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November 2013
Produce Straight-Sided Holes with
a Shaving Operation
When punching holes in sheet metal, the die must be larger than the punch. Depending on the
material type and thickness, the die might be oversized by 20% of the thickness (10% per side). During
punching, the top portion of the hole shears straight down roughly one third of the metal thickness,
then the material breaks away toward the edge of the die. This results in a “tapered” hole that in
some cases can be a problem. For example, if the holes will be tapped, the breakaway may reduce
the number of good threads in the hole.
In many cases it is possible to eliminate breakaway by performing a “shaving” operation on the holes.
The general idea with shaving is to pre-punch the hole using normal procedures, then post-punch the
hole using a very tight die clearance. This process saves time by keeping your material in the same
machine.
Shaving Procedure
Pre-punch Operation:
The pre-punch holes must be slightly smaller than your final desired hole size.
To determine how much smaller, choose a die size that is very close to the desired diameter of
your final hole.
Then, subtract your die clearance from the desired final hole diameter (or size of your die) to
determine your pre-punch size.
Also consider that the amount of material removed by shaving should be at least 10% of the
material thickness, which leaves enough material for the die to retain the shaved slug.
Post-punch Operation:
Post-punch operations require a tight die clearance of about 1 to 1.5% per side. Too much
clearance can cause the need to re-shear the hole.
The shaved hole size will be slightly smaller than the actual punch size caused by elastic
recovery of the material, (usually by 0.0002 – 0.0004) so you may need to increase the size of
your shave punch.
A guided stripper plate is helpful in maintaining accurate alignment, which can be difficult due
to the very close clearances and higher than normal cutting forces associated with shaving
operations.
A good lubricant should also be chosen to aid in your post-punch operation.
Fig. 1 provides a close-up view of the concept.
Sample Shaving Operation:
Looking to make 0.394” (10mm) diameter holes in 0.236 (6mm) thick mild steel.
Die will be 0.394” (10mm).
Typical die clearance for this thickness is roughly .05” (1.2mm), which means the pre-punch
size should be .344” (8.8mm).
Pre-punching to .344” (8.7mm) leaves .025” per side for shaving, which is just over the 10%
safe mark.
Knowing that the shaved hole size will be slightly smaller than the actual punch size of 0.394”,
we need to increase our shave punch to 0.395” (10.03mm) diameter. And the die clearance for
this should be between .004” and .007” (0.1mm and 0.2mm).
FABTECH FOLLOW-UP
All New In Blue
Despite some rocky (or windy) weather at
the beginning of the week, FABTECH 2013
had a great showing! A special thank you
to all of our customers who dealt with
travel difficulties to get there this year.
FABTECH is always a great way for
fabricators and manufacturers to see new
technologies, vendors and potential
purchases all in one place. We at Wilson
Tool enjoy this as well, but what we
mostly appreciate each year is being able
to talk with you, our customers, in person
about your successes and how we can
create solutions to your challenges.
This year was an especially exciting year
for us with a brand new tradeshow booth designed to give you a better experience and provide a
solutions based environment. Our booth featured live video conferencing back to Wilson Tool’s world
headquarters in White Bear Lake, Minnesota, where customers were able to instantly receive quotes
on tooling or follow up on current orders.
In addition to our new booth, we unveiled
an exciting new printing technology
created to enhance your production and
save you time and money. Watch for more
details on this in the future.
Other products featured this year were:
DuraBlade Trumpf® Style Punch Assembly
The new DuraBlade Trumpf style slitting assembly from Wilson Tool gives you consistently accurate
slits while our Optima® coating gives you more hits between regrinds and combats galling on the
punch tip. This tool is specifically designed to allow for slitting close to forms, but can also be used
for normal slitting operations. The punch blade is made from Ultima® steel for increased tool life and
is replaceable for fast, cost-effective tool replacement. Visit the DuraBlade product page >
Wilson Wheel® Rolling Forge
The Rolling Forge is the first tooling solution that helps you create sizeable, buckle-free embosses in
your punch press. Its innovative design works with the natural movement of your sheet metal to craft
smooth, impressively high shapes and forms that are completely free of distortion, every time.
With the Rolling Forge, you can create unique shapes, such as embosses and offsets, that were never
before possible in a punch press machine. For more information, click here.
View the Rolling Forge video >
Happy Thanksgiving!
The busyness of the holidays is upon us, and too
often we don’t enjoy them the way we should. We
at Wilson Tool would like to wish you all a happy
Thanksgiving with the hope that you would be able
to slow down and enjoy time with your family and
friends. We are thankful to have you as customers –
we wouldn’t be here without you!
Faces of Wilson Tool
Kelly Paulson
Credit Control and Payroll Specialist
Years at Wilson Tool: 2
What is your favorite aspect of your job?
Constantly learning, every day is a new day and no two
days are the same.
What do you enjoy doing in your free time?
Being my children’s biggest cheerleader.
The Art of Bending.
No other tooling provider understands the
complexities of bending metal like Wilson
What is something that people would be surprised to
Tool International®. Whatever your challenge
learn about you?
– increasing tool life, reducing setup time or
I walked 120 miles in the fight against breast cancer.
simplifying a complex bend – Wilson Tool
offers more choices for better bending.
If you had to eat only one food item for the rest of
Precision, staged and conventional press
your life, what would it be?
brake tooling. Manual and hydraulic clamping
Pizza!
solutions.
Where is the most interesting place you have been?
Custom tooling for challenging applications.
Why?
Whatever you need, Wilson Tool can provide
Mexico. Love fun in the sun!
a solution.
UPCOMING EVENTS
Wilson Tool on YouTube
Wilson Wheel Training
December 10, White Bear Lake, Minn.
SIGNUP >
Wilson Tool HPX Guide Assemblies
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Wilson Tool International 12912 Farnham Avenue, White Bear Lake, MN 55110 - 800-328-9646
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