[Vwdiesel] Cleaning threads for head bolts

[James Hansen]

Just a small correction Shawn.

Anneal is to make it soft, you heat to a bright cherry red (or more 
correctly the point of loss of magnetic properties), and let cool 
slowly, preferably insulated by fibreglass insulation, dry sand, 
speedi-dry etc.
It will now be as soft as you can ever make it, good time for working it 
cold- filing, drilling, sawing etc.

You harden by heating to same heat, (bright red) and quench as fast as 
possible.  Faster is harder.  Oil is slower, salt water is fastest, but 
swoosh it around in whatever you cool it in, so the cooling is as even 
as possible.  Oil sucks actually, as it is too smoky.  Water is just fine.

Temper (to soften) the hardened steel by reheating it slowly in a 
controlled manner.  Blacksmith way is to use a small fire, propane 
torch, etc, and heat the polished metal until the oxidation colors 
indicate the correct temperature is reached, then requench and cool as 
fast as possible. The warmer it gets, the softer it gets, until it is 
completely tempered, or back to its softest non-annealed state.  Makes 
you wonder what the marketing departments of some tool manufacturers 
mean by "triple tempered steel"... triple softened... so you can whittle 
it with your pocket knife that has been hardened?

this applies to mild carbon steel, higher carbon, you have to get a 
little fancy, non-ferrous metals are more or less opposite to the above.

To do your bolt into a tap, your slices into the bolt are essentially 
providing a cutting surface.  Take the head bolt, cut or grind with a 
slitting disc three or four times the long way, to a depth below the 
bottom of the threads, further isn't too necessary.  A slight angle if 
possible, so the pointy bit on the thread that will be doing the cutting 
is leading by a few degrees.  If grinding, make it a "c" shape as viewed 
from the end... just like a tap, so it has a place to collect crud.

Then if you want to fuss with hardening, carefully, so as not to burn 
any carbon out of the thin areas of the newly made tap, heat to a bright 
red, and quench.  Tempering shouldn't be necessary, as this is pretty 
low carbon stuff. The torque to yield fasteners are not very high in 
carbon so they DO yield in use, not snap, hence won't get THAT hard, but 
should harden up some, enough to be a little tougher, but for these few 
holes, you can pretty much do away with the hardening as well.
-james


Shawn G. wrote:
> if you wanna really do it up right, harden and anneal your new homeade
> tap, by heating it to a dull cherry red colour, then dip it in oil
>  and let it cool off there.  You can anneal it, by mildly re-heating it
>  afterwards again (not too hot, don't get near the colour change range).
> 
> S.
> 
> David Cook <vwdieselbunny at yahoo.com> [22 Sep 2006 22:09 -0700]:
>> Cut 4 grooves into an old bolt, and bring them across
>> the bottom so they make an "x"  which will help loosen
>> up any crud at the bottom of the hole.
>>
>> Run it in and out a couple times, spray something like
>> PB Blaster or WD-40 in there each time.  
>>
>> I then spray a bunch of PB Blaster into the hole and
>> suck it out with a shop-vac and some clear tubing
>> duct-taped to the end of the shop-vac's hose.
>>
>> Works great.
>>
>> David
>>
>> --- engle31 at comcast.net wrote:
>>
>>> I'm doing a partial rebuild of the 1.6na for my
>>> caddy project. I already replaced the rings and
>>> started the reassembly process. I have the head
>>> cleaned up and ready for the install with the new
>>> head gasket. I want to make sure that the bolt holes
>>> in the block are cleaned out but I don't have a tap
>>> to chase the threads. I have compressed air but was
>>> curious if I absolutely need to get the correct tap
>>> to ensure the threads are clean. I thought a heard
>>> you could make a tap-like tool from an old head
>>> bolt. Is this true and if so is it just a matter of
>>> cutting a few grooves in the threads of the old
>>> headbolt?
>>>
>>> Also when installing the new headbolts, are they
>>> supposed to install dry(no lube)?
>>>
>>> Thanks in Advance
>>>
>>> Paul in PA
>>> _______________________________________________
>>> Vwdiesel mailing list
>>> Vwdiesel at vwfans.com
>>> http://www.audifans.com/mailman/listinfo/vwdiesel
>>>
>>
>> David Cook
>> Red '86 Cabriolet Diesel Powered
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>> and others in various states of disrepair
>> Pictures here: community.webshots.com/user/superdave5599
>>
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