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  1. #1
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    Every once in a while, someone showed me a great little "trick" to fix a machining problem and I'll pass a couple along. Feel free to share your little tricks that someone taught you or you came up with yourself.

    Reamer not reaming to size:

    An old mold maker I worked for showed me this one. One day I was trying to ream a hole with a rather dull reamer in a Bridgeport. It was a good sized one, say 1". It got to the point where the reamer squeeled and spun in the collet and I couldn't finish the hole. So he showed me a quick fix. Took the reamer out and grabbed a dowel pin. He rubbed the pin along the inside of the cutting surface of each flute. (I've used HSS also) Put the reamer back in and no squeel and the hole was within tolerance.

    Turning a thin, long diameter:

    I had to turn about a hundred pins from 303 SS hex stock 3/8" with a diameter of a #6 screw and length of 2".

    The diameter was too small for our live center. Our smallest center drill was too big for the tip of the part (needed 6-32 threads on end), besides, the lathe tool would not clear the centers we had. We didn't have any box tools so I attempted to turn the pins unsupported with dismal results. Way too much flex. Solution was to take a broken center drill and grind it down to where it would clear the lathe tool and then ground a sharp point on the end. With the parts spinning and the modified centerdrill in the tailstock, I would feed the modified centerdrill into the end of the parts, say .015-.020", just enough to support the end for turning. Put grease in the hole, run the modified centerdrill as a center and it worked great. Just kept coolant on the center to keep it cool. It lasted for the whole order and could do another couple hundred.

    Dowel pin location:

    Always was told that center drilling and drillindg a hole in a bridgeport was only good for +/- .002-.003" accuracy. Not up to +/- .0005 for dowel pin hole locations. Without a jig borer we went to drilling the hole locations 2 drill sizes undersized. Then "bore drill" with the largest drill available to leave stock for the reamer to clean up. By "drill bore" I mean drill with slow enough feed so that the drill doesn't follow the existing hole but actually bores the hole true to the spindle axis. Stub the drill up as short as possible to get to your depth. If you have an undersized endmill, use that instead. I know that you are still at the mercy of how accurate your Bridgeport can locate, but this has woked for many a parts.

    If you guys have seen better ways of doing things, share away.


    Steve

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  3. #2
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    How dare you ask for the secrets of this trade?
    do you wish to have these guys take you work away?

    for really accurate positioning on a Bridgeport wring jo blocks of the desired distance to go and zero against a tenth indicator, the move the table to zero...jim

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  5. #3
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    toolmaker-

    Great suggestion. I've been burned on long distances in a B.P. trusting the digital. The dimensions would always be on the long side. So I tried what you suggest and it worked great. I would pin the first hole then gage block the distance and edge find the gage blocks.


    Steve

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  7. #4
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    well that works and i just finished a job using my DRO and gageblocks as a cord-ax moch the same way, but heres what i meant.
    machine a t-nut to fit the t-slot on the front of the table. take a 1-2-3 block and mount to the table. wring the jo-blocks for the moves you need and insert into the t slot and zero your tenth indicator. remove the jo-blocks and make your move...jim

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    Here's my tip -- I have a steel roll around cart that I load up with the tools I need for a specific task and roll it over to the job. I also use this cart for assembly and disassembly. I had a problem with small parts and stuff like sockets rolling off the cart. I covered the cart top with a piece of short napped carpet -- this keeps stuff from rolling off and gives the cart a nice soft surface to keep from scratching painted parts.

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  10. #6
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    toolmaker-

    I like your method better. Edge finding on gage blocks isn't a good idea.

