The vee block (Figure L-87) is a common and useful machine shop tool. Precision types are finish machined by grinding after they have been rough machined oversize (about .015 in.) and heat-treated. Finish grinding of vee blocks will provide you with a variety of surface grinding
experiences. Refer to a working drawing (Figure L-88) to determine dimensions and to plan the sequence of grinding operations.
Selecting the Wheel For these vee blocks, the best abrasive will be a friable grade of aluminum oxide. A vitrified wheel of 46 grit with an
I-bond hardness would be a reasonable selection.
The following procedure may be used in setting up the grinding machine for vee block grinding.Step 1 Select a suitable wheel.
Step 2 Clean the spindle. Use a cloth to remove any grit or dirt from the spindle. If you lay tools and wheels on the machine table or the chuck, cover the surfaces with cloth for protection.
Step 3 Ring test the grinding wheel.
Step 4 Mount the wheel. The wheel should fit snugly, and the flanges should be the same size. Blotters will probably be attached to the wheel. If not, place a correctly sized blotter between each of the flanges and the wheel.
Step 5 Install the spindle nut and tighten firmly. Do not overtighten.
Step 6 Replace or close the wheel guard.
Step 10 Check the chucking surface for nicks and burrs (Figure L-92). Use a deburring stone if necessary.
To avoid having to protect the chuck surface with paper, prepare the first part surfaces by removing any heat Figure L-91 Cleaning the magnetic chuck with a cloth. The wheel must be stopped completely before this is done. treatment scale with the use of abrasive cloth on a flat surface (Figure L-93). Do not use a surface plate for this activity.
Side and End Grinding Procedure The vee blocks should be match ground, that is, ground together in pairs so that they are exactly the same dimensions when completed.The following steps and illustrations will describe the process for side and end grinding.Step 1 Place the blocks with the large vee side up on the grinder chuck (Figure L-94).
Step 2 Magnetize the chuck. Remember to remagnetize the chuck after each setup change.
Step 3 Lower the wheelhead until it is about an inch above the workpiece. Adjust table and saddle position so that blocks are centered.
Step 4 Adjust table feed reverse trips so that the workpiece has about 1 inch of overtravel at each end of the table stroke (Figure L-95).
Step 5 With the grinding wheel stopped, use a feeler gage or piece of paper and lower the wheelhead until it is a few thousandths of an inch above the surface to be ground.
Step 6 Start the wheel and grinding fluid. Start table crossfeed and table travel.
Carefully lower the wheel until it just begins to contact the high point of the workpiece. Set the downfeed micrometer collar to zero at this point.
Step 7 The amount to grind from the workpiece will depend on the amount of extra material left from the original machining.
Downfeed about .001 in. per pass and grind to a cleanup condition (Figure L-96). About .003 to .005 in. should be left for finish grinding on each surface.
Step 8 Turn the vee blocks over and surface grind the small vee side (Figure L-97).
Step 9 The end of the block may be ground by clamping it to a precision angle plate (Figure L-98). Adjust the block into alignment using a test indicator. The end of the block should extend slightly beyond the angle plate.
Step 10 Set the angle plate on the chuck, and end grind the vee block (Figure L-99).
Step 11 For grinding the remaining side, clamp the ground end to the angle plate, leaving the side surface projecting above the angle plate (Figure L-100). Grind one remaining side square to the end and square to the first surface ground in Step 7.
Step 13 Grind the remaining sides leaving .003 to .005 in. for finishing to the dimension (Figure L-102).Step 14 Re-dress the wheel with a slow pass (or passes) of the diamond dresser for finish grinding. Use a light cut of about .0002 in.
Step 15 Check all sides and ends for squareness (Figure L-103).
Use a precision cylindrical square and dial test indicator.
Small errors can be corrected by further grinding if necessary.
Tissue paper shims (.001 in.) may be used to achieve squareness. Take as little material as possible if corrections are needed.
Step 16 Check all dimensions with a vernier micrometer (.0001 in. discrimination) or dial test indicator (Figure L-104).
Step 17 Finish grind all sides and ends to final dimensions. Both blocks should be match ground. Vee Grinding
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