OzVMX Forum
Clubroom => Tech Talk => Topic started by: John Orchard on June 18, 2017, 11:56:02 am
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Hey Guy's :-)
l have extended my footpegs but have only done it with mild steel, l guess it will wear away quite quickly? Is there an easy process to case harden my pegs?
I remember at school we heated metal red hot and dropped it in old motor-oil, is this a proposition or some other way to do it?
Regards, John.
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In my experience that's the way to do it John, aside from buying a hardening powder. Heating red and the quenching in oil will work well, but you might want to temper it afterwards to remove the brittleness - just heat it up slowly to around 400F and cool it slowly in air, or if you do it in an oven, just turn the oven off with it still inside - best to do this when your wife/girlfriend (or both) are not at home though.
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In my experience that's the way to do it John, aside from buying a hardening powder. Heating red and the quenching in oil will work well, but you might want to temper it afterwards to remove the brittleness - just heat it up slowly to around 400F and cool it slowly in air, or if you do it in an oven, just turn the oven off with it still inside - best to do this when your wife/girlfriend (or both) are not at home though.
Ha ha, thanks. Yep will use the oven once the Missus goes to work :-)
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If it is mild steel the oil quench will do next to nothing. The only way is to introduce carbon into the steel while red hot, the old blacksmith forge can achieve it but red hot into oil is not effective unless you start with a high carbon/alloy steel.
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If it is mild steel the oil quench will do next to nothing. The only way is to introduce carbon into the steel while red hot, the old blacksmith forge can achieve it but red hot into oil is not effective unless you start with a high carbon/alloy steel.
Do l have any options?
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You could weld the edge with a hard facing rod or build it up with stellite. The speedway boys used to weld the bottom of the steel shoes with stellite. I have a little bit here that I got for an engine shop that used it to build up camshaft lobes. There are heat treatment powders available or you could send them to a heat treaters.
A quick search found this stuff . http://www.brownells.com/gunsmith-tools-supplies/metal-prep-coloring/color-case-hardening/surface-hardening-compound-prod27119.aspx
You could also track down a local blacksmith how could do it in there forge.
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Thankyou. Would you do the same process to gears, or if they have been undercut?
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Ring me up if you do another set and I'll send you some 4130 chrome moly this stuff hardens well with an oil quench. Gears are made from a workhorse grade of case hadening alloy steel often 8620. This stuff is usually case hardened to a under a mm or so on gears so they usually do need re doing after undercutting. Proper processing would have the gears annealed and reworked.
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Induction hardening is used on gears in mass production. It is complex process and correct current must be used to achive desired penetration and correct hardness.
When you undercut dogs on your gears you only removing material from the face of each dog. There is minimal loss of strength when each dog is shortened by 0.5-1.0mm. Also removing material from face does not affect hardness of the rest of each dog.
Rehardening is not necessary.
You can undercut hardened gear dogs on a mill with high speed head using carbide end mills and carbide burrs of suitable shapes and diameters. Lots of setting up and measuring is needed to get this right.
For your foot pegs 4130-4140 is a good choice. After welding is done I would just heat up wear areas with oxy and bang it in some oil. You do not want to harden whole foot peg.
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Thankyou. Would you do the same process to gears, or if they have been undercut?
No gears are not from mild steel, they are made from special steels designed for case hardening.
Getting gears re-hardened is a very risky process. The case hardening make the metal grow and distort and in a lot of cases I've seen they do not fit onto the shafts anymore making them useless.
Most of the wear on gear dogs happen on the top edge and no matter how far it is machined or ground back that edge always stays hard. The trick is to grind it back without softening it, if the dogs are straight it is easy to do with the correct shape grinding wheels and an indexing head.
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That is exactly where my education has me too Sleepy....well done
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Thanks heaps Guy's, l think it is fantastic the knowledge that is shared here, love it ! :-)
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Hey Guy's :-)
l have extended my footpegs but have only done it with mild steel, l guess it will wear away quite quickly? Is there an easy process to case harden my pegs?
I remember at school we heated metal red hot and dropped it in old motor-oil, is this a proposition or some other way to do it?
Regards, John.
Lay down some nickel bronze on it that is very hard be lucky to file it.
Machined from solid gears don't move much as the sintered OEM gears.
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Is it really necessary to case harden extended foot pegs ?
I have fitted ready-made mild steel extensions to foot pegs on a couple of bikes , and the only problem I have had is the new extensions wearing away the rubber soles of my boots a lot quicker.
I must be doing something wrong ?
just saying
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Perhaps apply Nickel Bronze rods to the soles of your boots?
immutable force meets immovable object
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thanks Fred, I knew I was doing something wrong
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No gears are not from mild steel, they are made from special steels designed for case hardening.
Getting gears re-hardened is a very risky process. The case hardening make the metal grow and distort and in a lot of cases I've seen they do not fit onto the shafts anymore making them useless..
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I regularly make a couple of types of automotive trans and diff gears amd respline others. They are all from 8620 and machined frm bar supplied soft or if existing gears, annealed. They are always sent out with a close fitting mandrel for the bore which is
fitted to prevent shrinkage during quenching and left in for the subsequent tempering. I learnt the hard way years ago when some very short order Ford 9" lsd gears I resplined and sent to a bloke running in the Targa Tasmania where too tight. The epensive heat treater had quenched from too high a temperature and shrunk them a few thou.
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I think trying to case harden footpegs is a bit overkill, as stated carbon is the magic ingredient that is needed in steel to make it hardenable, from memory once the carbon content is greater than 0.2 percent it can be hardened.
The greater the carbon content the harder the steel can become, the trade off being the harder it becomes the more brittle it becomes.
Using a steel that can be hardened may make the pegs brittle which would not be desirable for a peg, the best option would be to lay some hard facing rod onto the tips, I have a couple of rods here you can have if you want to go down that path.
If you do you will probably find the peg face will outlive the hole elongation problems of old pegs!
I don’t believe hardening gears after undercutting is the way to go either, it’s my understanding that hardening nearly always distorts the original size and so gears are machined slightly oversize, then heat treated for hardness and then ground to size.
Also I am of the opinion that dogs aren’t that hard and are not meant to be. The gear dogs come into contact quite harshly but only every time you change gears.
Teeth on the other hand come into contact with each other several thousand times a minute.
Worn gear dogs usually have the corners rounded off, teeth usually chip, I believe that if the dogs were truly hard like the teeth then they would most likely chip instead of rounding their corners
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Gear teeth loads are shared on 3 teeth as are the point load on the dogs and slots of the gear. The same hardness is all over the gear. A gear is "soft as butter" on the inside to absorb the shock. A great FEA video of loads on a gear
https://www.youtube.com/watch?v=3HIJ0nvYF44&ytbChannel=thilak+raj
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Purchase old suitcase from local tip shop, open and half fill with wet concrete (a thick slump mix is preferred) place peg or cog on top of concrete then add remainder till full .Close lid ,reopen a week later, Job done.
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Purchase old suitcase from local top shop, open and half fill with wet concrete (a thick slump mix is preferred) place cog on top of concrete then add remainder till full .Close lid ,reopen a week later, Job done.
:-)