drilling/boring a very long hole?

[SPiN Racing]

Morning gang,

I have an idea/project I have, and Im trying to understand/crack how to accomplish it, and or ask for the proper thing when I go have this done.
I have a bolt, that is appx 2 feet long. It is a strong bolt, that is under some measure of tension, and will encounter a bit of vibration. The bolt is strong enough, and there is no real threat of it breaking as it is. I do not believe its hardened, it is a normal bolt.. even though its about 1/2 inch in diameter. You can drag a file across the shaft of it, and it will make a mark.
This being said... How does someone drill a hole through it? This is NOT a firearm.. but I was thinking something like a smoothbore barrel.. someone has to drill those out I would assume.
That being said... what would I ask for if I was gonna go someplace and ask them to do it? And or.. do they even drill them? Or are they forged that way?

The project needs a hole 1/8 inch or slightly larger through it. The inner bore is not critical.

 

Thanks for any insight!
(Yes I have a bridgeport, and a 11x36 lathe.. but dont think I have anything like the tooling to do it.)

[BillTodd]

For a 2 foot x 1/8"hole you will need a gun drill (e.g. http://www.sterlinggundrills.com/)

These are far too expensive and troublesome for a one off, so you'll probably want to find an engineering shop willling to under take the task - oh and take a well filled wallet with you ;)

[edit]

You might just be able to find hollow bar stock about that size , if the hole dims are not critical

[dickda1]

You might drop a note to Guy Lautard over in Canada.  He built a refiling machine and has written quite a bit about how to build and use gun drills.

http://lautard.com/rmv.htm

-Dick

[Lew_Merrick_PE]

Spin --  ø.125 X 24.00 deep is nothing trivial.  A gun drill would be the best way to drill it, but figure you will be paying for a full hour of shop time to get it done ($50-$125 depending).  However, a set of (12 + a skosh long) bell hanger's drill bits might work for you.  I would definitely set my nominal diameter as large as possible (ø.188 would be a major improvement).  Start with a ø.125 long drill and drill just short of half-way through from each end.  Move in very carefully.  Withdraw the bit to clear out the chips and relubricate everything about twice as often as you think necessary (or even four times as often).  Redrill to (say) ø.156 (5/32) going past the half-way mark from each end (being exceptionally careful at breakthrough.  Finish off by drilling out to (say) ø.188.

Keep all your lucky charms within reach.  Stroke them regularly.  Clear chips & lubricate (repeat, repeat, repeat) -- and you might be able to pull it off.  (I had to drill 200 gas-reaction latches ø.094 X 8.00 deep some years back.  It took me approximately 275 pieces of bar and probably somewhere close to 60 drill bits to finish the job.)

Good luck!

[AdeV]

You MIGHT be able to get a custom-made twist drill in that sort of size, but expect to pay $$$$ for it.  The one I used here: http://madmodder.net/index.php?topic=2726.msg30078#msg30078 cost me £180... but that's 5/8" x 600mm flutes; you want 1/8" which I imagine would be a tall order...

[75Plus]

1/2" OD X .188 ID steel tube is a standard size that can be found at most steel suppliers.  Is there any reason that it could not be used?

Joe

[SPiN Racing]

I really appreciate all the feedback guys.

I didnt realise the drills would be 100+ bucks PER DRILL.

I want to make a working prototype.. and see if the idea I have can be functional.. In my head it works. BUt in reality it may not be so functional LOL. I would have to spend 500 or a 1000 in drills only to find that its not functional.

I remember the issues Ade (i think) had with the sump project.. and I have been happily using my peck drilling fixture for holes up to 2" deep. BUT even with that in full peck mode.. the swarf still is a issue in the smaller holes and I broke my share of smaller drills getting used to drilling stainless. (sadly the majority of the material have IS stainless)

I think the option Joe mentioned of simply buying a steel tube with an appropriate ID may well be the simplest option. I can then add on with welding and or machining, a head to the bolt at the proper location, and still have the through hole in the length of it. Cut some threads in it, and harden as needed.

Thanks so much everyone.. THe difficulty of drilling, and COST of drilling.. I think is prohibitive cost and time wise since it doesnt need to be something silly strong like a barrel, to drill it myself.. or pay someone to do it.

[SPiN Racing]

Actually a clarification of purpose might work well for everyone LOL.

Mazda rotaries have tension bolts that hold the whole thing together. Like a big dagwood sammich. The bolts on those are around 18" long. They also make a tension STUD kit for them, that has very very hard studs that are a interference fit, and have nuts on the end of them. The studs are appx 18" long as well.

