Home made milling attachment

Russell, Looked at the pictures and as you say vibration seems to be the deciding factor but the groovy picture is what I would expect from milling on a lathe with one pass.
They are not designed to mill and can do so but lightly. To do a groove such as this you need three passes, one to hog out and two finishing passes to get the width as you need to cut on one edge only.
Many people only look at the attachment and cross side as mounting points but the whole setup is mounted on the carriage and this probably has more clearance than the other parts. Just locking the carriage off won't do a lot as the lock bolt usually just restricts one corner and if there is clearance it then allows it to swing and lift.
As a test slacken off the carriage gib strips, slide a piece of shim in and tighten up so the carriage can't move then try another test cut. -- Regards,
John Stevenson Nottingham, England.
Visit the new Model Engineering adverts page at:-

Good start Russell. One observation is that you're holding the mill in the lathe chuck, I would strongly recommend that you get hold of a collet chuck or make an end mill holder; I first started milling in the lathe using the 3 jaw and the results were poor, I made an endmill holder from a soft ended MT2 arbour, drilled it and reamed it to 6mm then cross drilled and tapped it to take a grubscrew to locate on the flat of the FC3 milling cutters I was using; I had to make up a draw bar to hold it in the spindle as well; this worked much better and gave much more clearance around the cutter to see what was going on. Martin

We can fix this: Great! :-))
A web (or just two triangles) on the back of the angle plate will help. Clamping the angle in 4 corners also helps. Removing any backlash helps. Also, I see that the angle plate is sticking out quite (to the left). Can you move it more to the right?
Any axis that is not moved should be tightened. Especially as you don't have much mass. With that "hack" you can't have deep cuts. Something in the range of 1/4 of the mill's diameter.
Nick

Thanks Nick, Martin and John
I've got a few things to try now.
I'll test it with all but one slide locked up and I'll try some lighter cuts too.
I can't fasten the angle plate down at the corners as it doesn't match the spacing of the T slots. I could try it on the front T slots as these are wider spaced but further off the lathe axis. I've been thinking about fastening it down and I'm going to use some thicker washers under the nuts to try and get a more positive fixing. (I just have to master parting off first).
I thought I might fasten a rule to the angle plate so that I can try and see if the visible vibration is the plate flexing before I make triangles for the ends.
I can't reduce the overhang of the angle plate without moving the holding down bolts closer together.
A collet chuck is on my list but making an endmill holder sounds a good idea too.
Thanks again - especially for not being underwhelmed.
Russell