Any tips on using very small drill bits?

[jazzphil]

I'm making some items which require a series of very small holes drilling. More precisely around 80 holes 1.7mm size in a 1 metre length of ash using a drill press.

I've done a few of these in the past with only the odd problem but yesterday I had four drill bits snap in drilling 3 lengths. Two I managed to extract the broken bit and recover but one snapped deep inside the hole so it's junk.

I'm plunging 4 or 5 times for each hole to try and ensure the bit doesn't clog and the hole is clear and I'm taking my time over each hole so as not to push too hard. Is there anything else I can do to prevent the bit breaking?

I have just ordered 100 new bits with the plan to use a new bit every 30 holes or so, will that help?

Any advice would be gratefully received

Phil

 

[Mcluma]

what kind of drill bit are you using??

 

[jazzphil]

I'm using an HSS drill bit. Spec as per where I buy them is rolled high speed, straight shank HSS drill bit. Split point 118 degrees.

These are the only 1.7mm drill bits I could find.

 

[tisdai]

I use MICROBOX HSS Twist Drills when doing extra fine drilling, I know you mention you are taking your time when doing it to be carefull, What wood are you drilling though and are you only putting a very light pressure when pulling down to drill.

Cheers

Dave

 

[jazzphil]

I'm drilling Ash. I have tried resting every 10 holes or so to let the bit cool. Initially when I started doing this I found a slower speed caused more breakages but I assume a higher speed will create more heat.

Sometimes I seem to be able to tell when the bits about to break, there's a different sound which why I wondered whether it was simply the bit was blunting.

 

[Harbo]

Could you try only having a small part of the drill extending from the chuck. Then keep extending it until the depth is reached?
A bit of a pain though?

In metal work I use a centre drill for starters (you can get them down to 1mm) but that is using my small Unimat with it's very precise milling head.
Have you tried a Proxxon or Dremel in a drill stand?

Rod

 

[jazzphil]

Thanks for the suggestions.

I'm using a pin chuck with the drill bit in as far as it will go.

I need to use a drill press with a drill vice as the holes have to be precisely aligned and spaced.

It's not really the drilling that's the problem, I've done 160 holes before with one drill bit, it's just the unpredictable nature of when the bit breaks.

 

[jasonB]

Any rolled drill is going to be quite poor quality, go for fully ground bits by a known make such as Dormer, somethiong like their A002 series should be fine, don't think you will want to order 100 as they are about £1 each.

You don't say what depth you are drilling but if its not too deep a better bet is to use stub length drills as these have shorter flute lengths so are more rigid. 1.7mm is a bit harder to come by in these sizes but they are available or 1/16" is only a few thou smaller and there is no problem getting them.

Have a look at J&L, I get most of my engineering consumables from them, its best to use the virtual catalogue rather than try searching the site.

http://www.mscjlindustrial.co.uk/cgi/insrhm

Jason

 

[tisdai]

jazzphil it sounds more like the bit is binding in the wood, have you tried clamping the wood so their is no movement at all. You could also try replacing the bit after doing say 5 hole's, then you could leave that bit cool down completley and use it again later.

Worth a try

Cheers

Dave

 

[jazzphil]

Jason

Thanks for the link, I'll take a look. Unfortuneately I'm drilling to just short of arriving at the pin chuck so stub drills are a none starter. It's a hole to take a pin so I need the depth.

Dave

The wood is clamped in a drill vice bolted to the drill press so I don't think there's any movement. Binding has been my favourite possibility and I'm wondering whether it's just the vagaries of the wood density that's causing some problems.

I've got about 500 holes to drill in the next couple of days I'll give the drill bit swapping a go, although I might try 15 holes or so. I think swapping every 5 holes might just drive me insane.

 

[9fingers]

At school, our woodwork master became fed up with the number of small twist drills we lads used to break. He used to give us wire nails with the heads nipped off to use as pilot drills for nails in vulnerable locations such as near end grain.

They work brilliantly and I still use this method 40-50 years later. Due to the elastic nature of wood, the pilot drills can be made from the same size nails that you plan to use.

In this application, I would used a 'nail drill' as a pilot before opening out with a 1.7 stub drill - the latter are much shorter than jobbers drills (the normal ones) and so are stiffer and break less often.

