Taper reamer with adapter peice.
The extension bar and reamer in position.
The expanding reamer kept in alignment by the extension bar. Note the cutting oil used in this operation.
The bronze bush pressed into position - actually 2 bushes inserted one from each side and pressed in with ½" Whitworth studding, washers and nuts.
Restoration of the rear suspension – repair of worn shackle bolt holes in the chassis.
At the very rear of the Riley chassis is a cross member connected to the chassis side rails by cast steel ‘dumb irons'. These each have a ½ inch drilling for the rear spring shackle top bolt.
Over time these holes can become oval through wear and inadequate lubrication. It is possible that worn holes could affect the handling of the car by allowing unintended movement of the rear spring shackles; I couldn't say, but if Rileys had wanted oval holes they would have no doubt made them so. Other shackle bolt connections have bronze bushes which can be fairly easily replaced; that just leaves the front dumb iron connection which is another matter altogether!
Three remedies seem possible –
pretend it hasn't happened
drill the holes to the minimum round diameter possible and make oversize shackle bolts to fit
drill and ream the holes to fit bronze bushes for standard shackle bolts.
During the current restoration of a '34 Kestrel ‘9' I discovered the holes were indeed significantly oval, so while the chassis was bare (before remounting the body) I took the opportunity to fit bronze bushes. In this way any future wear could be dealt with by replacing the bushes, as is the case elsewhere in the chassis. It was therefore necessary to open out the holes to ¾ inch for standard bushes. (I considered fitting oversize bolts, but concluded that this was far more complicated than keeping to standard size hardened bolts and standard shackles – and the holes would require opening out anyway.)
I was concerned that in removing 1/8 inch of material all round it would be possible for the resultant hole to be out of alignment. To avoid misalignment I decided to make up an extension drive bar which would locate through the opposite shackle bolt hole to the one being opened up. This would act as a kind of ‘line boring' tool. The drive bar consisted of a 5/8 inch diameter steel bar with both ends lathe turned down to ½ inch diameter over approximately 1 ½ inches. One end could then be fitted to a slow drill or large tap wrench; the other end was fitted with an adapter piece to which the reamer was fitted.
The oval holes were initially enlarged to 18mm using a drill operated taper reamer. An adapter piece was made for this as well so that the parallel section could be run all the way through the hole. This left the holes large enough for the extension bar to be offered up and close enough to the finished ¾ inch to reduce work with the expanding reamer. I found the cast steel rear ‘dumb irons' material worked easily provided the cutting tools were kept lubricated with cutting oil. Some misalignment of the initial hole enlargement was corrected in the process. By using the expanding reamer it was possible to leave the hole about 0.003 inches undersize to achieve an interference fit for the bushes. The bushes were lightly chamfered on the leading edge to allow easy starting when pressed in, and prepared with a parallel ½ inch reamer for the new bolts; I have found in the past that bushes, when pressed into position, can shrink slightly.
The extension bar, used in the way described, was very successful in maintaining alignment of the holes, so that the bolts fitted the shackles as intended without being forced. However, the enlarged hole centre was not necessarily coincident with the original hole. I suspect the job I carried out resulted in the new hole moving slightly up, leaving an uneven thickness of steel wall. The amount of variation looks fairly minimal and, happily, the shackle is entirely unobstructed. Nevertheless, some preliminary hand filing of the hole might have maintained correct centricity.
The photographs show the extension bar and reamer in position, and the taper drill reamer and adapter. Costs were quite negligible. The reamers were bought new for under £25, the steel bar was ‘begged' from a friendly local engineering firm, and the adapter pieces were made from small scrap steel offcuts. The time taken was about 3 evenings. I suspect the job could be done with the body in place, although on most models the rear wings and the boot lid would probably need to be removed to give clear working space.