On the Parameters of Hand Chipping-Riveting Hammers and Their Standard Sizes

V. F. Gorbunov, V. I. Baburov

(Presented by the Department of Mining Machines and Mine Transport)

At present, chipping and riveting hammers are manufactured by many enterprises of the Soviet Union. Their production is disorganized, and it is most often undertaken without any preliminary analysis of the designs and parameters of the hammers, without their scientific evaluation.

The purpose of the present work is to analyze the parameters of various types of hand pneumatic hammers and to develop recommendations for compiling their parametric series.

The material for this work consisted of the results of a survey, carried out by us at 26 enterprises of 9 economic-administrative regions of the Soviet Union, on the use of pneumatic riveting, chipping, scaling, and other types of hammers. These are mainly machine-building, metallurgical, and shipbuilding plants and combines of the Urals, Ukraine, and the Moscow and Gorky regions, which are among the principal consumers of pneumatic hammers manufactured by the Tomsk Electromechanical Plant (TEZ). The total number of hand pneumatic hammers surveyed by us was 5410 units. Of these, 3765 hammers were used for trimming and cleaning castings, 1545 for cleaning work in welding, and about 100 for riveting.

Some large plants in the USSR, solely because of the shortage of serially produced hammers (hammers of types KE, MR, and R), organize their manufacture in-house (Table 1). Naturally, in this case the manufacturing cost of the hammers is 1.5–2.5 times higher than at specialized plants.

Riveting hammers of the KE type, from the TEZ plant, are widely used for trimming and cleaning castings; 75% of them are used as chipping hammers. Their share in the total volume of consumption is 66.2% (Fig. 1). Chipping hammers of the MR type from the same plant account for 14.8% of consumption, chipping hammers of the R type for 10.4%, and hammers from other plants for 8.6% (Fig. 1).

Table 2 gives the technical characteristics of hammers manufactured in series. The parameters of the hammers have been taken by us from factory catalogs, although they are often unknown even to the manufacturers themselves, since they lack the appropriate measuring equipment.

Judging by their designs, all hand hammers used for chipping and cleaning castings, as well as for dressing welds and ingots, have a striker impact energy in the range of 0.7–1.8 kg·m. The exceptions are the KE-19, KE-22, and Ingersoll-400 hammers, which have a considerably greater impact energy.

Fig. 1. Distribution of various types of hammers used in chipping and cleaning castings (3,767 hammers), in percent/units.

Table 1

Manufacture of chipping-riveting hammers (according to survey data)

Comparing the hammers with one another in terms of dimensions and energy characteristics, they can be divided into the following groups:

1. Small-size riveting and so-called “chipping” hammers. The Moscow Council of National Economy produces riveting hammers of the KMP type (Tables 1, 2) with a single-blow energy of 0.33–0.85 kgm and a frequency of 1800–1500 blows/min (impact power 0.13–0.34 hp). KMP hammers are used for riveting metal products with rivet diameters of 3–6 mm.

Table 2

Technical characteristics of chipping-riveting hammers

“Chipping” hammers of the Chelyabinsk Tractor Plant (ChTZ) and other small-size hammers of the MZS type, used for cleaning welds, castings, and for riveting, have approximately the same parameters, namely: blow energy of 0.3–0.7 kgm, frequency from 3000 to 1800 blows/min. They are used at shipyards, tractor plants, and other factories. The demand for them in the country is approximately 10–15 thousand units per year.

1. Hammers RM-35, RM-55, MR-4, PM-D8-P type, R-1, which constitute 16% of the total number of hammers consumed, have a striker blow energy of approximately 0.85–1.2 kgm, a frequency of 3500–2500 blows/min (impact power 0.5–0.70 hp).

2. Hammers MR-5, PM-D8-1 type, Ingersoll-200, RM-75, R-2, and RMPZ-2 have a blow energy of 1.2–1.5 kgm, a frequency of 2400–1900 blows/min (impact power 0.63–0.64 hp). This group of chipping hammers is the most widespread and constitutes about 40% of the total number of hammers in operation.

3. Hammers MR-6, Ingersoll-300, R-3, and RM-1 are characterized by approximately the following parameters: single striker blow energy of 1.5–1.7 kgm, frequency of 1700–1500 blows/min (impact power 0.57–0.60 hp), and a prevalence of about 10%.

4. Hammers KE-19 and Ingersoll-400, having a blow energy of 1.7–2.4 kgm and a frequency of 1500–1300 blows/min (impact power 0.57–0.69 hp), constitute 8% of all hammers used. They are used primarily as chipping hammers.

1. KE-22 hammers, converted in the same way as the KE-16 and KE-19 from riveting to chipping hammers, have an impact energy of 2.5–2.7 kgm, a frequency of 1100–1000 blows/min (impact power, 0.61–0.6), and a prevalence of 15.4%.

2. For riveting rivets of 17–28 mm diameter and larger, riveting hammers of the KE-28, KE-32, RN types and possibly others are used.

The volume of riveting work at metallurgical and machine-building plants is insignificant. Riveting work is usually encountered in small quantities in various shops and in shops producing metal structures. At the enterprises surveyed, we rarely encountered riveting work carried out with KE-32 hammers. For this purpose, KE-22 hammers are mainly used and, to a lesser extent, KE-28 hammers. Thus, two shifts of five people each knock molding sand out of molds with KE-28 hammers at ChTZ. They are also present in small quantities at other plants (the Chelyabinsk Pipe-Rolling Plant, the Magnitogorsk Metallurgical Combine, etc.) and are used on a wide variety of jobs—riveting, trimming, road-construction work, and some others (dismantling masonry, etc.).

