Drill bits

Lance - You want fine bits cheap (as in free)? Next time you go to your dentist, ask him if he has some bits that are ready to be discarded. That's what I did. They have to be run through the autoclave before they can be dumped (that's the law in New York State) so they're sterile, and they will be plenty sharp for plastic or resin. I'm not too sure of the exact sizes, but the smaller ones are very small. HTH, -- John

Lance, here's a link to a drill bit chart. A .5mm is midway between a #76 & $77 bit. Model expo carries them and I think small parts inc does too. They should be pretty inexpensive but will certainly break easily.

I need .5 mm drill bits for putting some Fruilmodel tracks

Micromark has "book sets " of fine drills .

if you go for the 1/8" shank carbide ones (that I go for myself..) it's kinda pot luck what sizes you get. I sure do like them, and break them... carbide is very brittle. So I ordered two sets last time I bought from micromark.

-- Stephen

I find even the steel bits break very easily, but the 1/8 shank carbide ones REALLY break a lot. I have stopped buying them. I find model expo has good prices on three-packs, three bits of one size. I consider small drill bits expendable supplies.

Thanks guys!! I got some on the way from Micromark... but will definitely keep all your suggestions in mind. The carbide 1/8 shank bits are truely brittle...

| >

| | if you go for the 1/8" shank carbide ones (that I go for myself..) it's | kinda pot luck what sizes you get. I sure do like them, and break | them... carbide is very brittle. So I ordered two sets last time I | bought from micromark. | | -- Stephen

You can get a pretty good selection of sets at

Just a satisfied customer. I've bought mostly very, very small sizes there. #81 down to #97 are available most of the time. Larger sizes seem to be always available.

Norm

"Norm Dresner" wrote in news:a9twg.445142$ snipped-for-privacy@bgtnsc05-news.ops.worldnet.att.net:

Very good link! Thanks!

Frank

FYI, Those packs of 1/8" shank carbide drills sold by Micro Mark are USED circuit board drills. I use to be involved in the manufacture of military electronics. The machines they come off of are huge, mulitiple spindle computer controlled router / drills. The secret is that the RPM is extremely high, the feed rate into the material is precisely controlled and there is NO play (wiggling) between the spindle and the material being drilled. It's pretty difficult not to snap them off when drilling by hand with a Dremel tool !

It is standard manufacturing practice to replace the drills after they drill X number of holes. That's where Micro Mark is getting them and why the sizes you get in the packs is pot-luck. There's still lots of life left in them for the hobbist - they just too dull to reliably make a good hole in a circuit board.

I bought a box of them from Micro Mark years ago and immediately sent them back when I saw what they really were. (I recall they were advertised as assorted carbide burrs at that time.) I stick with steel drills. They are MUCH less likely to snap.

A couple of tips for drilling those #60 - #80 holes:

1) To keep your drill from skating all over creation, always start your hole with an indentation from a sharp needle or pin. Your'll find it a lot easier to get a non-moving object exactly where you want it. The drill will self-center in the indentation. If you want holes in straight row, lightly scribe a line, then prick with the pin. To get even spacing, use saw teeth as a guide for the pin. Or use dividers to "walk" down a scribed line.

2) Once you get the hole started, use a little lubricant to help the chips to clear the flutes of the drill without clogging up. Nothing exhotic. A little dish soap, candle wax, oil. Even spit is better than drilling dry.

3) If the chips aren't clearing the drill, pull the drill out immediately and wipe the chips off.

4) Drill at low RPM. Melting the plastic and binding the drill is the biggest problem. Go slow, use lubricant. The lowest speed on the speed controlled Dremels is OK for #60 down to #70. Smaller than that, I use a foot operated speed controller which runs the flex shaft so slow I can count the revolutions.

5) Use a pin vise and drill by hand. I find the standard double ended pin vise too unstable to use with small drills, so I added a yoke to the "big" end for my index finger. The yoke has a shaft that goes into the untightened 1/8" collet. This allows me to hold the pin vise steady with my index finger while turning the body of the vise with my thumb and middle finger. This feature is common on many jewelers screwdrivers, but I haven't seen it on a pin vise. It might exist. I've tried the miniature Archimedes drill (which has a high angle helix on the outside with a mating nut that you run up and down the shaft to make it turn) but I cannot recommend it. I found it too unstable.

6) A final tip. If you are having trouble - consider buying new drills. Styrene is soft - but it is surprizingly abrasive. Ever notice how often you replace your #11 blade? You may not use that #80 drill often, but its cutting edges are a lot smaller. It wears out, too!

Greg Reynolds, IPMS

"Greg" skrev i en meddelelse news: snipped-for-privacy@news.sf.sbcglobal.net...

Greg wrote:

Just saw the thread, and MikroMark sure are cheap on drillbits :-) But Greg, why did you send them back? 'cause they were used (dull)? 'cause they were resharpened? or something else? I'm only asking 'cause I'm thinking of ordering them. My use will primarly be for homemade PCB's. So, are these drill bits good enough for this task?

I'm sure Greg will answer about printed circuit boards.. but for our uses, models made mostly of styrene, they work great. Only problem is that they snap off VERY easily.

Worst catastrophe I ever had was when I was holding an open plastic box full of very fine carbide bits, and the hinge on the box gave. I managed to direct the box to the table and landed it upright, but it hit kinda hard. I think I lost an even dozen #77 - #80 bits. They didn't get broken by force, but by the jarring when the box hit the table.

Oh well.

--- Stephen

Uffe, using standard HSS (High Speed Steel) hobby drills on PC boards will make them dull really quickly.

You will have much better luck with TC (Tungsten Carbide) drills. Those are designed for drilling PC boards. They will drill thousands of holes without getting dull but they are very brittle. You will have best results using them in a drill press.

New ones are very expensive (I've seen then up to $20 US) per bit. But you can get used or resharpened ones much cheaper.

I buy mine on eBay or from Kevin Strel. Seems that Kevin no longer has a TC Drills website. But you could try to email him to see if he has any left. He used to sell them really cheap.

Here is his info:

Peteski