Page 1 of 4 1234 LastLast
Results 1 to 20 of 74

Thread: Billet & Forged Crankshafts

  1. #1
    Join Date
    Feb 2000
    Location
    Montana
    Posts
    11,382

    Arrow Billet & Forged Crankshafts

    Can anyone tell me the difference in strength & durability between billet & forged?

    Thanks,

    Jim

  2. #2
    Join Date
    Sep 2000
    Location
    usa
    Posts
    2,646

    Default

    Forged cranks, having the general shape of the finished product, need centering, cross drilling, do the hubs, snouts, crankpins and mains journals, and you're done, maybe some tuftriding and polishing

    Billet cranks are labor intensive, being totally machined from a round bar , or billet blank, the diameter of which must be greater than the throws\counterbalances.

    Would be my guess.

    Now, about those billet door knobs, steering wheels and columns, mufflers, brake pedals, license plate brackets, etc...............
    jd
    '96 Dodge 3500HD cc 2wd drw............'89 GMC 3500 cc 4wd drw
    5.9 12v #10TST 6sp SBC13-1.375.......6.5TD EFI maxEtorq v2.0 DSG
    DODGE makes it CUMMINS shakes it.....4L80E 205 4.10 Dana60\70HD
    6 in a row makes it go.......................Grandpa's big truck

  3. #3
    Join Date
    Apr 2001
    Location
    Newberg Oregon
    Posts
    12,282

    Default

    The forging starts with an almost white hot chunk of metal and they stuff it into the forging die and the giant drop hammer comes down and smashes the metal into its finished shape.

    Big, heavy and monsterous machines to do this.
    The advantage is there are few stress risers left after the process.

    With a billet it is as has been mentioned cut from a large chunk of round stock.
    After the initial machining the unground crank needs to be stress releived in an oven at temps just almost red hot and then cooled.
    This will allow the thing to settle into whatever shape it needs to be and not have any internal stresses left in it.
    Once the crank is just about done the journals are nitrided and then they are done.
    The nitriding /tufdriding (GM) gives the bearing surface a nice hard wear surface a couple thou thick..

    We used to hard chrome the journals and grind back to spec.
    If done right its tougher than the hubs of hell and will really make a nice crank.
    If done wrong it peels and your toast.
    Last crank we hard chromed was a 454 gasser and we underground it .005 and chomed it back .007 and then ground it to standard spec.

    It ran 5 seasons in the race boat and then ended up in a pickup. Have not a clue as to where it is now.

    Too many folks are using the term "Billet" for everything from door knobs to rocker arms.
    Its sounds way kewl so they use it as a selling point.

    I asked one of the crank companies a while back to quote me on a billet crank for the 6.5. $2600.00 plus freight to get it here.

    Ballanced and ready to go as long as I sent them the goodies such as rods, pistons, ballancer and such.

    Robyn

    Truth is its highly over used
    (1) 1995 Suburban 2500 4x4
    (1) 1997 Astro
    (1) 2005 Suburban (Papa Smurf)
    THIS IS BOW TIE COUNTRY

  4. #4
    Join Date
    Nov 2002
    Location
    Martinsville, IN
    Posts
    3,163

    Default

    The major difference is in the strength. The forging process yields preferential grain flow which improves strength (in one direction). As was mentioned, you start with a hot chunk of metal and progressively form it with dies until it is close to the final shape.

    Billet (a fancy way to say machined from solid) parts are just machined from a chunk of metal. The material is homogeneous. The machining will cut across the grain, interrupting the pattern.

    Depending upon how the initial chunk or material was formed, a machined from solid piece may be stronger than a cast piece, but a properly forged piece will be stronger than either.

  5. #5
    Join Date
    Sep 2000
    Location
    usa
    Posts
    2,646

    Default

    The billet piece has an added advantage - any weak points in the forged piece can be strengthened in the billet piece by leaving extra stock - this is easily seen in the aftermarket transmission shafts, where the shaft diameter is increased in critical areas, and splined areas are lengthened for more 'bite', or spline length is reduced for increased strength in the uncut diameter.

    And often the billet piece is 'tempered', where the forged piece is not, or is to a lesser degree

    GM offered forged crank blanks, totally un-machined, to be cut and finished by those with facilities to improve the piece, or alter stroke somewhat - also offered semi-finished pieces for minor alteration.

