Help with drills and drill bits

[Aeternus]

I'm just about to embark on a titan sized project, while following a guide for the build. However at one point it talked about using a Forstner drill bit to hollow out the slot for the magnet.

The drill bit I can find, however I have little to no experience with electric drills, and this would be my first purchase of one, so I'm hoping one of you can help me.

Will a 3/4" diameter Forstner drill bit fit in any sort of cordless drill from DIY stores, do I have to get something extra to get it to fit, or will it only fit in a few specific drills?

For reference, this is the bit in question. Drill bit

Also, any other advice is welcome

Thanks

[NiceGuyAdi]

I've no experience with Forstner bits but it doesn't look out of the ordinary in terms of fitting it to a drill. I had a look on Screwfix's website (there's a couple of sets there).

 

What are you planning on drilling, though? If it's resin or plastic I'd be worried about melting the material.

[Grotsmasha]

A smaller, variable speed drill is what your after. The name forstner refers to the head, and should plug and play with any drill.

 

Cheers,

Jono

[Major_Gilbear]

To accommodate and grip any drill bit, most drills have what's called a chuck. This is sometimes tightened with a key (comes with the drill), or is a key-less "twist-lock" system. A keyed chuck normally has a better grip on the drill bit, but makes frequent changing of the bits (marginally) more hassle than with a twist-lock. I prefer a chuck with a key for most situations - I feel the better grip is worth a few extra seconds of my life!

 

The chuck contains jaws that open and close as you twist the adjuster ring, and most variable-speed household drills are perfectly capable of holding most drill bits.

 

The drill bit you've linked has a 9.5mm shaft diameter, and this falls within what most drills will accommodate (you're normally good for anything between 2mm-10mm).

 

I would suggest a corded drill, as they are: cheaper, don't need charging (good for infrequent or unplanned use), and are often more powerful and comparatively lighter (once you factor in the weight of the battery) than the battery equivalents in that price-range.

 

Features that are useful/essential:

 

- Reverse

- Variable speed

 

Features you will not need:

 

- Hammer action

- Front handle

- Light

 

Since you are drilling resin, you will not need anything heavy-duty at all. As long as it has a reasonable torque (literally: "twisting power") and variable speed, you will be fine. If it does happen to have hammer action, make sure that it can be switched on/off, and if it does have a front handle, check that it can be unscrewed. You ought to be able to buy something more than good enough for about £30-40. Beware of anything cheaper than this unless you are not bothered about doing more than just one project with it.

[Isolia]

On the variable speed, I'd recommend something that can be very slow if it's not too expensive. My dremel kicks in at 3000rpm and goes up to ten times that which is great for many things, but it needs some time to get the hold of it for plastic and resin because they tend to melt at these speeds (not volcano melting but it makes bigger holes than intended, for example). The melted plastic quickly dries on the tip and can be difficult to remove without a scalpel or exacto, too

[Major_Gilbear]

Yeah, it's why I didn't recommend a Dremel really. Most household drills can go much slower than that depending on the speed setting and how far you depress the trigger. :)

[Ovidius Incertus]

Make sure you have some way of holding the piece in question while you drill.  A powerful and torqu-y drill with a big bit might yank the part out of your hand while you drill if you're not careful.

 

You will definitely want to drill a pilot hole first to make sure your hole will be centered and try to go slowly and not hog out too much material because that's when you lose control of the part or you might even find the bit is ripping your material and gives you a nasty hole instead of a clean cut.

 

I haven't used a Forstner bit (yet), so maybe its flatter cutting surface avoids some of these problems, but I'd still go as slow and steady as possible.

[Aeternus]

Thank you everyone for the replies, advice and help :)  Extremely helpful

 

Would you feel this drill would be suitable for the uses outlined?

 

Drill

 

Otherwise any suggestions for corded/cordless drills (preferably ones from uk sites) are very welcome :) 

[Major_Gilbear]

That drill looks fine to me, just take your time and don't force it to drill the hole in one straight go. The jaws open to 10mm, which is about 0.47mm bigger then the shank of the drill bit you've bought - it ought to *just* fit, but I suggest having the drill bit with you when you go to Argos so that you can test the drill's size right there. Afterall, if it doesn't fit, you can change it straight away!

 

When you come to make the hole, Ovidius Incertus's advice of a pilot hole is quite right: note the the design of you drill bit is such that the central part has a spike that will allow you locate it, so you do only need a small-ish pilot hole. A good tip to ensure that you don't drill the pilot hole too deep is to carefully put a little bit of tape around the drill bit, leaving a length of the tip exposed that matches how far down you want to drill. Then, when you drill, you know you need to stop when you reach the tape around the bit. Each time you drill, just re-check the tape and exposed tip to ensure that it hasn't moved. After you're done, remove the tape and clean the drill bit so that the tape doesn't leave a sticky mess on the bit. Finally, note that the Forstner bit's spike comes out past the bottom of the main cutter, so if you need a hole 4mm deep for example, be aware the the spike might go down a further 2mm or whatever deeper still.

 

If when using the Forstner bit you find the drill sticking or heating up the resin, use a q-tip (cotton bud) to periodically apply a thin film of clean cooking oil to the hole as you drill; this will help prevent the bit from biting the resin too much and yanking it/or jumping out and damaging your project. I suggest cooking oil as it won't damage the resin and is easy to wash out with warm water and soap afterwards.

 

With regards to your Forstner drill bit, I suggest wiping it properly clean with rag after use, and then rubbing a bit of 3-in-1 mineral oil over it to keep it sharp and rust-free. It's an expensive and specialised thing to buy, so you may as well ensure it stays in good condition should you need to use it again in the future! :)

[Paradigm]

The only extra advice I'd add is to turn the torque all the way down. Then if the drill stops cutting turn it up one setting. This way it is less likely to damage the resin part, or get away from you. 

One thing I recently discovered that has been very helpful for me, are stepper bits.

 

When drilling plastic or resin, if you aren't worried about going through something, or there is sufficent material, a stepper bit will prevent brittle fracture of the part. A large chunk of resin won't be an issue for this, but if it is a relatively weak spot, a forstner bit may crack the part. 

You'd want a particularly large diameter stepper, with very shallow steps relative to the overall width. Most hardware stores will have one. 

Steppers do melt the resin and plastic while in use. However they usually only melt surfaces actually in contact with the bit. So the actual detail is fine. This is why they aren't as likely to break things though. Hard to break something when it is above its ductile-brittle transition temp. 

That said, I think you are probably all set with the Forstner bit. Titan work typically involves large pieces of resin, that are unlikely to break with gentle drilling.