High Speed Miro Drills

Andy from Kenosha

Andy from Kenosha

Joined
Nov 16, 2018
Messages
145
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I have a problem that is most likely something I am doing wrong rather than the quality of my tools. I own a set of 10 tungsten carbide high speed PCB drill bits ranging in size from 0.3mm to 1.2mm, and are advertised that they will drill through metal. I am attempting to drill through 0.3mm thick brass, and so far I have broken 4 drill bits. What am I doing wrong? I tried it at high speed, low speed, and medium speed. The moment the hole is made, the drill bit breaks. I've decided that I won't drill the holes, but that's not really the problem/answer. I want to make the model correctly, including the holes--how can I drill these holes without breaking my bits? Thank you so much, Andy
 
I would say that you need something like a drill press. PCB drills are carbide because they have to drill through glass fibre which blunts conventional drills.
They are, however, fragile, and will break if there is much lateral movement. Care is your friend here.
I hope this helps, or at least explains what is probable happening.

Nigel
 
Nigeld said:
I would say that you need something like a drill press. PCB drills are carbide because they have to drill through glass fibre which blunts conventional drills.
They are, however, fragile, and will break if there is much lateral movement. Care is your friend here.
I hope this helps, or at least explains what is probable happening.

Nigel
Click to expand...
Thank you so much--my father-in-law said something similar; the careful use of a drill press.
 
Я сверлю ручной дрелью. Все дело в навыках и опыте. Если сверлить станком, оно должно быть очень точным, иначе отверстие будет шире сверла. И да, сверла 0,3-0,5 расходные. Они все еще ломаются

I drill with a hand drill. It's all about skills and experience. If drilled with a machine, it must be very accurate, otherwise the hole will be wider than the drill. And yes, drills 0.3-0.5 are consumable. They are still breaking
 
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One more thing, tungsten carbide bits do not like side loading. They are very brittle. Even larger drill bits will shatter. (From experience). And tiny drill bits perform better at higher rpm's.
Y.T. said:
I have this drill press. I highly recommend it. Just be sure buying one with collet type drill bit holders.View attachment 230220
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Does this drill stand take Dremels? Just wondering. I don't want to buy another rotary tool just to fit a xtand. I've been looking at this stand. I have a full floor 17" drill press but it just might be overkill...
 
A.L. Thorsen said:
I have a problem that is most likely something I am doing wrong rather than the quality of my tools. I own a set of 10 tungsten carbide high speed PCB drill bits ranging in size from 0.3mm to 1.2mm, and are advertised that they will drill through metal. I am attempting to drill through 0.3mm thick brass, and so far I have broken 4 drill bits. What am I doing wrong? I tried it at high speed, low speed, and medium speed. The moment the hole is made, the drill bit breaks. I've decided that I won't drill the holes, but that's not really the problem/answer. I want to make the model correctly, including the holes--how can I drill these holes without breaking my bits? Thank you so much, Andy
Click to expand...
Hello Andy, I don't think you doing something wrong. But let's discuss your trouble drilling in order.
  • First, I want to mention that PCB drill bits are not optimal tooling to drill the wood. If you take a close look, they are just twisted flat rod (I am serious). Yes, they could be made with carbon steel, but their primary use, still in CNC machines for drilling printed circuit boards for electronics.
  • For modeling purposes, a better option to use machinist drills. Those are ground using special machines and sharpen (angle) depending on the material used. Machines drill bits come in a variety of shapes and designed for a different job in mind. Most common for our modeling tasks are jobber and mechanic drill bits. The common difference between those two is the 'flute length. A jobber drill bit is a bit that has a long length compared to its diameter. Jobbers have a length anywhere from 8-12 or 9-14 (depending on who you ask) times the diameter. These bits can be measured using a number of different systems including a basic number range (1-80), letters (A-Z), wire (increase by the whole number), standard metric sizing, or fractional sizes. A mechanics length drill bit is simply a bit with a shorter flute length and shorter overall length than a standard jobber bit. This shortening of the bit makes it considerably stronger and less prone to breakage and shearing, making it suitable for harder drilling. Below is the image depicted both drill types
1619655267237.png

