Are rolled threads stronger than cut threads?
Rolled threads can typically be 10-20 percent
stronger than cut or ground threads primarily due to the cold working and
displacement of material rather than the cutting or removal of material. Thread
rolling can also add to the fatigue and wear resistance, and increase
smoothness and hardness of the threads as they are planished in the forming
process. Other advantages may include higher manufacturing speeds and reduced
Do all fasteners need to be baked after plating?
No, not all need to be baked. The
primary reason that fasteners are baked after the plating process is to
help eliminate the possibility of hydrogen embrittlement, an undesirable time
delay deterioration of the base metal after the plating process. The
phenomenon can occur on fasteners over a certain hardness which makes
product grades 10.9 and above susceptible. Although baking is an acceptable
treatment it cannot completely eliminate the possibility of this undesirable
condition. Care should be given when baking to avoid disrupting the original
intended tensile strength of the fastener by approaching the tempering
Why are bolts marked "8.8" mated with nuts marked only "8"?
The matching bolt and nut grades identifying markings are
designated differently to demonstrate the strength relationship of the two
components. Due to the advent of mass assembly it is an acceptable practice for
the matching nut to be the stronger component. The logic behind this theory is
that during assembly if the nut is stronger the joint should fail immediately
and thus reduce subsequent field failures. More specific information as
to this relationship can be found in Section 10 of our catalog on pages 10-1020
Is A4/316 stainless better/stronger than A2/304 stainless?
Not necessarily. Both A4/316 and
A2/304 are primarily indicators of the chemical composition of these Austenitic
( not heat treatable ) fasteners. They get their ultimate mechanical strength
from the cold working and forming process. That’s why stainless fasteners
have an additional markings such as 50, 70, 80 to indicate their mechanical
strength as well as their chemical properties. A2 may be magnetic and is
corrosion resistant, A4 must not be magnetic and has the addition of being acid
resistant. See our catalog pages 10-1023 and 10-1024 in Section 10 for more
What does "DIN" mean?
A direct translation to DIN is Deutsches Institute
fur Normung or better understood as German Institute
for Standardization. DIN is the internationally
recognized consensus standards body of Germany. Well established before ISO the
DIN nomenclature and practices continue to be prevalent in the
What are "PG" Threads?
PG threads are a common form of metric thin walled
conduit/electrical threads. The shallow 60 degree thread angle profile directly
translates to Panzer Gewinde. Due to the shallowness of the thread profile the NoGo
Thread Gage member is typically unthreaded.
Which is more popular in Europe, BSP or BSPT?
The popularity of British Pipe Thread
conventions, straight or tapered, depends more on application and design.
Whether BSP or BSPT they both have been adopted as metric type pipe threads.
BSP is a straight thread similar to a fastener thread and does not seal on the
thread surface but relies upon some sort of additional sealing
element. BSPT is a tapered thread ( 1:16 or ¾” in. per foot )that goes into a
straight or tapered hole and seals on the thread. American NPT thread is
tapered so in the United
States the BSPT thread is more familiar.
Why are British fasteners so expensive?
Expense is relative to the value gained. In 1974
completed their formal year conversion to the metric system. Over the past 30
plus years the supply and demand of these obsolete parts has dwindled.
Much of the technology that these parts were used in has long been replaced
with new equipment using metric parts. Inventories have been depleted many
styles, sizes, and materials are only available as Special Manufacture. We
still maintain a good inventory and close contacts with our British vendors.
Are B7 & 8.8 equal in strength?
To many, chemistry is equivalency. Add to that
the matter of proprietary alloys within a classification of steels and the
debate continues. However, how a material is processed can change its
performance characteristics. Originally B7 and 8.8 can come from a similar base
metal but B7 is mainly processed differently to give it its required heat
resistance. Within the normal operating temperature range of 8.8 they
have similar performance characteristics.
How do you calculate the tap drill sizes in metric?
Arriving at the tap drill size for general purpose metric
screw sizes is easy and doesn’t require a chart. For tap drill sizes in steel
the formula is simple: Subtract the pitch of the thread from the nominal
Example: M6 x 1 6 minus 1 is 5 Tap drill size 5mm
What does "B3B" mean on my print?
