Holes in kitchen plinth for lights

[Jupiter01]

I was installing some plinth lights in the kitchen over the weekend and it went reasonably well, except for some holes that were misbehaving. Let me explain…

I was using a Bosch spade bit (with screw tip) and the light had a flange which meant that some of the imperfections of the hole can be covered. The plinth had an acrylic type finish. One of those gloss kitchens.

I practiced lots of holes on a spare piece of plinth and found that whether I have the drill inserting the surface at full speed or very low speed, it didn’t make a difference. I got a reasonably clean hole. I decided to go with the slow speed insert into the plinth.

When I did it for real, approximately 3 of the 20 holes ripped the surface beyond what will be covered by the flange of the light. In the end I used a bit of glue to stick it back to the surface and since it is so low down, it’s hard to notice. Unfortunately, I don’t have a picture of the damage.

I am hoping this makes sense and there may be an explanation as to why everything worked fine in my test (pic attached) and for most of the holes apart from a few. There was no discernible difference.

I’ve added a bunch of pictures.

I welcome your thoughts on this.

 

[Deleted member 174758]

I'd forget those screw nose monstrosities! The Irwin (more trafitional) type of spade, which lack a screw nose, are a far better bet. The screw nose type are really designed to pull in fast, so are useful for producing rough holes in softwood, chipboard, OSB, etc but the emphasis is very much on speed over quality of cut.

The traditional type of spade bit do take more physical effort to use and need to be pushed into to work (having no screw nose they don't self-feed), but that does make for a more controlled cut with far less break out - my Irwins can even be run backwards if needs be - but they also have the advantage of being resharpenable (with a needle file or a warding file)

A little tip - place a piece scrap sheet material or softwood on the underside of the plinth where you are drilling and you will get a cleaner exit hole with zero or minimal break out

 

[Jupiter01]

I'd forget those screw nose monstrosities! The Irwin (more trafitional) type of spade, which lack a screw nose, are a far better bet. The screw nose type are really designed to pull in fast, so are useful for producing rough holes in softwood, chipboard, OSB, etc but the emphasis is very much on speed over quality of cut.

The traditional type of spade bit do take more physical effort to use and need to be pushed into to work (having no screw nose they don't self-feed), but that does make for a more controlled cut with far less break out - my Irwins can even be run backwards if needs be - but they also have the advantage of being resharpenable (with a needle file or a warding file)

A little tip - place a piece scrap sheet material or softwood on the underside of the plinth where you are drilling and you will get a cleaner exit hole with zero or minimal break out

Thanks for this.

Are these the ones you recommend?

Irwin IRWIW4041002 4041002 17pc 4X Blue Groove Flat Spade Bit Set Wood Timber | eBay

Irwin XMS23FBIT17 IRWIW4041002 4041002 17pc 4X Blue Groove Flat Spade Bit Set Wo. IRWIW4041002 IW4041002 17pc 4X Blue Groove Flat Bit Set. The Irwin IRWIW4041002 IW4041002 17pc 4X Blue Groove Flat Bit Set is just what carpenters, kitchen fitters and DIY enthusiasts need.

www.ebay.co.uk

Are you suggesting that I should refrain from using the Bosch bits on any wood that will be visible at the end of the job?

I was wondering if there was any explanation for why this damage only happened with some of the holes and not all or most holes.

Appreciate your help.

 

[Deleted member 174758]

Are these the ones you recommend?

Irwin IRWIW4041002 4041002 17pc 4X Blue Groove Flat Spade Bit Set Wood Timber | eBay

Irwin XMS23FBIT17 IRWIW4041002 4041002 17pc 4X Blue Groove Flat Spade Bit Set Wo. IRWIW4041002 IW4041002 17pc 4X Blue Groove Flat Bit Set. The Irwin IRWIW4041002 IW4041002 17pc 4X Blue Groove Flat Bit Set is just what carpenters, kitchen fitters and DIY enthusiasts need.

www.ebay.co.uk

Those are the ones I use, out of choice, but there are alternatives (many of them), so if you only need one size, why buy more?

Are you suggesting that I should refrain from using the Bosch bits on any wood that will be visible at the end of the job?

Yes. For the reason stated, namely that they are designed for speed over quality of cut.

I was wondering if there was any explanation for why this damage only happened with some of the holes and not all or most holes.

Mostlikely because of the plinth material. Most plinth strips are melamine faced chipboard (MFC) whilst some are vinyl- wrapped MDF or foil-wrapped MDF.

Melamine is hard and brittle and it doesn't take much to chip it - it is best drilled with a form of drill which scores the material before cutting it, e.g. brad point twist bit or spade bit with spurs, but equally the material needs to be fully scored through before starting to cut away the waste. Any drill with a screw nose will be a problem on melamine surfaces as it can potentially start to cut away the waste before the surface finish has been scored through. The result is a rough cut. Neither auger bits, nor new pattern centre bits nor your Bosch screw nose spade bits work well on melamine (or laminate) surfaces

Vinyl-wrapped MDF and foil-wrapped MDF, as used for many kitchen doors, deco panels and the like are a thin skin of vinyl or printed paper foil which are stretched over a smooth MDF surface which has been coated with a heat-activated PU glue and then glued in place using a heated vacuum press. The surface coating is thetefore very thin and delicate and it doesn't take much to damage it - attempting to cut away waste without first scoring through the wrapping material can octen result in a ragged opening with tears in thhe wrapping.

As to why some are good and others not, it's maybe the luck of the draw; perhaps on those good ones the drill bit didn't pull in as fast, or you didn't press as much, or the bonding between surface coating and substrate was slightly better, or maybe even that you were running the drill slower (most people seem to want to run drills flat out when in reality you often get a better quality cut by running the bit slower - the exception to that rule being traditional plain nose, i.e not self-feeding, spade bits). Who knows?

 

[foxhole]

Simple hole saw kit would have produced neat clean holes.