Rocker shaft education time. Nothing is easy!
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padam
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That’s what I’m talking about also.
This is a HSS about 5/8. I was able to turn the shank down to use in a half inch chuck.
Like I said, I’m talking about high quality general purpose drills.
I don’t know about stuff you buy from Home Depot or the tool truck.
padam
Well-Known Member
This drill has a burr from spinning in the Chuck a little. It will file right off.
If the shank was hard as the tip no way you would get that burr.
I would say that the shank is left soft to make it tougher, you don’t want it to snap off. Also it allows the chuck jaws to bite a little.
I’m not sure what process they use for. Heat treat, but my guess is they hold them buy the shank and quench the end.
But don’t take my word for it, grab a file and check it for yourself.
If the shank was hard as the tip no way you would get that burr.
I would say that the shank is left soft to make it tougher, you don’t want it to snap off. Also it allows the chuck jaws to bite a little.
I’m not sure what process they use for. Heat treat, but my guess is they hold them buy the shank and quench the end.
But don’t take my word for it, grab a file and check it for yourself.
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Twist drills are only hardened about half way up, not all the way! Larger diameter drills, like 3/4" and up are only hard for about an inch and a half. That's why you can only get so many re-grinds out of them before you throw them away. Go look at a youtube video on how they make twist drills.
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They have pills for that now
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The Damned pills don't work anymore!!!!! Impunity, or something like that!
HAPPY THANKSGIVING EVERYONE!
HAPPY THANKSGIVING EVERYONE!
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Geoff 2
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Sigh.
All the HSS drill bits I have seen have a shiny finish, not dull like in post #23. I am not sure what the material is in bits that have a dark colour, but they are a softer steel than HSS, will not drill tough materials like HSS will & they become blunt more quickly. The dark colour I presume is some sort of heat/hardening treatment. These drills are cheaper than HSS...for a reason.
A HSS drill is the same hardness throughout it's length. I have broken these drills, refaced the tip on the remaining section......& drilled holes with what is left. And I have done it many times....
All the HSS drill bits I have seen have a shiny finish, not dull like in post #23. I am not sure what the material is in bits that have a dark colour, but they are a softer steel than HSS, will not drill tough materials like HSS will & they become blunt more quickly. The dark colour I presume is some sort of heat/hardening treatment. These drills are cheaper than HSS...for a reason.
A HSS drill is the same hardness throughout it's length. I have broken these drills, refaced the tip on the remaining section......& drilled holes with what is left. And I have done it many times....
padam
Well-Known Member
Oh wait, are you using the yellow or pink bit with that playskool drill?
(JK)
Geoff 2
Well-Known Member
Think about this & then go and play with your toy fire engine:
One of my most used lathe tools is made of 1/2" square HSS. It is about about 1.5" long. Same material as HSS drill bits. It has been cut from a 8" length...That works because the material is the same hardness throughout.
One of my most used lathe tools is made of 1/2" square HSS. It is about about 1.5" long. Same material as HSS drill bits. It has been cut from a 8" length...That works because the material is the same hardness throughout.
padam
Well-Known Member
If you have a lathe you must have some tool steel drill rod around. Take a 6” long piece. Heat one end cherry red about an inch back and quench it. Check the hardness on each end. One end should be hard and the other much softer.
Ever hear of the Jominy end quench test? It measures steels hardenability when quenched from the end.
padam
Well-Known Member
My only intent responding to this thread was to provide some information on how steel is hardened.
Parts and tools can be made from different materials and processes, but still be functional.
The nitriding process that was applied to the rocker shafts is of interest to me. It is a process that has been in use for a long time, on race crankshafts for one.
I didn’t mean to get into a back and forth about it, just wanted to share some info.
Personally I don't want "hardened" steel shafts, I want "thick wall" shafts - which the good one's are. Just because its hardened doesn't mean it won't flex or pinch when you tighten them down. The extra material in a thick wall shaft will eliminate flex and any chance of pinching.
And hard chrome is what you need for roller bearings - such as Harland Sharps - but not necessary for aluminum or bronze bushed rockers.
And hard chrome is what you need for roller bearings - such as Harland Sharps - but not necessary for aluminum or bronze bushed rockers.
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The hardened shafts won't deflect as much as a soft ones of the same wall thickness. The rule of thumb for
a bearing surface is the two surfaces should be different hardnesses. I don't like roller bearings because they
"Point Load" and don't have as much contact surface as an aluminum or bushed rocker arm. The oil film provides
a nice 100% area for load. If a shaft is hard chromed and you use rockers with roller bearings, that hard chrome
better be thick enough to support that "Point Loading". My personal opinion on alot of brand name parts is that
they use their name to charge far more that the parts are worth because they can! They are not necessarily beter.
a bearing surface is the two surfaces should be different hardnesses. I don't like roller bearings because they
"Point Load" and don't have as much contact surface as an aluminum or bushed rocker arm. The oil film provides
a nice 100% area for load. If a shaft is hard chromed and you use rockers with roller bearings, that hard chrome
better be thick enough to support that "Point Loading". My personal opinion on alot of brand name parts is that
they use their name to charge far more that the parts are worth because they can! They are not necessarily beter.
Geoff 2
Well-Known Member
I have bought stuff from Mancini over a 40 yr period. I have always found them to be truthful.
In the 80s, I bought some s/s BB head gaskets. They were magnetic [ some s/s is ] & painted. How to tell between plain steel & s/s? My chemistry lecturer gave me the clue. Get some Copper Sulphate powder from the chemist & mix into a solution with water.
When put in contact with steel, it reacts to form a brown-ish stain, which is copper. On s/s, there is no reaction. And there was no reaction with these gaskets....
In the 80s, I bought some s/s BB head gaskets. They were magnetic [ some s/s is ] & painted. How to tell between plain steel & s/s? My chemistry lecturer gave me the clue. Get some Copper Sulphate powder from the chemist & mix into a solution with water.
When put in contact with steel, it reacts to form a brown-ish stain, which is copper. On s/s, there is no reaction. And there was no reaction with these gaskets....
Fury63
Member
The black oxide finish on the drill shown, is a form of lube to keep a drill from sticking or welding, at the cutting point. A large quantity of drills get that coating, it works well on tool steels. I have HSS black oxided drills and titanium nitrided(gold)drills and uncoated drills as well as carbide, with different coatings. They all have their place. This was what I done for a living, for 30 plus years. Now doing the same thing with sand and water.
Fury Fan
Active Member
This thread is an excellent example of going to/fro on accurate information.
Sometimes an accurate thought is rendered inaccurate due to omission of a single word.
Sometimes a statement, posed as always true, is inaccurate because in one set of circumstances it isn't true.
And sometimes some folks simply don't have a clue, but speak very confidently.
Not speaking of anyone in particular, just of the dynamics of a technically-challenging topic being discussed on a car forum.
Sometimes an accurate thought is rendered inaccurate due to omission of a single word.
Sometimes a statement, posed as always true, is inaccurate because in one set of circumstances it isn't true.
And sometimes some folks simply don't have a clue, but speak very confidently.
Not speaking of anyone in particular, just of the dynamics of a technically-challenging topic being discussed on a car forum.
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