# First project: Scriber



## Ngray (Feb 4, 2013)

So I've settled on making a scribe on my new-to-me 7x14. Not having access to (or experience with) a torch or oven to properly harden the tip, what can I do to get a durable point on the scribe? I was thinking about cannibalizing a 3/16 drill shank and grinding it to a point.

Other than ordering a set if replacement Scriber points from enco, anyone have thoughts?


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## mikey (Feb 4, 2013)

This sounds like the perfect time to learn how to harden and temper some tool steel, perhaps O-1. At some point in time you will want or need to make some tooling and the experience will be valuable. 

For a piece as small as a scriber, hang it from a wire and use a cheap Propane or MAPP gas torch from the hardware store to heat it to a non-magnetic state (heat it until a magnet won't attract anymore), then dip it vertically into a container of oil (ATF works okay for small parts and is cheap). Keep it moving vertically until it stops simmering, then take it out and scrub off the residue. I normally coat the steel with Boric Acid (termite killer in powder form from the hardware store mixed with denatured alcohol to make a thin paste) to reduce oxidation before heating it and that stuff cleans right off with a scotchbrite pad. For a scriber you don't even need to temper it but if desired you can pop it in a cheap toaster oven to draw it to whatever hardness you prefer. If you do temper it, do it as soon as possible after hardening.

None of this is really expensive or difficult for small parts as you describe. Give it a try - perfect time!


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## Ngray (Feb 5, 2013)

Well when you explain it that way, I think even I could do that 

I was thinking I'd need an acetylene set before I could harden stuff, but propane torches are cheap until that point.


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## mikey (Feb 5, 2013)

Propane is hot enough for very small parts but MAPP is better and not a whole lot more expensive. Just get the whole piece to the same temp before quenching. Be sure you get the piece vertical in the oil or it may warp. Give it a shot and let us know how it turns out.


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## DMS (Feb 5, 2013)

For larger parts, you can help things along by getting  some fire bricks and making a small "oven". It doesn't need to cover the whole part, just enough to keep some heat in. Fire bricks should be available locally, they are often used for fireplace repair, and you can find the better quality ones at ceramic supply.

For a scriber tip though, that's overkill, even MAPP is more than you need. Grab a common Bernzomatic torch with the trigger start. You can get MAPP or propane bottles to fit. They are dead useful for soldering, brazing, hardening, and lots of other things. I think they go for about $20us.

On the topic of steels, lots of folks love O-1, but I mostly use W-1. It's a bit cheaper, and you quench in water rather than oil (less mess). It does distort more on larger parts. If you are trying to source things locally, you may also try 1/8" music wire from the local hobby shop. It's spring steel, and comes pretty hard already. For that stuff, I would oil quench.


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## Hawkeye (Feb 5, 2013)

I made a surface gauge last year, so hardening the probe was part of the process. Take a look at this thread: 
http://www.hobby-machinist.com/showthread.php/5435-Surface-Gauge

You'll see the scriber toward the bottom of the photos. I made it from a piece of music wire, from a hobby shop. It is high carbon, so it will harden nicely. I used a belt sander with the probe held in a cordless drill to taper the ends, then pressed a curve into the one end. A propane torch is plenty for this size of material. when glowing, I quenched it in used motor oil. (Do that outdoors or in a ventilated area. I used the welding booth with the fan on.) I like the blackening from the heating and oil, so I left it like that.

Keep in mind that the steel will be at its hardest and quite brittle. Use it with respect and it should do you well. If the tip gets snapped off accidentally, you should be able to take it back to the manufacturer. :lmao:


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## DMS (Feb 5, 2013)

The state Hawkeye is referring to is often called "glass hard". The steel is at it's hardest possible state, and also it's most fragile. On my scriber tip I left it in this state because it's very hard, and stands up to mill scale pretty well, but it would not be good for say, a punch or a knife.

@Hawekeye, I hadn't seen your build before, but DANG that's a nice looking piece of equipment!


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## Ngray (Feb 6, 2013)

At the risk of hijacking my own thread, what is a good resource for coming up to speed with hardening/annealing/releiving? 

I seem to remember from a 'history of blacksmithing' book that they used a static color chart, where ploughs were to be dark purple, hammers were to be light purple, nails were to be just red (inaccurate examples), you get the idea.


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## Ngray (Feb 10, 2013)

So as a follow-up to this, I've learned some new things, and have some questions unanswered:

Don't quench by dropping straight down into a quart of oil container that you are holding. Oil gets hot and melts plastic. Also, you can burn yourself and drop the oil onto your garage floor. I'd say this is the #1 thing I learned. *Lesson*: Plan the container and quenching motion in a way that makes you mostly invulnerable to getting burned. Also, quench into a fairly large vessel that allows the oil room to expand and dissipate, bubble, and splatter boiling oil. Eye protection, long sleeves, and gloves are all in order.
The hot pointy tip of a scribe heats up very quickly. It also cools down quickly. I have no idea how to safely get the heat off of it, and quench it, faster than it can go from 'glowing orange' to 'dull gray'. In any case, the tip is still as soft as mild steel, while the body of the scribe is... I have no idea. I guess it's hard. *Lesson*: Learn to do this on thicker pieces that do not cool down so quickly.

I think I'm going to punt on this one. I'll order a replacement scribe tip, cut off my point, and drill my scribe for whatever size UPS brings me, and tap for a set screw. I'll save my next heat treating adventure for something thicker that I have alloy info for, and really plan on doing (and failure testing) several pieces.


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## swatson144 (Feb 10, 2013)

When I grind a case hardened scribe I'll usually quench in in a handy container of the proper fluid. Just focus on the unhardened tip. heat it and harden it. If the surrounding area gets a little annealed it won't matter. Wear safety glasses at any time using it, as it will be glass hard.

Steve


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## Hawkeye (Feb 11, 2013)

Keep in mind that the body of the scriber doesn't need to be hardened. Only the tip. And of the tapered part, only the fine point. If the hardness runs from totally annealed  in the body to glass hard at the tip, any breakage will leave less grinding to repair.

I hardened mine by heating just the tip to red hot, then plunging it tip-first into the oil. That cools the fine point very quickly, leaving it the hardest. As the shaft gets thicker, it cools slower, making the taper progressively softer. Heating only the required part means less heat to boil off in the oil, therefore safer.

If you did want to temper the tip, you would polish the dark finish off the hardened area, then apply heat to the shaft, away from the tip. As the metal heats up, it takes on various colours due to oxidation. You would watch the colours move from the heat toward the tip. When the desired colour (straw, blue, etc.) reaches the tip, quench. It won't be too dramatic this time, because you aren't heating it to red hot.


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## 12bolts (Feb 11, 2013)

Another method to control heating of small parts is to heat a larger piece of steel to cherry red then place the small piece you are tempering directly against the red hot steel. You can watch the colour change move through the part and as soon as your desired colour is reached remove from heat and quench.
On small parts I find it easier to control and you dont have the flame getting other areas too hot whilst waiting for the desired colour at the tip/edge.

Cheers Phil


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## Chrispy (Feb 11, 2013)

One tip that works well with something like this scribed point is to heat it in your drill press. Turn on the drill press to a slow speed and heat the tip. Place your oil quench container on you drill press table. When the tip is at the correct temp use the quill to plunge the hot piece into the oil bath. Keeps it vertical and keeps it moving.
Another tip - use a metal container for your oil quench. If you use a plastic container and drop a red hot part it will melt right through the bottom, releasing flaming oil. Ask me how I know about this :whistle:
Chrispy


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