1. [10] A standard ¼ inch UNC cap screw is specified to have a leng th of 1.5 in
ID: 2074164 • Letter: 1
Question
1. [10] A standard ¼ inch UNC cap screw is specified to have a leng th of 1.5 inches. The screw is to clamp a ½ inch plate to a base plate. Is the screw too short (Yes Is the screw too long (Yes a. b. No) No). 2, [10] A standard ¼ inch UNC bolt is specified to have a length of 1.25 inches. The screw is to clamp two 0.2 inch plates with a standard regular hex nut and no washers Is the bolt too short (Yes No) Is the bolt too long (Yes No) a. b. 3. [5] A double-thread power screw has an axial pitch of 0.3 inches and mean diameter of 2" If the screw is rotating at 1000 rpm with a motor delivering 20 in-lb of torque, how much power the motor delivers in horsepower. a. 0.16 b. 0.32 c. 1.6 d. 3.8 e. None of these [5] If the load is 15 lbs and the torque required to raise the load is 20 in-lb, what is the efficiency of the power screw? The screw is double thread with a pitch of 0.3 inch. 4. a. 0.22 b. 0.45 c. 0.61 d. 0.86 e. None of these (5] For a power screw to be self-locking, what is the minimum coefficient of friction if the screw is double thread with a pitch of 0.3 and mean diameter of 2 inches? 5. a. 0.05 b. 0.1 c. 0.15 d. 0.2 e. None of these [5) A power screw is lifting a load of 1500 lbs. The load is kept from rotating through a collar. The collar friction surface is circular with an inner radius of 1 inch and an outer radius of 2 inches. The friction coefficient is 0.08. How much torque in in-lb is needed to overcome the collar friction? 6. a. 180 b. 200 c. 220 d. 240 e. None of these 7, [10] A ¼ inch UNC bolt is clamping two plates of thickness ½ inch each without any exterial washers. If the bolt length is 1.5 inches, what is the length of the threaded part of the scre within the grip? a. 0.25 b. 0.5 c. 0.75 d. 1.0 e. None of these
Explanation / Answer
Answer 1.
There is a general guidelines regarding the selection of screw style, size and screw length.
For a more specific to your question regarding whether screw length is too short or long. one have to choose a length approximately half the length of material it is going into.If a screw is less than half the length of material it is going into will not clamp it properly with base plate. and if length is more than half the length then there may be risk of damaging the opposite side (base plate) material.
And it is also depends on weight of the material that the screw may support.
Lets come to our case, here length is 1.5 inches and clamp thickness is 1/2 inch. So here we can conclude (on the bases of length criteria) that our length is too long.
so answer are:
a. Is the screw too short. --- No
b. Is the screw too long. --- Yes
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