Hi guys thanks for the kind comments relating to the end products and my technique.
As you can possibly see the procedure's took place on two lathes, a Dominion Patternmakers wood lathe (unfortunately without the saddle and cross slide) and a large engineering lathe.
Initial sizing and a round tenon for the chuck was turned between centres on the wood lathe then the piece mounted in a nova chuck. I then placed the whole lot including the chuck in the metal lathe ensuring it was correctly centred by initially utilising the tailstock and centre
From there I mounted a 2 1/8" forstner bit initially in the tailstock chuck and bored as deep as it would let me, I then used an extension piece (which I had made on the engineering lathe) to get the bore down to approx 12"
From there I utilised the home made boring bar (made from a piece of M20 studding, this being the most suitable size of material available to me at the time I would ideally have liked it to more substantial) and continued boring until I got the diameter to the 80mm that the glass sleeve required (I allowed 3mm clearance to manage any movement in the timber used). The boring bar was surprisingly accurate, I initially started each cut slowly with the topslide then once established utilised the power feed on the lathe to the required depth (masking tape on the boring bar)
From there I made a centred end stopper for the hole and returned to the wood lathe turning the beads and coves for the bottom of the column using spindle gouges and a parting tool for the beads. I could have turned the main body here however I feel that to get the whole column perfectly parallel with a skew by hand is hard and if it were not perfectly parallel then the fluting would possibly not look right, also I did have to return it to the engineering lathe to carry out the fluting.
Once back on the engineering lathe and using the end stopper to support the loose end mounted a small router on the lathe's top slide (this is in a bracket I also made on the engineering lathe and fits to a height adjusting slide which fits where the tool post fits) from there using the powerfeed I paralleled the column then fluted it using a stop on the lathe bed.
Again back to the wood lathe for final sanding and polishing using a shellac based friction polish and wax.
The bit I was most worried about was sanding and polishing the inside of the bore as the piece was only supported one end however this was not a problem and I only wanted to sand/polish just past the depth of the glass tube (wouldn't want to stick my hand any further down with the thing whirring round)
tekno.mage":296t9xlb said:
katellwood":296t9xlb said:
If I were to make others I think I would invest in a 3” forstner bit as the boring for the glass got a little bit laborious
Not sure a 3" forstner would be much less laborious than using a boring bar - as you'd be repeatedly removing the drill bit to clear shavings and allowing it to cool down - especially the deeper you get into the hole - you also have the issue of drill wander.
I am intensely envious of your lathe and tooling - I've always wanted to try turning wooden items on an engineering lathe as the prospect of increased precision appleals - and I've often thought that using a boring bar would be the answer to difficult wood drilling jobs on the lathe.
Re the use of a 3" forstner bit, My technique would be (as Richard suggests) is to initially carry out a cut to a depth of approx. 1/4" with the 3" then bore out again with the 2 1/8" bit. Once bored I would return to the 3" which had already been centred and slowly carry out the 3" cut. The engineering lathe's lowest speed is 10 RPM in addition It is powered via an inverter therefore with a slow feed speed I could control the cut and any heat generated
There has been some really nice comments made on this thread and from some really professional and experienced wood turners. I would be interested to know any other techniques turners use for deep accurate boring
wem":296t9xlb said:
Really nice! What kind of wood?
Its a Mahogany based timber not sure what as identified above its an old snooker table leg so should be dry and pretty stable
Thanks again all, any further projects I will also post