cross-slide table modifications
It seems to me that all drill presses should have the same
work holding and positioning features as a milling machine. Recently
the availability of inexpensive Asian devices has made this capability
much closer to affordable.
For several years I used a simple X-Y vise as shown in Photo1
because it wascheap and reasonably functional. The
cross-slide table as in Photo 2 was available but was a couple of
hundred dollars and didn't seem worth it at the time. Then a small sale
and a big moment of weakness coincided and I made the switch. I bought
mine at Busy Bee in Canada but everybody else's product looks
pretty much the same.
The original was just a steel
disc with lots of non-adjustable
backlash determined by how (not very) close to it the outer
sleeve was pinned to the
shaft during manufacture. The new one carries a ball bearing and spacer
so the backlash is determined by the precision of the ball/race fit. If
I were doing it again, I'd make this block thicker and mount two
ball bearings with a spacer between and some bearing preload. It's
amazing how much
play there is in a single ball bearing. I never thought of this until
later but couldn't have done it originally
I was fitting it to the original leadscrew and was limited to the
thickness of the original thrust plate.
The leadscrew is far too long to be held between centers on a
Taig. To give the steady rest something to ride on, lock two 1/2-20
nuts together on a short length of rod and turn half of one of them to
a nice round.
Now cut a length of threaded rod about 1" longer than the lead
screw to be made. Grip it in the three-jaw and support the outboard end
with the just-made round riding in the steady rest, a kind of
substitute for a
tailstock dead center.
laboratory rod mill
The 21 Liter (5 gallon) 911METALLURGY 911MPE21BM dual function Laboratory RodMill / BallMill is designed to meet the industrial requirements to grind coal, cement and a wide variety of ores. The dual dutyLaboratory Grinding Mill consists of a gear motor mounted on a high precision solid steel underframe complete with outlet funnel and a set of separation screens plus sample collector.
The mill incorporates a yoke and locking mechanism to facilitate easy access to the contents of the mill. An appropriate ball or rod charge is provided with the mill. The motor incorporates a solid-state controller to accurately control the drum speed of up to 70 RPM. This controller has an internal overload protection. A revolution counter is included to allow accurate control of milling which will automatically stop the mill when the desired milling duration is reached. The lid incorporates a quick release locking mechanism.
Easy convertible from Ball Mill to Rod Mill. Drums, balls and rods available in different grades of steel: SS304, SS316, SS303, ST37, ST52 and other steel materials or liners on request. Easy tilt to empty the drum
As stated above, the purpose of this research was primarily to establish a quantitative relationship between a laboratory ball mill capacity and fineness of finished product. As is nearly always the case in research, the major problem cannot be attacked until a number of smaller ones have been disposed of: apparatus must be decided upon and designed to meet the needs of the research; experimental technic must be developed to accord with good scientific procedure, which will give data of practical use; and the data must be interpreted. This investigation, however, instead of being one of merely determining mill capacity (for a given mill) as related to fineness of finished product, also became a study of batch grinding in a laboratory ball mill as related to time of grind.
The selection of apparatus was necessarily more or less arbitrary. A cylinder 16 inches in diameter by 7 inches in length was chosen to contain the grinding mediaa 43 per cent full load of 1-inch steel balls. Mechanism was provided to rotate the cylinder, at a constant speed of 55 r.p.m. This speed was decided upon on the basis of observation made at one end of the mill, which was closed with a coarse-mesh screen. The mill speed chosen was not necessarily exactly the speed which would give maximum mill output, but it probably was close to what may be termed the best speed. That there is a best speed for each size of ball, ball load, feed size, etc., is shown in the researches of Fahrenwald and Lee and this is just one example of the complexity of the grinding problem. The selected speed must therefore be considered a more or, less arbitrary one, but it fully served the purpose of this investigation.
In the experiments of this study, grinding was done wet. Thirty per cent of water by weight was added to each charge. This ore-water ratio was arrived at from a series of experiments in which the percentage of water was the variable. Thirty per cent of water by weight gave approximately the maximum mill outputgrinding through 100 mesh.
The weight of feed charge introduced into the mill also was determined from a series of experiments in which weight of feed charge was the variable. The weight of feed charge giving the greatest number of grams of finished minus- 100 mesh sand was approximately 1,750 grams. As data later presented will show, this is not exactly the weight of charge which will give maximum mill output in a unit of time; it is, however, approximately that weight of charge which gives maximum output under the conditions of (1) the size (sieve analysis) of feed used, and (2) a short-period grind. This weight of charge served the purpose of the batch-grind experiments of this study.
