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deep neck mechanical pencil? marking tool

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You can mark holes with graphite by extending a mechanical pencil, for even really small holes.

The problem is for a deep bore, the graphite breaks.

Mechanical pencils have say a 3-4mm steel tube on the bottom.

I want a mechanical pencil that has say a 30mm steel tube on the bottom, that is a tight fit with the graphite, so you can stick it in a hole, and there is only a small amount of graphite that protrudes for making the marks.

I Mean for like 0.7mm graphite.

Does this exist?

I thought it might be possibly to modify one combining it with a long needle of the correct size.

It is possible to make this tool by gluing a lead into a long needle, but it has a short life.

I think the problem with this would be finding leads, since leads for thin mechanical pencils (0.9mm and thinner) are 6cm long, so with a full cm (at least) between the clutch and the beginning of the tube, and then your 3cm tube, and about 1cm inside the clutch itself, you’ve only got 1cm of lead to use before you have to replace it! (Never mind that any flex in the tube will break the lead prematurely.

Could you use a 2mm drafting pencil, with their much longer leads?

Otherwise, Edding sells special markers for marking inside holes.

Use a layout ink, like Dykem, and a scribe.

EDIT: Or hole center/transfer punch and ink.    They come in many sizes to fit virtually any hole. ( )

ehh i have most of those and transfer screw in punches but I like the graphite method alot. If your metal is fairly clean and polished you can make out the exact trace of the hole if you hold it to light at an angle and use a light thin punch to center it.

Its really gentle, with the transfer punch you get a precise center but you can easily disturb what you are tracing and it requires fixturing. The long graphite is extremely gentle. I guess the benefit of using a bare graphite is that it will break instead of moving your work. I will try to glue some graphite rod into a syringe needle and see if I like it before looking more.

It actually works pretty well, but in a set of graphite a few will be EXTREMELY fragile and a few will be strong enough to trace out fairly deep holes.

You don't get that much strength even from a thick graphite (wood 'mechanical pencil' that uses a thick graphite core).

But now I wonder if a sewing needle will mark a light hole on machinist blue..... that might be even better

So why did you supposedly ask for alternatives?

Do you really think there is a market for the pencil of your dreams?  Ask Pentel.   

There are also what are called "hole duplicators" that are used in aircraft repair (e.g., replacing a skin).  In that example, you want to duplicate a hole position for a layer on top, not under the desired hole.  You have so poorly described your current project, if there is one, that it's impossible to know what you want to do rather than your preconceived idea of how to do it.


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