    Be neat if the 454 blank could be machined for the 6.5, requiring also an altered camshaft.

    What's the thought(s) behind your question?
    Last edited by gmctd; 04-19-2007 at 17:49.
    jd
    '96 Dodge 3500HD cc 2wd drw............'89 GMC 3500 cc 4wd drw
    5.9 12v #10TST 6sp SBC13-1.375.......6.5TD EFI maxEtorq v2.0 DSG
    DODGE makes it CUMMINS shakes it.....4L80E 205 4.10 Dana60\70HD
    6 in a row makes it go.......................Grandpa's big truck

  6. #6
    Join Date
    Nov 2002
    Location
    Martinsville, IN
    Posts
    3,163

    Default

    Quote Originally Posted by gmctd
    The billet piece has an added advantage - any weak points in the forged piece can be strengthened in the billet piece by leaving extra stock - this is easily seen in the aftermarket transmission shafts, where the shaft diameter is increased in critical areas, and splined areas are lengthened for more 'bite', or spline length is reduced for increased strength in the uncut diameter.

    And often the billet piece is 'tempered', where the forged piece is not, or is to a lesser degree
    The only reason people advertise "billet" parts is to sucker gullible folks into thinking they're getting something that they aren't. The word actually comes from the fact that large chunks of raw material are called billet...hence, "machined from billet" which has been shortened to "billet" for advertising purposes. By making a redesigned piece from solid stock (billet), one can alter sizes and gain some strength in some areas. If one were to design and make a new forging that incorporated the increased section sizes and make a part from that, it would be by far stronger.

    The reason that new forgings are rarely made by the aftermarket folks who really like to use the "billet" advertising advantage is because a forging is expensive and their small production runs cannot justify it economically. In this case, a "billet" piece becomes a reasonable compromise, but it is a compromise none the less. To sell their parts, they crow about it being a "billet" piece that is "stronger than a forging" and leave the impression that forged pieces are somehow inferior. This is completely not the case.

    For the subject at hand, I would be very skeptical if someone claimed that a "billet" crankshaft for the 6.5 was very much stronger than the current cast cranks that we are using.

    As for your comments about tempering... What is your source for information here?
    Last edited by ronniejoe; 04-19-2007 at 21:07.

  7. #7
    Join Date
    Feb 2001
    Location
    Fort Worth, Texas, US
    Posts
    945

    Default

    we use cola, crower, callies, and bryant in the race stuff, they are machined from a billet and are $3800 for a v-8 or a straight 4.............

  8. #8
    Join Date
    Nov 2002
    Location
    Martinsville, IN
    Posts
    3,163

    Default

    Quote Originally Posted by grape
    we use cola, crower, callies, and bryant in the race stuff, they are machined from a billet and are $3800 for a v-8 or a straight 4.............
    Again, that's because they can't justify the cost of producing new forgings for such small numbers. If you think that price is high, try amortizing the cost of a forging over the same number of pieces. In reality, the same thing is true for castings.

    The "billet" pieces are the only economical way to get some of these low quantity parts. They've just spun the marketing angle so that gullible people think they're getting something better.

  9. #9
    Join Date
    Sep 2000
    Location
    usa
    Posts
    2,646

    Default

    I agree - you'll never see a billet down-pipe on my truck, or billet brake hose, or billet fuel-level float - even tho they are cheaper than the forged versions.

    Have been considerin' one o' them billet radar detectors, tho, and a forged Rolex ain't too bad, fer the price.

    But, I digress - I agree - I'd rather have the forged tuf-trided piece, maybe with a different firing order.

    The ease of making design changes in the billet piece is another strength over forged.

    But I 'spect the question is which will survive better than the cast-piece now in use.
    jd
    '96 Dodge 3500HD cc 2wd drw............'89 GMC 3500 cc 4wd drw
    5.9 12v #10TST 6sp SBC13-1.375.......6.5TD EFI maxEtorq v2.0 DSG
    DODGE makes it CUMMINS shakes it.....4L80E 205 4.10 Dana60\70HD
    6 in a row makes it go.......................Grandpa's big truck

  10. #10
    Join Date
    Nov 2002
    Location
    Martinsville, IN
    Posts
    3,163

    Default

    Quote Originally Posted by gmctd
    I agree - you'll never see a billet down-pipe on my truck, or billet brake hose, or billet fuel-level float - even tho they are cheaper than the forged versions.

