How to sharpen expanding reamer blades & how to adjust them?

[Grindstone CowboyParticipant @grindstonecowboy]

A bit of a theoretical question, really – recently obtained a couple of expanding reamers from a friend which are in a bit of a sorry state. Whilst taking them apart for a good clean, I started wondering if re-sharpening is possible. I’d guess the only proper way would be with a surface grinder and some sort of jig? Which is why it’s theoretical – I don’t have a surface grinder!

Obviouly you’d lose a bit on the diameter, but would that actually matter? Which leads me to my next question – do you set them up by adjusting, measuring across two opposite blades with a micrometer and re-adjusting until you get the size you want, or is there a better way?

Thanks,

Rob

[Neil LickfoldParticipant @neillickfold44316]

I have sharpened them in the past, I did it between centres on a tool and cutter grinder. Grinding them in place at the highest setting that allowed for the blades to be above the cones for grinding.

I guess in theory they could be sharpened as a set with a fixture so all are ground as a set, like they do with planer blades.

[bernard towersParticipant @bernardtowers37738]

Never sharpened them before but in use I tend to creep up the dim required mostly using the pin as a guide (Im talking heavy truck king pins) but have also done it with small end bushes on GPO Bantams!!!

[noel shelleyParticipant @noelshelley55608]

Like Bernard I usually use above 1″ and go one cut at a time and try with the pin. As for regrinding I would set up on a T&C grinder between centres and do 1 blade at a time. Do all adjustable reamers have the same taper ? Noel.

[JasonBModerator @jasonb]

And like a hand reamer is it only the first part of the blade that has the lead in taper?

I’m the same and just sneak up on the size until the male part fits in. Don’t use them that often but do have some 8mm PGMS that is a bit tight in the usual H7 reamer cut holes so use the adjustable to ease bearings.

[Grindstone CowboyParticipant @grindstonecowboy]

All good info, thanks. I hadn’t considered the lead-in taper at all.

I was imagining a stack of blades, just off vertical by the amount of relief angle required, could all be ground together to ensure they are equal. However, if the non-cutting edge is square with the width, they would be resting on one corner, so some kind of accurately made jig with a very shallow saw-tooth profile/section would be needed to support them fully.

Both of the reamers I have are around 19mm diameter – one cleaned up nicely but seems blunt, the other is sharp, but has rusty spots due to being stored in its original cardboard box.

Rob

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