using screw chucks

[narrowboater]

I am having my first go at using a screw chuck and am having problems.

I am using them in end grain. The problem is that when I screw the wood on the wood does not seem to go on square, Maybe the hole is too small.

When I manage to get the wood on, and start turning, the wood comes loose .

I have read that the correct drill size is the base diameter of the thread, is that correct.

I have seen people using these chucks on quite large bowl blanks, I am trying to turn some fruit after seeing Richard Finlay's WIP, so we are not talking large chunks of wood here.

 

[loz]

I have seen people using these chucks on quite large bowl blanks, I am trying to turn some fruit after seeing Richard Finlay's WIP, so we are not talking large chunks of wood here.

The most common orientation ( although not limited to ) bowl blanks is side grain though, I cannot see a screw chuck working well on end grain ( unless you can add more screws to pull the piece in )

Is it a screw chuck, or a screw to fit a 4 jaw chuck ? most screw chucks have addition holes to add more support.

got a face plate ? - or just a 4 jaw chuck ?

 

[thomvic]

I don't know what you really mean by "base diameter of the thread" but my advice is to drill your pilot hole as small as you can get away with. You can drill out more quite easily but putting some back is a pain.

Make sure that your pilot hole is square to the face of the wood.

As Loz says, most screw chucks have additional screw holes for the extra support that is desirable in end grain. If you are using a screw in a 4 jaw chuck then the thread should be coarse enough to hold anything but the softest of timbers - providing the piece is not to heavy.

Your work will not come off any screw chuck if you bring up the tail-stock for support.

Richard

 

[CHJ]

narrowboater, In my experience single central screw chucks do not hold very well in end grain as the short lengths of fibre, only as long as the pitch of the screw, tend to strip.
Anything much bigger in diameter than fruit or needing a lot of roughing off of the corners may be unworkable dependant on wood species.

Try reducing the pilot hole to the very minimum.

I have in the the past taken a small endgrain blank back off the screw and soaked the hole with sanding sealer and let it dry to add some strength to the fibres before remounting.

 

[OldWood]

Hi Narrowboater
Did you make the screw chuck that Richard used or is this a 'commercial' one ?

I followed Richard's WIP too without the problem you are meeting, but I did run into the problem that screwing a long screw through a turned block with a dovetail for the chuck always ended up with the screw non-orthogonal to the working face. I tried several ways and in the end just bent the screw adequately straight.

I had no turning problems following what Richard showed and produced a pretty acceptable apple in spalted beech, but I did query how he made his screw chuck and he agreed that whatever he tried the screw always came out squint, so he accepted that and held the screw in a Jacobs chuck and re-turned the block to be true.

Otherwise two thoughts - wood too soft, or screw too short.

Rob

 

[gasmansteve]

Hi NB
Hate to admit it now but when I started turning I used a commercial screw chuck but just gripped the ruddy thing in the jaws rather than install it properly in the chuck, of course the wood was never square and it kept coming loose. When I eventually sussed out that I had it held incorrectly in the chuck it was totally different. If the screw chuck is held correctly in the chuck then the wood has no option but to go on square as it presses against the jaws. Felt a right Plonker at the time but if no one shows you ??? thats my excuse and I`m sticking to it :lol:
Steve

 

[narrowboater]

I have been having another go today, with some success, after reading your posts and re-reading Richard's WIP again (I found more posts added regarding the screw chuck)

I made my own chuck using a 50mm Screwfix Turbogold screw. What I did after turning the wood chuck piece was to drill a 2mm pilot hole using a Jacobs chuck in the tailstock. I then put a screwdriver bit in the Jacobs chuck, and used the tailstock to hold the screw up to the block mounted in the Lathe chuck. I turned the lathe chuck by hand and followed the screw up with the tailstock. The screw went through the block dead straight.

When I used the screw chuck I supported the work with a tailstock for as long as possible, as I was nearly finished the work came loose due to me being a bit heavy handed, so I made another using a 60mm screw, and hey presto, I now have an apple, I just need to turn the stalk, and it is finished.

It is certainly not up to Richard's standard, but for a first attempt I am happy, SWMBO now wants some more and some pears. When I bought the blanks for the fruit I bought a 10"X3" Spalted Horsechesnut blank for the bowl, so I have plenty to keep me busy while the snow falls!!!

Thanks for the advice chaps, as always much appreciated..

Regards
Rod

 

[Jonzjob]

Come on then Rod!! Werz the pikkies please?

 

[Richard Findley]

Hi Rod,

Sorry, I'm a bit late on this one and everything seems to have been covered pretty well so all I can add is: Where's the pictures :?: :?: :wink:

Richard

 

[narrowboater]

Just need to turn and fix a stalk, and then I will do battle with photobuncket and upload some pics.

Regards
Rod