Determining if you should use a jobber bit vs a mechanics length (jobber) bit, is actually quite simple. A regular jobber bit is best used in softer materials such as wood, composite, and soft metals. For harder materials and hard metal drilling, a mechanics length drill bit is recommended as they are a stronger bit. Jobber length drill bits are the most common and popular type of drill bits.
  • One word of caution drilling brass. Brass has a tendency to grab the sharp edge on drill bits. Bits for brass, whether drill bits or turning bits for the lathe are supposed to have a zero rake cutting edge. That way, they will not grab, and, it’s simply the proper tool bit geometry for brass. here is the article talking about it
handycrowd.com

Drilling Brass: the easy and safe way ⋆ handycrowd.com

I remember my dad showing me this drilling brass trick more than 30 years ago. And who better to show you, other than the guys on the Home Model Engine Machinist forum because they really know their stuff when it comes to tricky machining jobs. Here is what Deanofid had to say about an easy way...
handycrowd.com handycrowd.com

This is in terms of the drill bits. Now the actual drilling. Specifically when you are dealing with the smallest diameter drill bits eg. 0.3mm or 0.4 mm, you must have a steady hand. The parts you are drilling must be pinned to a surface. For this, you most likely need to invest in a miniature drill press or drill stand and use a rotary tool. Just carefully choose both as they: rotary tool and drill stand are not interchangeable. For Dremel rotary tools, you will use a Dremel stand, and for Proxxon, showing early by Yuri @Y.T., you have to use Proxxon rotary tool. Also, the drill stand and the rotary tool will make sure the drill bit is steady and aligned, For part pinning you have to use a vise.

This all sounds like a bit of investment and a shopping spree, But this is a topic for another discussion :cool: Not sure, your Admiral will be happy.:eek:
 
Philski said:
To add to that, if you cannot get to the fractional bit size you need, look at number drills.
Click to expand...
I found a very good source buying miniature drill bit in metric.

www.ebay.com

10x HSS-R metalworking twist drill bits DIN338N Ø 0.45mm | eBay

Find many great new & used options and get the best deals for 10x HSS-R metalworking twist drill bits DIN338N Ø 0.45mm at the best online prices at eBay! Free shipping for many products!
www.ebay.com

Here are 0.45mm drill bits (10 for $2.00). Just click 'visit store' to find the drill bit you might need. The store located in Germany and most of their drill bits made in Germany. It takes from 2-5 weeks to deliver but hey, you get what you looking for! :)

* all the miniature drill bits I have ordered, from all sources, have a tolerance of 0.01mm ~ 0.02mm For example a 0.30mm will be 0.28\0.29
 
A.L. Thorsen said:
What does it take if not dremel-like tools?
Click to expand...
Hello, Andy. There is no such thing as Dremel-like tools. All tools made by Dremel company we call Dremel tools. In this particular case, the stand takes a Proxxon rotary tool.
In fact, Yuri @Y.T. setup is not a drill press, It is called a drill stand. Proxxon made many different rotary tools, where some of which will fit this drill stand. Drill press, however, comes with motor and drill chuck permanently mount and not interchangeable.

Here is the drill stand. Without a rotary tool, it is useless. If you own one of the Proxxon rotary tools, you can convert this drill stand to a drill press.
1619826136814.png

Here is the drill press. You can use it out from the box, no rotary tool requires, besides drill bits, perhaps.

1619826435431.png

Dremel also made a drill stand as well as the rotary tools. While both Proxxon and Dremel tools designed for the same purpose, they are not interchangeable in the drill stands. Here is the Dremel version of the drill stand. It will fit only Dremel rotary tools.

1619826595050.png

However, there are many diffrent drill stand compatible with dremel rotary tools. Like the one below from Milescraft. This one is Dremmel friendly.

1619826829064.png
 
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