Long hole drilling?

Have to drill a 0.062" hole, 3" deep in 7075 aluminum, needs to be very straight, what's the best way to do it?

Reply to
Terry Keeley
Loading thread data ...

Yowza...

Now if this is a serious job, that's a serious job!

Presuming it is a "blind" hole and not a through hole...

Peck lots. Maximum RPM. Coolant. Pray.

Reply to
Joe AutoDrill

You might get a shop with sinker and wire EDMs to do this job. Expect to pay big $.

Karl

Reply to
Karl Townsend

Or find another way to do what you want. If you need more than a couple, think seriously about redesigning the part so you don't have to deal with this potential nightmare.

Reply to
Jim Stewart

Never heard of using EDM on AL before, but not in that line of work. Always see EDM on hard tool steel or similar.

Reply to
Pete C.

Redesign it, or glue in a tube.

Nick

Reply to
Nick Mueller

Criminey! I'm not even sure where you would get a drill long enough to do that.

Pete

Reply to
Pete Snell

That is a 48xd hole. That is gun drilling territory.

formatting link
iirc, 1/4" od tubing for waterjet systems has a 0.062 id to handle the

60,000 psi operating pressures so maybe using a tube as Nick suggested would be an good idea. It would get the l/d ratio down to 12.

Back when I had responsibility for intensifier systems I purchased tubing and other items from:

formatting link

Wes

Reply to
Wes

The current stuff Hi Pressure sells is 0.083 id. Specs must have changed over the last 7 years. Perhaps autoclaveengineers has 0.062.

Sorry about false lead.

Wes

Reply to
Wes

Yow, lot's a "ya can't get there from here" answers, ahhh, I love a challenge...

Thought I'd throw it out to this bunch 'cause I know there's some pretty sharp minds in here.

Can't redesign the part, it's for a water pickup rudder blade for my "toy" boats.

My thinking is to center drill, then use a stub drill to start the hole right. I'll then use a Cleveland brand "taper length" parabolic flute drill to do the drilling. Obviously lots of pecking and coolant, but what about rpm?

Any other suggestions?

Reply to
Terry Keeley

I do too. Except my challenge is usually how to build 1000 units for $.25 each (:

Reply to
Jim Stewart

Make the part in two halves (thickness-wise!), mill a slot in each half, use a 1/16" dia ball nose endmill if you must, and rivet/stake/ weld/fold the two halves together.

If you must epoxy them together you should place a 1/16" dia filament of teflon or polyethylene in the slot so as not to fill it.

If the part is thick enough and the hole can be square, mill a slot

1/16" wide x 3/32" deep. Then mill a second slot say 3/16" wide x 1/32" deep, co-linear with the 1/16" slot. Epoxy or stake in a 1/32" thick cover strip to form the hole.

Let us know what worked.

Wolfgang

Reply to
wfhabicher

Mill a slot and glue/solder/bolt a cover over it or cast the aluminium around a steel tube.

Mark Rand RTFM

Reply to
Mark Rand

Greetings Terry, A gundrill shop can put that hole in for you. They drill very straight holes. You can also make a "D" bit drill to do the hole. I would be tempted to do that. An aircraft extension or a taperlength drill would work I suppose but they have a shank that tapers so that it doesn't bind in the hole. A "D" bit drill will fit the hole snugly the whole (hole) length. This method will take some time but may your best bet for putting a very straight hole yourself. ERS

Reply to
Eric R Snow

Novel idea but it'll never hold up to water pressure at 100+ mph...

Reply to
Terry Keeley

Thanks, never heard of that, is this right:

formatting link
Are they sold anywhere?

Reply to
Terry Keeley

Terry, what exactly are you trying to do here? It sounds like you've really painted yourself into a corner. Why does the hole have to be so straight and so deep? What if your part had .062" holes on the front and back but quite a bit larger in between?

It sounds to me like you might wind up having this part cast, and putting a piece of skinny graphite rod or something in the mold as a core. If your cored hole were slightly undersized, but really straight, then it would be a lot easier to get a long long drill to follow the hole. You'd still need to do a whole lot of pecking. A D-bit would be a really good idea for this job, but it would take awhile to peck your way through.

GWE

Reply to
Grant Erwin

So, how straight is "straight"? Does it actually have to be straight? Will you scrap the part if the hole bends a couple of diameters? What's going through the hole? You're not within the realm if idealism any more.

RPM for a 1/16" drill in aluminum? As fast as your machine goes.

Calculation:

RPM = (4 x CS)/dia

=(4 x 300)/.0625

= 19,200 RPM

Use coolant, not oil.

If you're feeding by hand in a drill press, make sure your machine is well oiled and the feeding mechanism isn't sticky. You're going to need to be able to feel any resistance as this generally means your flutes are jammed with chips (and it's time to pull the drill out to clear before the drill breaks at the bottom of your hole). Additionally, you'll need to be gentle when bringing the drill into contact with the bottom of the hole after each peck. Ramming it will likely cause issues.

Best of luck. The hole is certainly possible, but it's unlikely the hole will be "very straight" by any professional standard You will need to be patient and gentle. Hope you've got a really nice drill chuck, and drill press.

Regards,

Robin

Reply to
Robin S.

Reply to
Grant Erwin

The RPM is the same for a long drill as it is for a short one, you just have to make sure that you don't let the chips build up and jam the drill.

How thick is the rudder?

Can you just cut a slot on the leading edge of the rudder and form a piece of aluminum tubing into the slot? the leading edge of the slot could be reestablished with an aluminum filled epoxy.

Not sure about toy boats, but on our old boat the pitot tube for the speedometer was not attached to the rudder, there was a small fitting attached to the transom and a plastic tube was attached to that. Seems to me that kind of setup would be a whole lot easier to rig than an in the rudder solution.

Reply to
Roger Shoaf

PolyTech Forum website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.