    Edge Finding on a Bridgeport:

    This is probably pretty basic for most but for the newbies this is what I do. Set your knee at the height that will get your tools to clear the set-up. Lock the knee and don't move it if you're trying to hold accurate distances. Lock the axis that you are not edge finding. If you are setting your x, lock the y-axis. This will help eliminate the error in the ways. Snug up the x-axis lock and turn the spindle on with the edge finder in a collet. (I use a good drill chuck for general stuff) I run my edge finder at 1500 rpm. When it kicks out, zero the digital, back off and repeat to see if it kicks out at the same number. When I get two digital readings the same for the kick-out of the edge finder, I set zero there and move over the radius of the finder. Oops, almost forgot. Check that head to see it is trammed in.

    Weirsdale-

    I agree, a cart is so much easier than carrying your junk around.


    Steve

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  12. #7
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    a good point i forgot to mention.
    if you are working in a shop where some one may use the machine you were on yesterday ALWAYS check the head tram every day before starting work. just may save you a greater head ache at 9:30...jim

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    For dull reams that tend to cut very slightly undersize, i take a carbide insert and run it against the inside cutting edge of the flute. Kind of like using a "steel" on a good knife. slide it one way only, tip to end (the other way damages the tip cutting edge). This raises a slight cutting edge on each flute. do carefully, for doing too much, and you cut OS - WHICH LEADS ME TO MY NEXT ONE

    To ream a hole slightly OS, do the same. I can get .001 to .002 doing this, but the ream tends to stay that way.

    Another way of reaming OS slightly. take a small wood matchstick and fill one flute with matchstick. ream, keep the matchstick in the hole. The "offset' of the matchstick pressure will help the cut go OS. This is a "bedside reader trick".

    Had to mill a slot .498 width once in a machining test in my apprenticeship. All I had allowed was a 1/2 end mill, and it was actually .501. The tol was +.001, -.005. I remember this well, because I remembered my mean old german apprenticemaster who used to yell, scream, and beat our knuckles and minds - he showed us the trick in advance when the rest of the apprentices were hung over or just plain old 'acting stupid" and "too smart" (read - not freaking listening at all) that day (thus is why he put it on the machining test, to humble our young punk fannies). He did the slot very last for this reason, after finishing the rest of the part. He put the mill in the slowest speed possible, moved the end mill right up to the edge of the movable jaw of the vise- hard jaw, determined the slot depth, put the end mill a bit lower than that, and ran the end mill backwards very lightly against the hard jaw end edge. Just enough to burr it "forward" about .006 in diameter.

    Then he cut the slot, measured, and be darned, he had enough room to do a climb cut of .001 on each side of the slot to make an exact .499 slot.

    The rest of he apprentices were not listening, they wre talking going to the bar again, but I was listening, for I was flailing at that point, and decided a week before that if I really wanted to do this stuff, LISTEN to your elders. I decided to give him a chance

    Then - he burred it back to size with a piece of carbide - which is where I learned the carbide trick on reamers to begin with.....

    he was amazed that I learned this, and the others failed, we talked, he got my gist that i had been a bit of a fool the first 1/2 year, wanted to get back in right, and he took me under his wing (still yelled and beat my knuckles and mind with amazing consistency - and yes, I was not at all sad when my time was up with him). I learned more in two years from him than any guy on earth, and wrote it all down. Love to share this stuff now.....

  14. #9
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    An easy way to get to the center of a shaft or pin for drilling is to bring your c'drill down to the part and touch it lightly, just enough to make a mark.
    Lock the quill.
    Drag it back and forth once, and put it right in the center of the line you just made.
    Depending on your eyes you should be w/in a few thou.
    A quick and dirty trick.
    Takes 10 times longer to type it than to do it.

    jack

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    please keep these going!
    This is what a machine form is all about!!

  16. #11
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    Three jaw chuck that runs out:

    Ever get stuck with a lathe that only has a 3 jaw chuck that won't run true but you have a part that needs .001" concentricity? I saw this in the Illinois Railway Museum where they had a large lathe and in the big 3 jaw chuck was a 4 jaw chuck in which the work piece could be indicated in as accurate as needed. Beats the trial and error shim routine.

