Drills for oilways?

[Rik ShawParticipant @rikshaw]

I bought a large crate of tooling yesterday at the boot, mostly drills, reamers taps etc. about 15 kilos in all, some new and some hardly used from 2mm to 25mm dia. I was told that it was being disposed of at the end of a "one of" CNC product run. For the price of three pints of amber nectar I happily became the new owner.

In amongst it all were five of these of different diameters – 2, 3, 4 and 5mm. I have never seen anything like this before and can only assume they are for extending the depth of an already drilled hole. The chap I bought them from mentioned engines and if my assumption is correct could these have been used for finishing oil ways to depth?

As you can see from the pictures the last inch or so at the business end is made from carbide / like material. I am truly amazed at how ( especially the 2mm dia. one) how they managed to get that tiny curved thro' coolant hole machined down the 120mm long stem – spark erosion?

Rik

[Rik ShawParticipant @rikshaw]

………these are new on me.

[Michael GilliganParticipant @michaelgilligan61133]

… that's rather impressive !!

I suspect that the list price would make the eyes water.

MichaelG.

[martin perman 1Participant @martinperman1]

They look like deep hole drills, the hole in the end for pumping the coolant into the hole to clear the swarf and cool the drilling, funnily enough I have just written a short piece on Archdale deep hole drilling rigs for another magazine, the company I worked for used to drill 2 – 3 mm holes into fuel injector bodies for about 4 inches.

Martin P

[JasonBModerator @jasonb]

Rik, is it the photo or are they tapered? as the business end looks smaller

[Rik ShawParticipant @rikshaw]

Jason – It must be the photo – its the way I take 'em

No, the carbide business end is not tapered but it does stand proud of the rest of the stem by a few 'thou. All bar one are made by MOLLART the odd one out is by GUEHRING.

[martin perman 1Participant @martinperman1]

Mollart machine tools, that's a name from the past, I used to repair their deep hole drilling machine back in the eighties as a machine tool fitter.

Martin P

[Clive HartlandParticipant @clivehartland94829]

I am pretty sure they are known as, 'Gun Drills' for drilling deep holes in tough steel like crankshaft oilways and longer ones for actually drilling gun barrels. The coolant is force fed down the tube to flush out swarf so thatn it does not clog or mar the drill bore.

Clive

[jason udallParticipant @jasonudall57142]

Well…the spiral flute through coolant drills I uses were made by in effect the lost wax process…the coolant holes were made from nylon ( I think nylon..might have been another plastic).rods .twisted in a jig..then drill material sintered around.then part of the final sintering process burns out the plastic…
Straight flutes and holes would have other options. of course

[martin perman 1Participant @martinperman1]

We knew them as Gun drills back in the eighties but on Mollarts website today they refer to them as deep hole drilling machines.

Martin P

[Brian WoodParticipant @brianwood45127]

Rik,

I rather supect the coolant hole was formed into the final forged drill body using a blank having a filler wire in a drilled hole. Rolls Royce did very similar work in difficult turbine blade nimonic alloys where they called the process 'coining' with several small holes fitted with wires that could be acid etched out after forming the aerofoills to provide forced air cooling to the installed blades.

Keeping the correct wall thickness over the cooing passages in the finished aerofoil cross section was a special skill the forging deparment kept to themselves.

The outer shape of these drills is identical to that of gun drills where the drilled hole is burnished at the same time as being drilled , the head acts as a guide and with special machiinery depth to diameter ratios of 400:1 can be achieved.

Brian

[Oompa LumpaParticipant @oompalumpa34302]

Posted by Michael Gilligan on 23/03/2015 13:05:00:

… that's rather impressive !!

I suspect that the list price would make the eyes water.

MichaelG.

You are not wrong Michael. When they finally arrive you put them next to the job and studiously walk around them for the next couple of weeks really hoping the job will do itself before finally putting your (my) head down and getting on with it.

Hoping to God you don't break one!

It would be advantageous if I had the right machine. I don't so sooner or later it is going to end in tears.

graham.