"B3B"is a plating specification the breakdown goes like this. The first letter is
the plating material, the middle number is the code number for the plating thickness , and the last letter
refers to the final delivery appearance and/or passivation.
This information can be found
in our Catalog Section 10 on page 10-1031. In particular the B3B breaks down to :
3 (plating thickness) 8 microns or .0003 inch
B (delivery appearance) Dull matte finish
Are your hex head bolts made with a black oxide finish?
While the normal delivery condition of fasteners
may sometimes be referred to as Black Oxide, rarely is that the actual finish.
It is generally used in a broad form to distinguish them from plated fasteners.
The actual finish is more of a phosphate and oil ( phos & oil )
preservation. Actual Black Oxide and Parkerizing are proprietary finishes.
What’s the difference between “proof load” and “tensile load“?
Heat treaded alloy fasteners are designed to be stretched
to a certain point to retain their clamping load. It’s up to the design
engineer to establish which size fastener, how many, and
Proof load: the stretching load allowed before deformation
and or functional failure.
Tensile load: The ultimate stretching load allowed before
the bolt strips or fails. The proof loads of hex nuts are designed to exceed
the tensile load of the matching hex bolts in support of the theory that the
nuts should be the stronger component.
Why are there fine threads?
Fine thread have two advantages and many disadvantages. First they were thought to be stronger since the shallower
thread disrupted the base metal less and provided a larger
minor diameter. Second they offered finer dimensional and torque
adjustments. However in real world manufacturing and handling
applications general purpose fasteners lose some of these benefits
due to complications related to inadvertent thread damage. It is recommended
that the first choice for general purpose metric screw threads be standard
Why are the pitch diameters on the GO and NOGO thread ring gages I ordered not the same as the bolt I’m evaluating?
The gages you ordered are Working Gages intended to qualify
a specific thread size and tolerance class, not the gage. The gage must
have a specific and appropriate pitch gage tolerance its self to allow the
proper clearance and form a basis for re-calibration.
When using a NOGO thread gage they say the “gage should not accept the parts“ - what exactly does that mean?
This is a simple question that has complicated
answers. First there must be an agreement on the sampling size before the gage
come out of its case. Then there are quite a few different standards both
national and international that address this situation and range from a simple
‘not more than two threads’ to a “specific torque applied with resistance felt
along the thread after the first two threads”. ASME metric gauging practice
allows the part to totally pass through the NOGO ring providing the operator
can feel a definite drag once they go past the first two threads. There are
charts that are diameter sensitive and indicate the maximum torque that should
be applied to sense this drag. These charts are used so that parts aren’t
resized with the gage. Independent of which convention is used it is ultimately
the responsibility of the buyer and user to qualify the parts as acceptable
before use in their particular application.
Is there a special oversized gage to gage parts after plating?
Unless agreed upon before hand, metric parts should still
gage within the normal thread limits of the original classification. Care
should be given when plating existing product that it doesn’t exceed the
maximum condition after plating.
How are sheet metal screw threads different than wood screw threads?
Although they may look similar at first there are
differences that make them work properly in their intended materials. Sheet
metal screw threads are intended to displace the base metal and form a sort
of nut thread relationship into the hole in the base metal. Wood screws
have a deeper, sharper thread profile that is intended to cut into the wood
fibers. The wood screws thread pitch is slightly larger and has a more
pronounced taper on the end. There are also specialized proprietary wood
screw threads that are intended for the newer type composite and polymerized
How are British screw threads different than American?
Although the nominal sizes are similarly labeled
the main difference lies in the thread profile and resultant relationship of
the pitch diameters. Both systems identify their nominal diameters primarily by
factional inches however, the British use a 55 degree thread angle with radiused
root and crest. The customary American profile is 60 degrees with angular root
and crest. Even though you may find a diameter and pitch combination that may
seem to match it should not be used. The resultant assembly will be significantly
weaker since there will be excess play due to the different angles and the
threads will be binding on the root and crest rather than the pitch diameters.