What is normal quill play?

We have a Sieg X2 super mill and we're milling dreadful crooked lines in aluminium and wondering why. We can mill straight edges but not plunged slots. There is deviation of more than a millimeter from a straight line using a 6mm mill.

We noticed that - with a DTI on the quill sleeve, we can pull and push the quill to reveal a 0.1mm play. Is this normal? If not, do we need to replace the bearings?

If this is not the problem, any thoughts would be very welcome.

Alan

Not sure of the play in the Sieg but if you lock the quill that should help.

Slots have a habit of pulling the cutter to one side depending on direction of travel, I remove the major part of the material in a slot with a smaller cutter and then machine the sides separately to final dimension with the same cutter.

Bob

Can you give a bit more info such as

Depth of cut on each pass, speed of feed and rpm, any cutting fluid?

2, 3 or 4 flute cutter and make? sharp?

Is the quill locked, is the axis that is not moving locked?

My X3 did need the quill bearing preload adjusted as the nut was actually loose on arrivalbut not needed touching again in over siz years

J

The SX2 doesn't have a quill as such so there is nothing there to lock.

Things to look at:

Try to determine whether there is any movement in the spindle or the head itself. If the former check that the spindle nut is done up to the correct torque (there is a grub screw locking it). If it is the head itself try tightening the gib strip screws a little until the play disappears.

Russell.

Quill play is seen as rather unusual by most people, but it is perfectly acceptable behaviour for two consenting adults - just don't bring it up at a dinner party unless you know your hosts very well indeed.

Aunty Stub.

It sounds like the preload adjustment has gone slack. Take off the motor mounting plate to get at the end of the spindle. There's a locking grub screw in the ring, loosen it a couple of turns and nip up the ring until all play disappears but bearing does not bind. Retighten grub screw. Its a left-hand-thread BTW.

Neil

A "quill" moves up and down in the head like in most drilling machines. The SX2 (well mine at least) has the spindle rotating in the head but fixed in the up and down direction. The whole head is moved up and down to put the cut on.

On top of the spindle you will find a nut or locking ring which is held in place by a grub screw. Slacken the grub screw and tighten the nut until the play disappears but not too tiight to stiffen the rotation. There is a correct tightening torque to give the right degree of pre-load but I just did it by feel.

Russell.

Even on a big solid mill 7mm is too great a depth of cut for a full width cut with a 6mm mill, even in aluminium. The sideways force pulling the cutter off line will be very high.

It's probably the toolbit bending, and the forces generated by this may have loosened the spindle bearings or headstock gibs. Try a 2mm DOC and make sure the table gibs are snug too.

Neil

If you are trying to cut a decent 6mm slot you need to rough out with something smaller i.e. 5mm, 3/16" or best of all 7/32", the idea is to leave minimal metal for the finishing cut. Use a sharp 6mm cutter to finish and a slow feed rate.

Tony

7mm is way too deep causing you to have to feed very slowly. Try about 1/5 to 1/4 of that and feed faster.

A 4 flute cutter is not ideal for slots as there is a tendancy for the cutter to move sideways, Ideally you want a 2-flute cutter often known as a slot drill for obvious reasons.

J

Your original post stated that you were using plunge cuts ,you must never plunge cut with a 4 flute end mill,a two flute slot drill must be used, you also state that the slot wanders by one mm so even if there is 0.1 mm play in the bearings it should not produce an error of one mm, the cutter is probably blunt which does not help. On a small mill start with a 5 mm slot drill three cuts to achieve depth,then use 6mm slot drill to finish in one cut, lubricant ,soluble oil,or kerosene,or if the aluminium is bar i.e. he 20 or he 30 it can be cut dry,alloy plate is always best cut with lubricant,suggest you find someone who is a bit more experienced and get some instruction, when starting out in model engineering it is far easier to achieve good results on a small lathe,small mills never perform as well ,a mill needs a lot of weight and well supported spindle ,unlike a lathe if you want a 6mm slot ,you use the same cutter in a small hobby mill or a 1 1/2 tonne turret mill and the larger machine will give a better job.

