Dro Quil/Spindle Mill
Chris Mate | 22/03/2022 20:29:50 |
325 forum posts 52 photos | This is just a friendly question looking for opinions/thoughts around this, after thinking a bit different about the subject: I think I May have identified an accuracy standoff........ |
bernard towers | 22/03/2022 21:04:49 |
1221 forum posts 161 photos | Sorry Chris Mate what is this all about? |
Robert Atkinson 2 | 22/03/2022 21:40:41 |
![]() 1891 forum posts 37 photos | You can mount something to measure the spindle. A Linear Variable Differential Transformer (LVDT) connected to the drawbar. The core of an LVDT can rotate without affecting the accuracy. Not very practical for everday use and it needs a lot of head room above the mill. Robert G8RPI |
Nigel Graham 2 | 22/03/2022 21:41:24 |
3293 forum posts 112 photos | It may help if you tell us the machine make and model, or supply a photo, as there are two basic layouts of small milling-machine; and to show how your DRO is fitted. - One keeps the table at fixed height, on the machine's plinth, and raises / lowers the head. - The other is more like the industrial pattern with the table on a "knee" that can be raised and lowered. Both have a quill as well, but that is normally for drilling, not high-accuracy depth-milling. . The DRO's vertical axis may measure the movement of the quill, but usually is for the knee or the head.. Not the spindle. This does depend on machine type and how the DRO is installed, of course. For example, my mill is a Myford VMC and I have fitted the Z-reader to measure the knee travel. Backlash is less of a problem with the Z-axis because the moving unit's weight tends to keep the same thread-flank in permanent engagement, but in any case a normal DRO's long and cross-travel detectors measure the table not the lead-screw. ' Other than that I am really rather puzzled what you are asking, but To Mill to Depth accurately, using a DRO or handwheel dial: - If possible work with the quill fully raised, for maximum rigidity. - Use the head or knee control to approach the cutter tip to just touch the work. You can use a witness cut but a safer way, more likely to err on the side of shallow rather than over-depth, is to "glue" a slip of thin paper to the surface with oil, and bring the cutter down to just remove that. - Set the DRO's 'Z' reading or the elevating hand-wheel dial to 0. Now cut down from that 0 setting. |
Mike Poole | 22/03/2022 22:41:17 |
![]() 3676 forum posts 82 photos | I am not quite clear as to what the issue is that you are describing but a DRO should be attached so it measures the actual quill movement and unless their is a serious problem with the spindle bearings it should represent the cutter position. If the mill is a knee type mill then it is possible to have a scale measuring the knee movement and a scale measuring the quill movement, a summing module can be used to give the true position of the cutter in Z whether you move the quill or the knee. The same method applies even if the table is fixed and Z movement is effected by moving the head or the quill. I think most people will lock the quill for normal milling operations for maximising rigidity. For drilling it can be simpler to use the quill or boring work with the head at an angle will mean using the quill. Mike |
Hopper | 22/03/2022 22:52:08 |
![]() 7881 forum posts 397 photos | Easy peasy. Hold a ball bearing mounted on an arbor in the dpindle. The inner race will rotate eith the spindle. The outer race can be held still by the pressure from a dial indicator plunger which can measure running spindle movement. Compare that with your DRO and you can see any error between the two and make allowances. But worrying about such precision on a milling machine is a waste of time. They are not a super precision machine. If you can get within a thou or two thats all you need. |
JasonB | 23/03/2022 07:02:56 |
![]() 25215 forum posts 3105 photos 1 articles | I just leave my quill locked so that takes any movement due to locking out of the equasion There is also the argument that on a lathe the DRO measures the carriage and cross slide position, put on a heavy cut and there will be some deflection so you may not take off as much as the DRO shows. People don't seem to have a problem with that either. |
SillyOldDuffer | 23/03/2022 09:56:20 |
10668 forum posts 2415 photos | Apologies if I've misunderstood what Chris is saying. I come at this another way. I don't bother with the absolute position of the table (X,Y) or of the spindle (Z). Instead, I measure relative to the cutting edges of the tool. Typically,
