drill/mill vs knee mill

[Axkiker]

So I have been reading alot of good info on milling machines here lately. However I have a question

I see that alot of people feel a drill/milling machine can perform almost the same type of work with the same precision as a knee mill.

For those who have used both style machines do you think this is really possible?

I personally have used both style machines and cant say I had much luck with the drill/mill style machine. I had constant trouble keeping the head aligned and just never felt they had the strength to make consistant accurate cuts. Im also not a fan of round columns.

Now I could easily see how they would work for cutting aluminum etc. Or maybe making small light cuts in mild steel. I however just never felt they would have been capable of matching what I can do on a full sized knee mill.

anyways I thought I would see if anyone else had used both styles what they thought. Maybe I just had a couple bad experiences.

 

[precisionworks]

I've run lots of material through both. The biggest mill/drill, like the one just purchased by Mirage_Man, will do work to the same precision, and yield the same surface finish, as any Bridgeport or clone with an R-8 spindle. Raising & lowering the M/D head is not as quick as the same operation with a knee. Less mass means a more careful set up. Most of the result of any machining operation is dependent on set up & technique.

 

[Axkiker]

I've run lots of material through both. The biggest mill/drill, like the one just purchased by Mirage_Man, will do work to the same precision, and yield the same surface finish, as any Bridgeport or clone with an R-8 spindle. Raising & lowering the M/D head is not as quick as the same operation with a knee. Less mass means a more careful set up. Most of the result of any machining operation is dependent on set up & technique.

interesting take on things. I cant say I have had the same experience but hey whatever works and gets the job done.

 

[gadget_lover]

I have been of the impression that as long as you are working within the range of the quill on a mill/drill the experience is pretty close to a knee mill of a similar size. This assumes you are staying within the capabilities of the motor too.

The key is "of similar size". I must say I really like being able to crank down the knee, remove whatever tool is in the spindle and then crank the knee up again without losing my place. Once I finish setting up my DRO, it might be just as easy to move the table to the left to get that clearance for tool changes.

Daniel

 

[precisionworks]

with the same precision as a knee mill.

In my small world, which involves repairing & fabricating customer's parts, "precision" means being able to work to +/- .0001" . That's not a big deal on either a knee mill, a mill/drill, or a lathe, as long as you have a clear idea of the steps involved to achieve the end result.

IMO, press fits & bearing fits are the jobs requiring the most care. On the lathe, when turning to a critical OD, it works well to stop when the part mics .001" over desired size. A smoot cut ******* file will take about .0001" per pass, depending on the sharpness of the file teeth, the hardness of the material, rpm setting, and the pressure applied. When the diameter is within a tenth or two, cover the file with 600 grit silicon carbide paper and polish to final diameter.

Boring fits are more challenging, especially on the lathe when the bore is deep. Those go to the mill if possible. There are boring heads available that adjust .0001" per division, generally referred to as "tenth-set heads". EBay has supplied me with a good selection, most look like this:

http://cgi.ebay.com/KENNAMETAL-50-T...ZBI_Tool_Work_Holding?_trksid=p3286.m20.l1116

Whether you run a TenthSet head in a knee mill or a mill/drill, you can easily hit .0001", and just as easily hit .00005". They're pretty cool ... my smallest uses a 1/4" solid carbide bar with an insert that has to be handled with tweezers (and is available from one source), but its paid for itself many times over.

I really like being able to crank down the knee, remove whatever tool is in the spindle and then crank the knee up again without losing my place.

+1

If you have the space & the money, a knee mill is no-brainer choice. If space & funds are more limited, buy the biggest mill/drill available + the best tooling ... your customers won't ever know the difference.

 

[Axkiker]

I have been of the impression that as long as you are working within the range of the quill on a mill/drill the experience is pretty close to a knee mill of a similar size. This assumes you are staying within the capabilities of the motor too.

The key is "of similar size". I must say I really like being able to crank down the knee, remove whatever tool is in the spindle and then crank the knee up again without losing my place. Once I finish setting up my DRO, it might be just as easy to move the table to the left to get that clearance for tool changes.

Daniel

You are probably right... A alot of the machine work I do is probably too big for even the biggest drill/mill..... Or at least I have much better success with a full sized knee mill.