Sheet Metal Hole Locator

[awemawson]

I've been making missing panels for my Denford MIRAC lathe and this entailed matching up to existing holes in the frame, where there was no access to the rear - so 'spotting through' wasn't an option.

Now having finished the job more or less successfully by careful measurements I remembered a little simple tool I'd seen years ago that would have made the job SO much easier 

So I thought in true 'locking the stable door after the horse has bolted' fashion I'd make one and document it.

Trivial in the extreme it consists of two thin bits of sheet metal fixed together with a hole at the unfixed end that on the lower blade has a volcano shaped dimple erupting from it, that can be used to feel the hole to be located. Co-incident with this dimple in the lower blade is a hole in the upper blade that can be used for your scriber or centre punch to mark the hole in your new panel.

. . . simples 

So I used a couple of bits of tin plate. Clamped and blued the upper one, and scribed a centre line. Marked and drilled two 3 mm holes for bolts. Fitted a single nut and bolt, then drilled a 1 mm hole through both blades at the 'business end'. This 1 mm hole in the lower blade was used to locate a large centre punch, and using it against a soft material (a block of lead that I keep on the bench) I could raise the 'volcano' dimple. The hole in the upper blade was enlarged to 1.5 mm to suit my centre punch. Inserting the second nut and bolt and tightening it all up it was ready for use.

[awemawson]

In practise you'd make this tool to suit the hole sizes and panels you are working on - there are no critical dimensions - as the third hole is drilled through both blades at the same time the alignment HAS to be spot on.

The following are staged pictures, as, as I mentioned earlier this is 'solving yesterdays problem' 

[ZebraDriver]

An old colleague of mine once described a similar method for making new panels for aircraft. They wanted to make new panels to fit the existing holes for the rivets.  The solution was to hold the new panel over the existing panel before the rivets were removed then use a tool consisting of two hacksaw blades taped together the rivet could be located by feeling for the rivet head with the hole in the lower blade and marking the position of the new hole with the hole in the upper blade.

[tom osselton]

Thats a good idea to remember.

[Pete.]

That's a trick I'm going to remember. So simple it should be obvious - but it isn't!

[AdeV]

Yep, that one's getting bookmarked. Simple and effective!

[RodW]

Very cool idea. My secret weapon when I have to do this (and there is a threaded hole) is to use transfer screws
http://www.arceurotrade.co.uk/Catalogue/Measurement/Punches-Scribes/Transfer-Screws

I saw these in a video years ago and scoured the world looking for them and sourced a full set of metric and imperial ones from Little Machine Shop in the US. Mine have six transfer screws per thread size and I use them a lot. Shown here setting up to mount a chuck. Quick tap with a hammer and you are done.

[mcostello]

As an added hint worthy of the price of admission, transfer screws and transfer punches can be bushed up to make the odd size needed.