Honing vs reaming

Here's an update on my problem. I had to rebore the castings slightly oversze to get rid of the worst reamer effects, encountering some work-hardened areas in doing so. I obtained some 1/8" thick copper sheet and made up an expandable hone to the design given by Ramon in his thread. I had bought on spec some Silverline Polishing Compound, on eBay, and when mixed with 3-in-1 oil it looked useful, so away we went, albeit with a little trepidation, after all, these were a client's castings !

In the event I found the whole process remarkably simple and controllable. I was able to bring all three bores to the same diameter (there had been just over a thou. difference between them after reboring) and true circularity and parallelism. Bores were checked using an internal micrometer, which in turn was checked with an external micrometer, reproducing the 'feel' of the bore. Thanks Ramon, and all who pointed me in his direction.

The next requirement was to improve the surface finish a little, and here a small brainwave struck. I pass it on in the hope it may prove useful to you. I found some old but unused self-adhesive draught excluder, 1/4" wide grey nylon fur on a nylon backing strip, and having measured the compression available I turne down a length of broom handle to a suitable diameter. I drilled a transverse hole near the end, and another near the lathe chuck. I folded the excluder backing to get it into the first hole, pulled it through and trimmed off, then spirally wound the excluder round the wooden mandrel, finishing similarly at the second hole. The holes were tight enough to hold it in place. Taking my trusty green buffing compound block I mixed scrapingsinto a runny paste with oil which was then dosed onto the fur. A casting was threaded on and subjected to a few cautious passes up and down the length of the mandrel. Inspection gave me the confidence to proceed at a slightly higher speed, and in a short time all three bores were showing a polished finish with a fine underlying scratch pattern from the honing, which I think may well be close to the ideal mentioned by some contributors to Ramon's thread, and mine too.

Let me know if this idea is useful,

Regards to all contributors,

Ken.