The problem I have with the normal HSS drill bits in the #80 size, drilling in plastic mainly, is that they tend to flex. The end result is a hole larger than if I was using a #78 drill bit, which doesn’t flex much, and drills faster too. The carbide bits are more expensive than the HSS ones, but they would be worth it, if they drill clean holes, without a lot of effort.
Drill bits don’t bend they break. Too much pressure on the bit is the issue. If your bit is dull and you need to push harder the tool is not working and you are. For small holes such as these I only use a pin vise even in brass. HSS bits are designed for the size verses diameter scale for speed of bit. High speed for a #80 would be 3.5 rpm. This is for mild steel. Plastic would be even less.
Carbide drill bits don’t flex. Period. They snap or shatter even on low speed and the pieces go flying. I use the normal HSS bits any time I can get them.
A pin vise is something I’ve had but never used. A small very low speed drill serves me fine. All these years the pin vise has been laying somewhere deep in the bottom of my tool box if I haven’t given it away by now. It’s about as useful to me as a right shoe.
Quick Summary: Some approximate starting advice is to set the spindle speed between 700-1000 rpms for steel, above 2000 for aluminum, and slow down from there if you get discolored chips or heavy drill bit wear. In most cases the drill press will not be able to supply enough power or speed to follow the below recommendations. A 3/8" drill bit drilling mild steel at the recommended speed and feed could require around 1 hp. Going slower usually doesn’t hurt, and will prolong tool life.
Drill press spindle speeds depend on lots of things: the type of material being drilled and its hardness, the hole size, the type / hardness of the drill bit and its sharpness, whether or not a cutting / cooling fluid is used, and the rigidity of the drill and clamp, among others. Also, most speed recommendations are geared towards manufacturing environments where machining time is very expensive. As drilling speed increases productivity goes up, but tooling also wears out faster. The recommendations seek a balance between these two concerns, but this balance is not determined with the pocketbook of someone running a hobbyist or prototype shop in mind.
So, for the hobbyists shop, where longer tool life is probably more important than machining time, and where pushing the speed limit may ruin a valuable prototype, reasonable advice might be to start off at about 75% of the recommended drilling speeds. The “First Guesses” below are already a little slower.
Small assortments of resharpened carbide micro drill bits are available from Harbor Freight Tools at cheap prices. The actual sizes in each pack vary but there are usually several in the #75 and smaller sizes. As previously stated, these carbide drill bits are extremely hard and sharp but equally brittle. Any misalignment with the hole you are drilling and they will just snap. If you are managing to flex your #80 HSS drill bits, you will quickly break a #80 carbide bit.
The technique I use to minimize breakage (please note there is no way I know to eliminate breakage) is to place the tip of the bit against the work piece, then use the tip of the index finger of my left hand to hold and steady the top of the bit. I place the palm of my left hand flat against the work surface to keep my index finger from moving horizontally. I then use the thumb and index finger of my right hand to slowly turn the round plastic collar on the drill shaft. Carefully turn the bit until your hole is drilled or the bit breaks, whichever occurs first. If you manage to successfully drill your hole without breaking the bit, carefully back it out or it will break upon removal. If you successfully drilled your hole, it should be very accurate with regards to size.
Personally, if I could find them locally as easily and as inexpensively as the resharpened carbide bits from Harbor Freight Tools (three different stores within about 10 miles of my home), I would buy a set of HSS bits or even carbon bits as they are far more forgiving.
Like said above. Actually HHS would work batter then carbide. Carbide has to be run fast. A pin vise would be great in plastic. A HHS drill bit has to have some type of coolant on it spinning that fast thru plastic or it will melt the plastic in the hole causing it to drill bigger. But the problem with a pin vise is that it hard to keep the drill straight. Using a drill press or drill itself would require a slow speed. Like around 350 RPM
Your response to Pete was rather inappropriate and far from the spirit of the forum. If his advice was not useful either ignore it or just say “thanks for the input” and leave it at that. Perhaps an apology is in order.
One way to reduce the wobble in your drill bits, regardless of composition, is to chuck the bit so that only enough of the bit is showing to go through the thickness of the material you are drilling the hole in. This eliminates both the wobble and the bending that breaks so many bits. If you are buying the bits with a larger shank then chucking the bit short isn’t possible and breakage and wobble (likely the former) will occur unless you are using a drill press with tolerances designed for the use of the large shank bits.
