Help with lathe boring

[Bidgee]

I need to bore a hole (roughly 25mm) on the join line of two pieces of 40mm square bar. Each bar will end up with a semi circular channel. The end product is a barrel clamp.

See attached pics. One is what I'm starting with the other is what I'm trying to achieve.

The question is; how should I go about boring the hole? Do I bolt the 2 pieces together and setup in the 4 jaw or do them individually?

Obviously I haven't done this before so any advice appreciated.

Thanks

Scott

[Gavin Newman]

Have both pieces the same length and bolted together to make is more secure in the 4-jaw. Bore as one piece then cut one piece to the smaller length. If you try and clamp them cut as you have shown in your picture one set of jaws will have good purchase but the other set will be clamping on the edge of the longer piece and will be insecure.

[.RC.]

Does it need to be a slight crush fit??? When you bore it out put some shim material in between the two pieces..Then when you fit the alum rod it will slightly crush it to grip it...

[HavinaGo]

Only bit I'd add is get the bolts to hold the pieces together in place prior to boring the hole. The hole will then be in the right place when the 2 pieces are clamping a rod!

[barkersegg]

Scott, the procedure Gavin mentioned is recommended to hold barrels or pipes but I found with different thickness barrels, you may need to pack or make individual ones to suit the job and that can be pretty onerous without a larger self centering 4 jaw... :C ....another method you could try is with pipe stirrups which you can obtain from most hardware places or plumbing supplies and adapt them to fit with packing .....provided you don't need heaps of tension they will work - not as strong but quicker........I use aluminium strips as packing which doesn't score the barrels and usually leaves the bluing intact.....mostly.......purist can flame me now :o!!! ...........just a suggestion..............Lee

[Bidgee]

Thanks for all the suggestions.

Lee, I'm going to make bushes from aluminum to clamp the barrel in.

Scott

[malb]

Depending on machine size and speed range, and accessories available, you should be able to prep the item to the finished pic stage except for the hole to bored, and mount it to a faceplate with an angle plate for drilling and boring.

This allows the part size to approach the swing capacity of the lathe, as you don't have to allow for chuck jaw protrusion etc. Also allows for the upper half to be shorter as shown in your pics without interfering with grip etc. Counterbalance weights should be bolted to the faceplate to ensure that the entire unit is properly balanced.

For regular machine use, the clamp/angle plate/faceplate can remain assembled as a unit and be installed onto the spindle as required.