What is the difference between deep-hole drilling and ordinary boring on a lathe?

In ordinary boring on a lathe, the overhang and stiffness of the boring bar quickly limit the bore depth (typically a few times the bore diameter). In BTA deep-hole drilling, the drill head is supported in the bore itself via guide pads, while high-pressure oil cools and carries the chips out through the drill tube. This makes it possible to drill precise holes from Ø18 to approx. Ø850 mm in part lengths up to 20,000 mm.

Which bore diameters and lengths can be supplied with deep-hole drilling?

As part of our delivery programme we offer centric BTA deep-hole drilling in bore diameters from Ø18 mm up to approx. Ø850 mm and part lengths up to 20,000 mm (solid drilling up to Ø380 mm / 15,000 mm; counter-boring up to Ø850 mm / 20,000 mm). The maximum outside bearing diameter is Ø1,750 mm (flange diameter up to Ø2,000 mm) and the maximum part weight is 50 tonnes.

Can 42CrMo4 and 34CrNiMo6 be supplied through-bored in the +QT condition?

Yes. 42CrMo4 (1.7225), 34CrNiMo6 (1.6582) and 30CrNiMo8 (1.6580) are frequently supplied as quenched and tempered round bar (+QT), sawn to fixed length and deep-hole drilled to the required bore diameter. The part is then ready for finish turning on receipt.

Can both through bores and blind bores be produced?

Yes. In addition to through bores in round bar, shafts and tubes, blind bores can be produced, as well as bore bottoms with full radius or flat bottom with radius transition to technical drawing.

Does the blank need a centre bore before deep-hole drilling?

No – in BTA deep-hole drilling a centre bore must not be made in the end face, as a centre bore disturbs the guidance of the drill head during entry. A square sawn end face is normally sufficient, and for tighter precision requirements the end face and any bearing seats are face-turned as part of the job.

Are the EN 10204 3.1 certificate and traceability retained after deep-hole drilling?

Yes. Material marking and heat number are transferred under control (re-stamping to EN 10204 2.1, 2.2 and 3.1), so the finished bored and cut part is delivered with full traceability to the steelworks' 3.1 certificate.

Machining

Deep-hole drilling and through-boring of special steel to size

INDUSTRISTÅL A/S offers deep-hole drilling and through-boring of special steel as part of our delivery programme. Many of our customers already have their special steel bored to size, so the material is delivered with the required bore diameter and length, ready for further machining. We combine the supply of special steel with customer-specific machining and thereby offer a complete solution.

Request a quote +45 77 34 00 96

Technical envelope

Bore diameter (BTA): Ø18 – approx. Ø850 mm
Part length: up to 20,000 mm
Outside Ø / swing Ø: bearing Ø up to 1,750 mm · flange Ø up to 2,000 mm
Part weight: up to 50 tonnes
Methods: solid drilling, counter-boring, trepanning, pull boring and honing
Documentation: EN 10204 3.1 with transfer of heat marking

What is deep-hole drilling?

Deep-hole drilling (long-hole drilling) is a specialised machining process for producing centred bores with a large length-to-diameter ratio in solid steel and forgings. In centric BTA deep-hole drilling, cutting oil is supplied under pressure around the drill head while the chips are evacuated internally through the drill tube. Guide pads on the tool guide the drill head in the bore itself throughout the operation. This ensures a stable process, good surface quality and high straightness – also in long parts that cannot be produced on conventional lathes or milling machines.

Solid drilling: drilling directly into solid round bar, square bar or forgings
Counter-boring: enlarging an existing bore for higher accuracy or larger inside diameter
Trepanning: cutting an annular groove in Ø200–380 mm (up to approx. 3,000 mm depth), where the core is retained
Pull boring of tubes: internal boring of tubes in Ø45–300 mm in lengths up to approx. 13,000 mm

Through-boring of round bar and special steel

As part of our delivery programme we supply round bar, forged shafts, thick-walled hollow bar and square bar with customer-specific through-boring or as a blind bore with flat bottom or radius transition to drawing. By having the part bored before delivery, your own workshop avoids the most time-consuming rough machining, reduces tool wear in quenched and tempered grades (+QT) and shortens throughput time in the CNC lathe. We supply single pieces, small batches and running series.

Possible bore diameters and drilling lengths

The technical envelope for deep-hole drilling in our delivery programme covers everything from smaller machine components (from approx. Ø50 × 100 mm) to very large and heavy forgings. Specific tolerances, requirements for bore straightness (centre run-out) and any subsequent honing or pre-turning of bearing seats are determined from the drawing and on enquiry.

Standard bore diameter (BTA): Ø18 mm to approx. Ø850 mm (larger diameters in special cases on enquiry)
Solid drilling in solid steel: bore diameter Ø18–380 mm and part length up to 15,000 mm
Counter-boring to finished or pre-machined size: up to Ø850 mm and part length up to 20,000 mm
Outside part dimensions: bearing diameter in steadies up to Ø1,750 mm, flange/swing diameter up to Ø2,000 mm and piece weight up to 50 tonnes
Centric drilling in square/cubic solid material: inside diameter up to Ø380 mm (larger on enquiry)
Supplementary honing (cross-hatch grinding): inside Ø36–400 mm and length up to 5,500 mm (down to Ra 1.6 µm; tighter fits such as IT7 on enquiry)

Relevant steel grades

Deep-hole drilling is carried out in the great majority of structural steels, quenched and tempered steels, case-hardening steels, tool steels, pressure vessel steels as well as stainless and highly alloyed special alloys. In Danish machine and energy industry, demand is particularly high for through-bored round bar in the quenched and tempered condition (+QT).

