Any Suggestions for Marking Blind Holes?

[Iplayfarmer]

Does anyone have a foolproof trick for marking holes on a piece of sheet metal that are meant to line up with blind holes in something else?

Here's an example... There are a few threaded holes already in the frame of my tractor. I want to mount something to those holes. Is there some trick to marking out those holes besides measuring. (Measuring never seems to work for me. I'm always off just a bit, and I have to "finesse" it a little)

I can always hit the holes spot on if I can remove whatever piece I'm trying to adapt to. I just lay the piece over the sheet metal and mark through the holes. In a situation where there's a blind hole or where I can't remove the piece to mark through it, I'm always off on at least one hole.

There has to be a better way!

 

[6sunset6]

There are threaded inserts with hardened tips. Screw then in ,one in each hole with the tip just above the surface , lay the material in place and wack with a mallet over each hole. Called transfer screws look in Mcmaster Carr
Various types. They work well.

 

[tommu56]

Ttry laying a sheet of paper over the holes and gently hammer around the the holes like making a gasket then take paper to sheet metal.

I have used brown paper shopping bags for this.

They do make threaded transfer screws that you thread in to parts and tap the other surface to mark on it.

at the bottom of this link
Transfer Punches & Screws at Wholesale Tool Company | Industrial Machinery + Tool Supply

tom

 

[kennyd]

What you want are called "transfer screws" They are expensive but invaluable sometimes.

Also get some "transfer punches" for when the hole is through.

 

[kennyd]

Darn you guys are quick!

 

[RickB]

Ttry laying a sheet of paper over the holes and gently hammer around the the holes like making a gasket then take paper to sheet metal.

I have used brown paper shopping bags for this.



tom

I use this method with light cardboard and the ball end of a ball pien hammer. Very accurate if one is careful.

 

[sandman2234]

If your careful, you can make transfer screws out of a bolt, by cutting the head off, then grinding the end to a point. Be careful that your point is in the center of the bolt, so it transfers correctly. They don't last as long as hardened ones, but will get you closer than a measuring tape.
David from jax

 

[Sherweld]

A little different way I've used at times for awkward layouts is a suitable size piece of clear plastic packaging from the trash bin.

(the clear plastic stuff we hate, because its usually impossible to open without some serious tools and/or a small laceration or two)

It is pretty easy to fabricate an accurate template when everything is visible through the plastic sheet.

Sherweld

 

[PILOON]

Same trick as used to make gaskets!

I keep a selection of 1/2" and 3/4" steel bearing balls in the tool box.
Lay the paper or gasket in place. press the BB approximately and wack with a hammer.
The bearing ball automatically centers itself and cuts the paper hasket 'just right'.

If you need to drill a matching piece, just center the drill in the paper pattern and go for it.

 

[Iplayfarmer]

I knew I could count on you guys to have something up your sleeves. I think my favorite so far is Sherweld's idea. If only I'd have know that before I threw away all of the packaging after christmas.

I've got to have something around that will work. I wonder if any of my wife's picture frames have plastic in them instead of glass. I wonder if she'll notice if any of them are missing.