Tell us again how the end of your drill is sharpened. How accurately does the 5/16" drill enter the 1/4" hole, and start to walk? How fast are you feeding when the drill is "getting acquainted" with the new hole?
Just like in real estate... It's location, location. location...
I have a small lathe for occasional, quick jobs. The tail stock is not quite on center, but it doesn't bother for what it is used for. If I put a spotting drill with the flutes horizontal, the spotted hole WILL be off center. If I put the flutes vertical and feed in just barely, and back off, it acts like a boring bar on one flute, and the spotted hole is Dead on.
Same for you and your drilling technique in the plate. Just like with old people. It all depends.
Impossible to quantify. Too many variables. How much slop in the quill? How much wiggle in the table lock? How square is the table with the column and the head? How much runout in the chuck, mounting taper, drill bit? How good is the sharpening job? How are you going to check positioning?
Best way to do this is bore them out in a lathe, locating each one each time. Next best is to bore them out in a mill with a boring head. Third best is to use a piloted counterbore or some sort of piloted bit. About equal would be to make a jig with bushings, locating the bushing above the holes would be the catch.
For the best, accurate and predictible results.. start over with new stock.
A piloted cutting tool (for each different size) would probably be relatively accurate, if the pilot doesn't pick up a chip, and the cutting tool is nearly perfectly symmetrical (not as likely to wander from cutting forces).
A good set of eyeglasses to see the dimensions on the drawing.
Get the person that put the wrong numbers on the drawing to fix the parts.
And -- are the drills screw machine length, jobber length, or extended length? (Each listed is worse than the previous.)
For that matter -- how much drilling force? Crank down on the spider and the drill will bow -- and no bets as to which direction it will pick to go off center.
And the chances of finding a boring bar for the boring head which will handle enlarging the 1/4" hole to 5/16" may be difficult -- unless you make an adaptor for a tiny bar to an available boring head.
I have read the several replies. No one has mentioned using a reamer for the final cut. Am I missing something?
Bob AZ
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A reamer will give him accurate diameter and good roundness, but not location.
The whole job sounds like somebody messed up on the planning, or EA is trying to salvage or modify something that was intended for 1/4" holes.
Maintaining *accurate* location isn't going to be easy. But then, what kind of accuracy are you looking for, EA, since the holes were drilled to begin with? If you're looking for high accuracy, you're going to have to bore at some point in this process, because you can't rely on a stepped drilling process to give you much of anything, except holes.
I think I have missed the purpose of the thread. Opening up holes can be reasonably accurate for most purposes and the level of accuracy depends on common sense and your skill set, However, perfection cannot be reached with a common drill. If you are attempting to correct a slight position error, this is best done with a square endmill, not a drill. Steve
The reamer can produce final diameter fairly accurate, but they are known to follow pre-existing drill wandering, and will do nothing (in a drill press or by hand) to get accurate positioning if the position of the "just a bit smaller" hole is not already correct.
I don't know about a dishwasher for the task, but I have fixed a keyboard which was subjected to urine by a squirrel which we were raising in our house until he was old enough to want to move outside.
I took it into the shower, opened the case (to prevent pools forming, and rinsed it well with nothing but water.
I then stood it on end for a couple of days to properly dry out, reassembled it, and it worked fine. (This was back around 1976 or so.)
More recently, I've fixed Sun keyboards by complete disassembly (including separating the two flexible printed circuit boards separated by a clear mylar sheet with holes where the keys should deform the upper board to make contact with the lower), and blasting all of the parts (except the bucket of keycaps) with compressed air.
The problem with this keyboard was that cat hair had accumulated, first making it difficult to depress some of the keys (fixed by popping off the keycaps and cleaning with fine hooks), and later when the hair worked between the flexible printed circuit boards, some keys would not take without excessive force on the keycap. *That* was where the compressed air won.
Of course -- the Sun keyboards don't use foam rubber for springs. Instead there are a bunch of little "falsies" of rubber which give the snap feel as you depress the keycap, the keycaps and guides, occasional bails to keep wide keys from tilting and binding, and of course the circuit boards and the plastic chassis. If you have a keyboard which uses foam rubber, and need to clean out something like a soft drink or a beer, you'll have to separate the rubber and squeeze it quite a few cycles under water to work out the beverage which soaked in.
What works for a given keyboard depends on both what the original problem was, and how it is constructed. I could picture the dishwasher -- run without hot water and without drying heat, and with the keyboard stood to avoid pooling in the case working. But once it is out, especially if it has foam rubber, you may want to either let it dry for a week, or put it in a vacuum chamber for a few hours to properly dry it out.
Overkill, in more ways than one. Lean it up against a wall and spray a fine mist of household ammonia. Wait a few minutes and repeat, then another fine spray of water to rinse it. The crud runs off, not inside the case, due to the tilt. I've done hundreds of keyboards that way. I used to sell used computers, and a lot of the early ones were bought at Lockheed Martian auctions. They were almost black, having been used in their machine shops. I processed them five or ten at a time. I cleaned and waxed the computer & monitor cases, as well. They looked brand new with very little work, and no one ever came back with a bad keyboard.
Well there's always an off--chance that I was being facetious..
It was Boeing for me though I never sold any of the stuff--at one point they had several pallets stacked high with Dell Quietkey keyboards for 10 cents each and I simply couldnt resist dropping a few bucks...being careful to select only those that were from office areas--suffice it to say I still have enough keyboards to the rest of my life though at some point I may concievably need to wash a few loads. .
I'm down to about 200 spare keyboards, myself. Not counting a couple boxes of dead or damaged keyboards. I have people ask for a keyboard to use for a display or art project, so why give away the ones that work? :)
Posts, including my own, are disappearing left and right! In other ngs as well.
Inyone else seeing this? You know, first they get the dreaded line drawn through them, with the message no longer available on this server, then they disappear!
I called up optimumonline.net, and well, you know the story, newsgroups are not exactly their top priority.... But as far as they know, no real problem, and they aren't eliminating ngs...
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