Im not making studs/bolts for that application.. as the hollow stud may have vibration and strength issues. As the factory studs usually have a swirl of silicone in the middle of the shaft to hinder vibration. But I want to do a similar function on a different application.. and need some length to the stud/bolt. SO it needs medium strength and a hollow center. No specific inner bore.. but it will help as weight is a bigger factor. It needs the full length bolt.. and diameter. But instead of making a hourglass stronger bolt.. hollow seems a good idea.. and allows strength to remain resonable vs a skinny high strength bolt.

[75Plus]

A 1/2 X 20 thread on the end, capped with an acorn nut and Loc-Tited should retain most of the strength while taking on the appearance of a bolt. That end would also contain any liquid filler without leaks.

Joe

[loply]

I think you could make a drill like a gun drill quite easy.

What I would do is get a rod of suitable length which is just a tiny bit undersized, somehow attach a drilling end to it (like the end of a gun drill), and about 3 inches behind that I would put a bush that is the size of the final hole, and another bush another 3 inches behind that.

Then just drill away!

The bushes should keep it on-track once it's entered the hole drilled by the thing.

You will have to clear out the chips quite often.

Only tricky bit is designing/getting/attaching the drilling end...

[Fergus OMore]

The classic way to drill is to use a silver steel( that's key steel) and make a 'D' bit end. It is then tempered light straw and this will do exactly what a gun drill will do- but more slowly.

Ask yourself a question of 'How did all these bagpipe makers  make their instruments'?  In fact, all the parallel borings of less than 1/8th were done this way- and into far more awkward hardwood with grain etc.

The work was done on far less sophisticated lathes than you possess.  Many of the makers were shepherds working after a long, long day with no more than kniitting needles borrowed from their wives.

OK, let's come to your problem and make it a bit easier and the modus operandi is more or less as follows.

1. The bar is held at the chuck end in a 3 or 4 jaw chuck.
2. the working end is held in a steady. If the work is not round, you will have to make a cat head to fit the steady.
3. the end is centred with a centre drill
4. The tail stock poppet/barrel is removed and replaced with a bored out steady just over the 1/8th.
5, the D bit has a flat at the free end to take a tap wrench/or similar holder.
7, the real work of carefully drilling can now start and before the D bit flat is full of swarf, it is removed, cleared and the boring commences and is repeated until the lot is done.

If you dont know what a D bit is, it is merely a halved end -perhaps half an inch deep but the end is left -0.065" thick and the cutting end about 5 degrees.

[75Plus]

The bushes should keep it on-track once it's entered the hole drilled by the thing.

It is absolutely imperative that the hole is started accurately .

Once the drill is inside the hole no amount of bushings will have any effect on how true the hole will be.

Joe

[Fergus OMore]

The bushes should keep it on-track once it's entered the hole drilled by the thing.

It is absolutely imperative that the hole is started accurately .

Once the drill is inside the hole no amount of bushings will have any effect on how true the hole will be.

Joe

This why I stated the use of the  cat's head , the centre drilling  and the slow, steady drilling.

I think that Joe and I have 'been there'

[jim]

http://www.cromwell.co.uk/quicksearch?search=shr-024-2101m&x=0&y=0

not that dear!

[AdeV]

Unfortunately, the OP requires a 1/8" x 24" (600mm ish), the longest I saw was 315mm...

Although they don't go up to 5/8" x 600 (the size I got), based on their prices I wasn't ripped off (which is nice).

[Fergus OMore]

What you have to remember is that the chuck end of a drill is soft-- and therefore can be drilled-- and a  slightly undersized rod silver soldered to give the length plus room to work outside the tailstock.

I've seen pipe makers who have adopted these but the danger- IMHO- is clogging the flutes-- somewhere.
The drill then goes off centre, wanders  and pops out-- somewhere- but not where you want it.

It was with these points in mind that I penned my experiences.

[AdeV]

Fergus - John Bogstandard suggested the exact same technique to me when I was drilling out a motorcycle swing arm mounting tube, I used a blacksmith's drill with a mystery steel extension shaft; because the blacksmith's drill has a smaller shaft at the end, I drilled out my steel rod rather than the drill. I didn't bother with silver-solder, I drilled through both & used a pin, peened over at both ends to stop it falling out.

I initially had a lot of problems with it binding up in the hole; I had to grind a fair amount off the drill bit itself, probably only leaving 2" of flutes at the original size, before I could get it to drill straight & true without binding.