Enlarging a hole

[TiggerToo]

I would like to widen the diameter of a cylindrical hole (in a hard plastic). Current diameter is 30mm, and I need it to be 32mm. The depth is 130mm. What tool(s) would you recommend using?
NB I do not have access to a lathe.

 

[prv]

The standard answer to enlarging a hole is to fill it (tap in a suitable sized piece of wood) and re-drill with a suitably-sized holesaw. With such a small increase you'll have to be careful to start accurately on centre, though.

Pete

 

[Wing Mark]

What's it for ? How precise does it need to be? Its the item portable?
Depending on the circumstances I would have answers ranging from a drum sander to 'take it to Roy, who has a milling machine'.

One thing I have done which worked well enough for the job in hand was to take a 32mm flat spade wood bit and grind it so it starts at 30mm. (i was enlarging a 22mm trolley wheel hole to 25mm but you get the picture?) Did the job, but won't excite the model engineering community.... Just don't leave the bit with the others when you're done!

Some hard plastics are easily worked with abrasives, some are not.
A hole saw might do it, if you can rig up a good enough guide.
Some sort of fly cutter?

An actual skilled bloke might just use a file?
Somebody who did it all the time might have a reamer that fits.
Maybe a router bit guided by a bearing that fits in the existing hole?

If you need it to be really precise and smooth, you might make a reamer?

 

[TiggerToo]

What's it for ? How precise does it need to be? Its the item portable?

not precise, item portable (but fairly large).
Your suggestions are worth considering! Thanks

 

[LadyInBed]

32mm hole enlarger Drill Bit

PS once you have penetrated as far as you can, if you can access the other end of the hole repeat the procedure from there, then use a 32mm wood bit which should self centre.

 

[Iliade]

Perhaps
Collect todayScrewfix.com - Erbauer Step Drill Bit 6-36mm (5911V)£26.49Screwfix.com(128)

Darn too slow! I blame Safari 15 and its rubbish new tab system!

 

[coopec]

32mm hole enlarger Drill Bit

PS once you have penetrated as far as you can, if you can access the other end of the hole repeat the procedure from there, then use a 32mm wood bit which should self centre.

Agree with your solution 100% but they are a lot cheaper on eBay

 

[Wing Mark]

Agree with your solution 100% but they are a lot cheaper on eBay

View attachment 123597

Those things are OK, would work fine if the biggest size it does happens to be right.
But only for shallow holes, not the Op's 160mm deep unless you've got a drill with a small chuck?

 

[Daydream believer]

Lady in bed suggested a wood bit to finish the hole. I have had to re bush a lot of the club's RIB trailer wheels. Once I got a start I found a starret hole saw a better bet as it gave an even cut all round whereas the wood bit ( which I started with the first attempts) judders about due to having only 2 cutting spurs.
It will work but a lot depends on what is first available & how much the OP wants to spend & the quality of the finished hole.
If you cannot get a 32mm hole saw you could glue a layer of sand paper to a 30mm cutter with cyno adhesive & "lap the hole a bit larger

 

[prv]

Perhaps
Collect todayScrewfix.com - Erbauer Step Drill Bit 6-36mm (5911V)£26.49Screwfix.com(128)

LadyinBed's one is 32mm max, so will make a 32mm hole all the way through the block of material provided it can be driven. Yours goes up to 36mm, so that's the size it will expand it to.

Pete

 

[Daydream believer]

LadyinBed's one is 32mm max, so will make a 32mm hole all the way through the block of material provided it can be driven. Yours goes up to 36mm, so that's the size it will expand it to.

Pete

I believe that Lady in bed was suggesting chamfering the hole as a starting point to centre the drill. not going right through with the cone drill. A good idea in my view. Of course I suspect that he was assuming a cone greater than 32mm. I am sure that he will comment.

 

[pandos]

The step drill s will not work for what you describe unless the final size is 32mm even then how will it reach 130mm or even 65mm?

I would go with the modified flat bit if I were you and perhaps fill the center with a wooden block also as suggested elsewhere...

Realistically you will need something self centering unless you have a drill press...

 

[Praxinoscope]

You could use a 32mm blacksmiths HSS drill bit, the reduced shank means they will fit normal 13mm drill chuck. Cost about £15 - £25.

 

[anoccasionalyachtsman]

Since I have a 32mm hole saw (yes, Starret) and my step drills don't go that big, I'd nick a trick I saw on AvE's channel.

Get a piece of scrap ply and use the holesaw to make a 32mm hole. Screw it/double-sided tape/just generally bodge it onto your workpiece and use it as a guide to make the new hole.

 

[Caraway]

You could use a 32mm blacksmiths HSS drill bit, the reduced shank means they will fit normal 13mm drill chuck. Cost about £15 - £25.

How will you centre that?

 

[Praxinoscope]

I’ve found that if you chamfer the hole slightly then a slow rotating drill bit self centres

 

[Norman_E]

How will you centre that?

If you don't force it off centre it will follow the existing hole. Blacksmiths drills are quite short so access to both ends of the hole will be needed. Its important to control the feed rate or it risks jamming itself. Its best done with a bench drill.

A step drill with a maximum diameter of 32mm is a good solution if you can mount it in a small chuck fitted to a shaft.

 

[xeitosaphil]

I would get a 30mm dia piece of dowel, to match dia of existing hole. Cut about 2" off it and drill a hole in the centre of the endgrain size of the pilot drill.
Get a 32mm Arbor hole saw with an extra long pilot drill poss 4-5" long. Put dowel on the pilot drill as a guide for existing hole and new the hole saw will cut new hole right dia. Drill from both ends depending on the ability of the drilling depth.

 

[TiggerToo]

would this work?

Armeg Wood Beaver 4-Flute Wood Drill Bit 165 x 32mm

 

[Lightwave395]

if you have a router, you could use a 32mm cutter as long as you line it up accurately. I used my router to open a hole from 15mm to 22mm a while back, might need to do it from both ends to get 130mm though