But you could use a steel splined sprocket right, and therefore no durability issues?
Pretty popular business model though: 
The White Ind sprockets are case hardened 8620 steel. Thatâs doing it properly, the surface hardness will be ~60-90 Rockwell C depending on heat treatment / case hardening.
(Can anyone recall how hard the Chainring Transit Authority 440 martensitic stainless sprockets were? Those things were brutally wear resistant.)
Canât see your images H, but I assume theyâre of a disposable razor. The difference is that I can get blades in any supermarket, instead of maybe one shop in town or ordering from the US/France.
If youâd bothered to actually read my posts youâd see I said from an Engineering perspective. Itâs the industry standard, which is a standard because itâs been around for ages, and is very cheap for the manufacturers. Itâs not the best system however, due to itâs inherent design flaws which no-one, not you or I can ignore. But it works and works quite well, and Iâm sure I will continue to use it.
I did read your posts. Just because a method is better/ the best, doesnât mean it should be used. Engineering perspective is one thing, but price, compatibility, etc are also important. As underlined above, it works well, itâs cheap to produce & itâs compatible with the majority of components (and you can interchange with freewheels).
Iâm not saying all standards should remain forever, I love threadless headsets/stems, cassette hubs, cotterless cranks, but every CNC operating bike nerd shouldnât try to reinvent the sprocket. If there is to be a new standard, Iâd suggest either ISO disc mount (restricts small sprockets) or the White Industries spline.
My real issue is that they used aluminium for the sprocket, thatâs just dumb.
http://www.crptechnology.com/sito/images/PDF/7075.pdf
It might be aluminium, but itâs not any old aluminium.
According to this source the rockwell hardness of 7076-T6 is 80HRB, this is harder than many steels, although they all have their own test types within the Rockwell system.
And they say here:
Applications: Aircraft fittings, gears and shafts, fuse parts, meter shafts and gears, missile parts, regulating valve parts, worm gears, keys,
aircraft, aerospace and defense applications; bike frames, all terrain vehicle (ATV) sprockets.
Iâd say your man making these hubs and cogs has done his homework, and until he sells them and gets bad reports Iâm prepared to give him the benefit of the doubt.
Edit: Oh fuck it. Iâm done here. You have no fucking idea what youâre talking about if youâre going to compare HRB to HRC directly.
This seems like the best way forward and Phil Wood are making ISO bolt on track hubs.
However for people actually track racing and changing cogs often then it would certain suck.
The Charge Shaker hub is/was both slotted and bolted - nothing like being both overkill and proprietary.
So if there is going to be a trend to spline then itâs gotta be a standard, preferably ISO or the ISO committee adopting something that already exists without having to deal with IP/Patent or royalty issues.
I must be more bored at work than blakey 
Behold the columns in the green colourway and the pink colourway, therein the point of contention lies
Man I love this forum
I am not a metallurgist, nor profess to be. Serious question - Are you a metallurgist? I was having a discussion and was enjoying the different points of view from everyone, and figured I might maybe learn something in the process. Last time I checked this was the point of an Internet Forum. If you cant handle that without throwing your toys out of the pram then I suggest you get help or get those haemorrhoids checked.
From what Ive been able to glean just now you cannot compare different materials via a converision table - hence it being for Steel in this case.
I have 3.
Iâm not a metallurgist either and my writen communication skills are not the best but bear with me
Rockwell hardness scales are arbitrarily derived scales based on applying a given load to an indenter and seeing how far the indenter gets pushed into the material being tested.
HRB and HRC use differing loads and indenters.
The Vickers hardness scale is mathematically derived and is the same for all materials (click the linky).
As the Rockwell scales are arbitrary to convert Vickers to Rockwell you have to do both Vickers and Rockwell tests on the same bits of material, write down the results and come up with a table like the one I linked earlier. Yes itâs for steel but I think the correlation between different hardness scales doesnât vary greatly between different materials (as opposed to the correlation between hardness and mechanical properties, which does but is a bit OT)
Back to the topic at hand: we can use the Vickers hardness scale to compare 7075 aluminium wunder sprocket with steel
From the link you posted earlier 7075 is 175HV (yes itâs âconverted from the Brinell valueâ but the Brinell scale is another mathematically derived scale and the conversion from Brinell to Vickers is fixed. you can compare in brinell hardness if you like)
From my testing of various sprockets lets say a hardness of 45HRC for decent ones.
45HRC = 450HV = 425HBW from the table I posted earlier.
If that fails to convince you that decent steel sprockets are much harder than 7075 aluminium and therefore concerns about durability are warranted take a file or a hacksaw of a knife and try to do some damage to a steel sprocket and an aluminium chain ring or anything you can find with 7075 written all over it.
and yet neither of them are harder than jens voight.
Fantastic! Cheers for the post DaFROG. I didnât really doubt that the 7075 would be softer than most steels but itâs a very high grade of ali so wondered where the line fell.
What i am is curious of just how allegedly âbadâ these 7075 cogs are before we write them off altogether. There are quite a few on the market by the looks. It may not be as hard but it is still quite tough, as in has a relatively high tensile and shear strength - all important properties, and the way I see it there has to be more to it than hardness alone.
prepares to stand corrected
Iâm sure they would work okay, but definitely would not last as long as steel.
Anyone actually used one?
brendan wins!
Jens Voight is harder than 450 vicars? wow
Hoonz:
hardness is probably the most important property in determining wear resistance.
Heat treated 4130 (ISTR several track sprockets are advertised as 4130) has a yield strength (that is resistance to plastic deformation) of ~950MPa, about 2 times that of 7075.
MatWeb - The Online Materials Information Resource
So 7075 isnât as âgoodâ as heat treated 4130 but itâs lighter, choose weight or strength or titanium
Materials selection is all a juggling act, cost, weight, corrosion resistance, ease of manufacture, durability, etc. etc.