You also need the proper size collet in the pin vise for the smaller bits. And you do tend to get what you pay for, the cheaper ones do anything but actually center the bit, leading to egged out holes and frustration.
Previous answers are all correct. Carbide is harder than HSS, but harder also means more brittle. So that little off center that flexes the HSS bit will indeed instantly snap a carbide bit.The hardness of carbide is not needed for drilling plastic. A quality pin vide with the proper size collet to handle a #80 drill, and making sure it truly is centered, with as little of the bit exposed as needed for the depth of hole, will go a long way to getting proper size holes. If absolute precision is required, then a small drill press should be used, there’s pretty much no chance at all to get no measurable deviation in a #80 hole when drilled by hand.
If that was a worthless answer, then you know nothing about machining! Carbide and for that mater diamond are worthless unless you have the right powered set up, most hobbyist don’t even come close to the proper set up.
What I don’t understand in your questions,seeing as how,you appear not to like the answers,you were provided…Why don’t you purchase,the ten piece set,for 6.97 at the place you provided the link to.?? I find it hard to believe that 10 small hobby drill bits,for 6.97 is expensive and then if you find them not to your liking,tell them they are worthless,rather than put some down,that you don’t even know,that is trying to help you…I mentioned it and others,put the bit further in the chuck,so less is exposed and let the bit do the cutting,don’t force it…BYE!!
Let’s go back to the beginning for a moment. What are you using to turn the bit? Are you doing the drilling by hand, or with some sort of motorized device?
I have had the problem you describe. I put a bit in one of those small battery operated Dremels. I got the same enlarged hole efferct. But I determined that this was because the darn collect chuck was not holding the bit straight. The wobble of the bit caused the enlarged hole.
I apologize to Pete for my 'worthless" comment, as I know it was rude. It was just that his was the first comment, and it seemed somewhat arrogant to me, especially the part about how drill bits don’t bend.
I use a quality pin vise, drilled by hand. I think the main problem could be the quality of the bits I was using. I bought a ten pack of #80 bits, and they said Made in China. So, they were new bits and shouldn’t be dull, but I should realize the Made in China label. Anyway, after giving up on the #80 bits, yesterday I tried a #79 bit I had on plastic, that I am pretty sure is a Mascot brand, and it drilled very well. So now, I just need a source for quality bits, and perhaps stick to the #79 size. Even respected retailers like Micro-Mark and Internettrains.com don’t say where their bits are made and what brand they are, and so many things now are made in China, so it seems to be somewhat of a crapshoot in finding quality bits.
As to the carbide bits, I was hoping for someone to offer their opinion of actually using them for drilling into plastic, but I never really got that. Being involved with woodworking, I know all about carbide and it’s brittleness factor, but you can’t beat it for a sharp, long lasting edge.
As to diamond tipped bits, you won’t find them small sized like #80 and similar, so I don’t know why anyone would suggest those.
Actually, not an entirely correct statement across the board, John.
Carbide works great milling or drilling plastic. The important thing is to keep the plastic cool (lubricated) during the milling/drilling process to dissipate the heat. However, within the constraints of this conversation about drilling with wire gauge (#61-80) drill bits, I agree that HSS is the way to go because it’s less brittle than carbide and can flex a little without breaking.
As mentioned previously, let the drill bit do the cutting rather than applying more pressure. If the drill bit begins to flex then it’s dull and needs resharpening or replacing. I prefer using a pin vise over an electric drill for small holes because it gives me much better control and feel for what the drill bit is doing.
If you are pretty good friends with your,‘‘Dentist’’ ask him where he gets his drill bits… Another excellent source,Acetylene Welding supply stores,why?? Because they have drill bits very very close to the sizes of the Model drill bits,they are used for, drilling the torch tip holes that become damaged and filled with carbon,they even come with a pin vise,double ended collet,the vise is hollow and all the not used bits fit in there…I have had one set now for twenty years and have yet to break one and use them for plastic,brass,all metals,they go through plastic like butter…I use them a lot,to drill out miniature gun barrels of different Military equipment,usually a 1/4 in depth,piece of cake with those drill bits…
And I was the one,about the diamond bits…I’ve been around many blocks in my life, a lot of times more than once…