On 01/29/2016 02:03 AM, Gene Heskett wrote:
> All of the stuff I might use to make a pcb can be obtained with stop
> collars so the stickout is within a thou of 1.000".

If all you're using is 1/8" shank carbide PCB drills, I'd get a good 
high precision 1/8" collet.  It can be higher precision because it's 
designed to grip a 1/8" shank, and not a 3-4 mm range.  High precision 
means low runout.  There is a strong correlation between cost and 
quality.  You usually get what you pay for.

You are very unlikely to find a high precision collet that's 
inexpensive, but you may find a cheap collet sold at a high price 
because the seller knows that some buyers assume it must be good because 
it's expensive.  I've definitely noticed that there are items for sale 
that fall into two categories, genuine and counterfeit, with two 
corresponding price ranges.  Some crafty sellers have learned that their 
profit is greatly maximized by selling their counterfeit merchandise 
(complete with a copied Samsung logo, for example) at the low end of the 
price range for the genuine item, fooling buyers into thinking they're 
getting a good deal on the genuine item, when they're actually getting a 
very bad deal on a counterfeit item.  So if you want a good collet, I'd 
buy from a reputable source.  There are definitely low quality knockoffs 
of precision collets on eBay, complete with the copied distinctive 
red/blue packaging.  For some items on eBay and Amazon, it's almost 
impossible to buy the genuine article, because almost all of the items 
are fakes.

If you want to grip arbitrary diameters of shanks on your full set of 
drill bits, you'll probably want the overlapping metric set of collets.  
A higher precision collet tends to have a narrower grip range, so an 
overlapping set of collets that will grip anything in that range may 
have .5 mm collet increments, at least on the smaller sizes.

You may decide that you only need the high precision collet for those 
tiny carbide PCB drills, and a bargain set of metric collets will be 
good enough for an occasional HSS drill bit for a 10-32 tap hole.

My import mill/drill spindle is guaranteed to have a lot of runout, so I 
should only buy high runout collets and line them up so the collet 
runout nullifies the spindle runout.  That's my attempt at humor.  It 
doesn't really work that way.  But it is true that a high precision 
collet isn't going to fix a low precision spindle.

BTW - I was very impressed with the two water cooled Chinese spindles I 
bought on eBay for my two CNC routers.  The electrical and plumbing 
connections are the quality I was expecting, but the spindle bearings 
are phenomenal.  Spinning them by hand, they just felt like quality.  
They advertise German bearings, and I assumed that meant there was a 
Chinese company called German Bearings, but wherever they came from, the 
bearings and related machining in these inexpensive spindle motors are 
clearly of high quality, and justify the investment in a good high 
precision collet.





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