In part 4 we know that tungsten carbide reamers are used to enlarge or create a smooth surface finish to a hole already drilled since drilling followed by reaming generally produces hole geometry and finish that is as close to theoretical perfection as possible. And here we explain straight reamer.

Straight reamer

A tungsten carbide straight reamer is used to make only a minor enlargement to a hole. The entry end of the reamer will have a slight taper, the length of which will depend on its type. This produces a self centering action as it enters the raw hole. The larger proportion of the length will be of a constant diameter.

Reamed holes are used to create holes of precise circularity and size, for example with tolerances of -0/+0.02 mm(.0008") This will allow the force fitting of locating dowel pins, which need not be otherwise retained in the body holding them. Other holes, reamed slightly larger in other parts, will fit these pins accurately, but not so tightly as to make disassembly difficult. This type of alignment is common in the joining of split crankcase halves such as are used in motorcycle motors and boxer type engines. After joining the halves, the assembled case may then be line bored (using what is in effect a large diameter reamer), and then disassembled for placement of bearings and other parts. The use of reamed dowel holes is typical in any machine design, where any two locating parts have to be located and mated accurately to one another - typically as indicated above, to within 0.02 mm or less than .001".

Another use of reamed holes is to receive a specialized bolt that has an unthreaded shoulder - also called a shoulder bolt. This type of bolt is commonly used to replace hot peened rivets during the seismic retrofit of structures.

 (To be continued. This article is divided into several parts and this is part 5, for part 4 please refer to http://news.chinatungsten.com/en/tungsten-information/79531-ti-10169;for part 6 please refer to http://news.chinatungsten.com/en/tungsten-information/79554-ti-10174)

Tungsten Carbide Manufacturer & Supplier: Chinatungsten Online - http://www.tungsten-carbide.com.cn
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There are four kinds of tungsten copper processing, liquid phase sintering – repressing – re-sintering, solid phase sintering – repressing – re-sintering, infiltration – machining and pre-sintering tungsten (W) skeleton – melt dipping – machining. The last method is more popular currently, which make material has good mechanical properties. Because W grains is not longer individual in this process, which becomes firm tungsten skeleton after high temperature sintering. Therefore, this stable structure can endure the impact of machinery. Besides, the ability of resistance of cracks and expanding is much better in this way.

However, it is unavoidable that tungsten copper electrode also has weakness in structure. One is tungsten maybe has cracks, but it is unlikely. The other is more probable, which has pore in Cu when tungsten skeleton forming and condensation. Under high temperature and 10-times pressure, tungsten will emerge compressive stress, which will tear the cracks already exist. In addition, with the increasing of arc frequency, the stress of matrix enduring will enhance so that the cracks will expand and connected with cracks of surface outside.

More infomation about tungsten copper electrode erosion mechanism, click here:

http://news.chinatungsten.com/en/tungsten-information/79477-ti-10142

Tungsten Copper Manufacturer & Supplier: Chinatungsten Online - http://www.tungsten-copper.com/
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Tungsten powder re-sintering is can not be neglected when arcing. After Cu evaporating by pulsed arc, some W grains will be exposed in medium. This tungsten grains re-sintering and spheroidizing or transferring to the surface by surface effect at high temperature, which make the cracks expand inside skeleton inevitably. In general, tungsten copper will volatile and compound in high temperature arc, which the cracks is accelerating the erosion.

Those tiny pores left by Cu evaporating will become the source of the next cracks and the re-sintering accelerate cracks expanding. In addition, the oxides combine electrode contact with arc-blast medium and carbide is brittle so that they will be broken and spalling under mechanical impact until the electrode failed.

More infomation about tungsten copper electrode erosion mechanism, click here:

http://news.chinatungsten.com/en/tungsten-information/79477-ti-10142 
http://news.chinatungsten.com/en/tungsten-information/79543-ti-10144

Tungsten Copper Manufacturer & Supplier: Chinatungsten Online - http://www.tungsten-copper.com/
Tel.: 86 592 5129696; Fax: 86 592 5129797
Email: sales@chinatungsten.com
Tungsten & Molybdenum Information Bank: http://i.chinatungsten.com
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Molybdenum News & Molybdenum Price: http://news.molybdenum.com.cn

In part 3 we know that tungsten carbide reamers are used to enlarge or create a smooth surface finish to a hole already drilled since drilling followed by reaming generally produces hole geometry and finish that is as close to theoretical perfection as possible. And here we will show you some reamer types and first comes adjustable hand reamer.

Adjustable hand reamer

An adjustable hand reamer can cover a small range of sizes. They are generally referenced by a letter which equates to a size range. The disposable blades slide along a tapered groove. The act of tightening and loosening the restraining nuts at each end varies the size that may be cut. The absence of any spiral in the flutes restricts them to light usage (minimal material removal per setting) as they have a tendency to chatter. They are also restricted to usage in unbroken holes. If a hole has an axial split along it, such as a split bush or a clamping hole, each straight tooth will in turn drop into the gap causing the other teeth to retract from their cutting position. This also gives rise to chatter marks and defeats the purpose of using the reamer to size a hole.

(To be continued. This article is divided into several parts and this is part 4, for part 3 please refer to http://news.chinatungsten.com/en/tungsten-information/79530-ti-10168)

Tungsten Carbide Manufacturer & Supplier: Chinatungsten Online - http://www.tungsten-carbide.com.cn
Tel.: 86 592 5129696; Fax: 86 592 5129797
Email:sales@chinatungsten.com
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