ovenpaa wrote:Waterford, I do agree however the bore is seldom concentric to the OD and problems arise with very long barrels as it can be problematic to clock the bore. I spent some happy evenings designing an independent fixture that would be bolted to the back of the lathe and would allow for even the longest barrels to be supported and clocked plus give a rotating fixture for pressurised cutting fluid to be recycled through the barrel bore. I never did get around to building it
Equally I can think of a few people who simply use a bush in the outboard end of the spindle, arguing that it is merely there to offer some support to the barrel. Horse for courses really, I know what I prefer to do.
working between centres eradicates some the problems created by a non - concentric bore / od , firstly it will display the amount of concentricity , if severe this can lead to differential cooling and therefore uneven expansion / contraction in a rifle where multiple successive shots are fired , working between centres give you the opportunity to correct this .Secondly , because concentricity is guaranteed then threading the tenon and chambering will also be concentric. A thought occurred whilst reading Davy's thought, If I bore a hole through the dead mt2 centre I can attach a rotating fluid coupling to the muzzle end of the barrel for a force flush cutting oil system . I'll look at this tomorrow , I have a 6.5 x 47 barrel to make .
Last edited by waterford103 on Fri Nov 28, 2014 6:11 pm, edited 1 time in total.
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Depending on the size/grip stregnth of your chuck jaws I'd be tempted to put hole through the centre, start boring one side to smaller than the final diameter, then turn it round, grip internally using a 3 jaw with a tailstock to support and take it slow with the turning the edges off. Its only 3 inch so not going to be too bad, however I'm used to working on fairly sturdy machines (for things of this nature at least) and I'm not sure what your lathe is like.
That should be capable but I'd take it easy with intermittent cutting (i.e. turning square to round). Slow feed with conservative cutting depths is the way to go
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One of those might work. If you are prepared to wait for it to arrive in this Country my freind. The purpose of this exercise I believe is to learn how to use the lathe. I think that's were ovenpaa is coming from. As I said I don't think I have the necessary skills to re crown a barrel in my lathe. The challenge is to build a barrel spider. I am up for that. Ill give it a go but that's the extent of this exercise.
I have decided not to use the aluminium block I have a piece of mild steel bar stock about 3" OD by about 4" long it will not be as easy to machine as aluminium but trying to knock the corners of a square billet is probably not for a beginner.
I have some questions about carbide inserts if that's OK.
As with most precision operations, 90% of the hard work is in the preparation. Have a well mounted barrel (i.e. in good spiders), clocked in correctly, then other than having a sharp tool of the correct geometry set at the correct centre height with plenty of coolant, there isn't too much you can do wrong if you follow a sensible speed/feed for the finish you are trying to achieve.
