Machining
Drilling
We drill flanges to the ASME B16.5 and B16.47 bolt patterns, exchanger tubesheets and plates to drawing.
What we do
- Drilling of ASME flanges and to drawing
- Exchanger tubesheets
- Tapped holes
Materials
Capacity, maximum dimensions and lead time on request: send the drawing. See alloys in stock.
How drilling works
Drilling opens through or blind holes with drills, and may be followed by reaming, counterboring, countersinking or tapping. In flanges and tubesheets the position of the holes is as important as the diameter: the bolt circle and the angular spacing must match the mating part.
Drilling of flanges and tubesheets
Flanges follow the bolt pattern of ASME B16.5 (up to 24") or B16.47 (Series A and B, above 26"), with the number of holes, diameter and circle defined by the pressure class. Heat exchanger tubesheets have many holes with tight pitch and tolerance, and each hole must line up with the baffles and with the other tubesheet. The B16.5 and B16.47 flange tables show the standard dimensions.
Drilling difficult alloys
Stainless and nickel alloys work-harden at the bottom of the hole if the drill hesitates. We use carbide or cobalt drills, continuous feed, through-tool coolant when possible and chip-breaking cycles in deep holes.
What to send with a quote request
To get a quote, send the drawing with tolerances and surface finish, the alloy and standard, the quantity and whether the part starts from bar, from a forging or from material you supply. Parts in special alloys are usually cheaper when the forging is already made close to the final shape, and we do both steps.
Supply tolerances
Machining allowance and tolerance for forgings, band saw cuts, machined parts and waterjet cutting are in Dustre's tables (INF 002 and INF 003): see supply tolerances. To size the forging from the finished part, use the open-die forging calculator.
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Frequently asked questions
What is the bolt pattern of a class 150 or 300 flange?
The number and diameter of the holes and the bolt circle are defined by ASME B16.5 for each nominal diameter and pressure class. The flange tables on the site show these dimensions.
Do you make non-standard flanges?
Yes. Special, blind, reducing flanges or flanges with custom bolt patterns are forged and machined to the customer's drawing.
Does Dustre perform this service on customer-supplied material?
Yes, as long as the alloy and the specification are defined. We can also supply the material from our stock, with EN 10204 3.1 certificate.