Having established the apparatus to be used and, in part, the conditions of the experiments, other factors and variables having even greater bearing upon mill output came up. The most important among these was the time of grind. For a given weight of feed charge to be ground in a batch laboratory ball mill, there was no information available to show how the rate of production of finished product in the mill varied with the time, of operation of the mill; that is, for a 10-minute grind it was not known if the output was greatest for the first minute, the second minute, or the sixth or tenth minute of operation. This question seemed of such importance that a decision was made to investigate it rather thoroughly.
In this study, rate of grinding or mill efficiency is stated in terms of grams per minute, abbreviated GPM. A more scientific basis on which to calculate mill efficiency probably would have been that of total new surface produced per unit of time. This basis, however, was not thought to offer any advantage over the one stated.
The size analysis of the feed for experimentation was also more or less arbitrarily selected; and, as these experiments, show, it is not the proper sieve analysis to give maximum mill output. Here again the proper feed size could not be known in advance, and the arbitrary feed size selected serves for the work in hand. Quartz of the white massive variety was selected for this study because of its homogeneity and its known surface constants.
rod mill - an overview | sciencedirect topics
Rod mills have an industrial yield that is less than that of a ball mill, which explains the fact that balls have a much larger grinding surface than rods. The power needed to operate a rod mill could exceed 30% of the power used in a ball mill.
Rod mills have the highest rolling speeds, with interpass times in the finishing stand of 15150 ms. This is too short for either static recrystallization or strain-induced precipitation, and dynamic recrystallization is the main grain refining mechanism. Microalloying could limit grain growth during rolling by particle pinning and solute drag. However, austenite grain sizes of 10m can be achieved in CMn steels with optimally designed rod rolling schedules, so the main purpose of microalloying is precipitation strengthening. As-rolled rod is typically controlled-cooled at 15C s1 in loose coils (Stelmor process) to achieve a desired final microstructure and precipitate distribution. The principle application for HSLA rod steels is as cold-formed fasteners. An example of such a steel is given in Table 2.
Rod mill charges usually occupy about 45% of the internal volume of the mill. A closely packed charge of single sized rods will have a porosity of 9.3%. With a mixed charge of small and large diameter rods, the porosity of a static load could be reduced even further. However, close packing of the charge rarely occurs and an operating bed porosity of 40% is common. Overcharging results in poor grinding and losses due to abrasion of rods and liners. Undercharging also promotes more abrasion of the rods. The height (or depth) of charge is measured in the same manner as for ball mill. The size of feed particles to a rod mill is coarser than for a ball mill. The usual feed size ranges from 6 to 25mm.
For the efficient use of rods it is necessary that they operate parallel to the central axis and the body of the mill. This is not always possible as in practice, parallel alignment is usually hampered by the accumulation of ore at the feed end where the charge tends to swell. Abrasion of rods occurs more in this area resulting in rods becoming pointed at one end. With this continuous change in shape of the grinding charge, the grinding characteristics are impaired.
The bulk density of a new rod charge is about 6.25t/m3. With time due to wear the bulk density drops. The larger the mill diameter the greater is the lowering of the bulk density. For example, the bulk density of worn rods after a specific time of grinding would be 5.8t/m3 for a 0.91m diameter mill. Under the same conditions of operation, the bulk density would be 5.4t/m3 for a 4.6m diameter mill.
In the rod mill, high carbon steel rods about 50 mm diameter and extending the whole length of the mill are used in place of balls. This mill gives a very uniform fine product and power consumption is low, although it is not suitable for very tough materials and the feed should not exceed about 25 mm in size. It is particularly useful with sticky materials which would hold the balls together in aggregates, because the greater weight of the rods causes them to pull apart again. Worn rods must be removed from time to time and replaced by new ones, which are rather cheaper than balls.
As mentioned by earlier wire rod mills housed within smelter plant premises rejects large volume of waste emulsions which because of its toxic oil contents can not be discharged in open drains. Further since above toxic oil contain in the waste emulsion being only around 7% it is imperative that the residual water after breaking the emulsion needs to be recirculated to the plant itself. Present authors developed a process  for breaking the emulsion and release of the residual the water conforming to statutory norms for disposal of treated water in the open drain. In this process the waste emulsion was treated with calcium hydroxide in order to coagulate the toxic oil and separate it out from the residual water. Small contaminants in the residual water were finally removed by activated charcoal, pH adjusted to 7 and the water released. Typically for 7% oil content in waste emulsion, application rate of 3wt% calcium hydroxide and 2.5wt% charcoal brought down C.O.D. of treated water within permissible range. Table3.5 gives an example of such treatment process.