According to the nature of the work performed (chipping, cleaning, and riveting), the hand pneumatic hammers used may be subdivided into three groups:

1. In chipping and cleaning castings of burrs, flash, cavities, burning-on, and sand, and also in removing defects in the form of laps, cracks, and folds from ingots and billets, hammers with an impact energy of 0.8–2.7 kgm and an impact frequency of 3500–1000 blows/min are used. This group of hammers is the largest in terms of volume of work and includes more than 70% of the hammers out of their total number.

2. In cleaning small castings of scale, sand, and small burrs, “chasing” hammers are used, having an impact energy of 0.3–0.7 kgm and a frequency of 3000–1800 blows per minute. Approximately 15–20% of the total number of hammers are used for this type of work.

3. In riveting rivets with diameters from 3 mm to 30 mm and larger, pneumatic riveting hammers with an impact energy from 0.33 kgm to 3.0 kgm, and rarely higher, and an impact frequency of 2000–900 blows/min are used. This group constitutes 10–15% of the hand hammers operating on compressed air. Moreover, the prevalence of hammer standard sizes is very uneven. For the most part these are either small-sized hammers for rivet diameters of 3–6 mm with an impact energy of 0.33–0.85 kgm, or heavy hammers for riveting rivets larger than 17 mm with an impact energy of 1.8–3 kgm.

As can be seen from Table 2, the impact power of all chipping hammers varies only slightly (from 0.5 to 0.7 hp), despite the fact that they are represented by many standard sizes. The main differences between the standard sizes are the values of the impact energy of the striker, the impact frequency, and the weight of the hammer. In our opinion, the most important parameter of the pneumatic hammers under consideration, especially chipping hammers, is the energy of a single impact of the striker.

During the investigation of the operation of chipping and riveting hammers at the Donetsk Metallurgical Plant, we timed the work of two hammers, KE-22 and MR-6, in chipping a strip of specified length of different grades of steel (55S₂ and steel 4). The comparative data are presented in Table 3.

From a comparison of the chipping speed (Table 3) and the parameters of these hammers (Table 2), the conclusion suggests itself that an increase in chipping speed depends mainly on the energy of a single impact of the striker.

Enterprises operating…

…chipping hammers. It is no accident that, in the chipping and cleaning of steel ingots, blanks, blooms, and other products of the metallurgical industry, 87.0% are KE-22 hammers, which have a higher impact energy than other hammers used for this same type of work. And in the overall balance of hammers consumed (Fig. 1), KE-22 hammers occupy second place after KE-16. Third place in prevalence is held by KE-19 hammers, which are also distinguished by an increased value of impact energy.

Table 3

Time-study data on the operation of KE-22 and MR-6 hammers in steel chipping

From the results of the survey of hammer operation, as well as from the correspondence of the Tomsk Electromechanical Plant with its customers, it is evident that the principal influence on chipping productivity is exerted by the impact energy and the weight of the hammer. It is unproductive to process small castings with hammers of high impact energy, mainly for two reasons:

a) these hammers are heavy and quickly tire the worker;

b) during chipping, a large, thick chip is formed, which may cause defects. In addition, when cast iron is chipped, the chip flies off in different directions and may injure the worker.

Naturally, the smaller the casting, the smaller, as a rule, the dimensions of the defects, and it is more advantageous to remove them with lighter and less powerful hammers.

Proceeding from what has been said, we believe that, when compiling a parameter series for pneumatic riveting-chipping hammers, the impact energy of the striker should be taken as the main parameter.

In our opinion, the weight of hammers does not fully reflect the work, productivity, and, in general, the capabilities of the hammer. Having one and the same impact energy, hammers may have different designs of individual units—for example, starting and stop devices, handle shapes—and, consequently, different weights.

As one possible variant, we propose the following series of parameters for hand pneumatic hammers (Table 4).

For small-size hammers, the proposed striker diameters are 16–24 mm. This size of the barrel bore will make it possible to obtain a convenient, light design. The remaining standard sizes can be manufactured with the most common internal barrel diameter of 30 mm. The last standard size is proposed with a barrel diameter somewhat greater than 30 mm. This is explained by the fact that, with an impact energy of 3.2 kgm and a barrel diameter of 30 mm, the hammer design becomes long and inconvenient to handle.

We also propose changing the design of the front part…

hammers (this applies especially to chipping hammers of the KE type) and to equip certain standard sizes of hammers with cylindrical and faceted bushings instead of the combined one (Fig. 2).

Table 4

Proposed parametric series of chipping-riveting hammers

The advisability of using a cylindrical bushing in “peening” and riveting (peening-riveting) hammers is beyond doubt. But when moving to chipping hammers, the question of bushing design becomes more complicated.

Taking into account the demands of production and the nature of the distribution of individual bushing designs, we recommend installing cylindrical bushings on the 1st, 2nd, 3rd, and 4th standard sizes of hammers (Table 4). On heavier hammers intended for chipping large castings and removing defects from ingots (5th, 6th, and 7th standard sizes), it is better to use faceted bushings.

Conclusions

1. In view of the great variety of designs of pneumatic manual chipping-riveting hammers in use, it is expedient, on a national scale, to bring order to their production and consumption.

2. In general, for all types of work (chipping, peening, riveting, etc.), in our opinion, it is necessary and possible to develop a single general set of hammer types, taking as the basis the impact energy of the striker and the weight of the hammers. At the same time it is necessary to provide that the same hammers can be used for different kinds of work by replacing the end

Fig. 2. Designs of end bushings of chipping-riveting hammers:
a) cylindrical; b) combined; c) faceted.

bushings. The proposed parametric series of pneumatic chipping-and-riveting hammers, consisting of 8 standard sizes, may serve as the basis for developing such a type series.