Choosing a boring head

[JasonBModerator @jasonb]

You have two issues

Firstly as you mention will be distortion which is quite likely clamping as you have shown or even with a second Vee block, Better would be to bore a hole in a block of say aluminium then saw in half then hold the bush in what in effect will be nesting jaws.

Second issue is that Oilite bushed are made oversize in bot OD and ID with the idea being that when pressed into place they close down to the correct bore. You will need to work out how much oversize is needed so that you get a goof fit once installed. Alternative would be if you can fit to the part and then bore in position.

[Clive FosterParticipant @clivefoster55965]

Jason

A most excellent description of how to grind the toolbit, hope you don't mind me stealing it for next time I get asked!

Further to potential distortion issues when enlarging a bush bore my procedure is to make an alloy holder with the correct bore to take the bush then drop it in boiling water to expand it so the bush slides in more easily.

Bore out.

Make an extraction mandrel a stiff sliding fit in the new bore and a touch undersize in the holder.

Drop it back in boiling water to expand and push the enlarged bush out.

Not tried it with oilite, which needs a specified nip on the OD, but its worked for a bush of about 30 thou wall thickness made to repair a direct in the casting bearing with almost no spare metal around it. (Third time was the charm!)

Clive

[Bill PhinnParticipant @billphinn90025]

Many thanks for the further replies.

Jason, yes, I'd read about the likelihood of the bearing's inner diameter reducing after fitting. I think it may have been very wishful thinking on my part that I could hit the right ID with the bearing uninstalled and not have to rebore it after installation or scrap it entirely because I'd rashly overbored the whole 40mm depth of the bearing.

Given the additional need to encase the uninstalled bearing in a nest/sleeve of some sort in case it gets squeezed out of round in the vice, I'm not going to attempt to bore with the bearing uninstalled but bore each slice of bearing in situ using a setup like in the photo [held on parallels in the vice]. Obviously the bearing in the photo has not yet been installed, but it will be!

Hopefully the actual bearing won't need any clamping to stop it turning when it's being bored. I don't know the answer to that at present, unfortunately; all I can say is that it will be a good tight fit judging by the feel of things and by the OD of it and the ID of the big end.

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