# Help With Surface Gage Scriber



## Bob Korves (Feb 24, 2016)

I got a vintage Starrett 257A surface gage from a friend for free.  It was rusty, but has beautiful color case hardening.  The pic above shows their current version, which is dumbed down in every way.  No color case, plain black finish.  No ball on the end of the mast.  No square scriber on the other end of the mast.  At the current price of more than $200 they should be gold plated.

But I digress.  Mine is all cleaned up, looks and works great, has one small spot I could not get all the rust off without removing the color case finish at the same time.  It was missing the scriber.  I have made a new one out of drill rod, not sure if it is W-1 or O-1, probably W-1.  It is cut to length and rough ground to a point at both ends.  I still need to add that sexy curve to one end and harden and temper it.  I think I can make the nice curve without bending the straight portion by using a fixture to contain it and support the bend.  When it is done I will need to harden and temper it.  Any ideas of a low tech way to do that (no HT oven) and still get the points and shank all to the proper hardness and without warping the shank?  I figured I needed to grind the rough points on first, won't be able to do that as well after it is curved and hardened.  Ideas?


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## mmcmdl (Feb 24, 2016)

They don't make 'em like that anymore . Very nice piece Bob !


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## eeler1 (Feb 24, 2016)

Machinist karma coming your way, you must have done something good for a fellow machinist at some point in your past.  I just got back from Humboldt with a little 8" Paragon oven and some kasenite I'd had in storage.  Was going to bring up at our next show n tell.  So, we can do it, just need to figure out the answers to your tech questions.  Anyway, happy to help out if I can.


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## Andre (Feb 24, 2016)

Just heat it cherry red and quench in water. No point in hardening the entire shank of the scriber, it might actually be advantageous to keep it soft so it retains some spring in case it drops in the future. Heating can be done on a stovetop.


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## rgray (Feb 24, 2016)

I would temper it after hardening or it will be very brittle.


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## kvt (Feb 24, 2016)

I agree with Andre,  you do not really need to heat treat the whole rod, Just the ends.   Then you can put it in our kitchen oven and temper it. 
That does look nice.  If it was covered in rust your must have done a good job on the cleaning as it does not look like bad.   One of the things I though is if you the scrib in your lathe before you bend and treat it.   You could ensure you have a good centered point and also polished it up before you treat it.   Just a thought. 
 I just got a cheep Vernier Height gauge a few weeks back and have already used it several times and know I will be using it more in the next couple of weeks.  I had thought to get something like you got first, and may still go back and get one.


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## mikey (Feb 24, 2016)

Nice, Bob! I bet you can still get a replacement scribe from Starrett but making one is the HM way, right? I agree that only the points need to be hardened but I don't think it needs to be tempered. This tool will sustain no loads and is not going to encounter shocks that will shatter it. If you heat it to non-magnetic and cool it appropriately for the type of material its made from I should think that would work quite well.


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## Bob Korves (Feb 24, 2016)

eeler1 said:


> Machinist karma coming your way, you must have done something good for a fellow machinist at some point in your past.  I just got back from Humboldt with a little 8" Paragon oven and some kasenite I'd had in storage.  Was going to bring up at our next show n tell.  So, we can do it, just need to figure out the answers to your tech questions.  Anyway, happy to help out if I can.


Thanks, Jon.  I will probably be over to see you.


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## Silverbullet (Feb 24, 2016)

I too agree , heat the ends up to cherry red and quench . The whole thing dosent need to be hardened. If you only do the first inch or so it'll be hard yet able to give in the middle. Just my thoughts on the scriber, When we use to make them in shop a hundred years ago that's the way our shop teacher told us to do it. If you harden the whole thing every time you put pressure on the tip it's not going to be able to absorb the scribing being done. It needs to give a little , if it's too hard it will snap at more then the point. I may be wrong by new standards but it always worked for me . We made lots of tools in our years in the shop at vocational school and it really sticks with you if your good with your hands and have the abilities to do it.


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## Bob Korves (Feb 24, 2016)

rgray said:


> I would temper it after hardening or it will be very brittle.


I think I agree, Russ.  I have very little hardening and tempering experience.  I have another surface gage and the scriber on it is hard full length.  Not quite glass hard, a good file barely cuts it.  That scriber is much stiffer than the unhardened one I am working on now.  I think it probably needs to be properly hardened and then tempered a bit so it does not bend and chatter on the work, and so the point stays sharp.  I made another small scriber for my Starrett combination square, hardened the point with a propane torch but did not temper it, and it was hard enough that the the sharp point just crumbled when I tried to scribe with it.  After tempering it a bit to the first light straw color it is now holding a point.  I am also afraid of decarbing the point while I am getting the rest of the scriber to hardening temperature.

BTW, here is a couple pics of the scriber I made for the combination set.  I made it longer that Starrett makes theirs.  I used a PEC 18" blem blade off Ebay, ~$20 and I like it better than the Starrett blades.  I never could find the blemish on it, but there is a really weak attempt to obliterate the PEC name, which is still totally visible.  Beautiful blade.  The heads in that set are Starrett hardened steel units, were all rusty beyond belief, part of a large tool lot I purchased, but after some diligent cleanup and some light lapping and testing, they look very good and are quite accurate as well.  Total cost of the set, $20 for the blade and some drill rod and brass I had on hand.  And no, I won't sell it for that!


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## derf (Feb 25, 2016)

I have a surface gauge just like that, and I use it all the time. But tell me....what are those pins that protrude from the corners for?


