Anvils-5 Testing Rebound

To test an anvil's rebound which is a function of the face hardness:

Set it upright. Hold a 3lb or less, ball peen or smithing hammer, handle parallel to the face, over the center of the anvil with both hands, the tips of the fingers acting like pivots at the end of the handle the other hand supporting the head. Use the flat face of the hammers not the peen! About 8 to 10 inches height will do. THEN Drop the head and observe how far the hammer rebounds. It should rebound about 1/3 the height dropped, then 1/3 of that and so on. On a cast iron anvil it will bounce about 1/10 the initial distance or less. With a hard hammer on a really hard (smaller) anvil the rebound may be as much as 1/2!

WARNING! You should never strike the face of an anvil with a hammer! (It does happen though). This test is NOT the same as striking the anvil.

The Steel Ball Test:

A test inspired by Robert Bastow when he commented on anvilfire by saying, "You could bounce a 1" steel ball off the monitor!".

Obtain a steel ball bearing ball (1/2" (13mm) to 1"(25mm)) in diameter. Drop (DO NOT THROW) the ball 10" onto the face of the anvil. On a really hard anvil the ball will bounce about 75-90% of the distance dropped.

We tested a number of anvils and other items in several shops one weekend and here are the results. We have continued adding to the list.

93% - Peddinghaus 165# Forged Steel Anvil

85-90% - KOHLSWA 325# Swedish Cast Steel Anvil 55-57 HRC

90% - 70 pound "Smith Steel Casting" farrier's anvil

85% - Black Granite Surface Plate 8" thick

80-85% - High quality wrought anvils - Hay-Budden & Peter Wright (average)

65% - OLD 18th Century hornless anvil with 5th foot - about 75 pounds.

58% - Soft cast steel 50Kg Russian anvil (average test).

55% - Worn out old anvil, looks like an old Mouse Hole circa 1800

50% - Rail road rail - short section of modern 150# section

35% - Colonial Anvil 125# missing horn and worn out!

30% - Monel Boat Shafting (50/50 Cr/Ni)

25% - 2024-T4 Aluminium (hard, aircraft type)

25% - Annealed SAE 4140

20-25% - Ductile Iron Swage block

20% - A-36 Structural steel plate 8" thick

15% - Aged Concrete (Smooth)

15% - Milling machine Table (Mehanite)

10% - Imported Cast Iron ASO's or doorstops.

5-10% - Massive cast iron weld platen

5% - Red oak log (endgrain)

Testing was performed using a 1" (25.4mm) hard steel ball dropped from a 10" (254mm) height. Percent was read directly from a scale in inches. Results will vary dependant on the hardness of the ball used, sample surface texture/flatness and mass. We found it best to test several different places on the anvil and take an average. In each spot the highest bounce is the correct one. Erratic Lower bounces are due to surface irregularities. Materials below 30% rebound were visibly marked by the ball. These are NOT scientific results.

NOTE: Rebound is a good indication of hardness but not always a perfect indication. The soft Russian anvil tested well due to being a solid steel casting but was easily marked by a misblow of the hammer. The Mouse hole anvil it out performed has a hard enough face that it does not show hammer marks after hundreds of years of use and abuse. Cheap cast iron anvils will resist marking to some degree but have no rebound and will chip and break easily.

COPYCATS: Others have poorly described the ball bearing test as throwing the ball at the anvil or droping it from several feet above the anvil. This tells you nothing. If you throw the ball it can bounce higher than the release point due to the added energy. A pointless test. If you drop the ball from an unknown distance then the results are are difficult to acertain especially since they tend to fly off where they want. We generally have to carefully test 4 or 5 times before getting a clean bounce AND looking at the correct spot to catch the highest point in the bounce. Without using a scale and a reference height the best you can do is about +/- 20%.

Model D-1

SHORE SCLEROSCOPE
The technique above is similar to the method of operation of a Shore Scleroscope which is one of several rebound type hardness testing devices. The scleroscope uses a diamond tipped "hammer" which is bounced off the test surface. The rebound height was recorded on a direct reading scale (much easier than trying to watch the bouncing ball). This test is no longer used for determining hardness as it is affected by resiliency, however, for our purposes this is exactly what we want - combined hardness and resiliency. Other methods of testing hardness (Rockwell, Brinell, Vickers. . .) use a heavy "penatrator" to produce a circular depression in the surface tested and the size of the depression is measured.

For testing the hardness of steel balls by the rebound method a blacksmith's anvil was recommended by the 1942 Edition of ASM Hardness and Hardness Measurements handbook! Shore's hardness tester is used little today however his hardness/resiliency scale for elastomers "Shore's durometer" is the industry standard.

CORRECTIONS: We retested the KOHLSWA and the Peddinghaus after testing several other anvils. The Peddinghaus always exceeds 90%. My KOHLSWA seems to have a soft place toward the heal. Retesting showed that most of the face was harder than the original data (85-90% vs. 75%) and it moved up in the list. The Rockwell number listed for the KOHLSWA is from their sales data. The Hay-Buddens we tested were all over 200 pounds. Our experience with these is that the smaller anvils are quite a bit harder.

Revised Sept. 20/26, 1998, Dec. 27, 1998, April 17, 2000, Oct. 2003

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