Best Dremel for Plastic?

[Firepower]

So I've recently become a habitual magnetization fanatic, because most of the squads I'm building these days are defined by a wide array of wargear choices (Vanguard, Terminators, and the like).

 

My pin vice disagrees with Power Armor torsos.  It basically tries to (and sometimes succeeds in) tearing torsos in half once it bites in deep enough.  From what I've seen, the speed of a dremel mitigates the issue well.  But I dunno what sort to get, aside from a metric one, as all my magnets are likewise metric.

 

Any suggestions?  Preferably something quite cheap, naturally.

[D3L]

use a pin vice, start with a 1mm drill bit, then 3mm drill bit to widen it for the magnet

 

using a dremmel is going to shred your polystyrene models

 

it sounds like youre using the pin vice incorrectly, somehow

[Firepower]

The 3mm drill 'bites' in deep once it clears a certain point in just about any model, typically once there's a void of some sort.  Once it bites, it rather bend and tear up the plastic it's in than continue deeper.  The usual solution is to pull as I drill deeper, but that has mixed results at best.

Edited February 2, 2018 by Firepower

[D3L]

The 3mm drill 'bites' in deep once it clears a certain point in just about any model, typically once there's a void of some sort.  Once it bites, it rather bend and tear up the plastic it's in than continue deeper.  The usual solution is to pull as I drill deeper, but that has mixed results at best.

to me, that sounds like your drill bit isn't sharp enough, but of course that's a complete guess without seeing what you're actually doing, a void is fine, anecdotally I've never had an issue and I've drilled 3mm into cataphractii assembled torsos (void inside) all day long

 

I can't stress enough pilot holes, even a grade in between

 

for reference I'm using the Tamiya set (1 1.5 2 2.5 3mm)

[Major_Gilbear]

As D3L says, I think this is a technique/drill bit issue rather than a tool issue.

 

With a small drill bit (like 1mm), the swarf (the little bits of plastic that come out as you drill) is relatively fine and normally comes out pretty easily.

 

When you then step up to a 3mm, the distance between the cutting faces increases, creating larger pieces of swarf that prevent the drill bit from making a smooth hole.

 

To solve this, you need to reduce the size of the pieces of swarf, and this really means that you need to edge up to the final size you need more gradually. Start with a 1mm, then a 1.5mm, then a 2mm, then a 2.5mm, then a 3mm. If you wax the bits (drill into an old wax candle first), this helps to stop the bit from binding and helps the swarf come out more easily. If you're still having trouble, try a 2.75mm drill bit after the 2.5mm before then going onto your 3.0mm. Generally, the bigger the hole diameter you need make, the more benefit there is in reducing the size increments in drill bits until you reach the size you want. Patience is key!

 

High speed and a slow progression of the drill bit is another way to break up the swarf info smaller pieces as you drill, but this generates a lot of heat and tends to melt the plastic. You also need everything to be very firmly secured as one little bit of wrong movement ruins everything at that speed and level of power. I would therefore stick with hand tools, which are much more appropriate for these sorts of tasks, and are safer for what you're trying to acheive.

 

Next, a note on the drill bits themselves. You can buy "rolled" or "ground" - always buy "ground".

What this means is how the bit was made: rolled means they stamp a blank, sharpen the edge each side, and then twist the bit; ground means they cut the grooves and sharpened the cutting edged directly onto a cylindrical bit. The rolled bits are often not even enough in their twist along their length, and the swarf can get stuck and bind the drill bit as a result - this is especially true in dense materials and small hole diameters. The ground bits cost more (2-4 times more, depending on size) but are much more precise and regular, which means they cut better and the swarf comes out neatly and easily as you drill.

 

In terms of material for your drill bits, I recommend getting hard-wearing bits that are Cobalt or similar - these are very hard-wearing (even if drilling metal models) and are not so brittle that they snap every other time you use them.

 

Finally, a quick note on technique. If the faces and/or edges of the holes you drill are not smooth and even enough, it's possible for the drill bit to catch them and "tear" the material unevenly as you drill. I find that once I get to the larger sizes (2mm +), it's helpful to use a little sanding rod/stick to briefly smooth the face of what you're drilling to let the next size of drill bit cut more evenly. You don't need to fully sand or anything - just a quick twirl or two to help smooth it a little before you use the next size of bit, and it really helps with delicate or thinner parts especially.

 

Hope that helps, but do let me know how you get on - if you're still having trouble, I'll see if I can help further. :)

[D3L]

* snip *

completely agree with what you say, and that's an interesting thing to know about the roll versus ground bit types

[Major_Gilbear]

Yes, it's often not especially clear when buying drill bits which is which. It took me some research and experience to discover that, and I broke a lot of bits in models along the way.

 

Rolled bits are sometimes referred to as "twist" instead.

 

For example, a 1mm HSS Twist Drill Bit means its 1mm diameter, high speed steel, and that it's rolled. Low prices for these make them tempting, and they are also typically sold in little multi-bit kits that have about 30 different sizes ranging from 0.3mm up to 1.5mm. Whilst at sizes under 0.6mm I would really only expect rolled bits (too small to for them to be ground), I would expect ground to be available from around that size up.

 

And -as with so many things in life- you get what you pay for, which is worth keeping in mind as you drill into your expensive models that you will later paint with expensive paints using an expensive brush! :P

[Firepower]

Based on what you've written, I've a feeling the 3mm bit isn't "ground."  The spiral is quite stretched, which has always been something of a visible problem just from using it, though I didn't know there were categories for such a thing.  Among other problems, often when it passes into a void, it simply ceases cutting the plastic and just goes in and out of the half-cut hole it's made as a path for itself.

 

Sounds like I'll be needing a more complete bit set and vice...cheaper than a dremel, at least.

 

Although finding any vices that handle more than around 2mm is tricky, and bit sets are rarely sold with any bits much higher than 2mm as well.  Any suggestions there?

Edited February 2, 2018 by Firepower

[Major_Gilbear]

For larger diameters, I use one of these. :)

[Firepower]

Bloody hell that's a chunky beast 

[TheOneTrueZon]

I use a Dremel 8220 and these bits which are made for wood carving & engraving but are perfect for plastic & resin as well. Most dremels come with adapters for 1/8" & 1/4" shanks.

 

http://amzn.to/2s795yy

 

However, if you go too fast (over 10,000 rpm) these kinds of bits will melt the plastic a bit and it will get in the grooves, it comes off easily enough once it's cool, but worth noting. 

[Semper Fortis]

You can also pick up pin vices with multiple collets to accommodate multiple drill sizes.

 

Something else you might consider in addition to all the great advice above. Any muscle you use should be focused on keeping the pin vice steady and perpendicular to the hole. If your drill bit requires force to advance into the hole, it's way too dull. And honestly, if your bit is mangling the model when it enters the void , you're using way too much force. Be gentle. :)

Edited February 3, 2018 by Semper Fortis

[Firepower]

Update:  

 

I managed to find a pin vise that came with a collection of bits: .8, 1, 1.2, 1.5, 1.8, 2.0, 2.2, 2.5, 2.8 and 3mm.  Gradually working up from low to the full 3mm...seems to work like a charm.  Thanks for the guidance

 

I will come for you in the night when it suddenly stops working.  

 

As an aside, when trying to get a tiny drill bit out of its slot in the bit case, don't use a magnet.  The whole damn set is magnetized now

Edited February 10, 2018 by Firepower

[Razblood]

Alternate option is to drill with 1/1.5 mm and then widen to hole with a cylindrical file, I've had some success with this on dread powerplants and the like.