Enlarging knockouts & drilled holes

[pickleye]

Does anyone have any tips / easy ways for enlarging existing holes?

eg. recently had to replace a SWA through a 20mm bush with a larger SWA requiring a 32mm bush. We decided to relocate rather than enlarge. If we could have enlarged easily we would not have had to reseal the existing hole.

Any tricks of the trade appreciated

 

[Evans Electric]

For a 20m hole up to 25mm just fit a 20mm bush and the 25mm cutter will sit on the outside.

For the 32mm I'd probably fix a box lid across the hole and drill the centre hole through it .

There are also cone cutters , I have one that will open up a 20 to a 25 not sure if there are bigger 'uns.

 

[roys]

A wine cork is slighty tapered and fits nice and tightly in a 20mm hole allowing your pilot drill in the holesaw something to drill into.

 

[pickleye]

Do the cone cutters work on metal clad boxes? I've seen them and noted most state not suitable for ferrous metals. Thanks for the suggestions. I'd thought of blanking off hole and redrilling, I'll give it a go next time it crops up. Thanks Deke.

Maybe a more appealing idea stock the van with wine, wonder if the stores stock it ?:| Damn how do i get home after downing the bottle??? :Y

 

[sellers]

or start your new larger hole cutter on an angle in one of the edges of the existing hole taking it easy and it will work.

 

[Evans Electric]

I use the cone cutter on metal boxes , thats why I bought it , seems to work OK on mild steel , just take it easy .

The Starretts etc are a far cry from the rubbish we used to have to use in the Stone age . They were called Enox Cutters , a bit like a wrap-around hacksaw blade with two tiny screws to hold it in position (or not) . The body slid onto an ordinary HSS twist drill with a grubscrew to hold it in place (or not)

During the course of drilling one 3/4 -20mm hole it would work lose about 1000 times or the tiny screws would fly out . Then Black & Decker brought a Starretty type one out but the bosses wouldn't buy them because of costs .

 

[Andy™]

fit the holesaw size required to arbour, then the existing hole size to the arbour. smaller will act as pilot

unfortunately, doesnt work between 20/25 & 32+ since they have different arbours

 

[NozSpark]

Personally I use step drills,,

I've one that goes from about 4mm to 22mm and another that goes from something like 18mm to 45mm

I've had mine a few years now and they seem to work well on sheet steel although my small one is starting to get blunt

 

[Sidewinder]

Noz,

They can be sharpened, though I can't do them any more!

There is a special adaptor for holesaw arbours which will take the small and large size and fits in place of the pilot drill, it is called an "oops" adaptor.

Made by Starrett.

Available here, but may also be available elsewhere.

OOPS ADAPTOR - Buck & Hickman

Also, hole saws can be sharpened too!

Cone cutters and step drills are fine on ferrous materials including stainless steel if used at the correct cutting speed with cutting compound as required.

Step drills and cone cutters are available up to 51mm here:

http://www.buckandhickman.com/find/category-is-CT+Cutting+Tools/category-is-CT03+Standard+Machine+andToolroom/category-is-CT0301+Drilling/category-is-CT030113+Step+Drills/pgs-is-50

Other suppliers are available.



HTH

 

[Andy™]

Also, hole saws can be sharpened too!

not when they have no teeth left....

 

[col]

Great ideas guys, now how do you reduce the size of the hole

 

[sellers]

Great ideas guys, now how do you reduce the size of the hole

use a reducer!

 

[Andy™]

Great ideas guys, now how do you reduce the size of the hole

duct tape

 

[Barx]

or start your new larger hole cutter on an angle in one of the edges of the existing hole taking it easy and it will work.

Yup, that's how I do it. Fairly high speed but next to no pressure until your 'started'. T'other hand loosly round chuck to keep steady. Wouldn't recommend a numpty to do it though, plenty to go wrong and that.

 

[kerching]

hold a piece of timber on t'other side of hole. secure with 2 mole grips or an Apprentice....drill hole. I have one of the oops adaptors [never knew it was called that!] called mine a co(k up adaptor... :coat

 

[steptoe]

hold a piece of timber on t'other side of hole. secure with 2 mole grips or an Apprentice....drill hole. I have one of the oops adaptors [never knew it was called that!] called mine a co(k up adaptor... :coat

remember to remove apprentice when finished,

 

[sellers]

and give magnet to remove swarf from hair, elbow crease and down polo neck

 

[kerching]

remember to remove apprentice when finished,

the apprentice is usually set to 'self / auto remove' depending upon attention span, passing totty, lunch, brew, boredom, texting on mobile, answering mobile, pulling up pants, yawning, looking at watch. Attention span is also inversely proportional to difficulty/severity of job and directly proportional to b0110ckings received. Well it was when I used to have apprentices [ again not in a Glitter/Jackson sort of way ]... :coat

 

[Phoenix]

sheet metal punch? q max | eBay UK makes a neater hole than a cutter bit as well

 

[Sidewinder]

[quote name='Andy