The new -2017- CAST touring system thread
Quote:
Originally Posted by
galibier_numero_un
That makes sense. Both the CAST boys and Cascade folks seem to be dedicated to improving their respective products.
Some folks might not get my "tolerance stacking" comment in my previous post. I was in a rush, so I might as well clarify for those who might be interested.
When you're fabricating a part that mates to another (lets say a male rod and a female hole ... 'coz this is TGR), each part has a specified tolerance range. It depends on the machine shop as to what their default number is, as well as how tight a range they're either willing or able to achieve. Typical default is .005".
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Let's say you have a male thingie that's specified at 1.000 (-.005/+0). That's .995 to 1.000. Any part that meets this spec is considered acceptable.
So now, you're another manufacturer (let's say Cascade) and you need to make a female thingie to mate with that part.
You're no doubt, in the dark as to the spec the male parts are manufactured to, and you're only avenue is to sample as many parts as you can, and then assume that these are representative of their (CAST's) tolerance range. You probably add a bit of extra wiggle room, due to uncertainty.
So, let's assume you derived the above spec (.995 to 1.000). I'll write the tolerances in this format from here on out, for simplicity. Due to uncertainty, you expand the spec to .993 to 1.002.
Now you have to make a batch of parts that have their own tolerance range. So, you specify holes that are 1.003-1.005 (a .002 range). This "ensures" their biggest rod will fit in your smallest hole (that's what she said).
So now, your customer has a small rod (.995) and you present them with a big hole (1.005). It's not very satisfying, as .010 is a lot of slop in some applications.
What if your sample size wasn't representative and it is in fact .995 to 1.005. Your smallest hole is now too tight (1.003).
... Thom
In my case, three out of four toes fit fine, and the one that didn’t (purple toe) was 0.012” thicker than its mate. That’s a QC fail, in my opinion.
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