    Have been considerin' one o' them billet radar detectors, tho, and a forged Rolex ain't too bad, fer the price.
    So, you're shown to be blowing smoke and you start mocking... I tried to be gentle.

    Quote Originally Posted by gmctd
    The ease of making design changes in the billet piece is another strength over forged.
    This is it's only advantage...not "another" one...as I already stated in my earlier post.

    I've attached an image of a section of a crankshaft forging for your viewing enjoyment. Notice how the grain follows the contour of the shape. This is what makes a forging stronger than a "billet" piece or a cast piece. This is called "preferential grain flow".

    Even if you cold work the piece of billet stock or even if you forge the billet stock into it's bar shape, the machining operations to get the shape of the crank will cut through the grain so that the grain pattern is interrupted. This yields a loss of strength in the finished part.

    Bottom line: Make two identically shaped parts (in this case crankshafts), one from a forging and the other from "billet". The forged one will be stronger every time. End of story.
    Attached Images Attached Images
    Last edited by ronniejoe; 04-19-2007 at 22:07.

  11. #11
    Join Date
    Feb 2000
    Location
    Montana
    Posts
    11,382

    Arrow

    Let's not get testy... I just asked a simple (in retrospect maybe not all that simple...) question that I needed more info on....

    I'm surprised someone didn't ask why I posted this in the "6.5L Turbo Diesel Forum".

    I'm in the process of gathering more information... I received a couple of really cool photos (which I'll share soon), and I asked a few folks what they all meant. Aside from a factory girdle, billet cranks came up in the conversation (I had heard last year they would be forged - more later).... I still need to talk to a few who really have the scoop on what I saw...

    Jim

    PS... Did I mention an electric fan clutch?

  12. #12
    Join Date
    Sep 2000
    Location
    usa
    Posts
    2,646

    Default

    Just as I suspected - those things have changed hardly at all since back in the late '50's- early 60's, when I first saw several comparisons for cast, forged, and 'cut', or totally machined from 4130 or some such steel, cranks.

    Odd how those 'cut' cranks could survive <1500hp for ~4secs in a motor that consumed 1.5gals fuel per second

    Nice pic, ronniejoe, very informative - got one with similar slice thru a billet version?

    Also be interested in seeing sliced inductive hardening, carburizing, and also nitriding examples - notice how I separated 'tempering' examples from nitriding.

    Then there's tempering by 'quenching', but that's very smokey - as is burning weeds........
    jd
    '96 Dodge 3500HD cc 2wd drw............'89 GMC 3500 cc 4wd drw
    5.9 12v #10TST 6sp SBC13-1.375.......6.5TD EFI maxEtorq v2.0 DSG
    DODGE makes it CUMMINS shakes it.....4L80E 205 4.10 Dana60\70HD
    6 in a row makes it go.......................Grandpa's big truck

  13. #13
    Join Date
    Jun 2006
    Location
    Okanagan BC, Canada
    Posts
    66

    Default

    Billet parts have become popular in recent years due to CNC machines that throw alot of metal chips in a hurry with a minimum of supervision/cost.

    I agree that a forged crank is likely to be better than a billet crank as long as the metal used in the two processes are of equal quality/design for the job at hand. I suspect the material used in the billet cranks that Grapes speaks of is of a superior quality than what GM uses in thier forged cranks. So it is very possible to have a superior billit crank to that of a forged crank.

    Other issues to consider when assessing the durability of a crank is surface finish, and the size of radius corners. Smoother the surface, and larger radius corners, better the durability.
    93 Chev C2500 HD extended cab, long box, 6.5TDF, 4L80E, DB2 injection pump turned up 1/4 turn, flowmaster downpipe, EGT/Boost/Trans. Gauges, 97+ dual thermostates and HO water pump, 97+ round air filter, manual lockup torque conveter switch, homemade wastegate controller set at 8psi, de-snorckeled, 97+ air filter, 3.43 ratio rear gears, autometer gauges, 19 mpg.

