Blunt hand rea.mers

I am housebound at the moment with a nasty bout of sciatica. Having nothing better to do, I started thinking of sharpening some blunt hand reamers. If you have the right kit, this is a not a difficult job. BUT the reamer will finish up a thou or two undersize.

I started to consider my machine reamers, now these can easily be sharpened, and as the cutting edge is at the front of the reamer. You finish up with the original diameter.

So why not regrind the hand reamers in the same manner? OK these are plain shanks and you will need to make a MT adapter for machine use. Maybe not quite so easy to get everything in alignment. However if you have a self aligning reamer attachment, then any alignment errors do not matter.

Sounds a great way of saving your blunt reamer. There must be a snag somewhere otherwise the idea would have been hit upon before now! So where am I going wrong?

Andrew.

Edited By Andrew Tinsley on 15/08/2017 16:08:04

I have a chipped 1/2" hand reamer. the chip is on the taper and I have thought about cutting the end off and resharpening it as a machine reamer as an experiment.

The only reason I haven't is because I already have two 1/2" machine reamers!

The bugbear is that the flutes may not be evenly spaced, so I guess you need to index using the flute you are actually grinding.

Have a try and let us know how you get on.

Neil

I have heard/read that if you draw a carbide tool down the face of the flute it will sharpen the reamer, anybody ?

Clive

Clive Hartland:

Yes, the same tip was given to me by a toolmaker friend. I think the effect is rather like setting up a cabinetmaker's scraper.

Hi Guys
Yes Clive its called bumping up a reamer . we used ot quite often you can also put a shim say about 2 thou along side the reamer
Nobby

It is true that any hard edged tool such as a high speed lathe tool bit can be scraped very firmly along each flute of a reamer to raise a minute burr that will have the effect of sharpening it. This may not work on a badly worn reamer as it can only be expected to increase the diameter a maximum of 0.002" ​at the cutting edge.​ I used this method occasionally during my toolmaking years to make a reamer cut oversize. Colin

Back to the original question:- You can sharpen hand reamers in the same fashion as machine reamers, but you'll need to cut off the tapered part first, otherwise it'll still be cutting on that (blunt) tapered length.

Doesn't a hand reamer size the hole on it's parallel section? Colin

I would just run a small sharpening stone up the side of it or maybe a diamond lap or file, normally on 1/2" theres plenty of room to do this without scuffing up the geometry.

Michael W

I had a problem with my change wheels on my warco not fitting on the bushes & even the ones fitted had to be removed with a puller. I took them to a toolmaker friend who ran a 14 mm reamer through one but it was still slightly tight. He ran a carbide burr up the face of each edge of the reamer & not only did it cut better but it took anothe couple of thou off & the gear wheel fitted as did all the rest after reaming.

Wonder how far down the parallel portion does a blunt hand reamer get blunt?

By analogy with a machine reamer the part that does the final sizing will be round the transition from taper to parallel. Once the hole is bought to size surely the rest of the parallel part is pretty much along for the ride doing little, if any, cutting so should remain sharp much longer.

So you sharpen the taper reducing making it longer and reducing the diameter at the front. Transition point to the parallel part moves backwards hopefully intercepting a still pretty sharp portion of flute.

Unfortunately none of the T&C manuals I have really address the problem of sharpening remorse without altering size.

Clive.

Hello,

I had forgotten the taper portion of a hand reamer. I suppose that could be cut off and sharpen the end of parallel section as per machine reamer.

To be honest I am not much of a fan of hand reaming. Sometimes it works, but often the finish is poor and cuts oversize. I have read the books and have learnt how to get the best out of hand reaming. But I am still not overly impressed.

I find a machine reamer and a floating reamer holder, to be just about bullet proof. I have yet to have anything but an excellent finish and a correct hole size. I can't claim that from my hand reamers.

OK so where am I going wrong again?

Regards,

Andrew.

Edited By D Hanna on 15/08/2017 23:59:47

I believe most, if not all, reamers are sharpened while supported between centers. If the end of a reamer is cut off The center will be lost. I suppose a reamer could be sharpened while held in a collet but suspect the accuracy will be less than if sharened between centers.

If the flutes are not indexed accurately, don't worry, this can ofted eliminate chatter by putting the cutting edges "out of step", that alone will not effect diameter.

Ian S C

One of the excellent Machinist's Bedside Readers has info about a reamer stoning jig. Basically the reamer is mounted between centres, indexed by a blade engaging with a flute, and sharpened by a hone supported between the edge and an inclined plane that is set up parallel to the tapered bit. I'll try to dig it out.

Andrew Tinsley:

What floating reamer holder are you using, please?

I assume you are boring before reaming.

I would also be interested to know what allowance you leave for the reamer.

Trust the sciatica is better.

Hi ega,

I use the one that Hemingway sell as a kit. It's self aligning properties are surprisingly good and makes up for any lack of skill on the operators part. I usually bore to about 10 thou undersize before reaming. That is both for hand reaming and machine reaming. Sciatica rampant, can hardly walk! Getting old really is good fun!

John I completely forgot about the fact that the reamer is sharpened between centres! So that rather complicates the issue and probably makes it a non starter! Quite why I forgot this, beats me as I currently sharpen reamers on a friend's Quorn (until I finish mine!). So big black mark I am afraid. Did I say something about getting old?

Andrew.,

Andrew:

Thanks for the recommendation about the Hemingway kit.

I didn't like to ask if you had finished your Quorn (!) and hope you will soon be able to get back to it.

A senior moment about chopping off the tapered portion of a hand reamer. All one need s to do is stick it in the Quorn and grind off a couple of mms of the flutes back to the parallel portion and then grind the machine reamer profile on the end of the complete flutes. That way you retain the centre.

Andrew.