N_Cook wrote:

Michael A. Terrell wrote in message
...

Jim Yanik wrote:

"N_Cook" wrote in :

Where holes are drilled for thru-board components but of diameter far
too big , thru-hole plated , but no eyelet/inserts used to fill the
gap. So 1N4001 size leads in holes twice their diameter and 1N4148 in
holes twice their diameter. So not a case of only one drill size for
all. So in area terms about 1 to 4 ratio of lead to solder. Bad
enough practise with proper solder but with PbF, ring cracks starting
all over. Is it to avoid mutiny by the by-hand board populators ?




perhaps PCBs designed for machine parts insertion have those sort of
"oversize" thru-holes? Perhaps the insertion machine prefers big holes
and
besides,they crimp over the leads anyways.


Microdyne stopped bending the leads or using the special cutters that
cripmed the leads back in the '80s to reduced damage to the PTH.


Maybe it's too much trouble to
drill PCBs for different size thru-holes,and/or not worth the effort.


It's more likely that there was no design review, or the cad operator
was too lazy to verify the hole sizes.


certainly stocking and inserting eyelets would be an
additional,unnecessary
expense.


--
You can't fix stupid. You can't even put a Band-AidT on it, because it's
Teflon coated.

As the drill bits tend to be very brittle carbide rather than HSS I imagine
doubling the drill bit diameter drops the breakage rate by 1/10 or so,
reduced bit replacement costs, plus reduced down-time manual intervention
to rectify stoppages, due to such breakages.


A properly run PCB drilling system doesn't break the bits, and they
are replaced before they are dull enough to cause a problem. If it is a
cheap, in house product, all bets are off. You can get properly made
boards, if buying the cheapest you can find is at the top of the list.
Boards with over sized holes use more chemicals to plate the PTH, and
waste solder in the hand or wave solder process. We stuffed and placed
our boards at Microdyne, but used outside PCB houses to produce the
blanks. Some of our boards were 16 layer and cost over $8,000 to
populate.


--
You can't fix stupid. You can't even put a Band-Aid™ on it, because it's
Teflon coated.