Edited By Oompa Lumpa on 23/03/2015 20:42:53

[websnailParticipant @websnail]

We called them gun drills and used them to drill holes (dia 8mm) around 800-900 mm deep in 316 Stainless.

Not by hand but two holes/workpieces at a time. Re sharpening them was also done on a cutter grinder in house.

I can't remember what bar oil pressure we used but it was a bit silly, I do remember the machine took over 40 gallons of cutting oil which after a days drilling was rather warm!

[Trevor WrightParticipant @trevorwright62541]

Know them as 'gun drills' and will cut dead straight, dead size and highly polished. Must have coolant through the centre tube though.

The best peice of kit I have ever used. Officially they guarantee a 1mm wander for every 1 metre drilled, pretty good.

The first time I used them on a Nimonic alloy we had a spray mist device working off the air line and it stank, didn't do the chest a lot of good either.

Second time years later on Titanium I used the 'through the spindle' coolant on the CNC. It cut like butter but sprayed the whole shop with coolant…….cutting time was 2 hours for the batch and 2 days to clean the mess. The bore to cut was Ø11.03/11.00 so we ordered Ø11.015 drills and it cut Ø11.015, straight through in one cut. You have to pre-bore to start though but after that just watch the swarf fly out of the hole.

Trev

Edited By Trevor Wright on 24/03/2015 13:20:46

Edited By Trevor Wright on 24/03/2015 13:23:41

[Michael GilliganParticipant @michaelgilligan61133]

Impressive tales of Gun Drilling … but what really amazed me about Rik's collection is that they start at 2mm.

MichaelG.

[Ian S CParticipant @iansc]

Trev, that's why machines these days are in cabinets, and you see what's going on through the window.

Ian S C

[Clive HartlandParticipant @clivehartland94829]

I have seen a video of Tank gun barrels being bored and they were using a massive Gun drill, just a big brother of the one in the picture.

Then they showed how the rifling was cut and the retractable cutter. In use the whole operation was smothered in cutting fluid which washed away all the cuttings.

Clive

[Trevor WrightParticipant @trevorwright62541]

Was apprentice then NC miller at the ROF Nottingham where all the tank barrels were made, 'solid centre boring' as it was called then always fascinated the visitors. The 'drill' had 3 cutting teeth and carbide runners down the side to make it follow the hole already cut. It was never more than 1/4" out over 25ft. There were stories from the old boys who drilled them during WW2 of drills going from either end and completely missing each other, the barrels were 4-5" bigger on diameter to accomodate the drill wander.

Fascinating place to work – all flattened now with a Homebase, Experian and a bank on the site. Went the same way as Raleigh cycles another major Nottingham engineering company, it is student accomodation now……progress.

Trev

[Rik ShawParticipant @rikshaw]

Tank gun barrels / artillery barrels? Reminds me of a conversation down the local a number of years ago when someone had heard that a bunker busting device had been dreamed up by some boffin. It involved welding sheet metal fins to the thin end of a large gun barrel and then filling the barrel with explosive.

It was all contrived with the utmost haste to the extent that the "stores" were still hot from poured explosive when loaded onto their delivery platforms.

I believe that the idea met with a degree of success!

Rik

[Clive HartlandParticipant @clivehartland94829]

When the barrels have fired their EFC's they are condemned and replaced. A tank gun can fire a variety of projectiles like APDS and HE. The HE has the least effect on the barrel as it is slow but the APDS is very fast and wears the barrel away very quickly in as little as 200 rounds.

The idea of bunker busting bombs is an American idea as they had need to get the explosive very deep under ground and make a mini earthquake to disrupt the reinforced concrete structure. Using worn out gun barrels is a good way of using them instead of scrapping them. A delayed fuse and dropped with Laser precision marker and weighing maybe 1 and a half tons they penetrated very deep in the earth alongside structures.Disrupting caves where things are stored like in Afghanistan was one area of operations. Also concrete aircraft hangers.

Clive

[Ian S CParticipant @iansc]

Like Barns Wallis's earthquake bombs, they were up to 20,000 lb, a full load for a Lancaster.

Ian S C

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