Having a go at bowls now. Cut the tenon as advised, turned it round and tightened my Record chuck down onto it. I note that, to get it tightly held enough to not throw itself across the room when I am trying to cut the inside out, I have to get the chuck to grip really hard, so much so that it cuts teeth marks on the tenon. Am I missing the point here - is there a way to avoid this, or should I improve technique so I dont have to grip so hard?
Avoiding chuck marks
- Thread starter wabbitpoo
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PowerTool
Established Member
If you are making a tenon,then gripping with the jaws in contraction mode,then I would always play safe and make sure it grips tightly (and re-check and re-tighten if required whilst turning)
Don't want it coming loose and flying across the workshop,or even slightly loose and going off-centre.
Presumably you are going to either part off above the tenon,or reverse the bowl and turn it off anyway,so what does it matter if there's some marks on it ?
Andrew
Don't want it coming loose and flying across the workshop,or even slightly loose and going off-centre.
Presumably you are going to either part off above the tenon,or reverse the bowl and turn it off anyway,so what does it matter if there's some marks on it ?
Andrew
pete honeyman
Established Member
Hi
if you grip a tenon, you'll inevitably get some marks, usually very noticeable. The solutions are either to reverse the bowl again when hollowed (using a jam chuck or cole jaws in the chuck) and turn the foot away, or use a recess instead of a tenon, then the marks are inside the recess and virtually invisible. I believe you get a stronger grip from chucking inside a recess, and it gives you somewhere to sign the bowl when it's done.
Pete II
if you grip a tenon, you'll inevitably get some marks, usually very noticeable. The solutions are either to reverse the bowl again when hollowed (using a jam chuck or cole jaws in the chuck) and turn the foot away, or use a recess instead of a tenon, then the marks are inside the recess and virtually invisible. I believe you get a stronger grip from chucking inside a recess, and it gives you somewhere to sign the bowl when it's done.
Pete II
Dave Huxley
Established Member
I usually wrap a piece of kitchen paper around the spigot, you don't have to go over the top in tightening the chuck especially if the wood is soft or green as this will distort the spigot.
I usually mark the chuck and spigot with a pencil incase you want to take the work piece off for any reason then it goes back in the same position.
Are you putting a dovetail on the spigot to accomondate the chuck jaws? Assuming your Record chuck has dove tailed jaws as mine used to be.
Dave
I usually mark the chuck and spigot with a pencil incase you want to take the work piece off for any reason then it goes back in the same position.
Are you putting a dovetail on the spigot to accomondate the chuck jaws? Assuming your Record chuck has dove tailed jaws as mine used to be.
Dave
cornucopia
Established Member
it also helps if the spigot is a good fit in the jaws- ideally fully close your jaws then back them of about 1/2 a turn that is the ideal place they should be in when fully tightend onto a spigot. at that point they are as near to concentric as is possible and so will grip at their strongest and mark wood less as the force is spread over a larger/concentric area.
wow. so many replies so quickly.
Yes, in contraction mode. Its the jam chuck bit I am not yet clear about - maybe I should read the entire book before starting!
Is that just a rounded lump, held by the chuck, against which I push inside the bowl with pressure from the tail, so I can then turn off the tenon? If so, how do you get the bowl nicely centred again on it?
Yes, in contraction mode. Its the jam chuck bit I am not yet clear about - maybe I should read the entire book before starting!
Is that just a rounded lump, held by the chuck, against which I push inside the bowl with pressure from the tail, so I can then turn off the tenon? If so, how do you get the bowl nicely centred again on it?
cornucopia":b7zrqg03 said:
As above,
In your booklet there will be the optimum gripping diameters for recesses and spogots.
Eg my RP3000 says 42mil spigot and 40 mil recess. As George says this is with the jays just opened. This is due to the jays being made from a disk, that is then cut into 4.
( Learnt that last week ! )
Loz
CHJ
Established Member
cornucopia
Established Member
wabbitpoo":3dd3eixl said:wow. so many replies so quickly.
Yes, in contraction mode. Its the jam chuck bit I am not yet clear about - maybe I should read the entire book before starting!
Is that just a rounded lump, held by the chuck, against which I push inside the bowl with pressure from the tail, so I can then turn off the tenon? If so, how do you get the bowl nicely centred again on it?
a jam fit chuck can be acheived in a few ways- you can mount a larger diameter blank then create a recess so the rim on the bowl just fits, or a variation on that theme is to create a dome in scrap wood pad it out with some foam or router matting the using your tailstock reverse the bowl onto it leaving a little nib where your centre is to cut away and clean up by hand. how you acheive centre is to mark it when you first create the spigot either by pencil or a little indentation in the wood.