  14. #14
    Join Date
    Nov 2002
    Location
    Martinsville, IN
    Posts
    3,163

    Default

    Quote Originally Posted by More Power
    Let's not get testy... I just asked a simple (in retrospect maybe not all that simple...) question that I needed more info on....

    I'm surprised someone didn't ask why I posted this in the "6.5L Turbo Diesel Forum".

    I'm in the process of gathering more information... I received a couple of really cool photos (which I'll share soon), and I asked a few folks what they all meant. Aside from a factory girdle, billet cranks came up in the conversation (I had heard last year they would be forged - more later).... I still need to talk to a few who really have the scoop on what I saw...

    Jim

    PS... Did I mention an electric fan clutch?
    I apologize for getting "testy"...

    I've explained the differences and provided justification for the technical content of my comments. You choose who to believe.

    It seems to be a safe assumption that GEP is developing some new stuff. Their choice of "billet" over forged is nothing more than an economic choice. They will probably be able to engineer a machined from solid piece that will out perform the cast pieces presently used. However, their decision mirrors that of GM in the first place when the decision was made to use cast cranks in these engines.

    As for the electric fan clutch... I saw such a device on pre-production prototype gas pusher motorhome chassis using Chevy 8.1 liter engines last year. I thought then that this could easily be adapted to the 6.5. At that time, I was not allowed to speak about what they were doing for competitive reasons.

    As for sections with carburize etc., look them up in your engineering texts. This stuff is usually covered in second year engineering classes. I've posted photomicrographs of nitrided surfaces in the past. That generated more questions than it answered.

    Briefly, carburizing, nitriding, induction hardening, "tuftriding", nitrocarburizing, etc. are processes that increase the surface hardness of a part while leaving the core in a softer state. This increases the fatigue resistance of cyclically loaded parts because of the residual compressive stresses produced near the surface. This is due to the change of phase of the material from the hardening process (reference your metallurgical texts for a discussion of the phase diagrams for various materials) that increases the volume of the material at the surface.

    These hardening processes all have advantages and disadvantages that must be carefully considered. Esentially, materials that are used with nitriding are different from materials that are used with carburizing and are different from materials used with induction hardening. The processes are not interchangeable.

    The "best" process, from a strength standpoint, is carburizing. However, there are many other considerations that dictate the use of the other processes in many situations. These other considerations make the other processes "better" in those circumstances.

    This discussion, though, is off the topic of this thread.

    4130 steel was mentioned in a previous post. Can anyone explain what the numbers in the designation mean? How about 9310 steel or 1010 steel or 8620 steel or 5150 steel? What are each of these materials commonly used for? Which heat treat process or processes should be used with each?

  15. #15
    Join Date
    Dec 2003
    Location
    SC
    Posts
    939

    Default

    Here is some info on steel numbers

    http://shopswarf.orcon.net.nz/sae.html

    I can't regurgitate it very well. I use to work in the tooling business and selection of material is a whole host of compromises of economics, supply, bar stock size, machineability, processibility, compatibility, strenght/hardness/toughness etc etc.

    If you don't have a great memory and I don't I generally have to look up specific properties each and everytime dang it.
    97 5spd K2500 Ext Cab short Bed ~160K miles.
    TM, 3" downpipe & 4" exhaust, remote FSD, remote oilfilter, Gauges: EGT, Boost, Fuel Pressure, B&W Gooseneck Turnover ball, Prodigy Brake Controller. Hi-Temp Hydraulic Oil Cooler Lines.

  16. #16
    Join Date
    Nov 2002
    Location
    Martinsville, IN
    Posts
    3,163

    Default

    Thanks Hubert.

    That link does a good job of explaining the designation system. I actually asked the question in a rhetorical sense to be a bit of a smart alec...please forgive me.

  17. #17
    Join Date
    Jun 2006
    Location
    Okanagan BC, Canada
    Posts
    66

    Default

    Quote Originally Posted by More Power
    Can anyone tell me the difference in strength & durability between billet & forged?

    Thanks,

    Jim

    I suspect GEP or who ever will have a HP/service life number in mind and will engineer a crank around that number. If GEP were to make a forged crank they would use a cheaper metal, if they build a billet crank it will have better metal in it to meet the engineered service requirements.

