Mounting square section accurately between centres

[starcott]

I am about to prepare some square section timber planing it down to 40 mm,
to make them into staircase spindles.

The ends of the finished spindle will remain square at 40mm.

How do I mount each piece of timber accurately between centres so that the parts which I am leaving square will turn true and not slightly off centre?

Or is it better to start with over-size timber and plane the square parts down to 40 mm after turning the shaped parts?

 

[Wood spoiler]

By etching across diagonal corners it will mark your centre on each end. Mark the centre with a punch and then use the centres of the drive and tailstock and all should be neatly done on the correct axis

 

[Jacob]

Or marking gauge from each side set near to half thickness. Produces a little square which you punch in the centre. Unless you have it exactly half thickness in which case it produces a cross, and ditto.

 

[Spindle]

Hi

If you have to find a lot of centres you may wish to invest in a centre finder similar to this - http://www.amazon.co.uk/Silverline-Cent ... 190&sr=1-2 - speeds things up no end.

Regards Mick

 

[Jacob]

Not as fast or as versatile as a marking gauge however.
Would that gadget do square sections anyway? Doesn't look like it. Marking gauge will do for round sections too.

 

[jumps]

Colin and Jacob have outlined solid methods of establishing the centre, if you have a lot the same size you could also make up a quick jig as well.

However, whilst the centre is easy enough to locate accurately, there are some drives where the 'point' isn't pronounced enough to do so and the 2 or 4 prongs can react with the grain to create an off centre location - otoh a Stebcentre will get it right every time!

 

[Wood spoiler]

Colin and Jacob have outlined solid methods of establishing the centre, if you have a lot the same size you could also make up a quick jig as well.

However, whilst the centre is easy enough to locate accurately, there are some drives where the 'point' isn't pronounced enough to do so and the 2 or 4 prongs can react with the grain to create an off centre location - otoh a Stebcentre will get it right every time!

Agree

Steb centres are great at workholding without throwing work off centre

 

[dickm]

Would an alternative be to make a cup centre out of any harder wood than used for the spindles? That is, fix a blank in chuck or on faceplate and turn an accurate conical recess in the blank, large enough to accommodate the square section. Then the turning has to be "concentric" with the square and the friction drive should be more than adequate with care.
Someone used to make a set of alloy cup centres with a morse tape shank, but can't remember who.

 

[Spindle]

Hi Jacob

Yes will do all sections and requires no initial set up - functions in exactly the same way as a combination set centre finder.

Regards Mick

 

[woodpig]

The suggestions above are very good, and it's the method I've used for marking and turning square stock but it's still not very accurate. I carefully punch the ends but the grain of the wood will often decide for you where the centre is! :roll: I think for your application it would be a good idea to use oversize timber and square up afterwards. It's still a good idea though to mark and punch the centres as closely as you can before turning.

 

[CHJ]

I guess whichever method Richard uses does the trick, and as far as I'm aware all his stock is finished to size before turning.



On the few I've done I've allowed some extra scrap length and gripped the square section in the chuck jaws so avoiding any headstock centre drift or loss of drive.

 

[woodpig]

On the few I've done I've allowed some extra scrap length and gripped the square section in the chuck jaws so avoiding any headstock centre drift or loss of drive.

Thats a good idea. In fact if you have lots of spindles to do it would be well worth making a square jig of some sort for the other end as well.

 

[Richard Findley]

Hi

I think you'll find that mounting the timber will be the easiest part of turning a stair spindle! The biggest issue you will have to battle is going to be the flex that you will experience during turning.

Start off with properly sized and squared timber, an inch or 2 longer than needed.

I use a combination of the things listed above: I find the centre using the marking gauge method, as described above. Don't worry too much, a mm or 2 won't make a noticable difference.

I also use a chuck to hold the top of the spindle. Not so much for the centreing reason but so that so I don't have to put too much pressure on the ends of the spindle, too much pressure here will make the centre deflect and increase your difficulties so only tighten the tail just enough.

I hope this is of some help

Cheers

Richard

 

[starcott]

Thank you one and all for those helpful suggestions.

I've decided to use the chuck on one end, with a revolving centre at the other end.

John

 

[Jonzjob]

I have one of these http://www.axminster.co.uk/veritas-veri ... prod22794/

A lot more now than when I bought mine. I use it a lot and it's so easy! Center punch thec enter and stick it between 2 steb centers. Works for me, but now I have heard Richards method just use the tailstock steb center and a chuck...