Quenched and tempered steel (+QT): 42CrMo4 (1.7225), 34CrNiMo6 (1.6582), 30CrNiMo8 (1.6580), 25CrMo4 (1.7218) and 34CrMo4 (1.7220)
Non-alloy structural and engineering steel: C45 (1.0503), C60 (1.0601), S355J2 (1.0577) and 20MnV6 (1.5217)
Case-hardening, nitriding and bearing steel: 16MnCr5 (1.7131), 18CrNiMo7-6 (1.6587), 31CrMoV9 (1.8519), 34CrAlNi7 (1.8550) and 100Cr6 (1.3505)
Tool steel: 1.2343, 1.2344, 1.2379, 1.2714 (56NiCrMoV7) and 1.2510
Pressure vessel and creep-resistant steel: P250GH / C22.8, A105, 16Mo3, 13CrMo4-5, 10CrMo9-10 and P91 (1.4903)
Stainless steel, duplex and nickel-based alloys: 1.4301 (304), 1.4404 (316L), 1.4057 (431), 1.4462 (Duplex 2205), 1.4410 (Super Duplex 2507), Alloy 625 and Alloy 825

Typical industrial applications

Through-bored special steel is used wherever rotating or pressure-bearing parts require a precise longitudinal bore for fluid flow, weight reduction, cooling channels, passage of tie rods or as a pre-bore before finish turning.

Hollow shafts, gear shafts, reel shafts and spindles in machine building
Hydraulic cylinders, cylinder blanks and piston rods (possibly combined with honing)
Rolls, cooling rolls and rotors for process and heavy industry
Thick-walled hollow bar, bushes, liners and hollow-forged components
Moulds, mould tools and energy/offshore components

Advantages of buying material and machining together

When you order steel and deep-hole drilling as one delivery from INDUSTRISTÅL A/S, we coordinate the whole process from raw bar or forging to sawing, heat treatment and deep-hole drilling.

One overall price and one supplier – no separate purchasing of raw steel, coordination of subcontract work or intermediate freight
Less process risk – responsibility for the raw material's dimension and straightness matching the deep-hole drilling sits in one place
Option of drilling in combined lengths with subsequent sawing to fixed length when this gives a more economical unit price
Full heat traceability and re-stamping to EN 10204 3.1, so the certificate follows the finished bored and cut parts

Technical information for an enquiry

To calculate an accurate quote for through-bored special steel, please state the following parameters in the enquiry or attach a technical drawing:

Steel grade (e.g. 42CrMo4 / 1.7225, 34CrNiMo6 / 1.6582 or C45) and delivery condition (+QT, +N etc.)
Outside diameter (or cross-section of square bar) and whether the outer surface is rolled, forged or pre-turned
Required bore diameter (inside Ø) and whether the bore is through or blind
Part length (finished length incl. any sawing allowance) and the required number of parts
Any requirements for bore tolerance, straightness (run-out), surface roughness (e.g. honing) and certificate (EN 10204 3.1 / 3.2)

Frequently asked questions

What is the difference between deep-hole drilling and ordinary boring on a lathe?: In ordinary boring on a lathe, the overhang and stiffness of the boring bar quickly limit the bore depth (typically a few times the bore diameter). In BTA deep-hole drilling, the drill head is supported in the bore itself via guide pads, while high-pressure oil cools and carries the chips out through the drill tube. This makes it possible to drill precise holes from Ø18 to approx. Ø850 mm in part lengths up to 20,000 mm.
Which bore diameters and lengths can be supplied with deep-hole drilling?: As part of our delivery programme we offer centric BTA deep-hole drilling in bore diameters from Ø18 mm up to approx. Ø850 mm and part lengths up to 20,000 mm (solid drilling up to Ø380 mm / 15,000 mm; counter-boring up to Ø850 mm / 20,000 mm). The maximum outside bearing diameter is Ø1,750 mm (flange diameter up to Ø2,000 mm) and the maximum part weight is 50 tonnes.
Can 42CrMo4 and 34CrNiMo6 be supplied through-bored in the +QT condition?: Yes. 42CrMo4 (1.7225), 34CrNiMo6 (1.6582) and 30CrNiMo8 (1.6580) are frequently supplied as quenched and tempered round bar (+QT), sawn to fixed length and deep-hole drilled to the required bore diameter. The part is then ready for finish turning on receipt.
Can both through bores and blind bores be produced?: Yes. In addition to through bores in round bar, shafts and tubes, blind bores can be produced, as well as bore bottoms with full radius or flat bottom with radius transition to technical drawing.
Does the blank need a centre bore before deep-hole drilling?: No – in BTA deep-hole drilling a centre bore must not be made in the end face, as a centre bore disturbs the guidance of the drill head during entry. A square sawn end face is normally sufficient, and for tighter precision requirements the end face and any bearing seats are face-turned as part of the job.
Are the EN 10204 3.1 certificate and traceability retained after deep-hole drilling?: Yes. Material marking and heat number are transferred under control (re-stamping to EN 10204 2.1, 2.2 and 3.1), so the finished bored and cut part is delivered with full traceability to the steelworks' 3.1 certificate.

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Get a quote for through-bored special steel

State grade, condition, outside diameter, bore diameter, length, quantity and tolerances – or attach a technical drawing. We reply in English.