Lathe-Only Machining of 'Bar Clamp'

[ntdenman]

I'm interested in suggestions for setups to machine a tricky feature from the attached drawing; the parts are basically cylinders with a right-angle cylindrical 'bite' taken out of them at an offset location. I'd be making them out of brass rather than steel, which should help a bit.

It seems like it would be pretty straightforward to do the 'bite' in a mill, but I currently only have a small lathe. My first thoughts are:
- fix the cylinder with a sacrificial v-block in the 4-jaw, then drill and bore as if it was solid
- make an offset boring tool for the 4-jaw and then set the cylinder up on the cross slide (horizontal? vertical?), do an interrupted cut with the right radius and increasing depth
- set the cylinder up on the cross slide and then use a short line boring tool, otherwise same as above

Not sure what's likely to work, pretty sure it'll be slow going no matter what. I'd be interested to hear what you all think is a reasonable way of doing this. (I'm really hoping it's not 'buy a mill'.)

Cheers!

 

[Six O Two]

Those look a lot like seat binders.

I think your second option makes sense. Alternatively, if you made a jig to hold the part in place horizontally and had a drilling guide in the vertical axis, you could probably do the operation with a drill press. If you're stuck, you could also just abrade away the cutout with a file or dremel/die grinder.

 

[ntdenman]

Ah, those do look really similar, cool. The drill press fixture is a great idea, I'll make that the backup plan if boring doesn't work. Seems like it's less likely to fail but that's a lot of fixtures to make. Thanks!

 

[whydontu]

Do you have a faceplate? Clamp to faceplate, hole saw in tailstock?

 

[Susquatch]

Do you have a faceplate? Clamp to faceplate, hole saw in tailstock?

Even if you don't have a faceplate, make a holding fixture for the 4 jaw and do the same thing. As an alternative to the hole saw, use a big milling boring tool in the tailstock - but take very small cuts to avoid spinning the tool. Depending on the MT in your tailstock, I might have a boring tool you could buy cheap or borrow for the cost of the shipping. PM me if you are interested.

 

[trlvn]

Do you have a faceplate? Clamp to faceplate, hole saw in tailstock?

Harold Hall's site has a number of examples of faceplate setups that might provide inspiration (even if his writing style is a bit unfamiliar):

FacePlateSetups

Setups showing the lathe's faceplate in use

www.homews.co.uk

Craig

 

[eotrfish]

I noted the spring seating holes d=3.2" dia. x 1/8 deep - must be an April 1 drawing

 

[Susquatch]

Harold Hall's site has a number of examples of faceplate setups that might provide inspiration (even if his writing style is a bit unfamiliar):

FacePlateSetups

Setups showing the lathe's faceplate in use

www.homews.co.uk

Craig

OMG Craig! I could drive over there and kiss you right now!

FINALLY! A great full scope technical source of info that isn't YouTube videos! As you might know, I don't like YouTube. This is exactly what I like! A website that documents various things all in one place with photos and great write-ups. I can even print it if I want and read it at my leasure. No more pause, rewind, wtf. I LOVE THIS!

Thank you thank you thank you!

 

[ntdenman]

Funnily enough, I have a faceplate but no hole saws; I think I'll give the headstock boring a shot, and see if that works for me.

Harold Hall's site has a number of examples of faceplate setups that might provide inspiration (even if his writing style is a bit unfamiliar):

FacePlateSetups

Setups showing the lathe's faceplate in use

www.homews.co.uk

Craig

Looks like a great resource, I'll definitely be looking more at that when I have a chance. Thank you!

 

[whydontu]

other thought. 2”x2”x2” cube, drill x-axis for brass rod, drill offset hole on y-axis for milling bit. True up the y axis hole in the 4-jaw, milling cutter in tail stock.

Split the x-axis for a couple of clamp bolts.

 

[Mcgyver]

These look like split cotters, they are about the best way to clamp to a shaft. I've made a ton of them over the years. In every single instance, I've bored the hole for the (I use brass) cotter, then clamp a bar of brass in the hole, and the bore the intersecting hole - that forms the arc cut out in the cotter. Drill and thread before this, and cut the cotter in half after this. Each one gets cross drilled and reamed while in it is final hole so everything fits perfectly.

 

[ntdenman]

Aaaaaah, beautiful!