Drill wander is a major feature of all deep hole drilling and deep hole boring machinery and service provision. This is where the drilled hole will start perfectly on centre and although the bore will be completely straight, the exit will be off-centre by an amount relative to the length of the hole drilled.
We try to minimise this in a number of ways, for example, ensuring contra-rotation of the billet. This is where the billet is rotated in the opposite direction to the chuck. In some cases, customers allow for us to drill the billet from each end as mismatch in the middle of the bore is permissible if the bore is for lightening, air or fluid flow.
Another way is by ensuring that the faces of the components are clean, even and chamfered. Again, even this simple act of chamfering the billet can add additional cost to the quotation and reduce our competitiveness as the handling, loading, set-up then facing and machining of a 45° chamfer on a billet 200mm diameter x 2 metres long can take up to an hour depending on the sawn face supplied potentially adding a cost the customer was not expecting.
However, without this, drill wander can be worsened from the industry standard of 1mm per 1 metre drilled or how it is usually referred to in the industry: “one thou per one inch drilled”. Therefore, we quote a method that we believe will offer the best possible result for the customer but again, at initial review, the customer may only see the price we quote, not the reason we are quoting it.