Bob

 

[Shultzy]

Do you clean the flutes after each hole drilled? I found with small drills they get clogged very easily.

 

[jazzphil]

Plunging 4 or 5 times in small steps seems to clear the flutes reasonably efficiently and I do stop and clear if the flutes seem clogged before starting a new hole. I suspect part of the problem is over a number of holes concentration drifts and I probably just get sloppy.

 

[Shultzy]

Maybe getting good vacuum extraction across the drill bit might help in cooling it down.

 

[jazzphil]

I hadn't thought of using my vacuum for cooling, I'll give it a go.

Thanks for the idea.

Phil

 

[kirkpoore1]

Phil, when I've had thin bits break it was due to flexing. I'd try Bob's pilot nail trick first. If that doesn't work for you, you can try chucking the drill bit up so that only 10-15 mm are sticking out, then drilling all holes to that depth. Extend the bit another 10 mm or so, and drill to the new depth. Repeat until you're through the material. Since so little of the bit will be extending out of the hole, there is little chance for flexing and breakage.

Drilling at a high speed might help clear the chips better, too.

Kirk

 

[JoinerySolutions]

The biggest factor is probably due to the grain orientation and growth rings.
Ash can be very hard and quite soft even in the same board.
The softer parts may clog the bit while the harder parts cause it to flex, much depends on the feed speed.
Any timber will have similar characteristics, even greenheart, metals are fairly consistent in their mass so a given bit speed and feed speed (with appropriate coolant) will almost always produce the required result.
The vagaries of timber will often throw up this kind of problem.

Another point to think on is, how often have you tried to use a HSS twist drill to drill a hole in timber and had it slide off the mark you placed it on because it found a softer part to prefer, or a panel pin that took the path of least resistance and ended up breaching the face of the work even though you hit it square on?
Does anyone make dowel point drills less than 3mm? They tend to make life easier when drillng wood.

Rob.

 

[Eric The Viking]

Coupla' thoughts I haven't see so far in this thread:

I assume you're using a decent drill press? Mine's a Clarke cheapy, and although it's got a decent Rohm chuck (now!) it's not very true, either because of really cheap bearings or because it's made badly (or both). If the drill isn't concentric, you're asking for lots of trouble.

I have several pin chucks - a couple of good olde worlde Eclipse ones, and a set of the Chinese ones. The latter are not concentric! It might be worth checking yours, and trying Chronos Engineering or possibly Tilgear for a good one if it's a bit rough.

What speed are you using? Given it's a relatively tiny drill, it needs to run at fairly huge RPM to cut reasonably at the edge. I'd put the belts on the fastest available and feed the quill fairly slowly (and keep reversing out to clear sawdust).

As for starting in the right place: putting masking tape on the surface might help the skipping, if that's what it's doing. Given the size of the hole, clear Sellotape might be a better bet. The residue comes off fairly well with Acetone or Xylene.

What are the holes for, anyway? Could you achieve the same result by putting a point on the back end of one of your broken drills, holding that in the pin chuck and driving it in with the chuck not rotating (i.e. just using the quill)? I fear the diameter is slightly too big to do that, though.

 

[xy mosian]

I think the problems you are having are down to the drill being very flexible and clogging. The latter generating heat.
My first thoughts agreed with Eric's 'drive a sharpened steel bit into it' ( to paraphrase, sorry if that's not what you intended Eric). I also think that the diameter is a bit big for that, quite a lot of splitting could occur. However if the steel drill shank mentioned is ground with a flat to a half circular 'D' section, then you will have a much stiffer drill. Used as a normal drill, but at a lower speed, I think that you would get good results. Wind instrument makers have been using D-shaped reamers over lengths many times their diameter for a great length of time.

xy

 

[ondablade]

Too low an RPM is a fairly common problem with small drills. http://www.woodmagazine.com/woodworking ... eed-chart/

Clogging is the other biggie, too much feed rate, soggy or resinous timber, not enough lifting to clear and the fact that stock twist drills are not really made for wood so the angles are not 100% are other reasons.

Guessing, but spritz of Pledge polish on the drill might help it to clear a bit better.

A good center punch mark might help too as a hard growth ring in the wood could deflect the drill enough as it starts to cause problems, although if the placing is unfortunate (near the edge of one) some other method like Bob's may be necessary.....