The process uses the DRO to move cutters relative to fixed references on the job. Doesn't matter what the quill and head do provided the operator knows where the cutter is relative to a datum, as understood by the DRO. If the cutter or table moves because of backlash, the DRO is still correct and the operator can trust it to reposition the job under the cutter. The DRO can also be reset on a reference datum at any time to make sure accuracy is maintained: errors can accumulate! On a simple job, the DRO might be set once but anything remotely complicated will have several datums and much shifting between them. In short, always locate the job under the spindle relative to a fixed point on the job, as touched by the tool, resetting X,Y and Z to new zeros as necessary. Dave
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Circlip | 23/03/2022 10:08:00 |
1723 forum posts | Gerra Mic and a set of clapperlipers, the battery never runs out. Regards Ian. |
Baz | 23/03/2022 11:04:26 |
1033 forum posts 2 photos | Blimey I’m still trying to work out what the question is, but DRO——how accurate? I can answer that, good enough for industry to use for the past 40 years so plenty good enough for chasing microns in your garden shed. |
Neil Lickfold | 23/03/2022 18:56:53 |
1025 forum posts 204 photos | Most DRO mounts are not very rigid and are often just piece of ali plate screwed together and then that is to transfer the movement of the axis it is connected with. The very short plate to the machine is never an issue, but on some installs there is 3 or 4 pieces to connect. Once the axis is moving it will show where it went to. But just moving back and forwards a minimum amount , like +-0.1 on an indicator and then watch the DRO read out. Some installs can have 0.03 mm difference. Cast iron is a better choice because of its higher rigidity. Other option is to make the connection from a single piece of steel or cast iron. |
Chris Mate | 23/03/2022 21:09:49 |
325 forum posts 52 photos | This is a ZAY705 ZX-45 Mill DRill setup... Lathe:The spinning part don't slide but spin.(Chuck/Collet etc) 1-The apron movement along the bed(Horizontal) Not spinning. |
Hopper | 23/03/2022 21:34:44 |
![]() 7881 forum posts 397 photos | So the spinning spindle will move the same amount as the non spinning quill it is mounted in. Plus or minus the negligible clearance in the ball bearings holding the spindle into the quill. One thou or less. Not enough to be of concern. Or if you have taper roller bearings that clearance will be zero. So how much the easily measured quill moves, the spinning spindle also moves. Edited By Hopper on 23/03/2022 21:38:32 |
Pete Rimmer | 23/03/2022 23:43:15 |
1486 forum posts 105 photos | Put the DRO on the quill like the rest of the world and read the quill movement. If the spindle moves any differently in the vertical direction to the quill at all then the problem isn't with the DRO placement it's with the spindle bearings. |
Chris Mate | 24/03/2022 03:17:06 |
325 forum posts 52 photos | Maybe how I am trying to say something is confusing. I used 2x indicators at the same time. |
Hopper | 24/03/2022 04:08:50 |
![]() 7881 forum posts 397 photos | No idea what you are talking about now. Pictures needed to explain your problem. I am totally unclear on where you have the two dial indicators mounted and where they are measuring. Are you having problems with your mill not producing accurate work? If not, then you are probably overthinking the problem. Best to have your machinist friend look at it in person. It seems whatever your problem is, it is not commonly known about among the mill owners on here or one would have jumped in with a solution by now. |
Pete Rimmer | 24/03/2022 06:52:27 |
1486 forum posts 105 photos | Now it sounds like the quill is loose in the head. Chris, post a photo of how you have your dial gauges arranged. |
Chris Mate | 24/03/2022 07:45:29 |
325 forum posts 52 photos | Here is an illustration: This is about using the Fine Adjustment for quil/spindle. Edited By Chris Mate on 24/03/2022 07:49:48 Edited By Chris Mate on 24/03/2022 07:50:27 |
Nicholas Farr | 24/03/2022 08:06:40 |
![]() 3988 forum posts 1799 photos | Hi Chris, all I can think of is there is too much clearance in your spindle bearings, the quill and spindle should move as one, but perhaps you are chasing microns. Regards Nick. |
Nick Wheeler | 24/03/2022 09:12:10 |
1227 forum posts 101 photos | This all sounds like an excuse for not getting any work done to me. The only time I've put a DTI near either of my lathes is to dial a part into the 4 jaw chuck. What is the OP intending to make that justifies this sort of inspection? |
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