Please critique my setup

[SparWeb]

Hi
I got this set up on my lathe and just questioning what else I should do to make it work. Photo below.
I'm doing this crazy set-up because I don't have a milling machine.

In the lathe chuck is an end mill that I will use to mill a flat on the bar that's on the cross-slide.
I'm using the boring-bar holder on the QCTP to hold a round bar of the same diameter.
The end is sticking out so that I can mill a flat on it.
Then I will rotate the round bar, tighten again, to mill another flat. I am making 3 flats on this rod.
I am going to mill a fairly long flat at each position, although honestly I only need it to be long enough to grip in the chuck of a power drill.
I have the measurement tools I need to make the flats 60 degrees from each other.
I guess I don't believe this is rigid enough - any suggestions will be welcome!

This is the lat step I need to do for this drill guide project. I made a quick-and-dirty drill guide last year and found it quite useful. However it was terribly jiggly. This is my attempt to make a much more sturdy drill guide.

Given the overhang, I plan to cut rather slowly with the 1/2" end mill, and keep the feed rate and depth of cut shallow, too. Have to bear in mind that (unlike milling) the feed rate is proportional to the chuck speed. I will start at 400 RPM and maybe edge it up to 600 RPM for finishing passes, when the feed rate is as slow as this lathe can go (112 tpi). At that speed I think it will take 30 seconds to complete a single 2-inch pass!




Is there anything I can do to make the setup more rigid? Can you think of a way to use the tailstock for support?

Or is there something better that's totally different?
(Aside from buying a milling machine, of course!)

 

[trlvn]

Chuck jaws aren't the best had holding end mills. If you see yourself doing this semi-regularly, you might want to invest in one or more end mill holders that fit the taper of your spindle. Something like:

End Mill Holder, 3MT, 1/2" 1633

Mill Tooling 1633 1/2" Hole Diameter; 3 Morse Taper Shank; Uses a 3/8"-16 NC Drawbar; Compatible with Mills with 3 Morse Taper Spindle; Adapter for 1/...

littlemachineshop.com

The cutter will be held more securely and should be more concentric to the spindle. You will need a drawbar, though, to retain the end mill holder. Luckily you have a lathe to make what you need!

Other than that, what about the material? Does it have to be steel? Aluminum or brass are so much easier to mill. If steel, would 12L14 or another free-machining product but suitable?

Craig

 

[Dabbler]

Here are a few thoughts...

o A vee grove standard holder might have less overhang, and if your cross slide is less-that-rigid, then reducing overhang might help.
o Reduce stick out to the absolute minimum, and only mill what you need.
o change your compound by 90 degrees, so that the feed direction is the same as the cross feed, and lock the compound down. This reduces the number of degrees of freedom, and should increase rigidity.
o lock the carriage
o snug the cross feed locking screw so the gibb is firm.

that's all I can think of off the top.

 

[Mcgyver]

Agree with Craig on endmill holding. Unlike drills they are hardened for the whole length which is never a good idea to hold with a jawed chuck. Same reason you can't hold an end mill (successfully) in a drill chuck.

Here's an easy to make an end mill holder. Turn the OD of a suitable sized bit of steel, stamp the end #1 and mount it with the OD gripped the three with the #1 aligned to jaw #1. drill, bore ream whatever to suit the end mill and put a good sized, ideally fine thread, set screw in to hold it. While three jaws all have a fair bit of run out, a work piece will repeat fairly well like that if you get it position on the same jaw. You can put this holder in the 3J with pretty good repeatability this way.

 

[YotaBota]

o A vee grove standard holder might have less overhang, and if your cross slide is less-that-rigid, then reducing overhang might help.

If the EM will fit inside the opening of the holder you could lock the work piece totally inside the holder eliminating the overhang. Of course very CAREFUL test fitting is in order to ensure clearance between the EM and the holder. This may not be for the faint of heart but if testing goes well there should no worries about the EM contacting the holder.

 

[SparWeb]

I will definitely try some of these improvements out and get back to you all.
The toolholder has a 5/8" opening so the end-mill does indeed fit inside. Whether there's enough clearance to complete the cut is another matter, but I'm optimistic. With the compound rest spun around I can't see much movement in the setup any more at all.

The cutter in the 3-jaw chuck... yeah that doesn't look good at all and I had hoped to get away with it by taking cuts about 0.001" deep so that the jaws wouldn't feel much torque. Just to clarify what you just said, Mcgyver, do you intend for the set-screw to land on the indented flat on the end-mill shank? I don't have many reamers but I have several other end-mill sizes so I'll see if I can find a match.

Long-term thinking: I do want a milling machine. when I get one, it will come with its own set of tooling. That may be either ER## or R8 or something similar. Once that's decided by the mill, then there might be a chance to "standardize" the collet tooling from mill to lathe, and then I'd invest in the lathe collet chuck if I can find a compatible holder. It would be nice to minimize my tooling costs that way.

 

[Susquatch]

Long-term thinking: I do want a milling machine. when I get one, it will come with its own set of tooling. That may be either ER## or R8 or something similar. Once that's decided by the mill, then there might be a chance to "standardize" the collet tooling from mill to lathe, and then I'd invest in the lathe collet chuck if I can find a compatible holder. It would be nice to minimize my tooling costs that way.

I like the ideas the guys have suggested. I bet you will be fine.

I had wanted to commonize my collets too, but abandoned the idea. Generally speaking the lathe holds parts and the mill holds tools. (once in a while it's different like you are doing now.)

That means the best collets are different for the two machines. Not that it won't work, just that it's not ideal.

I have a 5C collet chuck for the lathe (which also doesn't need a draw bar - also nice on a lathe), and an ER32 to R8 adapter and ER32 collet set for the mill. The 5C also works on the spin Indexer on my mill to do jobs like yours.

 

[SparWeb]

That worked really well. Thank you everyone again.

It really never occurred to me that I could install the part in the tool-holder. Once I did, I found several possible ways.

In other news, the mounting plate for my 4-jaw chuck just arrived. On to the next project!