Powder milling process, using ball or rod mills, aim to produce a high-quality end-product that can be composites and nanocomposites, and nanocrystalline powder particles of intermetallic compounds, amorphous, hydrides, nitrides, silicates, etc. Powder milling process has been continuously improving by introducing numerous innovative types of ball mills in order to improve the quality and homogeneity of the end-products and to increase the productivity. This chapter discusses the factors affecting the mechanical alloying, mechanical disordering, and mechanical milling processes and their effects on the quality of the desired end-products. Moreover, we will present some typical examples that show the effect of these factors on the physical and chemical properties of the milled powders.
To equalize the charge segregation at the ends of the mill, the mill is rotated in the level position for eight revolutions then tilted up 5 for one revolution, tilted down 5 for one revolution then returned to the level position for eight revolutions and the cycle repeated throughout the test.
A study of the movement of materials in a rod mill indicates that at the feed end the larger particles are first caught between the rods and reduced in size gradually towards the discharge end. Lynch  contended that the next lower size would break after the sizes above it had completely broken. He described this as stage breakage, the stages being in steps of 2. The size difference between the particles at the two ends of the mill would depend on
The presence of this size difference indicates that a screening effect was generated within a rod mill and that the movement of material in the mill was a combination of breakage and screening effects. The breaking process was obviously repetitive and involved breakage function, classification function and selection functions. Therefore for rod mills, an extension of the general model for breakage within each stage applies, where the feed to stage (i + 1) is the product from stage i. That is, within a single stage i, the general model defined by Equation (11.18) applies
The number of stages, v, is the number of elements taken in the feed vector. A stage of breakage is defined as the interval taken to eliminate the largest sieve fraction from the mill feed or the feed to each stage of breakage. The very fine undersize is not included as a stage.
The breakage function described by Equation (11.2) could be used. For the classification matrix, which gives the proportion of each size that enters the next stage of breakage, the value of the element in the first stage C11 equals 1. That is, all of size fraction 1 is completely reduced to a lower size and all the particles of the classification underflow are the feed to the second stage of breakage and so on. Hence, the classification matrix is a descending series. If we take the 2 series, then the classification matrix C can be written as
The selection matrix S is machine dependent. It is affected by machine characteristics, such as length (including length of rods) and the speed of operation. Both B and C have to be constant to determine the selection function S within a stage.
Thus for each stage a similar matrix can be developed resulting in a step matrix which provides a solution of the rod mill model. Calculations are similar to that shown previously for grinding mill models.
The industrial comminution process under consideration has the following four units: Rod mill, Ball mill, hydro-cyclones, and water sumps. Fresh feed from the bin is fed to the rod mill along with water. The slurry generated from the rod mill is mixed with the slurry from the ball mill in a primary sump. The primary sump outlet stream is sent to the primary cyclone. The overflow from the primary cyclone goes to the secondary sump and the underflow is taken as a feed to the ball mill. The slurry generated in the secondary sump is taken to another hydro-cyclone which is called as secondary cyclone. The underflow of the secondary cyclone is recycled back to the ball mill for grinding and the final product is the overflow which goes to a flotation circuit as feed. Water is added to both sumps to facilitate the flow of the slurry smoothly within the circuit. Complete circuit configuration can be found in Figure 1.
Modeling of individual unit operations of the grinding circuit is performed separately using an amalgamated approach of population balance and empirical correlations. A simulation of an entire circuit is done by using a connectivity matrix which connects all the unit operations in terms of binary numbers. Here 0 denotes no connection and 1 denotes existence of a connection. Multiple simultaneous differential algebraic equations were formed using the entire set of equations which can be solved using well tested public domain software, called DASSL (Petzold, 1983). Details on these model equations can be found elsewhere (Mitra and Gopinath,2004) and not attached here for the sake of brevity.
The product size from HPGR can be much finer than the corresponding ball or rod mill products. As an example, the results by Mrsky, Klemetti and Knuutinen  are given in Figure6.8 where, for the same net input energy (4kWh/t), the product sizes obtained from HPGR, ball and rod mills are plotted.