Gun Drilling - Again - Expanded

Ok, my previous deep drilling operations went off pretty well. Carbide 3 flute drills worse used on a couple of them. One to start holes for a
hand ground split point, and the smaller hole with just a carbide jobber drill. Both actually met up in the middle close enough. One for a hinge pin and the smaller one for an injection cavity feature. They worked. Didn't actually do any gun drilling.
Now I am looking at an application that will need to drill straight (size is not highly critical), for from 20 to 28 inches for a water jacket.
The only machine i have I think would be suitable for it is the 14x40 engine lathe. Throwing a 20x30 inch piece of plate on the chuck is obviously not the answer. LOL. I was thinking to use some sort of tool holder in the spindle, and make a mount and support for the plate on the carriage. After doing a bit of reading gun drilling does not just use hydraulic pressurized oil. It is also done with pneumatic air mist under pressure. Now the trick I think is to figure out how to pressurize a spinning gun drill inside a lathe spindle. I have some ideas, but they are kind of vague at this point.
The thought of buying and setting up a dedicated machine down the road is not out of the question. Right now I am looking for the shade tree get it done short term solution.
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On 05/01/2020 17:50, Bob La Londe wrote:







If the pressure rating is OK SMC make some rotary couplings which take up to 10bar IIRC and are designed for continuous rotation at pressure. I use a SMC KSL06-01S https://www.smcpneumatics.com/KSL06-01S.html for an application but that's an elbow, I think they also do straight variants and I suspect other makers will do similar. May be suitable for your fluid feed.
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On 1/5/2020 11:01 AM, David Billington wrote:








If it can handle a modest continuous RPM that might just a good start.
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wrote:

Mounting the drill and delivering the oil (you're going to need oil for a hole this deep) to the drill is straightforward. A shaft that goes thru the headstock with a socket for the drill on the chucked end, and a female thread to mate with an appropriate rotary union on the opposite end, will do the trick.
Here's an example of a suitable union: https://www.deublin.com/1116-048-059/ There are somewhat cheaper options, but you want a union with ball bearings and a mechanical seal, not plain bearings & lip or o-ring seals.
The most expensive part, depending on how much you can scrounge, is probably the oil pump, reservoir & filtration. The drill mfrs supply data on req'd flow & pressure according to drill diameter.
You'll also need a way to control the chips & oil as they exit the hole, an accurate starting hole, and perhaps, depending on the depth to diameter ratio of the hole, intermediate supports for the drill shaft.
This is a typical setup, it could be simpler if you prebore an accurate starting hole instead of having the drill start itself, guided by a drill bushing, as shown. The chip box itself can be quite crude, depending on your tolerance for spraying oil. This chip box does not show where the chips & oil go; obviously you need to separate the chips and return the oil to the pump system. http://www.gundrill.com/
--
Ned Simmons

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On 1/5/2020 11:44 AM, Ned Simmons wrote:

Very helpful. Thank you.
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Air hose reels have rotary couplings.
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On 1/5/2020 11:46 AM, Jim Wilkins wrote:

Yep. Maybe something along those lines, but on an air hose reel they don't have to handle continuous steady RPM. Thank you.
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They also don't normally benefit from oil mist lubrication. You don't need the full drilling setup to test it, and if it doesn't last long enough just replace the O ring and put it back on the hose reel.
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On 1/5/2020 4:04 PM, Jim Wilkins wrote:

Yeah. I get it. I even considered a simple friction fit o-ring setup in an o-ring groove. O-rings are cheap to replace and then keep going. They would last a while at modest RPM.
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wrote:

Greetings Bob, I have had to design and build custom rotary unions for gundrills using o-rings for the sealing. I learned from Parker, the seal folks, how to do it. I had to do calculations for pressure and RPM but the gist of the design was to let the seal leak a little bit. This provides constant lubrication and keeps the seal from burning up. The reason I had to make the custom rotary seals was because we needed a few VERY high volume rotary seals for not that many parts and it was considerably less that buying a new rotary union from Deublin. If you do go the rotary union route then I suggest eBay for buying one because you can save a ton of money that way. Bear in mind that rotary unions can withstand much higher pressures and RPM if oil is being pumped through rather than air or air/oil mix. Eric
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If you don't have an air hose reel to borrow from you could try making a "shade tree get it done short term solution" from a pipe tee with close nipples in the ends and bored-out pipe caps compressing o-rings or graphited faucet packing string, running on a smooth brass pipe nipple or chromed shower arm (1/2" NPT).
According to my data the ID of 3/4" pipe is only 0.016" smaller than the OD of 1/2" pipe, so you could bore the nipples to whatever fit as you want on the rotating inner pipe, or use brass close nipples and turn the inner steel pipe smooth.
I use machined brass fittings chucked in the 3- or 6-jaw to turn or bore steel pipe concentric with its threads.
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On Sunday, January 5, 2020 at 9:50:47 AM UTC-8, Bob La Londe wrote:

A taut wire and EDM can expand a hole if you open both ends first.
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On 1/5/2020 10:50 AM, Bob La Londe wrote: > Ok, my previous deep drilling operations went off pretty well. Carbide > 3 flute drills worse used on a couple of them. One to start holes for a > hand ground split point, and the smaller hole with just a carbide jobber > drill. Both actually met up in the middle close enough. One for a > hinge pin and the smaller one for an injection cavity feature. They > worked. Didn't actually do any gun drilling. > > Now I am looking at an application that will need to drill straight > (size is not highly critical), for from 20 to 28 inches for a water jacket. > > The only machine i have I think would be suitable for it is the 14x40 > engine lathe. Throwing a 20x30 inch piece of plate on the chuck is > obviously not the answer. LOL. I was thinking to use some sort of tool > holder in the spindle, and make a mount and support for the plate on the > carriage. After doing a bit of reading gun drilling does not just use > hydraulic pressurized oil. It is also done with pneumatic air mist > under pressure. Now the trick I think is to figure out how to > pressurize a spinning gun drill inside a lathe spindle. I have some > ideas, but they are kind of vague at this point. > > The thought of buying and setting up a dedicated machine down the road > is not out of the question. Right now I am looking for the shade tree > get it done short term solution.
I think I have most of it figured out if using the lathe is the answer. Just the details of the actual fluid delivery and recovery to work out, and you guys have given quite a lot of information to help figure that out.
I figure I can mount a big right angle plate (I have one) in place of the compound, stand the plate on edge, and clamp it to it. I can stack blocks to get height if needed, and adjust with the cross slide. By putting the plate on edge it will virtually eliminate any material sag (a concern at 30 inches long) from over hang as long as the clamps do not slip.
The whole thing gives me ideas for solving some of my other deep drilling issues as well. Making them easier. Next is a stop switch on the carriage, so I can walk away for a minute without fear of a crash because I got distracted. I think the same kind of roller micro switch as is on the chuck safety cover. Maybe with a mag lock mount for rapid positioning. Allow it to over travel as it comes to a stop of course.
If only I could easily automate peck drilling with it. LOL.
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wrote:

I just set up an air cylinder to release the half nut on the carriage. I used a proximity switch to sense the carriage and thereby close a relay which powers a solenoid air valve. It works very well and allows overtravel of the carriage past the switch. The system repeats within .003" Eric
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On 06/01/2020 21:46, snipped-for-privacy@whidbey.com wrote:

An interesting modification but I wonder how fail safe it is in the case of power failure, the lathe would coast to a halt so I guess it depends how close the stop point is to the chuck. The reason I mention it is that a guy I used to work with mentioned operating a lathe with an air
jettisoned the part narrowly missing the guy, they fitted a UPS to that circuit shortly afterwards.
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wrote:


It's plenty safe because I'm at the lathe ready to stomp on the brake. I suppose I could connect the setup like all my other air operated clamping stuff so that when the power is off the part is clamped. So on the lathe power off would mean half nut disengaged. Eric
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You may already know, but this is a good place to show the motor control circuit that prevents the machine from starting unattended when the interrupted power returns. https://www.ecmweb.com/content/article/20885794/standard-motor-control-circuit-primer
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On Tue, 7 Jan 2020 16:45:55 -0500, "Jim Wilkins"

JPGs not available. Keywords: magnetic contactor, right?
--
There is nothing more frightening than ignorance in action.

--Johann Wolfgang von Goethe
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"3 wire control"
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