Using a Mill as a Lathe?

[Chris64]

Someone was just asking about knurling on a mill and it got me thinking.

Could you use a mill as a lathe for basic (small, aluminum) turning projects? I searched around the web and found several people who say it could be done but I would like to hear some feedback on whether this is a good idea or not.

I only have about 6-7 inches of Z travel so it would be limited to very small tasks anyway but I was thinking that if I could somehow adapt a 3-jaw lathe chuck to the collet...then build a small pedestal that mounts to the bed with a lathe quick-change tool clamp on top it seems like it should work (all these parts at HF under $99). Not only would I have a small lathe, but a CNC lathe at that. I would very rarely need a lathe and at those times don't need to have threading (which is the one aspect that would be impossible I know).

Anyone try this or can offer advice? On the other thread, knurling was highly discouraged...can you elaborate? Does knurling require a large amount of force? And while I'm asking about the knurling, how does it always look so perfect when finished...do the little cutters just automatically slide into the privious grooves?

[Geof]

Knurling does require a large force. The knurling wheels are not cutting they are forming metal and yes they do find their own engagement. The other thread enquiring about knurling in a mill implied the spindle was going to be stationary holding the knurl and then just running it along a surface. Not a good idea; the forces involved could cause the stationary balls to make dimples in the bearing races. This is brinelling and it is a good way to knock 99% of the life off your bearings.

Using a mill as a lathe? Entirely possible; I have done it for small diameters that could be held in a collet. Mounting a small chuck may be feasible but you would have to be careful about how far out from the spindle nose everything was. Using the mill spindle as a lathe could subject it to greater side forces than it would normally experience as a mill. If these forces are applied an unusually large distance away from the spindle nose the bearing load is compounded by the leverage effect. Knurling with this setup may not be a good idea because the forces involved would be much larger than those normally encountered in milling. Lathe spindles and bearings are generally much heftier than mill spindle bearings.

[DareBee]

I agree entirely with Geof and have also used the mill to do small parts held in a collet.
I would tend to shy away from mounting a chuck. Barstock should easily be holdable in a collet, especially the ER style.
There is no reason to mount a lathe tool post (unless you really want to), just clamp your turning tool in the vise.

[InspirationTool]

Yup, stock in a collet and a bit in a vise is what I've done as well...

I've heard of people going crazy with the idea on an VMC. Fill the toolchanger with stock, and lay out various cutting/threading/drill bits on the table and presto, you have a barfeeder toolchanging lathe.

[Chris64]

Originally Posted by InspirationTool Yup, stock in a collet and a bit in a vise is what I've done as well... I've heard of people going crazy with the idea on an VMC. Fill the toolchanger with stock, and lay out various cutting/threading/drill bits on the table and presto, you have a barfeeder toolchanging lathe.

Oh, that's a good idea! I was wanting little custom aluminum bevel washers. I figured I could mount the stock in the spindle, cut the bevel underneath, change the tool and chop it off...but I could just put different tools in different spots and run the spindle all over the place to use the different tools. Plus I could leave enough stock exposed to run off about 8 or so at a time. The only reason I was thinking of a pedestal was if the projects are longer than the depth of a vise (not very deep). Really just a nice block of aluminum would probably do the trick.

My problem is that the collet is a Kwik-switch and the largest tool holder I have would only accomodate up to 1/2 stock. i do have a 1 inch collet holder with no collets. I had some idea's of things to make that could be as much as 4 inches in diameter, but very short length (1-2 inches). A self centering chuck is an easy way to switch your project on and off. I had actually considered try to make a custom tool holder. Has anyone tried this? They're really expensive and this way it could be built as shallow as possible to prevent putting too much strain on the spindle. I figure I could pre-mill it with the CNC, and finish it with the lathe.

[Geof]

Originally Posted by Chris64 ....I had actually considered try to make a custom tool holder. Has anyone tried this?....

I have not but a 'reliable source' recently described a VMC he had seen that was equipped with a great number of custom cat 40 holders made out of aluminum. Let your imagination run wild, if things work then you are a step ahead and if things don't work you are also ahead because now you know what not to do.

[J Solinger]

I have a Bridgeport with a 2 axis controler on it. I had a hundred small alluminum parts that needed turning. So I put a right angle head on it and set the cutting tools up in gang tool fashon on the table. It made short work of the parts. I think that a 3 or 4 inch lathe chuck mounted properly would work just fine.

[tobyaxis]

I have only done this once when all the CNC Lathes were Busy. I made a Gang Tool Block for a Kurt Vise that was raised an additional 4 inches off the Table. I didn't have to do ant Threading on the part thank God but did all the Turning, Grooving and Back Turning including Cut-Off on a Hitachi Sieki VM 35.

Setting the tool center hieght was very easy. The Program was a different Story

What are you trying to make?

[mxpro32]

sherline and taig use the same headstock for there mills and their lathes. granted the lathe work done on these machines is light duty, but if such light duty headstocks work as a lathe, then any reasonable mill spindle should be fine with lathe cutting forces. just a thought

[Chris64]

Originally Posted by tobyaxis What are you trying to make?

Nothing really specifically right now. Some of the parts I'm planning on making will need custom spacers and collars etc. Which is why I would prefer to not dedicate a large space for a nice lathe. I considered getting a cheap mini-lathe...but they seem like they have way too much slop in all the controls for a $400 lathe (cheap, yes...but way too much to throw away). I bought some lathe cutting tools yesterday so I was going to play around with it this weekend. If the results aren't embarassing, I'll post pics.

[daking]

We used to use a Bridgeport Series 1 R2E3 for small lathe jobs before we got a CNC lathe. Made a gang tool bar that clamped in the vise and put the stock in a collet. It took a little time to get it dialed in just right but if the run was big enough it was worthwhile.

Dave

[Chris64]

Well, I did a little test. It worked OK. I'm going to need to make a better tool holder. It will definitely need more functionality to allow it to rotate on the Y axis and I need it to hold the tool tighter on the Z axis. I would still call it a good proof of concept. Now I need to read about how to get a nice finish on a lathe. I ran a 1/2 piece of mild steel from 400-800 RPM with feed rates from 40-20 IPM and I was removing .01 inch. I couldn't really get a finish that looked really smooth...it looked OK...just not great.