December 1, 2009
This article is the fifth in the Snips series on hand brake troubleshooting that originally appeared in 1986. This article is from September 1986.
Last month we began the second of a series of hand brake troubleshooting articles authored by Vince Bellik for machines that were made after 1965. In preceding months, Bellik put together some important troubleshooting pointers for brakes that were manufactured before 1965.
In our travels out in the field during the past month, we have received some fine comments from dealer-contractors who are owners of hand brakes on the value of this series of articles.
Vince Bellik, who has prepared these articles and furnished us with the photos, is one of the industry’s most knowledgeable individuals on taking proper care of hand brakes. He had many years of experience with Dreis & Krump Manufacturing Co., and Pacific Press & Shear Co.
For Bellik’s second in the series of articles on the newer hand brakes, he will be covering: clamp adjustment, bending leaf adjustment (and) clicking and snapping of the bending leaf and how to correct the problem.
Clamp adjustmentFor easy operation of the clamping handle, apply only enough pressure so that the top leaf clamps the material and it cannot be moved by applying hand pressure regardless of the thickness of the material.
For clamp adjustment, here are some suggestions:
1. Release clamping handles sufficiently to allow material to pass between the top leaf and the bed.
2. Adjust by means of clamping handle-adjusting nuts as shown. To tighten clamping pressure, release the top nut and tighten the bottom nut. Do this on both sides of the brake. It is recommended that this adjustment be made for each thickness of material.
Note: When hemming and flattening material where a double or triple thickness is required, clamping pressure must be adjusted to suit the combined thickness.
Bending leaf adjustmentThe bending leaf must be in proper alignment at all times since this will affect the material being formed. After a brake has been in operation for a while, the bending leaf will have a tendency to settle. Therefore, periodic checks and adjustments are required, as follows:
1. Raise the bending leaf until the bending edge is in the 90-degree position.
2. If, when sighting along the “vision line” (vertical line), the bending edge away, or not in the same plane (misaligned as shown in Figure 1), release the bolts that fasten the hinge to the bending leaf plate as shown in the photo. Then tighten the adjusting screw at the bottom. The bending leaf is adjusted properly when the edge and bottom bar edge coincide (as shown in Figure 2).
3. Lower the bending leaf and see that it is flush or slightly below the bottom bar when in the down position (as shown in Figure 3).
4. Follow the same procedure at the opposite end.
Clicking or snapping bending leaf causesThe noisy condition of a clicking or snapping bending leaf results from the bending leaf being set too low in the center. It is noticeable only when forming lighter-gauge material.
As explained earlier, the brakes are set for capacity material when the top edge of the bending leaf is flush, or slightly lower than the bottom bar on the ends, and the center of the bending leaf is below the bed approximately 1/32 inch.
When forming lighter gauges, the bending leaf does not have the tendency to follow the material upwards in the center; therefore it contacts the bottom bar causing a snap. This may also cause a bow in the part being formed.
How to correct clicking or snapping bending leafTo correct the clicking or snapping bending leaf, the following procedures should be followed:
1.Tighten the truss rod nut sufficiently on the bottom of the bending bar as shown.
2. Adjust bending leaf center truss nut.
Note: Step No. 2 may or may not be necessary. If, after following the procedure as in Step No. 1, and a bow is still evident, this may be the result of too much crown on the bed. (This crown is necessary to compensate for deflection.)
Release the center bed adjusting nut as shown. Also, if a pinching action is noticed in the center, between the top leaf and bending leaf, release the top leaf adjusting bolt slightly.
3. If the bending leaf becomes bowed, or a gap is noted between the bending leaf and the bed in the center of the brake, correct as follows: With the leaf in the down position, tighten the bending leaf adjusting bolts as shown. These are located next to the lifting handles on the lower bending leaf. This will force the center inward into a straight alignment.
Next month, Vince Bellik will cover such troubleshooting matters as: top leaf and bed adjustment; over-bend adjustment and how to correct; counterbalance; and box- and pan-brake jaw alignment.