Belleville Spring Washers

Stock sizes in high-carbon and stainless steels

Belleville spring washers are especially suited for high loads in small spaces. By combining them in varying sequence, each size gives numerous load-carrying possibilities. These washers have had all set removed during manufacture.

Material

• Spring Steel
  Commercial - 1074 - Certified to ASTM-A684
• Stainless steel
  Thicknesses up to and including 0.072 in.
  Commercial - Type 302
  Government - AMS 5906 Type 302 Chemistry only
  Thicknesses over 0.072 in.
  Commercial - Type 17-7 PH certified to AMS 5528
• No charge for certificate of compliance when requested; certificate of chemical analysis available, see price book.

Tolerances

• Contact our engineering department for tolerances.

Typical load-deflection curves for three characteristic proportions of washers listed are as shown in Fig. 2. From them, loads at intermediate heights may be estimated. The nominal amount of dish or cone (h) is found by subtracting "t" from "H".

Example

Using part no. B1250-040, estimate the load at 75% of deflection:

h = H - t = 0.082 - 0.040 = 0.042

h ÷ t = 0.042 ÷ 0.040 = 1 approx.

From Fig. 2, using the curve "h = t", the load at 75% of the deflection is 87% of the load at flat position. From the table, calculated load at flat is 330 lb.; .87 x 330 = 287 lb. The typical curves in Fig. 2 are shown with dotted lines beyond 75% of deflection to indicate that load characteristics in this area are not reliable because of partial bottoming of the washers.

Stacked Belleville Spring Washers

Since the deflection in a single belleville spring washer is relatively small, it is often necessary to combine a number of washers. Stacking them in series increases the deflection in proportion to the number of washers, the load remaining the same as with a single washer.

In order to increase the load, the washers may be stacked in parallel as shown in Fig. 1. Theoretically, this increases the load in proportion to the number of washers. However, friction between the washers causes an apparent "hysteresis" in the load-deflection curve as illustrated in Fig. 3. This figure shows test curves made on laboratory equipment without vibration using part no. B1000-035. The width of the "hysteresis" loop is in the order of 6% for each washer added in parallel, but it may vary with lubrication and surface finish and may change during the life of the mechanism due to burnishing of adjacent surfaces. The test curve in Fig. 3 for five in parallel also illustrates the extra deflection which occurs due to imperfect nesting of the washers. The graph in Fig. 3 is labeled to show the loads and deflections of the single washers in the stacks.

A stack of washers may be installed either on a rod or in a cylinder. For dynamic applications the guides should be hardened to Rockwell C48 minimum. Also hardened flat end plates may be added to prevent indenting adjacent parts.