Enlarging Conduit Holes

[awemawson]

I've been getting flexible conduit laid into my CNC mill for the 4th axis, and needed to enlarge some 16 mm conduit entry holes up to 20 mm. Normally I'd use a Q-Max cutter, but the cabinet is 2 mm thick steel so no chance. Or I'd use a stepped drill, but other cables are too close for comfort. Or I'd use a hole saw with a piece of material clamped to the rear to centre it - but there is no access. Or I'd just drill another 20 mm hole and blank the old 16 mm one, but things are too tight to get more 'holes' under a cover that surrounds them.

So what to do? Well the solution is so very obvious having done it, I don't know why I've not done it before 

Make a bit of steel to slip over the drill bit, that widens it to 16 mm allowing the hole saw to do it's work. So I offer the idea here in case anyone else has the issue.

[awemawson]

The set of the teeth mean that the inside of the holesaw was smaller than 16 mm hence the 'adaptor' had to have a step in it.

(It didn't help that I'd left the drill on 'hammer' at first so a raged hole was produced, but the conduit fitting doesn't seem to mind )

[dsquire]

Andrew

Very nicely done. I'm going to have to keep that in mind for the next time I need to enlarge a hole diameter. Thanks for sharing with us. 

Cheers 

Don

[hermetic]

Not only common sense, but pure practical genius! My hat is off to Mr Awemawson!

[Meldonmech]

Hi Andrew

                       I normally use a tapered drill for enlarging holes in sheet metal, but like your step drill could damage your cables.
 Your solution is simple and effective.       

                                                            Well done    David

[Pete W.]

Hi there, Andrew,

Yes, I add my praise for your ingenuity.                   

How many holes did you need to enlarge?  If more than one, did you get much of a burr on the later (non-hammer) holes? 

[Stilldrillin]

Thanks Andrew! 

The last time I needed a larger hole, I spent ages, filing a weird shape. But, as you say, the fitting doesn't mind......

David D

[vintageandclassicrepairs]

HI All,
As a recently joined member of the forum I have been watching this and the Traub lathe threads along with enjoying all the other MadModder projects
I have spent 34 years of my working life as a spark, instrument tech in the power generation industry,
So may I make a comment or two here?
When panels etc are full of delicate wiring and so on the hot metal from holesaws can be a source of danger / trouble 
I have had a set of "Greenlee" punches for yonks and they are ideal for enlarging conduit or gland holes
A demo here,
       

Onsite or when there are no cables about I have often whittled a timber plug and bunged this in the hole to be enlarged and used the required holesaw rather than have to trek bck to the workshop for the alternatives, I have also used "cone cuts" and stepped drills but prefer to keep these for use in a pedestal drill as they are easily damaged in a pistol drill

Regards
John

[awemawson]

Gents one and all, thanks for your comments.

John, I'd love to be able to afford a Greenlee set - they are superb, but not only VERY expensive, in this case they wouldn't have worked. I've only about 25 mm behind the panel. It runs parallel to another member. Getting the nuts on the conduit fittings is only going to be possible by sliding them down the cables ! (I do have a very comprehensive set of Q-Max punches, which are the manual version of the Greenlee)

I'm afraid I lay the workshop hand towel over wiring that might get affected by hot chips - don't tell the wife - a quick shake and NOBODY knows 

PeteW: this time only a couple of holes, and the second was distinctly better ! I'm trying to pull rather a lot of cables though a pair of Adaptaflex 20 mm conduits inside a channel that crosses the machine to connect the 4th Axis to the servo driver and TNC355 controller. I'd hoped to be able to insert a 50 mm tube, but the obstructions on the way don't permit it.