How to drill holes in ABS plastic without splintering?

[choochoo_balooParticipant @choochoo_baloo]

I used standard jobber drill bits to drill a line of holes in an ABS plastic enclosure.

Final dimeter is to be 10mm. I centre punched then pilot drilled 3mm (rightmost hole) at a slow speed, then went straight to final size, and the plastic snatched.

Clearly my technique is wrong. Please give me clear instructions on how to get it correct on the replacement! Thanks in advance.

[choochoo_balooParticipant @choochoo_baloo]

[Ady1Participant @ady1]

Other more capable people will come in after me

Nice sharp drill (wood drill?)

sandwich between 2 bits of wood?

[Ed DuffnerParticipant @edduffner79357]

Some good advice in this video.

Ed.

Edited By Ed Duffner on 04/08/2018 03:37:37

Edited By Ed Duffner on 04/08/2018 03:37:55

[Peter KroghParticipant @peterkrogh76576]

Yes sir, that's good information!

Pete

[I.M. OUTAHEREParticipant @i-m-outahere]

I use a step drill as it only has one cutting edge it wont't dig in

[Neil LickfoldParticipant @neillickfold44316]

Having support material above and below the part. Negative or dulled off a drill bit like the video is good for plastics. Also withplastic , not too hi a rpm. Otherwise it will want to melt the material. Same for a lot of other plastics.

Neil

[not done it yetParticipant @notdoneityet]

As NL. Alternatively use a slot mill.

[JasonBModerator @jasonb]

Step drill as they have almost zero helix and as they take small cuts per step won't rip into the work

Or a lip & spur bit as used for wood though watch the exist side with that.

[HopperParticipant @hopper]

A wood drill, or a metal drill reground like a wood drill so it has two cutting tips and a tit in the middle. These work well for thin sheetmetal too.

[J HancockParticipant @jhancock95746]

You need to use one of those tapered drills for cutting holes in very thin plate or ,perhaps a countersink drill

with many cutting edges ( don't let it get hot ! ).

[Anonymous]

Are you sure it's ABS? I've drilled hundreds of holes in plastic boxes, mostly for work, and never seen it chip like that.

I use standard 4-facet Dormer A002 drills. Like in brass they'll snatch if given a chance so you have to clamp the work properly. The clamping doesn't need to be tight, but it needs to be in the right place to prevent the work from lifting. I don't bother marking out and centre popping, just use the DRO on the mill. For a 10mm hole I'd start with a pilot hole around 6-7mm and finish off with 10mm.

Incidentally stoning the edges of the drill as shown in the video has never worked for me. You just end up badgering a perfectly good drill. For brass and bronze I've got a small selection of slow spiral drills for bulk removal of material. If the width of cut is small for subsequent enlargement the drills don't have much of a tendency to snatch.

Andrew

[LambtonParticipant @lambton]

Are you sure the material is ABS?

I have worked with ABS for may years and have never found any difficulty in drilling holes in it using normal jobbers drills other than a bit of "rag" sometimes on the exit side. The material sown it the photo looks as if it has a lot of filler in it.

Eric

[David George 1Participant @davidgeorge1]

This is what I use for plastic and brass one is a slow spiral and one has definite flat to prevent grabbing. I keep them just for that use.

David

[Neil WyattModerator @neilwyatt]

Clamp it down, close to the holes.

Step drills do work well,

[choochoo_balooParticipant @choochoo_baloo]

Defo ABS plastic apparently from datasheet. To elaborate: I had it clamped in the bench vice with a softwood block behind supporting.

The work definitely didn't lift, it's like the bit (a normal 118 deg jobber) started tearing into the plastic due to too quick material removal, leaving the unsightly ragged edge.

[Adam MaraParticipant @adammara]

Another vote for a step drill, never had a problem with drilling Perspex at work with them.

[NigeParticipant @nige81730]

Clamp it down firmly on a sacrificial wood surface and use a hole saw with the finest teeth you can find.

