DEEP HOLE DRILLING IN IT FOR THE LONG HAUL
One of the Unisig
machines at Ryerson’s
Houston facility
The company says that the successful
drilling of this component proves it can drill
holes in any shape of component by utilising
the versatility of the HD1, which has a
working capability of drilling 150 mm holes
in material with KSI values up to 140 (965
MPa). In addition, the machine can
counterbore up to 250 mm diameter and up
to 3 m deep, while encompassing an overall
workpiece diameter of 700 mm.
Of course, there are occasions when it
makes more sense for manufacturers to
invest in their own deep hole drilling
machinery as an alternative to outsourcing.
One company that has taken this very route
is Ryerson, a provider of bespoke metal
products with over 100 locations in the US.
The company’s Houston facility has recently
installed two Unisig deep hole drilling
machines (www.unisig.com), including a B600
model.
“We’ve been expanding our presence in
the bar and tube market in recent years,”
says Kevin Bury, oil and gas market manager.
“As a result, we decided to purchase two
deep hole boring and drilling machines. Now,
instead of having to expedite something with
one of our third-party drill shops, we’re able
to bring it in house and supply products to
our customers faster.
“We use a counter-rotational drilling
method for our bars,” he continues. “To
explain further, the bar is spinning in one
direction, with the drill head rotating the
opposite way. This technique creates a
straighter hole for our customers and gives
them better starting material for their nished
products. A lot of companies can offer deep
hole drilling, but few have invested as heavily
as us.”
Matt Cockerell, operations manager at
Ryerson, adds: “With our capability to drill bar
in house, it saves the customer time and
money; less transportation costs and less
handling costs. In addition, they are assured
of quality, as we use state-of-the-art
technology such as ultrasonic thickness
gauges. Through this process, we’re able to
adjust our Unisig deep hole drilling machines
in real time to make sure that we drill a
straight hole.”
The Unisig machines can drill bar
measuring up to 444 mm outside diameter,
with a length up to 6.1 m. Ryerson can
produce holes from 50 to 150 mm diameter,
with the envisaged future potential of going
up to 200 mm.
How long should gundrilling take?
Gundrilling is a special machining process, so there can be a lot of
confusion about basic variables such as cost, quality and lead
time.
“The design and speci cation phase is absolutely crucial to
successful gundrilling,” says Andrea Rodney, director at Hone-All
Precision (https://is.gd/ozenof), which is based in Leighton
Buzzard. “This is where a little time should be allocated, as
checking the ner detail on technical drawings makes all the
difference to a successful outcome. Crucial determining factors
are the bore and concentricity tolerances, as these affect the
requirements for additional honing or turning and, therefore, lead
time.”
A good manufacturer will review and invest a little time into this
part of the process. Some orders are very easy to calculate;
others may be more complex.
“High quality gundrilling is all about technique,” Rodney
continues. “There are four critical variables that need to be
calculated and controlled: ow rate, pressure, speed and feed
rate. In addition, the calculations depend upon the material, as
well as the diameter of the bore.”
Other process factors that need to be considered include
preparing for material property variables or other machining
issues. The size of the order will also make a signi cant
difference.
“As such, the length of the manufacturing process can be quite
varied,” she reports. “An average feed rate is around 10-20 mm/
min, but the real key is how smoothly the workshop operation is
managed. Here at Hone All, we usually dispatch orders within a
week when they are for the gundrilling process alone. Should bore
tolerance or concentricity requirements be tighter than the industry
standard of ±0.1 mm, then a honing or turning operation will be
added, which can potentially add a few more days to the lead
time, but inevitably ensures the overall quality of the part prior to
nish-machining operations or treatment.”
74 September 2019 www.machinery.co.uk @MachineryTweets
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