Turning a Tenon

[Bill21]

The topic of whether you should accommodate the lip on standard chuck jaws came up recently.
I use Axminster C jaws and cut a very slight recess to locate the lip. I’m pretty sure I read somewhere or perhaps saw in a video that you should not do this.
The lip is supposed to bite into the wood. The lip is quite pronounced on the Axminster jaws whilst the RP have what they term a “Hawks Beak”.

It’s certainly the case that Record Power tell you not to cut a recess for their standard jaws. See their instructions in the picture below.

I’d be interested to hear others thoughts on this. Perhaps someone has a link to Axminsters advice on the topic?

Do other manufacturers have jaws with these features?

[Bill21]

For anyone that doesn’t use Axminster C jaws this is what the lip looks like.

[BrianH]

First opinion.... Far too many of us woodies get over-involved with angles and sizes. Advice .... leave all that precision to the engineers who are working with material with little or no movement or 'give'. Experiment and If a technique works... use it again!
Second opinion... where possible always use a chuck in contracting mode. The alternative has you turning away the wood away, reducing its inherant strength, while the chuck is doing its best to drive the grain apart.
Third opinion ... a bowl, as drawn, with a base size around 1/3 its diameter will look elegant at the cost of stability whereas one with a 2/3 base will be far more likely to be used. Advice... decide if you making an ornamental piece, or one intended for useful service BEFORE you start.
Fourth opinion ....aside from proper names there are no facts in woodyturning..... only opinions, no matter how strongly those opinions are believed.
Look forward to hearing your views
Brian

[Twisted Trees]

If the wood I am putting into the chuck is really hard, then I cut a suggestion of a grove for the C Jaws to bite into, if it is normal hard then I let them make their own, except when I feel like making a groove for them! completely not helpful, but in use I have found on 99% of tenon's without a groove there is on when I take the chuck off so it successfully makes it's own, in the right place and with "stops" where the gaps in the jaws are. which is better than an all-round groove in my opinion.

[Bill21]

If the wood I am putting into the chuck is really hard, then I cut a suggestion of a grove for the C Jaws to bite into.

That’s a good way of putting it, that’s pretty much what I do.

[seventhdevil]

i always thought the lip on C jaws was more to to with the retention of the screwchuck insert that went with it rather than the grip on the tenon?

i does both i know but it's fairly robust as a lip.

[Twisted Trees]

i always thought the lip on C jaws was more to to with the retention of the screwchuck insert that went with it rather than the grip on the tenon?

i does both i know but it's fairly robust as a lip.

Pretty sure the lip is tougher than any wood I have, though you may be able to set it a challenge Steve 

I think like a dovetail it stops sideways force on the piece of work from forcing it out of the jaws, but that is really only when you have a long piece in there without tailstock support, maybe a tall goblet or something similar. Pretty sure Colwyn Way has said somewhere not to cut a grove let the chuck do it, but I can't find that now.

[Bill21]

Yes, I’m sure I saw it somewhere but I can’t find it now either, It may well have been Colwyn?
I think it’s a pretty secure looking design though either way. Far better than just a dovetail that some other manufacturers use.

[Bill21]

As for recess rather than Tenon, I no longer do that. Our club demonstrator suggested that a Tenon offers more options for re-turning the foot than using a recess and I don’t turn platters so not much need for a recess for me.

I’ve seen a few bowls give way on social media when the remaining wood wasn’t enough to support a recess.