Correct boring with a steady - advice please :-)

Hopper read my post again more carefully. You use the dial indicators to true the part with the fingers not touching. That gets the end of the part turning on-axis with no runout. Then you zero the dials and bring the fingers in until they are all touching and the dials are both zero. That means you have it constrained by the fingers AND still on axis. It's about as accurate as you can get it, the only rotational axis error then is in whatever runout you have in the 3-jaw at the other end (and he has a grip-tru so that could be brought to zero).

Setting the finger at the chuck works most times, done it many times but you can still have the part walk out of the jaws especially on thin walled parts. If you set the fingers touching at the chuck then slide it back, your fingers will be centring the part the other end off-axis by whatever runout you have in your 3-jaw. Flat bed ways have the extra potential for error by the amount of clearance between the steady and the inside shears.

Both methods work but to different degrees of accuracy.

OK. Now I understand. Critical point being to not have the steady fingers near the job in the initial setting up. Thank you.

Hi.

So - following the advice, I've turned the OD true with a centre on the end, and found around 0.4mm of out-of-round was present where the steady was set, which is the lion's share of the 0.6mm taper I'm seeing on the bore, and will of course depend on exactly how that interacts with the steady fingers.

With just that, and some care taken around swarf build up, I've got to <0.2mm taper on the bore, which is good enough for this purpose (It's a model light-saber handle I'm making with my son......).

Next will be working out how to hold two indicators as suggested by Pete for better setting of the initial and steadied locations of the stock, but I think that will need to be for when I next need to do something like this again - perhaps a new handle design in a couple of weeks...

On other comments - yes, that's a rather thinner and flexible boring bar than I'd like to use, but is the only one that was both long enough and would actually fit in the largest drilled hole I'm currently tooled up for (25/32" ). For reasons that escape me, I do have a larger bar, but it needs a 1" starter hole...

Thanks everyone, and many good pieces of advice to get my on the road to nice parallel bores !

Youra.

Edited By YouraT on 14/04/2020 21:53:36