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## Tony Wells (Feb 25, 2016)

You push them thru and let them ride against the edge of your surface plate to scribe a line on the top surface of a part that is set up parallel with the edge, or parallel with another line or existing feature.


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## f350ca (Feb 25, 2016)

I use them on the edge of the mill table with a test indicator instead of the scribe to align parts to the table.

Greg


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## P T Schram (Feb 25, 2016)

To bend it, screw three SHCS into a 1-2-3 block and use the SHCS as the "Mandrels" to bend against. I needed a bent hypodermic needle to inject oil into a bearing and was able to bend it using this method without collapsing the tubing.


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## derf (Feb 26, 2016)

That's what I kinda thought about the pins, but mine seem to be stuck, at least I can't move them with finger pressure. Mine only has 2 pins, where the one in Bob's picture has 4. I just wanted to make sure I wasn't missing something like maybe a mount for another sub base or something.


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## rgray (Feb 26, 2016)

Bob Korves said:


> I made another small scriber for my Starrett combination square, hardened the point with a propane torch but did not temper it, and it was hard enough that the the sharp point just crumbled when I tried to scribe with it.



There is a book by William E Bryson called "Heat treatment, Selection, and application of tool steels"
Member ray c on this site put me on to it.
Bryson has plenty to say about how important tempering is. Helped me to understand that crumbling/shattering that happens in non tempered tool steel.
As for stiffness. Seems to make alot of difference as you have noticed. A hardened rod is much stiffer than one not hardened.
That will bring up the Young's modulus argument. "Young's modulus, which is also known as the elastic modulus, is a mechanical property of linear elastic solid materials."
And engineers will tell you that all steel has the same elasticity so hardening won't make it stiffer. 
All I can say to that is nuh-uh no way ain't so.


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## uncle harry (Feb 26, 2016)

rgray said:


> There is a book by William E Bryson called "Heat treatment, Selection, and application of tool steels"
> Member ray c on this site put me on to it.
> Bryson has plenty to say about how important tempering is. Helped me to understand that crumbling/shattering that happens in non tempered tool steel.
> As for stiffness. Seems to make alot of difference as you have noticed. A hardened rod is much stiffer than one not hardened.
> ...



Apparently classic Japanese sword makers didn't know about Young's Modulus !


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## Billh50 (Feb 26, 2016)

f350ca said:


> I use them on the edge of the mill table with a test indicator instead of the scribe to align parts to the table.
> 
> Greg



I have done that many times. I have also use the pins to align something to the edge of a jig plate that was not pinned. Those 2 pins can come in handy at times.


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## benmychree (Feb 27, 2016)

Bob Korves said:


> I think I agree, Russ.  I have very little hardening and tempering experience.  I have another surface gage and the scriber on it is hard full length.  Not quite glass hard, a good file barely cuts it.  That scriber is much stiffer than the unhardened one I am working on now.  I think it probably needs to be properly hardened and then tempered a bit so it does not bend and chatter on the work, and so the point stays sharp.  I made another small scriber for my Starrett combination square, hardened the point with a propane torch but did not temper it, and it was hard enough that the the sharp point just crumbled when I tried to scribe with it.  After tempering it a bit to the first light straw color it is now holding a point.  I am also afraid of decarbing the point while I am getting the rest of the scriber to hardening temperature.
> 
> BTW, here is a couple pics of the scriber I made for the combination set.  I made it longer that Starrett makes theirs.  I used a PEC 18" blem blade off Ebay, ~$20 and I like it better than the Starrett blades.  I never could find the blemish on it, but there is a really weak attempt to obliterate the PEC name, which is still totally visible.  Beautiful blade.  The heads in that set are Starrett hardened steel units, were all rusty beyond belief, part of a large tool lot I purchased, but after some diligent cleanup and some light lapping and testing, they look very good and are quite accurate as well.  Total cost of the set, $20 for the blade and some drill rod and brass I had on hand.  And no, I won't sell it for that!
> View attachment 123134
> ...


As to a scriber or any other tool being stiffer when heat treated or hardened, this is simply not true;  look in "Tool Steel Simplified"  there is an experiment shown where two rods of tool steel are held at one end and weighted with equal loads; increase the loads, and they bend equally, until the hard one snaps off or the soft one bends permanently; also, alloy steels do not have any significantly  greater resistance to bending under the same situation than mild steels, this can be appreciated by looking up the modulus of elasticity for different steels; the modulus varies by only a very small fraction, and is not effected by heat treatment.  A good illustration is a boring bar; one may think that if one were to harden it, it would be stiffer and chatter less, this is simply not true, the only way to make it stiffer is to increase the diameter or lessen the unsupported length, OR change the material to one of a higher modulus, such as solid carbide.  A small increase in diameter has a much larger effect than it's percentage of bulk would suggest; a good example being a milling arbor of 1- 1/4" has 5 times the stiffness as a 1" diameter arbor with the same conditions.
As to the scriber, there is no need to harden the whole thing, and the end can be bent by hand  with suitable soft hammer at the same time the hardening is to be done, just hammer it over a piece of round bar while it is red hot, then quench in water or oil, depending on what material you are using; the correct temperature is reached when a magnet is no longer attracted to the heated part.  After hardening, it can be drawn back by first polishing off the scale then heating it back from the working end until the temper colors start running; for the scriber, the straw color would be appropriate, giving a point that is not so brittle but retaining a good cutting edge.


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