Clearance holes
90° CSK
Post-bend
Drilling & countersinking, in Bolton.
Clearance holes and flush-head fixings done in-house — including features that need to be positioned after bending, or in material the turret punch can't handle cleanly.
Secondary machining
Holes that can't be punched or lasered — done here.
Laser cutting and CNC punching handle the vast majority of holes in sheet metal work. But there are always exceptions — features that need to be positioned after the part has been bent, holes in material that's too thick for the punch to handle cleanly, or countersinks that weren't in the original punch program.
Our pillar drills cover these cases in-house. The Pollard 130F/4 and the English Electric ADBM5A are both solid, accurate pillar drills that handle drilling and countersinking across the full range of materials we work in — mild steel, stainless, aluminium and galvanised. Jobs that need drilling go straight to the drill after punching or bending without leaving the building.
Countersinking is available as a combined operation: drill to clearance size and countersink in one setup, to the correct included angle and depth for your fastener. For flat parts, in-turret countersinking on the Amada EMZ 3510 punch press is often faster and better suited to volume runs.
What we do
Two operations. Both in-house.
01 / Drilling
Clearance and close-tolerance holes
Drilling to a specified diameter — clearance holes for bolts and fixings, pilot holes for tapping, large-diameter holes that the punch tooling can't produce cleanly, and holes positioned after bending where the punch can't reach. We use HSS and cobalt drill bits across mild steel, stainless and aluminium.
02 / Countersinking
Flush-head fixings — 90° included angle
Countersinking to accept flush-head fasteners — countersunk screws (ISO 10642 / DIN 7991), flush rivets, and similar. Standard included angle is 90°; other angles on request. We set depth to bring the fastener head flush with the surface or to a specified stand-off. For flat parts, in-turret CSK on the punch press is available as part of a punching program.
Capability
Drilling specifications.
Two pillar drills for in-house drilling and countersinking. In-turret CSK also available.
MachinesPollard 130F/4 · English Electric ADBM5A
In-turret CSKAvailable on Amada EMZ 3510 (flat parts)
CSK angle90° standard — other angles on request
MaterialsMild steel · Stainless steel · Aluminium · Galvanised
Post-bend drillingYes — confirm access at quote
Lead time5 working days standard
Drill vs punch/laser
When drilling is the right call.
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Post-bend — punch can't reach
Once a part is folded, the turret punch can't access features on bent flanges or inside profiles. Drilling handles post-bend hole placement accurately and in-house — no second supplier required.
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Thick material — punch would mark or deform
For material above the punch's practical limit, or where punch marks on the face are unacceptable, drilling is cleaner. Particularly relevant for stainless in heavier gauges.
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In-turret CSK for flat parts
If the countersink is in a flat part and it's already going through the punch press, in-turret countersinking is faster and more cost-effective. No separate operation needed.
For your quote
What to send for a quote.
Clear callouts on the drawing make the quote faster and the job right first time.
- A DXF or dimensioned drawing with hole positions, diameters and any CSK callouts.
- CSK spec if applicable — included angle (usually 90°), head diameter, flush or to dimension. The fastener standard (ISO 10642 etc.) is fine if you prefer.
- Material and thickness — affects drill selection and whether in-turret CSK is possible.
- Quantity — and whether this is a one-off or repeat run.
File formats accepted
DXF
DWG
STEPPDFSketch
No DXF? A dimensioned PDF, STEP, or a sketch with hole sizes and CSK angles noted is fine.
Why BSM
Drilling in-house keeps the job together.
No second supplier for secondary ops
Drilling and countersinking run alongside punching and bending in the same production order. Parts don't leave the building to have holes added.
Post-bend features handled in-house
Folded flanges that need drilled or countersunk holes are a common requirement. We handle these in-house without any additional logistics.
Right process for the feature
Flat parts with CSK go in-turret on the punch. Post-bend or awkward features go on the pillar drills. We route correctly — not everything needs to be the same process.
The family trade since 1979
Sheet metal runs in the family. Bolton Sheetmetal Ltd since 2011, family-run, debt-free. Documented processes and first-off sign-offs in place — working towards ISO 9001 certification.
FAQ
Drilling & countersinking, asked & answered.
What hole sizes can you drill?
We drill a wide range of sizes on our Pollard and English Electric pillar drills. Send the drawing with hole sizes called out and we'll confirm at quote stage.
Can you countersink and counterbore?
Yes to both. Countersinks for flush fasteners and counterbores for socket-head cap screws. Call the angle and depth on the drawing and we'll match it. CSK features on flat sheet can also be formed in-turret on the punch as part of the punching cycle — no secondary operation needed.
What materials do you drill?
Mild steel, stainless steel and aluminium — the standard fabrication materials. For anything unusual, send the drawing and we'll advise.
Can you drill post-bend or in awkward positions?
Yes. Folded flanges that need drilled or countersunk holes after forming are a common requirement. The pillar drills handle features that can't go in-turret because the part is already bent.
Do you drill free-issue parts?
Yes. If you're supplying flat or formed parts and need drilling or countersinking only, we can take them in as free-issue. Call out the features clearly on the drawing.
What tolerances can you hold on hole position?
Standard positional tolerance is ±0.25mm. Tighter is sometimes achievable on smaller parts — tell us what the drawing demands and we'll confirm at quote stage.
Ready when you are
Need holes drilled or countersunk?
Send us your drawing with hole positions and any CSK callouts and we'll come back with a price within the working day.