Involute Splined Arbor
The Involute Splined Arbor was developed by one of the principle designers at Delta Dynamics to more easily meet the concerns of many sawfilers while establishing standards that could be used by all manufacturers. Improved manufacturing methods such as gear hobbing and CNC laser cutting have allowed tighter tolerances to be achieved. The tooth form of the conventional lobe style arbor did not lend itself to being easily modified to achieve reduced clearances and better contact.
The involute spline is a common, recognized method of power transmission. The term "involute" describes the type of curve used on most spline teeth as well as gear teeth. This curve ensures that, regardless of clearance, full form contact is achieved across the flank of the tooth under load.
The standards of the Society of Automotive Engineers (SAE) have been long established to set forth various fits. SAE standards specify 4 basic classes of fit: Class 4, Class 5, Class 6 and Class 7. Class 4 is the tightest fit, Class 7 is the least tight and Class 5 is the most common fit. The Involute Splined Arbor has been designed with a Class 5 fit, while saw clearance can be specified with the different class of fit in the saw eye. Class 4 may be preferred for fixed saws while Class 7 may be preferred for shifting or curve sawing.
Benefits of Involute Spline Arbors
· Manufactured from high tensile alloy steel
· Cut on precision gear hobbing equipment
· Induction Hardened 62-65 HRC
· Available in 37.5 Deg. or 30 Deg. pressure angle
· Available in solid arbors or sleeves
· Full form contact
· Good self-centering properties reduce vibration
· Good load distribution for increased life
Saw arbors are manufactured with 30 deg. & 37.5 deg. pressure angle teeth. The pressure angle (PA) refers to the angle of one flank of the tooth. A 60 deg. common thread would have a 30 deg. PA. The 37.5 deg. PA spline has 33% more tooth contact surface than the 30 deg. PA spline for better load distribution.
The 37.5 deg. PA spline has better self-centering properties due to the larger angle. This will make it more stable under load but will be more difficult to shift on the fly than the 30 deg. PA spline. The 30 deg. spline has a larger ratio between radial clearance and diametrical clearance. This is the amount that a saw can be deflected off-center when the tangential load on it is greater than the drives ability to hold it on center. If a saw had .010" of backlash, or radial clearance, it could be deflected off center .0066" for 37.5 deg. splines and .0087" for 30 deg. splines, a 32% difference. The ability of the 30 deg. spline to accept more deflection may make it preferable for curve sawing. Evaluate your particular needs and concult with your saw manufacturer and Delta Dynamics to choose what’s best for you. The staff at Delta Dynamics will be happy to share whatever information you may require.