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  1. #1
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    Default Deep hole drill questions

    I have been plagued with having to drill roughly 1/2"D holes through 4140 pre hard round stock. 20-30" deep. I do not own a gun drill machine. Any method of doing this on a lathe better then a few hundred pecks with a long twist drill? Fab up a drill bushing holder and buy a gun drill, hold in tailstock, have at it?

    It's for a grease passage. No tolerance on size, shape, location, etc.

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    I've gone that deep in 1045, but never 4140. I have a Sterling gun drill with spray mist. Hi pressure is better, but too pricey. You'll need a very slow feed rate. Like maybe .0008, or even less. RPM @ 1000 max. If you should chose to buy one, Doug Holley at Sterling is a great guy and very helpful. And you can always contact me with questions as well.

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    Quote Originally Posted by Mebfab View Post
    ....Fab up a drill bushing holder and buy a gun drill, hold in tailstock, have at it?
    .
    If you have the length this can be done as a sort or make-your-own gundrill.
    You can even eliminate the bushing if you can bore a straight starter for the drill. (drill a bit under and plunge bore with a endmill).
    Gundrills do require blow through to move the chips out and high pressure works best.
    Remember that they only have one effective tooth so feed rates need to comply with that.

    OR- find a source with a high pressure gundrill. It might be worth your time and effort saved.
    Twist drill this length wind up and unwind like springs when pecking.You have to go so slow and the tip has to be centered just so right on the body.
    A OD guide land like a reamer side for the first bit of the drill helps keep you from wandering, snaking and locking the whole thing up. Sort of making a flexie gun drill with two flutes but now that becomes a very special made tool.

    I'm surprised you get away with the poke,poke,poke method at all at your max lengths in pre-hard.
    Care to share cycle time doing so?
    I'll go first with a gun drill on production parts so very optimized. 20-26 inch long, same hole and about same material with a carbide gun drill.
    2-3 minutes per part but a dual drill spindle machine so 40 parts per hour. I know way slow and yes, this was a major bottle neck in the flow.
    Some like their axle shafts solid, some like them cored and others like them tubes. You make what they want.

    So easy to poke this hole in the CAD in any material, maybe not so easy for those who have to actually make it.
    Is this one to ten holes or ten thousand and more over the next one to two years?
    Bob

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    I had a similar job years ago. I had a W&S #4 turret lathe and drilled halfway from both sides.
    It went fairly quickly.

    Probably not the answer you were looking for.

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    We have never used these guys ourselves but our tooling rep recommended them for a project we were looking at. Might be worth a call. Drill Masters Eldorado Tool | DMETool.com
    We were looking at getting a gun drill to run on our lathe at the time. The plan was for a Capto connection that we could quickly swap in and out. Thankfully the rods are coming in pre-drilled so never had to deal with it.

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    30 years ago that was a $40 dollar hole on a gun drill. The owner was an old man who used modified lathes for his round stock drills. He spun both the part and the drill where possible. All the carriages had variable speed drives so he could get the chip he needed.

    1/2" is an awfully large grease hole.

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    On a manual lathe I would mount the (parabolic deep hole) drill to toolpost and use carriage for drilling. Much faster than (normal) tailstock for pecking.
    Probably faster than gundrilling when you have no tolerances or surface finish requirements.
    You might be able to use only about 50% of SFM compared to gun drilling but your feed per rev is about 10 times bigger.
    Getting any coolant to your bore is the biggest problem with twist drills but frequent pecking helps a lot.
    I'd also probably use at least 3 different length of drills for the job. (I have also used through-hole ER collet chuck on toolpost and withdrawn the drill more as the bore gets deeper)

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    Do you want to drill 20 inches with a 3/16 drill? Its half inch cuz thats much easier, not cuz it needs to be that big. I would drill it from each end. Pilot drill then core drill 3 or 4 inches at a time? Make a long holder for the pilot drill?

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    Quote Originally Posted by MattiJ View Post
    On a manual lathe I would mount the (parabolic deep hole) drill to toolpost and use carriage for drilling. Much faster than (normal) tailstock for pecking.
    Probably faster than gundrilling when you have no tolerances or surface finish requirements.
    You might be able to use only about 50% of SFM compared to gun drilling but your feed per rev is about 10 times bigger.
    Getting any coolant to your bore is the biggest problem with twist drills but frequent pecking helps a lot.
    I'd also probably use at least 3 different length of drills for the job. (I have also used through-hole ER collet chuck on toolpost and withdrawn the drill more as the bore gets deeper)
    Closest response to what I could "afford to do" if the useful "poor man's W&S / Gisholt" of the HBX-360-BC "capstan" TS with its generous clear-through-bore wasn't here.

