Drilling Hole In Sandblast Cabinet For Bulkhead Adapter

[pollys1dad]

The cabinet is 16 gauge steel I have a Wolfcraft mobile drill stand same as in attached photo, also have an unused set of metal drilling bits.
The bulkhead adapter has 3/8 hose barbs. I've enquired what diameter the threaded part of fitting is, not heard back yet.

Not possible to lay cabinet flat on its back, will need to drill hole into the front of cabinet in upright position.
I'm not sure about the correct way to drill the hole out? Do I use a small size drill bit to make a pilot hole, then over to a larger one, or just select a drill diameter a bit larger to accept the threaded part of the fitting and drill the hole out in one go? File down any burr on exit hole?
I have a couple of drills one quite light weight the other heavier duty.
Thanks.

[whateg0]

Is the fitting in the screenshot the one you are installing? Because according to that, the diameter is 10mm, right? So a 13/32" would work fine. I find that drilling into the side of something is hard work, so even though it takes a little longer, I start with a pilot hole, maybe 3/16", then step up in 1/8" or 1/16" steps. This keeps the pressure to a minimum, though on sheet metal, that's less if a problem than in something thick. Another reason for that is I tend to end up with holes that more closely approximate a circle.

Dave

[pollys1dad]

Yes fitting in the screenshot is 10mm. thanks for your opinion.

[John Evans]

Get a "step bit" multiple sizes on one bit ,designed for sheet metal work. They make a set of three either 1/16 or 1/8 steps depending on the bit size. In US Harbor freight has them cheap and seem to work well for home shop use, have had a set for years.

[pollys1dad]

Get a "step bit" multiple sizes on one bit ,designed for sheet metal work. They make a set of three either 1/16 or 1/8 steps depending on the bit size. In US Harbor freight has them cheap and seem to work well for home shop use, have had a set for years.

How do you use one of these step bits?
Thanks.

[John Evans]

Just like a regular bit ! The end has a normal drill grind on it and each step is sharpened . Bits are marked with each size ,what I do is wrap a piece of tape around the bit on the step above the desired.

[pollys1dad]

Do you need to make a starter hole with a metal bit to get started, then change over to the step bit and just keep drilling until get to the desired size?
Thanks.

[John Evans]

The step bit starts it's own hole ,then keep drilling to the desired size. You do much hole making in sheet metal you will love them.

[pollys1dad]

The step bit starts it's own hole ,then keep drilling to the desired size. You do much hole making in sheet metal you will love them.

OK thanks.

[BadDog]

Yes, as usual, John is on the money. Hard to be without step bits, and that's the right tool for this job. I've also got a really large one by Neiko (IIRC?) from Amazon for not much money. Goes up to 1-3/8.".

However, in a bind, I've used brad point (wood) bits when I need smaller sizes or finer sizes. They won't last long in steel, but will work on lighter gauges. And they work pretty well for thin aluminum. I now have some finer increment step bits (like shown), so haven't done this in a while, just adding as a point of reference.

[NP317]

Step bits are fantastic for drilling out sheet metal holes.
I wish I had understood that years ago. My fabrication life would have been so much simpler...
RussN

[RSG]

Step bits like others have mentioned, anything bigger and a bi-metal hole-saw works great! That's what used recently on my cabinet.