How do I ream a 15mm hole on a Unimat 3 ?

[paul1956Participant @paul1956]

As first proper project I’ve bought a Beng Danni stationary engine kit.

From what I read before purchase everything ought to be able to be machined on my Unimat 3. Now the kit has arrived I see that the cylinder will need to be 15mmH7 finished in the brass bar stock.
I think I can work up through drill sizes with what I have available to ½” (12.7mm) and then use a boring bar to get close to 15mm. That leaves the final reaming, but a 15mm reamer won’t fit in either my chuck or ER16 collet set.
Do mount a 15mm reamer dialled into a 4 jaw chuck mounted on the tailstock ? Or is there another method that won’t involve great expense ?

Thanks in advance for any suggestions.

[egaParticipant @ega]

Do you really need to ream? A bored hole can be as good as a reamed one.

[DustyParticipant @dusty]

Paul

Do not use a reamer, the chances are the bore will not be round. Bore to finished size. Your bore will be round and not threepenny bit shaped (slight exagaration) Reamers are sizing tools not boring tools.

[JasonBModerator @jasonb]

Even if you could hold the reamer chances are it will be too long. But for future reference I used to hold large drills etc in the 3jaw lathe chuck either on the tailstock or milling attachment.

As others have said if you are set up to bore it out to reaming size you may as well just bore to final size. Use the piston to gauge the fit rather than working to actual measurements.

[noel shelleyParticipant @noelshelley55608]

Assuming the reamer has a square shank and is centre drilled then using a large tap wrench and align with a tailstock centre ream out as needed. Rotate the work by hand in the chuck.  Noel.

[Michael GilliganParticipant @michaelgilligan61133]

I don’t know the kit, so this may not be practical … But

The job seems to cry-out for a between centres boring bar, and the component clamped firmly to the cross-slide

 

MichaelG.

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