BFW General Purpose-Backlash

Please note: Metric numbers are for reference only.

BFWB SERIES: BARREL MOUNT


BFWR SERIES: FLANGE MOUNT(Rectangle)





BFWT SERIES: THREAD MOUNT




BFWA SERIES: FLANGE MOUNT (Triangular)




BFWF SERIES: FLANGE MOUNT (Round)

5/64" (2 mm) Diameter Lead Screw. Diameter Code 008
** Listed efficiency for Micro screws are theoretical values based on non-coated lead screws.
Shaded areas have been translated from their designed inch or mm dimension to an equivalent mm or inch dimension.
1/8" (3.2 mm) Diameter Lead Screw. Diameter Code 012 *Listed efficiency are theoretical values based on Kerkote^® TFE coated lead screws.
Shaded areas have been translated from their designed inch or mm dimension to an equivalent mm or inch dimension.
0.132" (3.3 mm)) Diameter Lead Screw. Diameter Code 013 *Listed efficiency are theoretical values based on Kerkote^® TFE coated lead screws.
Shaded areas have been translated from their designed inch or mm dimension to an equivalent mm or inch dimension.
9/64" (3.6 mm) Diameter Lead Screw. Diameter Code 014 *Listed efficiency are theoretical values based on Kerkote^® TFE coated lead screws.
Shaded areas have been translated from their designed inch or mm dimension to an equivalent mm or inch dimension.
5/32" (4 mm) Diameter Lead Screw. Diameter Code 016 *Listed efficiency are theoretical values based on Kerkote^® TFE coated lead screws.
Shaded areas have been translated from their designed inch or mm dimension to an equivalent mm or inch dimension.
3/16" (5 mm) Diameter Lead Screw. Diameter Code 018
*Listed efficiency are theoretical values based on Kerkote^® TFE coated lead screws.
Shaded areas have been translated from their designed inch or mm dimension to an equivalent mm or inch dimension.
7/32" (5.6 mm) Diameter Lead Screw. Diameter Code 021 *Listed efficiency are theoretical values based on Kerkote^® TFE coated lead screws.
Shaded areas have been translated from their designed inch or mm dimension to an equivalent mm or inch dimension.
1/4" (6 mm) Diameter Lead Screw. Diameter Code 025 *Listed efficiency are theoretical values based on Kerkote^® TFE coated lead screws.
Shaded areas have been translated from their designed inch or mm dimension to an equivalent mm or inch dimension.
5/16" (8 mm) Diameter Lead Screw. Diameter Code 031 *Listed efficiency are theoretical values based on Kerkote^® TFE coated lead screws.
Shaded areas have been translated from their designed inch or mm dimension to an equivalent mm or inch dimension. 
3/8" (10 mm) Diameter Lead Screw. Diameter Code 037 *Listed efficiency are theoretical values based on Kerkote^® TFE coated lead screws.
Shaded areas have been translated from their designed inch or mm dimension to an equivalent mm or inch dimension. 
7/16" (11 mm) Diameter Lead Screw. Diameter Code 043 *Listed efficiency are theoretical values based on Kerkote^® TFE coated lead screws.
Shaded areas have been translated from their designed inch or mm dimension to an equivalent mm or inch dimension. 
1/2" (13 mm) Diameter Lead Screw. Diameter Code 050 *Listed efficiency are theoretical values based on Kerkote^® TFE coated lead screws.
Shaded areas have been translated from their designed inch or mm dimension to an equivalent mm or inch dimension. 
5/8" (16 mm) Diameter Lead Screw. Diameter Code 062 *Listed efficiency are theoretical values based on Kerkote^® TFE coated lead screws.
Shaded areas have been translated from their designed inch or mm dimension to an equivalent mm or inch dimension. 
3/4" (19 mm) Diameter Lead Screw. Diameter Code 075 *Listed efficiency are theoretical values based on Kerkote^® TFE coated lead screws.
Shaded areas have been translated from their designed inch or mm dimension to an equivalent mm or inch dimension. 
7/8" (22 mm) Diameter Lead Screw. Diameter Code 087 *Listed efficiency are theoretical values based on Kerkote^® TFE coated lead screws.
Shaded areas have been translated from their designed inch or mm dimension to an equivalent mm or inch dimension. 
15/16" (24 mm) Diameter Lead Screw. Diameter Code 093

Haydon Kerk Motion Solutions™ offers multiple options for lubrication. All Kerk® lead screw nuts feature self-lubricating polymers. When maximum performance is required, Kerkote® and Black Ice™ TFE coatings provide unmatched results in the most demanding applications. 

Kerkote® TFE Coating 

Kerkote TFE is a soft coating, a long-term dry lubricant that is optimized for softer plastics like acetals and nylons, with or without mechanical reinforcement. Lubrication to the nut / lead screw interface occurs by the nut picking up Kerkote TFE particles from the coating as well as from the migration of the internal lubricant within the plastic nut. The lubricant, although solid, also has some “spreading” ability as in fluid lubricants. Kerkote TFE coated screws provide the maximum level of self-lubrication and should not be additionally lubricated or used in environments where oils or other lubricant contamination is possible. 

Black Ice™ TFE Coating 

Black Ice TFE coating shares many of the benefits of Kerkote TFE but, in contrast, is a hard coating that offers exceptional durability in all types of environments, with virtually any type of polymer lead screw nut. Rather than acting as a dry lubricant, Black Ice TFE is an anti-friction coating whose surface properties displace the metal to which it is applied. Though it is not intended for use with metal or glass fiber reinforced nuts, Black Ice TFE is bonded securely to the surface of the lead screw and can withstand abrasion from contamination, rigid polymer systems, fluid impingement and wash down applications. 

Available Greases 

TFE coatings are intended to be used without additional lubricants. There are certain applications where external lubrication may be desired. These include the use of nut materials such as glass reinforced plastic or metal. Haydon Kerk Motion Solutions does offer a selection of greases developed specifically for these applications. Please contact a sales engineer for assistance selecting the best lubricant for your requirements.

BFW	A	K	R	-	018	-	0020	-	XXXX
Prefix	Nut Mounting Style	Lubrication	Thread Direction		Diameter Code		Nominal Thread Lead Code		Unique Identifier
BFW	A=Flanged (Triangular) F=Flanged (Round) T=Threaded X=Custom For Mini and Micro Series Only: B=Barrel mμ R=Rectangularmμ   mBFW Mini Series μBFW Micro Series	S=Uncoated K=Kerkote TFE Coating G=Grease N=Nut only B=Black Ice TFE Coating	R=Right hand L=Left hand (Refer to lead-screw charts for availability)		008μ=.078-in (2) 012m=.125-in (3.2) 013m=.133-in (3.3) 014m=.141-in (3.6) 016m=.156-in (4) 018m=.188-in (5) 021m=.219-in (5.6) 025=.250-in (6) 031=.313-in (8) 037=.375-in (10) 043=.438-in (11) 050=.500-in (13) 062=.625-in (16) 075=.750-in (19) 087=.875-in (22) 093=.938-in (24)		Refer to LEAD CODE Specifications		Proprietary suffix assigned to a specific customer application. The identifier can apply to either a standard or custom part

For applications assistance or order entry, call your the Haydon Kerk Motion Solutions Leadscrew Assemblies technical advisors at 603.213.6290

NOTE: Dashes must be included in Part Number (–) as shown above.

Not all thread leads are available in all screw diameters.
New nuts and leads are continually being added. Contact Haydon Kerk Motion Solutions for latest availability.

Screw Accuracy
Haydon Kerk Motion Solutions, Inc uses a unique precision rolling process for screw manufacturing. Standard lead accuracy for Kerk screws is .0006 in./in. (mm/mm). Lead accuracies are available up to .0001 in./in. (mm/mm). Please consult the factory for higher lead accuracies. Assemblies have an extremely high bi-directional repeatability of 50 micro-inches (1.25 micron).
 
End Machining
Haydon Kerk Motion Solutions can custom machine screws to your specifications or provide cut-to-length screws for your own machining.  

Critical Speed
This is the rotational speed at which a screw may experience vibration or other dynamic problems. See CRITICAL SPEED CHART to determine if application parameters result in speed approaching critical. To minimize critical speed problems: use a longer lead, choose a larger diameter or increase bearing mount support.



Lengths
Lengths can be specified up to 12 ft. (4M) from stock, (depending on diameter and lead). Cut to length screws are offered in 6-in increments (6-in, 12, 18,....) +1.0-in/-0-in.

Lead
Advancement per revolution. All screws are listed by lead, not pitch. Lead = Pitch x Number of Starts

Pitch
Crest-to-crest distance or one divided by threads per inch. (On a multiple start thread, the pitch equals the lead divided by the number of starts.)

Traverse Speed
The nut materials we use provide long wear-life over a wide variety of conditions. However, very high loads and/or speeds will accelerate nut wear. Special materials may be required for these situations. We offer the following guidelines for continuous duty linear traversing speeds for optimum life:

Lead	Traverse Speed	Lead	Traverse Speed
1/10 - 1/2-in	4-in/sec.	1 - 12 mm	100 mm/sec.
1/2 - 1-in	10-in/sec.	12 - 25 mm	250 mm/sec.
1 - 2 1/2-in	30-in/sec.	25 - 60 mm	760 mm/sec.

Maximum Load
Although the Kerk® Anti-Backlash Assemblies are capable of withstanding relatively high loads without catastrophic failure, these units have been designed to operate under the loading shown in the size charts.

Efficiency
Efficiency is the relationship of work input to work output. It should not be confused with mechanical advantage. Listed efficiency are theoretical values based on Kerkote® TFE coated screws.

Torque
The required motor torque to drive a lead screw assembly is the sum of three components: the inertial torque, drag torque, and torque-to-move load. It must be noted that
this is the torque necessary to drive the lead screw assembly alone. Additional torque associated with driving frictional bearings and motor shafts, moving components, and drag due to general assembly misalignment must also be considered.


Drag Torque:
The Kerk Anti-Backlash Assemblies are typically supplied with drag torque of 1 to 7 oz.-in. The magnitude of the drag torque is dependent on the standard factory settings or settings specified by the customer. Generally, the higher the preset force, the better the Anti-Back- lash characteristics.

Torque-to-Move:

T=        LOAD x LEAD
  L    2 π x EFFICIENCY

Back Driving:
Sometimes referred to as reversibility, back driving is the ability of a screw to be turned by a thrust load applied to the nut. Generally, back driving will not occur when the screw lead is less than 1/3 the diameter for uncoated screws or 1/4 the diameter for Kerkote® TFE coated screws. For higher leads where back driving is likely, the torque required for holding a load is:

T =         LOAD x LEAD x BACKDRIVE EFFICIENCY     
 b                                   2π

Screw Straightness:

Patented Noise Reduction Centralizer
Certain mechanical arrangements may result in excessive noise and vibration in the leadscrew assembly if the natural frequency – or resonance frequency – of the system is excited. Haydon Kerk’s Noise Reduction Centralizer is a patented technology that provides ultra-quiet performance for applications requiring virtually no audible noise, by incorporating a dampening element to the translating nut. The embedded compliant member not only adds damping, but also centralizes the nut relative to the outside diameter of the screw. Dampens noise and vibration without changing screw lead, nut style, or screw/nut materials Improves co-axial alignment between the leadscrew and a freewheeling nut Can overcome thermal expansion issues, and normal manufacturing tolerance issues Available with the following standard lead diameters: -012 -025 -031 -037 -050

In addition to The Kerk® standard nut types, modified and complete custom configurations represent a large portion of the company’s production. Modifications may be simple changes such as different mounting hole patterns or mounting threads, small dimensional changes, or special materials. Haydon Kerk Motion Solutions can provide tremendous value by producing a multi-functional acme nut. Using custom molds and specialty machining, nuts can also include guide bushings, carriages, timing pulleys, gears, syringe components, sensor mounts and flags, encoder features, clamps and many other complimentary elements. In addition, custom designed nuts can offer quick release mounts, partial thread engagement, half nut construction or special shapes and geometries. Special materials are offered to extend the performance of our assemblies. Materials can be chosen for extreme temperature, chemical compatibility, autoclaving, agency approvals, special loadings and many other specific requirements.