Confurion sharpening hand reamers!

[Andrew TinsleyParticipant @andrewtinsley63637]

Still down with sciatica, so an excuse to do some reading. Professor Chaddock states in his book on the Quorn, "Sharpening hand reamers on the Quorn will result in an undersize cut of about 2 thou" Or words to that effect. OK, this implies that the parallel section of the hand reamer is sharpened as well as the taper section.

Picking up Harold Hall's book on sharpening tools, I found the following statement. "Hand reamers cut on the tapered section". Now if this is correct, one only needs to sharpen the taper section, The parallel section is left alone and the reamer should cut to dead size after sharpening.

Who am I to judge the apparent difference of opinion between these two eminent gentleman? Who is correct or am I missing something as usual?

Andrew.

[Andrew TinsleyParticipant @andrewtinsley63637]

[Michael GilliganParticipant @michaelgilligan61133]

Andrew,

I think the problem might be that Harold's statement is "the truth, but not the whole truth"

Yes, they cut on the tapered section, but they also cut on the parallel section [if only to remove the residual taper from the hole]

MichaelG.

[Andrew TinsleyParticipant @andrewtinsley63637]

Hello Michael,

Thanks for your response. So if you have a less than sharp hand reamer, sharpening just the taper section should give a big improvement in reaming? Obviously it would be good to keep the reamers nominal size.

There have been comments in a previous thread about hand sharpening the whole reamer by "bumping up" the cutting edges using say a piece of HSS or something similar. This dodge can make a reamer cut oversize, although perhaps not for long as correct sharpening?

Seems a bit of a murky topic!

Andrew.

[HopperParticipant @hopper]

If you sharpen the face of the reamer cutting edge and not the outside diameter, the reduction in diameter will be in tenths of a thou. This can usually be done with a cup wheel or dish wheel suitably dressed.

You can probably get away with just sharpening the tapered section as this does 99 per cent of the work. Thus the maximum OD is left as is.

It might be worth your while to try to track down a user manual for a commercial T&C grinder and consult the section on reamer sharpening the way the professionals do it.

[Michael GilliganParticipant @michaelgilligan61133]

Andrew,

I think Muzzer has covered the taper question nicely … so I will just comment on the 'bumping up'

Whilst I am not really convinced that this is a very practical idea with good multi-flute reamers, it certainly works on a home made 'toolmakers reamer' [not sure if that is the accepted term] … I remember my Dad showing me how to size a bronze bush, by cutting a single longitudinal groove in a piece of silver steel and then raising a 'scraper edge' on one side … for a one-off job, it's effective [and cheap!].

MichaelG.

[Rik ShawParticipant @rikshaw]

Andrew – Stop confurion yourself you will only make your sciatica worse. Chuck it in the bin and buy another.

Rik

[Andrew TinsleyParticipant @andrewtinsley63637]

Thanks Hopper,

Then it looks as if Professor Chaddock got this one wrong! He obviously was recommending the outside edge of the reamer should be ground and hence the reduction in diameter. I was confused by this as I thought, like yourself that if the inside edge of the cutting area was given a lick over then it would sharpen the parallel part of the reamer, with minimal decrease in overall diameter.

So it looks like problem solved, thanks both.

Andrew.

[not done it yetParticipant @notdoneityet]

Theoretically you should sharpen to just past the old parallel bit. That way both the taper cut and the last little bit will be cutting with a keen edge. Ie the taper will be slightly extended each time the reamer is sharpened.

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