  17. #12
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    a trick to get a 3 jaw to run closer.Indicate piece and use a brass or lead hammer and tap on the high jaw.Will work on wore chucks.Never hammered on a good one. [img]tongue.gif[/img]
    Jim

  18. #13
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    Another 3-jaw trick: after measuring TIR, shim the "high" jaw with a shim thickness of 1/3 TIR. (e.g. TOTAL measured runout = .006, use .002 shim in the high jaw.)

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  20. #14
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    Thanks guys, I love this stuff!

    If I knew ANYTHING, I would share it.

    Rick

  21. #15
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    When ever I have tapped a hole and the threads are a little tight, I have had good luck wraping a rag around the tap and doing it again. An old toolmaker showed me this 35 years ago.
    Michael

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  23. #16
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    Deep hole drilling in a lathe:

    Ever have to drill several inches in a lathe and got worn out cranking on the handle to back the drill out to clear the chips, just to have to crank the drill all the way back in to start drilling again?

    Set your starting depth and lock the tailstock in place. Now move the saddle back until it bumps against the tailstock and lock it in place. Start drilling. When you're getting to the point where it takes longer to crank on the hand wheel than you care for, loosen the tailstock, pull it back to clear the chips, shove the tailstock forward until it bumps the saddle, lock the tailstock, and start drilling again. This is faster than doing all of that cranking but you won't lose track of how deep you have drilled.

    Steve

  24. #17
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    Forrest Addy turned me on to this nice shop tip a couple of years ago.

    When tramming your mill use a solid 1-2-3 block to span over the T-slots in the table.

    Works like a charm and you won't ever damage your test indicator by mistakenly smacking it into the side of a T-slot.

    -Matt

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  26. #18
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    Got yourself one of those 3/4 id by 4" long bushings you bored that are just a hair undersize and don't really want to take another cut 'cause you might blow it? Too long to get your finger in there with abrasive paper, and besides, don't want to twist off a finger anyway.
    Take an old broomhandle, aluminum rod, whatever, cut a slot with your bandsaw, hacksaw, in the end , wrap the paper around in the direction the spindle's rotating, insert it in the bore, and go to town.
    Your large handground drill cutting on one side only? Driiling oversize?
    After grinding, blue both cutting edges, start drilling again.
    Take the drill out and check the cutting edges.
    The side thats heavy will have the blueing removed.
    Re-grind that side only, re-blue and try again.
    Keep it up until you have equal blue removed from both edges.
    That should give you a nice free-cutting drill that cuts close to size.

    jack

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  28. #19
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    When I am working on extremly messy tasks like cleaning bearings, painting, etc., where I don't want to spend a half hour trying to clean my hands, I use exam gloves available at home healthcare stores. Get the Synthetic Vinyl (I know that is redundant, but that is what the box says), Powder Free ones as they seem to hold up to solvents a little better than latex ones.

    Everyone may know this, but when repacking bearings, put some grease in a plastic sandwich bag and squish the grease into the bearing.

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  30. #20
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    I don't have a solution to a problem, but do have a question if someone wants to educate me.

    A few years back I was working in a racing engine shop on a part time basis. One of the operations we did in a Bridgeport clone, was to drill out crankshaft counterweights to accept Mallory metal to aid in balancing the total rotating mass, i.e crank, rods, pistons, pins, etc.

    I had made an adaptor to hang the cranks off the mill table and we would rotate the mill head, so we were vertical over the crank flange. We then drilled the hole undersize by about .015 and reamed to size with a .750 (new) straight shank reamer (with cutting fluid hand sprayed on the operation).

    The problem was the reamed hole was coming out about .003 oversize. While this was not a major problem, because we welded the balance metal into the flange, I never understood why it was not reaming to size, so the metal slug would be a slight interference fit?

    For clarification, the reamer was measured and it was to size. Also, nothing was moved between the drilling and reaming operation.


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