    This job, grease not being fussy as to alignment, I'd "go halves" for two shorter drills producing easier to clear holes, coolant-thru HSS helicals.

    They'd be juiced at "shock, awe, and gawdawful MUCKING FESS" levels. No "neat" way to do that cheaply that isn't also SLOW.

    On the big column drillpress. Not the lathe.

    "Holes" is ALL it does, but it does them faster, hence cheaper.

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    Sometimes you can do this sort of hole as a step process, using extended "regular" drills with rod or tube shanks pressed or soldered on.

    In other words, first 8" 1/2", next section 15/32" for 8", etc. Keeps friction to acceptable levels, allows standard long fluted drills, and doesn't compromise the intended purpose (lube hole). May want to turn the ends of the drill down a little to beef up the extension wall, or have a larger step (1/16" rather than 1/32").

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    I wonder if someone will chime in with spreadsheet data.

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    Quote Originally Posted by Mtndew View Post
    I wonder if someone will chime in with spreadsheet data.
    I want to see that picture of the drill in the monitor again.

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    Quote Originally Posted by Mtndew View Post
    I wonder if someone will chime in with spreadsheet data.
    It ain't but a grease passage. F**k-about data good enuf?


    Ex: AB5/S is a tad short of max stroke, even dual-sided as yah need 2 sides X approx 12" to not make it into a career screwing with no-space setup.

    But then again, I'm sleeving down off a native 5 MT. So all I need is to break the march, insert an extended MT adapter, once per side.

    Or go over to the mill, which has powered Z as well as an advancing quill and thru-bored spindle.

    JMNSHO, but THIS hole on a lathe is a waste of time and skill if all it be is an oil or grease passage. Should be better-paying work for the lathe, DP faster and cheaper for-sure, mill "maybe" as well.

    "Decent" mill, of course. Average BirdPort may not have powered Z or much twisting force, either.

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    Quote Originally Posted by tonymor View Post
    We have never used these guys ourselves but our tooling rep recommended them for a project we were looking at. Might be worth a call. Drill Masters Eldorado Tool | DMETool.com
    We were looking at getting a gun drill to run on our lathe at the time. The plan was for a Capto connection that we could quickly swap in and out. Thankfully the rods are coming in pre-drilled so never had to deal with it.
    I can vouch for their gun drills. I've used them quite a bit before switching over to the Mitsubishi MVS drills, though we still use them for certain projects.

    Another, though more expensive option would be to use the Iscar Sumogun. It comes in 400 or 800mm lengths and works pretty well as long as you can get the feeds and speeds just right. Took us a bent drill to get it figured out, but out Iscar rep comp'ed us for it.

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    I have drilled quite a few deep holes with standard gun drills and a lathe. I made an adapter that is turned down to fit into a drill chuck on one end, has a socket for the drill on the other, and has a 1/4 pipe tap in the side. Buy a line lubricator, fill it with 10% coolant, and plumb into the 1/4 pipe hole, use full line pressure and all the RPM you got. Put the grooved side of the drill down to deflect the chips and crank it slower than you think you should. If the chips make a sound like constant popcorn you are about right. I sneezed one time and lost a $100 drill do to the twitch on the handle.

    Ed.

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    Quote Originally Posted by atex57 View Post
    I have drilled quite a few deep holes with standard gun drills and a lathe. I made an adapter that is turned down to fit into a drill chuck on one end, has a socket for the drill on the other, and has a 1/4 pipe tap in the side. Buy a line lubricator, fill it with 10% coolant, and plumb into the 1/4 pipe hole, use full line pressure and all the RPM you got. Put the grooved side of the drill down to deflect the chips and crank it slower than you think you should. If the chips make a sound like constant popcorn you are about right. I sneezed one time and lost a $100 drill do to the twitch on the handle.

    Ed.
    Yep, here's the popcorn.
    YouTube

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    Quote Originally Posted by tonymor View Post
    We have never used these guys ourselves but our tooling rep recommended them for a project we were looking at. Might be worth a call. Drill Masters Eldorado Tool | DMETool.com
    We were looking at getting a gun drill to run on our lathe at the time. The plan was for a Capto connection that we could quickly swap in and out. Thankfully the rods are coming in pre-drilled so never had to deal with it.
    I've used the Eldorado Tool drills before & they're great, as long as you have the coolant pressure to evacuate the chips. Just drill a pilot hole and go straight through with the gun drill. Follow their recommendations and the holes come out true & straight.

    Otherwise just send the parts out to a gundrilling shop. For what they charge it's not worth your headache & tooling cost.

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    I'm sure Mebfab has this base covered - but I'll ask anyway, because it wouldn't be the first time it's been ''missed''

    Has the lathe you're planning to use enough length for both the workpiece and drill?


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