Knowing how well these machined then I'd be more than confident that the crankpin centre dimple would be more than accurate. Obviously if they were done using a collet then you'd be more confident but seeing as its only a dimple then people can choose to use it or use a slot drill to set they're own position up.
Yes I agree. The crankpin centre dimple will always be accurate relative to the machining of the spoked blank, it being part of that milling process. It was Unklian's suggestion
that crankpin holes might be drilled at this initial stage that alarmed me - a cart before the horse situation.
![Smile :) :)](/styles/default/xenforo/smilies/smile.png)
Crank pin holes should ideally come after turning operations have produced the axle hole.
While there is every chance that crankpin holes can be drilled satisfactorily, by using the dimple on any wheels "turned with the accuracy of Elliot's supplier equipment", the end result, when turning is done in the home workshop, may lead to variations and any pre-drilled holes would be quite frustrating. Use of a slot drill with wheels locked on an axle spigot is preferable to making use of a dimple in such circumstances.
An S scale colleague goes so far as to turn crankpins to finished diameter - after they have been secured in the wheel. [With wheels mounted on an offset spigot, it becomes an easy turning operation - rather than a slot-drilling one.]
I'm no CNC engineer, but I'm afeared you might be right Brian.
If the lathe chuck is even a smidge out of whack then the crank throw won't quite be consistent; and that's before considering the alignment accuracy of the mill that's used to produce the original items. But:
You've both really made me think though and it's worth noting that in a perfect world Elliot is 100% correct and in a reasonably precise world it may well be good enough.
"The perfect is the enemy of the good enough" - it might be that easing a crankpin hole is enough to overcome any issue, in which case it's good enough and I might not worry about perfection, which generally costs more.
Steph
Good thoughts, Steph - and I should plead guilty if charged. In my defence, the many exactly scaled wheels delivered to some very discerning EU modellers, but probably few with quite the elegance of Elliot's production. Have a full range of toolroom gear at home which does usurp some model railway space. Such toys 'smoke my tyres'
![Big Grin :D :D](/styles/default/xenforo/smilies/biggrin.png)
though, pun intended.
-Brian McK. (We had a good chat at Guildex some years ago)
![Mitutoyo Optical Comparator_Wheels.jpg Mitutoyo Optical Comparator_Wheels.jpg](https://www.westernthunder.co.uk/data/attachments/83/83533-3490cd2c48333c1866b208be241f6622.jpg)