1
MGR — Mécanique Générale
Gerzat (63)
Workshop located in Gerzat offering machining, milling, turning and drilling services on high-precision parts. Serves a diverse industrial customer base including aerosp…
Machining process
Deep Hole Drilling: Machining Subcontracting Guide
Deep hole drilling refers to the machining of holes whose depth greatly exceeds their diameter, with length-to-diameter ratios ranging from 10:1 to over 100:1. This process uses dedicated tooling (gun drills, BTA/STS systems) fitted with a chip evacuation system and high-pressure coolant delivery to maintain hole straightness and clear material along the entire bored length. It produces bores for hydraulic cylinders, shafts, injection mold cooling channels, gun barrels or heavy mechanical parts, wherever conventional drilling becomes unstable or imprecise.
Where to find a deep hole drilling workshop
Cities are ranked by number of listed workshops. Each page details the companies and their specialities.
Choosing the right supplier
When to choose this process over another
Deep hole drilling becomes necessary once a bore exceeds a length-to-diameter ratio of about 10:1, beyond which conventional drilling drifts off-axis, overheats or breaks the tool due to poor chip evacuation. It is used for hydraulic cylinders, long transmission shafts, cooling channels in molds, precision gun barrels or components for the oil and gas sector. Depending on the target depth and diameter, the shop will select either gun drilling (for smaller diameters and moderate depths) or a BTA/STS system (for larger diameters and very deep bores), which directly affects lead time and technical feasibility.
The criteria that truly set two shops apart
Machine capacity is the first filter: maximum achievable depth, diameter range covered and the length-to-diameter ratio genuinely handled without repositioning. Next comes guaranteed straightness, expressed as deviation per meter of drilling, often the most discriminating parameter for this type of part, along with diameter tolerance (typically IT8 to IT9) and the resulting surface finish. Machinable materials also differ: standard steels, stainless steels, nickel-based alloys and aluminums do not behave the same way under deep hole drilling and require different cutting parameters. Finally, available inspection means (ultrasonic straightness checking, borescope inspection, coordinate measuring machine, roughness testing) and the ability to hold repeatable runs are good indicators of a shop's real maturity with this process.
What to prepare to get an accurate quote
A dimensioned drawing specifying depth, diameter, location and expected straightness tolerance is essential, as is the exact material grade and its condition (raw, heat-treated, hardness). State the quantity of parts to be produced, since the resources involved (tooling, setup) differ between prototype and series production. Any heat treatment or surface treatment planned after machining should be mentioned, as it may affect the final dimensions to anticipate. Finally, communicating the desired lead time and, if possible, providing the raw part geometry allows the shop to assess feasibility and quote without guesswork.
Materials most often worked with this process
deep hole drilling workshops
A selection of listed workshops, all cities combined.
2
BMP — Berland Mécanique de Précision
Clermont-Ferrand (63)
Support from design to delivery: milling, turning, drilling, tapping and grinding of medium-sized parts, with drawing optimisation by an in-house design office.
3
C.F.U.P
Montpellier (34)
4
Harreguillier
Roanne (42)
5
L.A.T.S. Précision
Besançon (25)
Company based in Besançon specializing in wire EDM and micro-drilling from 0.15 mm. Processes steel and carbide parts for tooling and prototyping applications. Meets sin…
6
MGP - Mécanique Générale de Précision
Mazières-en-Mauges (49)
7
MPI Mécanique de Précision Issoirienne
Saint-Rémy-de-Chargnat (63)
8
Paret-Gris
Montpellier (34)
9
PROMECA
Colmar (68)
PROMECA is a precision general mechanics workshop offering CNC machining, twin-spindle turning, milling and surface and cylindrical grinding. The company processes ferro…
Frequently asked questions
What drilling depth can be achieved with this process?
This depends on the target diameter and the technique used. With gun drilling, length-to-diameter ratios of 20:1 to 30:1 are common; with a BTA/STS system, ratios can exceed 100:1 on larger diameters. The actual depth available depends on the travel capacity of the shop's machine.
What straightness can be guaranteed on a deep hole?
Deviation depends on diameter, depth and the material being machined. It is generally expressed as a fraction of a millimeter per meter of drilling. This value should be specified in the technical specification, as it determines the technique and tooling chosen by the shop.
What materials can be machined with deep hole drilling?
Most steels, stainless steels, aluminum alloys and certain nickel-based alloys are compatible with this process. Hard or poorly machinable materials require adapted cutting speeds and coolant flow rates, to be confirmed with the shop before starting production.
What's the difference between deep hole drilling and conventional drilling?
Conventional drilling is suitable for holes whose depth stays close to the diameter. Beyond a length-to-diameter ratio of about 10:1, chip evacuation and tool guidance become critical, requiring the dedicated tooling and high-pressure coolant system specific to deep hole drilling.