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Harold Hall

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BORE HOLE IN THE BASE

Before starting this actual operation some decisions have to be made. Almost all existing machined surfaces are to be machined, and as a result the vice would rest lower at the handle end. This would be due to machining both the underneath of the vice itself, and also the pads at the handle end of the  base, on which it rests. To overcome this, the pad could be raised by the addition of a pad, typically a large flat headed rivet. This approach was rejected in favour of lowering the pivot pin in the base.

 

It had already been decided to open up the holes and fit a larger pin, lowering the hole added very little extra complication.  The decision to increase the diameter was due to the existing pin not being a good fit.

 

It will be required to place a long rod through the pivot holes on a number of occasions. This is so that the part can be checked with a dial test indicator, to establish that it is correctly positioned on the machine table. In view of this, preferably chose a pin diameter for which a suitable rod is available, this will avoid having to turn a long length specially. If a reamer is also available at that diameter, ensuring the holes are a close fit will be easy.

 

If a reamer is not available, then first turn a plug gauge to the required diameter. This will be used to test the bore, to see if it is at the correct size. Make the gauge as is frequently advised, with one, or maybe two steps, at 5 thou. and 10 thou. under size. These are used as early indication that the hole approaches its required size.

 

When machining the base of the vice itself, and the pads on which it rests, it is probable that about 10 thou. will be machined from each. The hole in the base should therefore be lowered by a little under 1/32 inch, this will also allow for the pin to be increased in diameter by 1/16 inch. Of course check the vice to see if these figures are appropriate for the one being machined.

 

Now set up the base on the lathe cross slide as shown in Photograph 1. It is essential the the packing to bring the pivot hole to the correct level has parallel faces. This is to ensure the the pin will be parallel to the base. If it is not, the accuracy of the finished assembly will not be as required.

 

The holes can be bored using a top slide boring tool, mounted in a four jaw chuck as shown. The four jaw chuck will enable adjustments to the hole diameter to be easily made. Alternatively the hole can be bored with a boring bar between centres. The latter benefits from greater rigidity, but then it becomes more difficult to test the hole diameter.

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Metalworking

Workshop Projects

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Tee Slotted Cross Slide

 

If your lathe does not have a tee slotted cross slide, consider adding a plate secured using the top slide’s fixings.

 

The plate can then be drilled and tapped to take fixing studs with which you can secure the item being machined, the vices base in the above case.

 

You will of course need in some cases to add further tapped holes as new tasks for the plate emerge.

 

Personally, I consider that all lathes in the home workshop should be equipped with a tee slotted cross slide, or similar.