Aligning extension beds..

[Keithie]

I have the Record DML320 and its extension bed.

I've attached and bolted the extension to the lathe (funnily enough)
I've checked they are aligned with a 12" metal ruler along the edges.. looks good ..but only 6" in on either side
I've checked they are flat with a spirit level (after adding some scraps of card etc) and its pretty good

Not bolted extension bed to the worktop yet (lathe is bolted down...it wandered about a fair bit with just a 12" 3x3 before bolting and chasing the lathe round the bench with a small parting tool wasnt easy!)

Can anyone tell me how I would figure out if the headstock and tailstock are really aligned (ebough for there to be no practical problems than usual when reversing pieces) when the tailstock is at the far end of the extension bed....or is it just obvious that they wont really be aligned too well and there's nothing to do to get it 'spot on' ? Don't really want to bolt the extension bed down until things are really quite close.

thanks in advance

 

[flh801978]

I don't think that it matters a jot whether the centres are aligned when you get more than 6 inches from the headstock.
Its only if you are holding a piece in a chuck and using the tailstock for support...it needs to be on centre.
If you are turning between centres it does not matter
Ian

 

[Keithie]

I think that is almost certainly right ..as far as I can make out ... perhaps until you want to reverse the piece on the spindle (boring a narrow tube from both ends).

Maybe its me doing something wrong, but when I turn a longer piece around its nothing like centred, even though it was before ! I was assuming that was to do with headstock/tailstock misalignment ..but maybe its just 'useless user syndrome' lol!

 

[flh801978]

I cant imagine what you mean ? If you are turning a spindle between centres and turn a spigot say at both ends and then reverse.... its out of round?
If you are using a hollow centre in the tailstock to drill holes again the misalignment shouldn't matter..if you holding say a short length in a chuck and drilling from a jacobs chuck then alignment is important
Ian

 

[CHJ]

.........Maybe its me doing something wrong, but when I turn a longer piece around its nothing like centred, even though it was before ! ....

Turning between centres is just that, reversing between them should be identical.

And as said bed extension 'perfect alignment' is not necessary for spindle turning, tailstock alignment is only essential when drilling from a tailstock and using the quill travel or long hole boring through the tailstock, but in the long hole boring case I think it would have to be a significant/obvious mis-alignment to have any more influence than the pull from spindle grain direction influences.

What you may be getting is a less than perfect pronged drive location in the headstock to drive the piece or the pronged drive has moved its centre point as it bedded further in as you tightened up your tailstock or started turning.
This would result in an over size or elongated 'centre point' in the headstock end which could be a less than perfect register for the tailstock centre when reversed.

Any sharp catches on square stock when you start rounding off the piece can move the headstock end sideways a small amount on a less than good drive location, especially softwoods with a wide grain pattern.

 

[Keithie]

Thanks both ... I've now ordered a spigot jaw for my chuck so that should help.

I've been using a four prong drive and standard tailstock revolving head to get a cylinder then switching out the tailstock centre to a jacobs chuck and smallish wood augur (hence the tailstock moving to the bed extension) boring some way and then swapping ends. Hopefully the spigot on a chuck will be better for me at my skill level than trying to pin the piece between a 4 prong drive and drill bit.

(I must also buy a scraper, presumably a heavyish round nose one, soon too...so many basic techniques to try to get right and so much stuff to buy!)

 

[Keithie]

oh ...and yes, I am using cheap softwood and offcuts for practice ..mostly ex-Jewson from other home projects and also from the local dump's wood recycling 'skip',

 

[CHJ]

The chances of your wood auger boring dead on centre is very problematical, much depends upon the auger not following the grain.

If you need the hole you are boring to be perfectly centralised, say for a matching component spigot to fit then you need to bore the hole first and locate this on a suitable (drive) centre or pin jaws to finish off your outer cylinder.

 

[Sheptonphil]

Thanks both ... I've now ordered a spigot jaw for my chuck so that should help.

I've been using a four prong drive and standard tailstock revolving head to get a cylinder then switching out the tailstock centre to a jacobs chuck and smallish wood augur (hence the tailstock moving to the bed extension) boring some way and then swapping ends. Hopefully the spigot on a chuck will be better for me at my skill level than trying to pin the piece between a 4 prong drive and drill bit.

(I must also buy a scraper, presumably a heavyish round nose one, soon too...so many basic techniques to try to get right and so much stuff to buy!)

From this description it sounds like you are using the auger as a live centre and boring at the same time?

Seriously dodgy and dangerous way of turning if my take on the situation is right.

You should only be boring from the Jacob chuck if the work is held in a chuck in the head or through a proper hollow live/ring centre in the tailstock.

Phil

 

[Keithie]

^ agreed ....no wonder I was struggling, realising there was a problem and asking for help ! ... I now have a nice spigot adapter for my chuck (1" O'Donnell) ....far less scary/stressful!

 

[gregmcateer]

Another possibility regarding reversing not being centred is what I had a while back - I was tightening the tailstock too much, so when reversed, the pressure was pushing the piece off centre.

 

[Keithie]

thanks Greg ...I almost certainly do that ...I use tailstock to makes sure headstock drive centre is biting well...I'll be lighter with that, see if it helps.