserted and clamped firmly in the chuck, because there of this lack of alignment the bit 'wanders'.

Next will be a hand-drawn picture if necessary - I can't be the only person who has experienced this, it seems to be a design flaw with the bloody little buggers!

Mike

[travissk]

I can see where you're coming from, and I think I experienced something similar in project about a year ago. We ended up going with bigger holes and twine instead of one of those adjustment chucks and some thread. Obviously not an option for this hobby

For PCBs, I have to agree that the Dremel-like tools don't seem to have that problem. Unless someone has positive experience with a different brand of 'adapter,' see if you can borrow a Dremel or smaller tool from a friend. Is that an option?

[mikeb]

Heh-heh .... my Mum uses a Dremel at work - she works as a forensic scientist .... .... I don't WANT to borrow hers!

Borrowing ain't an option as I need to drill stuff all the time. Perhaps time to get out the credit card again!    

Mike

[gez]

Mike, I think I know what you're talking about.  Rather than go from open to closed to tighten it, do it the other way round.  Fully close the chuck and gradually open it until you can just slip in the drill.  This way it should be straight.  

Or is it time for a new drill?!  

[gez]

Ah, I think I've misunderstood....time for the hand-drawn picture!  

[RobB]

Mike,
Those mini chucks are poorly engineered and so will never hold a drill bit true.  I keep a 1mm drill bit in one of those for opening up 0.8mm holes to 1mm by hand only.  
I did get a 0.8mm bit to run true in a regular sized chuck by wrapping a strip of thin copper sheet around it.  
If you try this approach be prepared to tighten it in the chuck several times to compress the copper evenly, then the bit will begin to spin straight.  
It would be nice if purpose made collets for this application were readily available.

[Paul Perry (Frostwave)]

here is some negative advice: heat shrink is no use for building up shafts :x

[RobB]

Just then I built up a 0.8mm drill bit shaft with a 2cm * 30cm strip of alfoil.  Started and finished it with small tabs of sticky tape.  
Tested it in my drill press.  Runs true enough!  
Give it a go.

[Ansil]

Heh-heh .... my Mum uses a Dremel at work - she works as a forensic scientist .... .... I don't WANT to borrow hers!

Borrowing ain't an option as I need to drill stuff all the time. Perhaps time to get out the credit card again!    

Mike

might i suggest building a mini pcb drill on a small cord to aid in the ease of drilling i started mine after i saw gringos on his site. and now i have a decent one however i broke it as i decided to use it on bigger stuff which i never intended a little 12v motor for. i canabliized the end piece of a dremel and had a friend weld the rod that connects to the motor to a endpiece i foudn lying around my uncles shop.. the housing is pvc pipe.  total cost about 12 bucks or less. i think i have a technical drawing if someone needs it.

[Gilles C]

Ok, I see the chuck you're talking about now.

I have the same one that I bought to be able to use normal drills in my cordless drill that uses only quick connect hex bits like that.

(Btw, It's fast, but not very precise, because there is always a sideplay when I use the quick-connect drills that came with the drill.)

But I know you're talking about the chuck itself.

I bought mine at Wallmarts and I must have been lucky, because I used it in a press-drill at work that doesn't accept small drills, and the drill stays centered when I use that set-up.

...but a Dremel is still the best bet.

[R.G.]

OK. The scoop is this.

If you want to drill PCBs in any fashion more than casually, you need a Microlux drill press. You can get these from Micro Mark tools. Mine cost $139 on sale. A good Dremel costs $70 - $90 if you don't already have one, the press accessory is another $20.

The Microlux lets you use carbide bits with some surety. You will only break the bits where you move the board if you hand-hold. If you clamp per hole, you won't break... any....

Use 1/8" shank solid carbide bits with these. I've never dulled a carbide bit on PCB's. They break (because I'm too impatient to clamp for every hole) before they dull. High speed steel bits are too dull to use after 100 holes.

I gave up on dremel drill presses because I out of the three I went through, I didn't get even one that had runout and wobble small enough to avoid breaking carbide bits. I'm sure there are good ones, I just couldn't find one.

[mikeb]

(for the hundredth time curses not being in America as regards tools and stuff)

Thanks for the tip RG! I've got a video clip of what I mean regarding my drill wobble as soon as I find my camera -> USB cable.....

Mike

[Mark Hammer]

I use a regular $80 drill press from Canadian Tire.  The drill bits themselves are the wide shank types, about 1/4" I think.  What's also nice is these bts tendto have a plastic ring at the boundary between the wide shank and the cutting portion of the bit so that the bit size can be indicated.  Just slide the bit in up to the ring and away you go.  Having a wide shank helps tremendously in centering the bit properly and also gripping it more firmly within the chuck.  I bought an assortment of such bits from Lee Valley Tools near me, but also found a bin of suitable ones last time I visited Active Surplus in Toronto.  I was first introduced to them when I bought an assortment at a lapidary show in Dallas 6 years ago.  Since I started using them, I don't think I have broken a single one through "wobble" the way I would routinely do with standard narrow-shank bits (where the shank and bit width are the same).  On the other hand, I've broken plenty because I bumped into them while they were in the chuck. :oops:

[Jason Stout]

Mike, These bits are for board routers, but they look like they would fit into a standard chuck on a full size press.

http://www.store.yahoo.com/drillcity/5pcnewwirsiz.html

Cheeper than a new press/drill.

[MartyB]

The first several pcbs I drilled were done with a regular Dremel chuck.  It wouldn't get small enough....   I made it work very well by coiling a thin bare wire around the bitshaft in one layer  for a better grab.  Now I use bits with larger standard chuck-friendly shanks - Harbour Freight sells them in assortments for ~$5 US /8.

[mikeb]

Jase, Martin and Mark - thanks. Yes, the main problem is that the shank of the small drill bits is too small to be gripped securely but .....

here is some negative advice: heat shrink is no use for building up shafts

.... as Paul said, but I gave it a shot anyway - and it worked a treat! With my main hand-held drill the chuck was *almost* tight enough to hold the small bits, so just one tube of thin heatshrink did the trick; well, it's worked for 100+ holes so far, and drilling is *much* faster also.

Errr .... thanks Paul!

Mike (still doing the opposite of what he's told)