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I want to drill holes in MDF of varying thicknesses, laid out to sub millimetre precision. In other words, I need the positioning of the center of the holes to be accurate to within a half millimetre (0.5mm or 0.02 inch) or better.

My problem is that I can't decide whether MDF is considered a wood or a grain free composite material. So would it be best to use brad point wood bits with centre punched holes as in woodwork, or HSS bits with pilot holes as in metalwork? Or anything else?

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    Would this be the best type of drill bit that you are looking for? – Adam Zuckerman Dec 7 '15 at 22:38
  • I would be curious what you are making and what tools you decide to use. Press or hand held? – Matt Dec 8 '15 at 1:33
  • @Matt I'm making the enclosure and support structure for a true random number generator in the steampunk style. You shouldn't have asked. ( More details at www.reallyreallyrandom.com where there is a CAD drawing available for the sad and lonely) I'm using a drill press. I've had success with some cobalt bits which go through MDF like butter but are expensive and I'm looking to expand my range. – Paul Uszak Dec 8 '15 at 2:13
  • So the comment We have posted some specific details of Paul's efforts in constructing the hardware for this site. And we will continue to do so whilst he has the strength on go on... is referring to you then? Awesome – Matt Dec 8 '15 at 16:32
  • No matter which tool is used , you have to keep the tool from heat I suggest using a cool air nozzle works great .keep the wood chips out too the best you can more peck drilling helps . – james brisbane Jan 11 at 12:14
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The brad point is the way to go.

Whenever you are making precisely located holes you should always use a bushing or jig of some type if you can.

Of course, making jigs is time consuming. One quick and dirty alternative is to use what is called a "tap guide" which is a block of steel with standard sized holes in it. Get a set of transfer punches and put the fitting punch in the hole you want in the guide and move it around until the punch settles into the center punch divot. Clamp the tap guide to the work and drill.

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I want to drill holes in MDF of varying thicknesses, laid out to sub millimetre precision. In other words, I need the positioning of the center of the holes to be accurate to within a half millimetre (0.5mm) or better.

That's mostly a matter of accurate layout and a starter mark/hole (a single push from an awl can be sufficient) than a call for one particular style of bit.

So with regard to your question:

So would it be best to use brad point wood bits with centre punched holes as in woodwork, or HSS bits with pilot holes as in metalwork?

Yes :-)

All bits that you could use, from basic twist bits through brad-point to auger can achieve the required accuracy.

I'd add both flat/spade bits and Forstner bits to that list as well, but only if you can use a drill stand or drill press. It's possible to control both with a power drill used freehand, but it requires experience and maybe a bit of luck and as such I would not recommend it where accuracy is paramount.

My problem is that I can't decide whether MDF is considered a wood or a grain free composite material.

It's closer to the second option here. It's not quite grain free, see previous Question Does MDF have a grain direction?, however it's close enough that it doesn't matter much in practice.

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I think you would be safe with forsner bits or HSS brad points.

Both have the advantage to cut from the outside so as long as you start slow you can reduce tear-out to near zero. Some people use spade bits but they would not be my first choice.

If accuracy is important make sure that you clamp down your work and use a drill press. If you only have a hand held drill then follow some of the tips you see in this question to increase your accuracy:

How do I ensure my drill is perfectly vertical before cutting a hole in my desk?

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None of the answer provide a satisfactory answer as far as my amateur experience is concerned. I am fitting handles to new kithen cupboards and drawers, where there was no predrilling or marking by the manufacturer. I started off with Irwin jetpoint bits. I think you wold call them bradpoints as they have a spike in the centre of the bit. It went well but after only 6 holes the bit became blunt and burned. The most successful was my HSS bits which I bought to use for drilling through metal. These I would use with a narrower pilot hole as without the spike the bit could wander even with a bradawl induced starter point.

  • FYI no decent bit (of any type) should last that little time drilling MDF, which is by no means hard. Different story if you were drilling holes in purpleheart maybe, but MDF is like cheese by comparison. Now you say you burned the bit, but Jetpoints are supposed to be HSS and getting them hot shouldn't make any difference to that type of steel. It's specifically intended for high-speed use and for running hot (waaay past the point the tip would go blue). Is there a chance the bit isn't blunt but the flutes are just clogged, or there's some resin buildup just under the cutting edges? – Graphus supports Monica Apr 17 '18 at 12:26
  • It's a misconception that wood (or board) hardness is a good predictor of tool wear characteristics. MDF is very wearing on tools. I work in a joinery workshop where we machine large quantities of woods and boards and MDF is the most wearing material - more so than oak, for drills and spindle tooling, and whether it's steel or carbide tooling. Our tooling supplier recommends diamond tooling for MDF because it's the only thing that lasts long enough. Not sure where I've seen it but I'm sure I saw a list of wood species tool wear and some softer woods are more wearing than other very hard woods. – WhatEvil Apr 28 '18 at 21:15
  • So actually @Graphus where you say "FYI no decent bit (of any type) should last that little time drilling MDF" actually I would say the complete opposite and say "no type of bit lasts very long when drilling MDF"! – WhatEvil Apr 28 '18 at 21:18
  • @WhatEvil, that's fair enough for a production environment but the differing scales of work are critical here. High-speed tooling used repeatedly versus drilling literally a few holes, that's pretty much opposite ends of the spectrum. And for some middle-ground perspective, I've used just one set of twist drills (TiN-coated HSS) for everything woodwork-related for the past few years and they still don't need resharpening as far as I can tell. This includes drilling MDF, melamine-faced chipboard, and plywood. – Graphus supports Monica Apr 29 '18 at 18:09

protected by rob Jan 12 at 14:42

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