    Fordged or billet isn't the issue service life is and the number that was decided on for this crank. Lets hope it is high and affordible.
    93 Chev C2500 HD extended cab, long box, 6.5TDF, 4L80E, DB2 injection pump turned up 1/4 turn, flowmaster downpipe, EGT/Boost/Trans. Gauges, 97+ dual thermostates and HO water pump, 97+ round air filter, manual lockup torque conveter switch, homemade wastegate controller set at 8psi, de-snorckeled, 97+ air filter, 3.43 ratio rear gears, autometer gauges, 19 mpg.

  18. #18
    Join Date
    Apr 2001
    Location
    Newberg Oregon
    Posts
    12,282

    Default

    I agree with the materials as posted so far.

    The cost of the machinery to forge crankshafts has got to be pretty hefty and unless the production runs are going to be in the 7 figure numbers it may well be more cost effective to use a billet piece.
    And has been mentioned with the new CNC machines they can chew up steel in a hurry and poop out cranks pretty fast with minimal effort once the machines are set up.

    Even with the high cost of materials the scrap is not going to be staggering compared to amortizing a drop forge.

    I have seen and run cast iron, cast steel, forged steel and billet steel shafts.
    I have personaly seen iron go away and do so in pieces.
    The steel shafts I have owned (all types) have done well.
    Now I must admit these were all in chevy big blocks from 396-500+ Cu in engines which have a fabulous reputation for durability and longevity.

    I have seen 4130 cranks and have seen some billet cranks made from 8620
    The 8620 will surface harden well and still retain a very tough core.
    We have used 8620 for track roller shafts on Cat dozers.

    Whatever product that comes down the pike for the 6.5 almost has to be better than the taffy shafts that we have now.

    I personaly would like to see a forged shaft available .

    One thing for sure, unless these are mass produced the price is bound to be a bit spendy.

    I dont see these engines ever being used in a mass produced products slated for public consumption as was the case with pickups,SUVs ect by GM.

    The military simply cant suck up enough of this stuff I dont think.

    Possibly if these engines find there way into enough other high sales uses the costs might be palatable.

    This has been an interesting thread though.

    In getting back to the use of the term Billet.
    Still highly overused me thinks
    My son inlaw gets all these catalogs for dirt bike goodies and everything is a billet something.
    Billet chain guides, billet fork covers, billet, billet billet AAAAAACK


    I want a set of billet seat covers

    OH on a serious Note


    RJ
    Please enjoy our humor, its the only way some of us can stay sane!! ;0)

    Nobody is mocking or making fun, its just to bring a smile and give us all a bit of relief from the crap we all have to endure every day.

    OH BTW if you find smiles and giggles in short supply, I have a unopened package of "Billet smiles" I'll send over..

    Love ya guys

    best to ya

    Robyn
    (1) 1995 Suburban 2500 4x4
    (1) 1997 Astro
    (1) 2005 Suburban (Papa Smurf)
    THIS IS BOW TIE COUNTRY

  19. #19
    Join Date
    Apr 2001
    Location
    Newberg Oregon
    Posts
    12,282

    Default

    Just a passing thought
    Overall the serviceability on the 6.5 has not been all that bad.
    The addition of just a little more durability in the block and the crank will most likely put the 6.5 over the top and make it a very dependable piece of equipment.

    The only issue I see coming into play is all of "US" folks who like to see just how much more boost we can add or how much heavier a load we can pull.

    The design will be put to the ultimate test no matter what is done to it by the wild ones.
    If used as designed is the issue! The rest of us crazies are going to push the limits to the edge and beyond and then sweep up the pieces and go again.

    No matter if its a little scooter or a heavy duty off road truck, someone is going to take it all the way to its point of failure and then complain that it did not hold up.


    Where does it all stop????

    Robyn
    (1) 1995 Suburban 2500 4x4
    (1) 1997 Astro
    (1) 2005 Suburban (Papa Smurf)
    THIS IS BOW TIE COUNTRY

  20. #20
    Join Date
    Sep 2001
    Location
    Lubbock TX, USA
    Posts
    4,194

    Default

    Glad that this tread was created, finally settled some underlying questions I've had about the new rumored cranks and a custom one.

    More good stuff to chat with the gear heads about here locally!

    Humor is good, but stabs are not...

    Testing shall continue!

    J

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •