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N G I N E E R I N G

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N F O R M A T I O N —

Q: What does the (R) designation mean in 2-ton and 50-ton part numbers? A: The R indicates "reverse" base sleeve. Refer to catalog pages 25 and 35.

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A C K S

FAQ

Q: Can I buy a screw jack with a clevis on both ends? Q: How much backlash is in a Joyce machine screw jack? A: Yes, when freedom of movement in two axes is re quired, a double clevis jack may be specified. This design in cor po rates a A: In machine screw jacks there are two types of back lash. Worm to worm gear backlash (typically 8-15 de grees worm rotation) and lifting screw to lifting nut backlash, sometimes called endplay (up to .020 inches on new standard jacks).Note: Due to the high ratios in worm gearing, worm to worm gear backlash is not a significant factor in most jack ap pli ca tions since it normally corresponds to less than .002” back lash of the lifting screw. clevisma chined or pinned on the screw end and a clevis welded to the protection tube. Double clevis units are useful in ap pli ca tions that require ac tu at ing a hinged platform or door. Q: Can I reduce the screw backlash? Q: How is the clevis Positioned on keyed jacks? A: The hole in the clevis end is parallel with the worm input shaft. Contact Joyce for other clevis end positions.
Clevis End Options Q: What are the standard end conditions for the lifting screws on a screw jack? A: Yes, screw backlash (endplay) can be adjusted via any of threefollow-ing optional anti-backlash devices: Stan dard split-nut design;A90 external nut adjustment; and our A95 design.Please consult page 127 for the fea tures and benefits of each design. A: Joyce Machine Screw and Bevel Gear
® Jacks are avail able withany of the following four standard end conditions: Type 1 is a plain, turned-down end; Type 2 is a circular load pad with mount ing holes; Type 3 is a threaded end; and Type 4 is a male clevis. Please refer to the jack drawings for di men sion al in for ma tion.Note: Ball Screw Jacks and Bevel Ball Actuators have a Type 3 screw end standard. Optional ends are available. Please refer to the jack drawings for di men sion al information. A: Our standard lubrication and seals are rated for a tem per a ture range of 0-250 Q: What is a screw jack's normal operating temperature?
o F. For operation outside of this range, special lubricant and/or seals can be pro vid ed. Please contact Joyce for recommendations. Q: What do I need to consider when ordering a bellows boot to protect the jack lifting screw? Q: Are Joyce screw jacks lubricated prior to shipment? A: When a bellows boot is ordered for a jack, the closed height dimensions may change from those listed on the jacks without boots. Refer to the chart on pages 124-126 for jack closed height dimensions. When ordering a bellows boot for an in vert ed jack, the collar diameter for the end of the boot that fastens to the mounting struc ture must be customer specified. Zippered boots are available upon request. A: All Joyce Machine Screw, Ball Screw Jacks and Bevel Ball Actuators are lubricated for normal op er a tion before leaving the factory and are ready for use. The standard lubricant provided is an extreme pressure NLGI grade #1 (EP1). Specific in for ma tion and com mer cial brand names can be found in our O&M manual. Q: How is the load pad positioned on keyed jacks? The Bevel Gear
® Jack utilizes both grease and oil. The upper bearing and jackscrew are both grease lu bri cat ed while the remaining internal com po nents are oil lu bri cat ed. These jacks are grease lubricated prior to ship ment; however oil must be added to the unit prior to op er a tion. A: Two mounting holes are parallel with the worm input and two are perpendicular to the worm input. Q: Can I order a mechanical stop to limit jack screw travel? Q: What is screw lead error? A: The deviation from the mathematical lead expressed in inches per foot cumulative.
Load Pad Option Q: What is the amount of lead error in a standard lifting screw? A: Thread Milled Acme Screws up to .003"/ft. cumulative; Ball Screws up to .007"/ft. cumulative; Rolled Acme Screws up to .010"/ft. cumulative. A: Yes, an optional stop can be ordered on either or both ends ofthe screw. However, mechanical stops are not intended to be usedas operating limits. Engaging the stop may prevent dam age to your Q: How much side load can I place on a screw jack? A: Standard jacks are not designed to accommodate side structure but will most likely damage the jack. To control jack travel, please refer to the limit switches shown on pages 134 & 135. loads in a dynamic condition. We recommend the use of external guides when dynamic side loads are expected. Jacks can however ac com mo date some side loading in a static condition. The screw column length generally be comes the limiting factor in these ap pli ca tions. Please contact Joyce Application En gi neer ing direct at 1-800-523-5204 for ad di tion al assistance. Note: Mechanical stops are standard on all Joyce ComDRIVE
® jacks. Q: How can I determine wormshaft rotation for raising and lowering the jack? A: The worm shaft rotating as shown (looking down on the jack) raises the load.
Screw Center Line LeftSideRightSide 1-800-523-5204 Visit our website now for 2D and Interactive 3D models of all our Jacks and Actuators. www.joycedayton.com

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