.

Nigel,

I agree with most of what you said; but must just mention that there is a useful integer between two and four

Three flute cutters are very versatile.

MichaelG.

Nigel

"Even on a big solid mill 7mm is too great a depth of cut"

I have cut 10mm + depth with a 12mm cutter in 6082 alloy on my Marlow mill but it is a heavy solid mill but would not get any where close on the Dore Westbury mill.

And a 12mm cutter is going to be a LOT stiffer than a 6mm...

Neil

If a movement of 0.1mm is detected in the quill with a DTI, but over 1mm deviation is seen in the cut, could this be a problem with the collet chuck being loose, either not tightened onto the cutter or not pulled up correctly by the draw bar?

Unless its a centre cutting 4-flute design in which case you can plunge and ramp with them bit like the one on the right that I was using at the weekend.

Thanks again people. You've given us a lot to think about and to try. So we need to adjust the pre-load thingy, verify we can plunge our cutters, cut smaller slots first and finish to size on a second pass, and cut shallower passes.

I think we'll print this all out and set to again at the weekend.

Thanks again, Alan

Alan,

Not sure if yours is a Super X2/Super X2 Plus, as not from ARC. Regardless, your post seems to suggest that you have low or limited experience of using a small size milling machine. At ARC, we come across this/similar issue about once a month. By the time a matter such as this is raised, the machine has been 'shagged', because of lack of experience. Many of us go through this hard learning process, especially if we do not have access to the words of wisdom being expressed on this thread by the experienced users, or if we think that we are cleverer then them.

I too have gone through this process - on an SX3...videos on our website on that page, being an example...where I forgot to lock down certain axis before milling/drilling, too fast speeds and feeds resulting in poor finish, and respective axis becoming loose. End result - shake rattle and role - machine shagged - get a bollacking from our experienced engineer who ends up having to re-adjust gib screws...

Now that you are in this state for sure, as suggested by others, adjust/lighten gib screws, check/adjust spindle locking nut/s (depending on if it is a SIEG two nuts/non-SIEG - one nut with grub screw). Before your next milling exercise, lock non-moving X or Y axis - normally the screw with/without handle to be found in the middle of all gib adjusting grub screws. If you have a SX2/SX2P, lock in the three pronged handle which moves the head up and down on the rack, fine feed the cutter to the depth of cut you need, and then lock the Z axis gib onto the dovetail of the column, using screw with/without handle to be found in the middle of all gib adjusting grub screws. The idea is to get maximum rigidity before you start milling.

Generally, for aluminium, do consider two flute slot centre cutting endmills, ideally a cutter which does not have a coating (I dont know the technical reason why). If not available, most centre cutting end mills - with/without coating will do, giving variable results based on depth of cut, spindle speed, feed rate, with/without coolant, and grade of material being cut. Oh yes, it does help to have a sharp cutter.

The best way to figure this out is to experiment, but generally, start with about 0.5mm to 1mm depth of cut, and a spindle speed between 2000 to 2500rpm, spread some coolant/WD40/paraffin on the area being cut. Then start feeding the cutter into the aluminium and listen to cutter, feel the machine for vibration, and reduce the speed of spindle, and speed of feed, if necessary. If happy, experiment up to a maximum of 2mm dept of cut. You are unlikely to get anywhere with a 7mm depth of cut in one pass.

BIGGEST MISTAKE I have seen/hear every time is expectation for 'small mills' to behave like a big mill/Bridgeport with higher depths of cut, feed and speed. This really gets me annoyed at first, but then I have to remember that the user probably does not have any experience of using a small mill, or this is the users first experience of using any mill. This is OK, if the user is accommodating about his lack of experience, but difficult to consider if they start going up the 'I AM so and so with X years of using a milling machine over Y number of hours (usually a big machine or a CNC machine!) ' route or 'not fit for purpose' route. We come across both types

Good Luck, Ketan.

Correction to last post: 'adjust/tighten' gib screws - not 'lighten'...

Ketan.