[MuzzerParticipant @muzzer]

Could well be ABS – but with high percentage of degraded regrind, used as a way to dispose of ("recycle" ) flashing and sweepings. Every time the material is melted in the moulding machine, it degrades but many moulding companies like to minimise the amount of stuff they have to dispose of, so they feed it back into the mincer.

I have some of those "Hippo" type builder's buckets from Aldi that are nothing like as tough as the real thing but that also includes the price which is bargain buckets in comparison. I expect they have recycled everything but the kitchen sink into those.

Murray

Edited By Muzzer on 04/08/2018 17:49:57

[Anonymous]

Posted by Muzzer on 04/08/2018 17:49:43:

I have some of those "Hippo" type builder's buckets from Aldi that are nothing like as tough as the real thing but that also includes the price which is bargain buckets in comparison. I expect they have recycled everything but the kitchen sink into those.

Hmmm, given your recent travails with kitchen sinks it may well have the kitchen sink in it.

Andrew

[richardandtracyParticipant @richardandtracy]

I always drill through plastic into wood. Pallet timber is adequate.

Regards,

Richard.

[Sam StonesParticipant @samstones42903]

As is becoming my habit, I’m a bit late in the day, Choochoo.

I must ask … How many of these mouldings do you have to drill? If just a couple or three, then ignore my initial comments about the material.

Like Andrew, Eric and Murray however, my first reaction was – ABS ??? Surely not!

The sample in your photograph displays characteristics of serious contamination as observed by Murray. Second grade, off spec. and regrind are one thing, but this stuff is delaminating.

Virgin ABS doesn’t do that.

I suspect the inclusion of incompatible, perhaps none polymeric (floor-sweepings) material. Without extensive/intensive mixing, contaminants will striate and delaminate as seems to be the case. Such materials should be destined for the bin or moulded into plant pots.

It was practice in certain establishments to have a moulding machine set aside for chuffing out plant pots. It would sit alongside another machine moulding drip-trays for those other (moulding) machines which leaked oil badly.

Along with previous recommendations especially securing the work-piece, machining thermoplastics requires recognition of their low thermal conductivity and therefore their propensity to melt. Mr Hancock mentioned this in his contribution.

In this context, I would add; use sharp cutting tools (e.g. for woodworking), and cut slowly.

Have fun,

Sam

[Russell EberhardtParticipant @russelleberhardt48058]

I suspect it is talc filled ABS. The filler is used to improve rigidity on things like car body parts and also of course to reduce costs. It does however make it a bit more brittle.

Russell

[BazyleParticipant @bazyle]

Nobody has mentioned masking tape or better tape over the top, as used for laminates, nor a top sacrificial board as well as backing (aligned by the piot) holes).

Perhaps as it is liable to melt if drilled fast you could use that with a tube run at high speed.

[Sam StonesParticipant @samstones42903]

Your point is taken about talc as a filler, Russell.

An ‘ash content’ test (better conducted under safe laboratory control) would establish the presence of particulate/fibrous mineral fillers, e.g. talc, calcium carbonate, glass, etc.

However, and although I’m not completely convinced from Choochoo’s photograph, since the fracture appears striated/delaminated, this emphasises the probability of contamination with incompatible polymeric/non-polymeric material. Phew!

Drifting off ABS into plastics in general and having been sensitised to looming problems of stress cracking, the aspect of frictional heat generation is challenging, and from personal experience, acrylic in particular may need attention.

Referring to … **LINK**

scrolling down the page to the paragraph commencing …

On a totally different subject, ………….

I made a note about underlying stresses and their release as micro-crazing.

In particular, the paragraph …

By the way, I have occasionally noticed this same stress-cracking effect has introduced crazing to the edges of acrylic security screens, where human body oils and other substances have made contact.

This incipient problem was also reviewed in my 3 Part article of Model Engineer reference …

Making a miniature changeover valve in plastics

#4555 – 3 Mar 2017, #4557 – 31 Mar 2017 and #4559 – 28 Apr 2017

Sam

[Author]

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