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Harold Hall

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In use

As already indicated the jig is primarily intended for use on the lathe's top slide but can be used on the drilling machine as the rear face has been machined parallel to the front face. Photograph 10 shows a chuck key being cross drilled for its Tommy bar. Again the saddle is being fed with the tailstock using a centre in the 3/8" through hole in the jig. The cross hole in the part mentioned above should be made using the same set up.

 

Small diameters, 1/8" to 1/4", can be cross drilled with them being secured by  being passed through the hole in the part, bottom right of Photograph 9, and clamped using the knurled nut, bottom left, on the rear. In this case, the bush holder assembly is not used and the hole is first positioned with a small centre drill.

 

Collars can also be cross drilled as shown in Photograph 11. The collar can either be on a rod on which it is eventually to be assembled, or the rod can be there purely to assist with positioning the part whilst drilling. The photograph was taken with a mirror behind so that the method of securing the collar is shown.

 

When being used on the top slide the jig's use is not confined to drilling at 90 degrees to the workpiece. Photograph 12 shows a bush being drilled at an angle for a simple locking handle of the type that I often use as an alternative to the ball handles often suggested. A centre drill would first be used in both photographs 11 and 12.

 

If using unhardened bushes they should be satisfactory for a few hundred holes at least. A wise precaution would though be to enter the drill into the bush before starting it to rotate. This will avoid any wander of the front end of the drill attempting to bell mouth the bush as it enters.

 

If, like me, you do not have any specific tooling for cross drilling, then like me I am sure you will ask yourself, why did I not make one before?

Metalworking

Workshop Projects

Cross Drilling Jig, using
Cross Drilling Jig, using
Cross Drilling Jig, using
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12

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11

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10

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Drawings