As we all know, to perform a particular operation in any machine we need to use some attachments, mandrels and rests are one of them.
The Mandrels and Rests both are generally used in Lathe machines to perform operations on cylindrical jobs.
Mandrels are used for hollow cylindrical jobs, where rests are used for solid cylindrical jobs.
So why we need to use Mandrels or Rests?
Suppose you are going for facing operation on a hollow cylindrical job, you generally hold the job with the help of chuck, and then performed the operation. So what would be its effect, when you apply the depth of cut to the job, due to that it may be misaligned from the lathe center, as a result, you see some error on the workpiece.
So mandrels are used for holding and rotating the hollow jobs, as you can fit the mandrel inside the hollow job, and start the machine due to the friction, mandrel along with the job will start rotating, and when you applied the depth of cut to the workpiece as it compact in setup, it can't be misaligned with the center and you can get a good surface finish.
Generally, the mandrel is placed in centers and being rotated by driving plate and lathe dog.
Almost all the Mandrels are made of High Carbon Steel and Mild Steel also.
Types of Mandrels:
As of now, you learned mandrel is used to hold and rotates hollow jobs, now you are going to learn what are the types of Mandrel?
Mandrels are classified into 7-different types. And those are:
Now let's see one by one.
This is a very simple type of mandrel generally available in all the machine shops.
It looks like a solid cylindrical tapered bar whose one side is larger in diameter and the other side is smaller in diameter.
At both the ends of the mandrel, there is a slot, one is for lathe dog, and the other one is a protected center hole for the dead center.
This type of mandrel can be used for several different diameters jobs.
It is not just a hollow round bar, some of the different diameter step collars are fitted with it so that a single mandrel can be used for holding various diameters jobs.
This is some kind of step mandrel the only difference is here a number of equivalent hollow jobs can be machined at a time.
It is used to reduce machining time and generally used in mass production purposes.
In this mandrel, a fixed collar is fitted on the one side of the solid bar (mandrel) and then Jobs are placed through another side and then a nut is tightening the jobs with the help of washer, here is the diagram:
Generally, this type of mandrel is used for a job diameter of over 90-100 mm.
In this type of mandrel, there are two fixed collars attached at the two ends of the bars.
We use this type of mandrel to reduce the weight and cost of the mandrel as if we used a solid bar the cost and weight of the bar are very much, so instead of that, we can use this type of mandrel.
As the name denotes screwed, that means threaded are cuts on the peripheral area of this type mandrels.
In this type of mandrel, the collar is fitted on one side of the round bar, and the other side will be open when internally threaded workpieces can be entered.
The jobs are screwed on the mandrel against the collar for machining purposes
This type of mandrel is suitable for any diameter of hollow jobs.
Here two different types of adjustable cones are there, one-sided is fixed and another sided is adjustable or can be removed, so first, we need to remove the one-sided cone block then fitted the hollow job and then put the cone block and tightening with the help of nut.
It is used for jobs of different diameters of hole variation.
The hollow job can be fitted on the sleeve and the job is tightened by the expanding nature of the sleeve with the help of two slots one split-up portion after pushing the pin into the sleeve.
After fitting the hollow job over the expansion mandrel, we need to push a pin through the center of the mandrel, so that the slots expand and fitted with the workpiece.
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