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How do I adjust the quill?

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Gary Wooding15/06/2017 11:31:11
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I've got a Chester Micro-Mill in "as-new" condition. Everything works OK except that there is too much vertical play in the quill. There's no noticeable play between the spindle and the quill, but after setting the quill to a particular position, either by the lever or the fine control, it can be pushed upwards by about 1mm. Which makes drilling to a particular depth with a 0.6mm drill rather hazardous.

Does anybody have an exploded view of the mill, or know how to remove the play?

chester micromill1.jpgchester micromill2.jpg

John Stevenson15/06/2017 11:50:14
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The lever a few fine feed control both work through the rack and pinion so it may be here where your play is.
This usually doesn't matter as you drop your cutter or drill on the work, then set the depth of cut. Any play above this doesn't matter unless I'm not reading your post correctly
Samsaranda15/06/2017 12:02:29
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Your Chester Micro Mill appears to be similar to the Arceurotrade Micro Mill, probably same manufacturer, if you go on the Arc website, look under milling machines and at the Micro Mill, there is an exploded view available which should show all you need.

Dave

Gary Wooding15/06/2017 12:04:48
909 forum posts
233 photos

When the depth of cut has been set it is possible to lift the quill by about 1mm.

I noticed the problem when I needed to drill a 0.6mm blind hole, 1.8mm deep, in a piece of precious metal 2.3mm thick. With such a small drill there is a real possibility that the weight of the quill will cause the drill to descend too far.

John Stevenson15/06/2017 12:23:26
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Sorry Gary, still don't follow you.
Set your drill on top of the work. Drill down 1.8mm using the DRO then turn the graduated ring until it stops. This is now a dead stop and the drill cannot drop or go any further.
Retract drill, move to next hole an drill until it stops and that will be your preset 1.8mm

Edited By John Stevenson on 15/06/2017 12:24:11

SillyOldDuffer15/06/2017 12:38:03
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Umm, I may be misunderstanding the question? Or perhaps the Micro-mill is different?

What I do when depth accuracy matters is:

  1. Tack a bit of spit moistened cigarette paper, thinner the better, over the top of the work
  2. Lower the drill point to just above the paper, but not touching it, using the coarse setting.
  3. Start the mill, then lower the drill point using fine-feed until it just catches the cigarette paper .
  4. Set the zero point.
  5. Use fine-feed to drill down the required distance.

My cheap drill stand has a good few mm upward play in the spindle. Provided I push down after establishing zero it doesn't matter.

Dave

duncan webster15/06/2017 13:42:05
3597 forum posts
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I'm not that familiar with this litle machine, but the problem sounds the same as I had on my Naerok. What I did if depth of cut was important was to use finger and thumb to hold the quill up against the backlash when putting the cut on, keep hold until you've locked the quill downfeed, then remember to get hold again before unlocking the downfeed for the next cut. People with a less pragmnatric approach have designed spring or weigh driven devices to keep the quill pushed up. My Centec uses a spring, and I've seen some big machines with pulley and counterweight systems

Clive Foster15/06/2017 14:46:42
2889 forum posts
104 photos

The only fully satisfactory solution is to arrange some form of hard stop independent of the quill rack. No other way to completely avoid the risk of the drill or cutter being sucked down an indeterminate amount when the system goes free at cessation of applied downforce. Maybe some sort of arm clamped to the spindle with a slider on a rod or screwed stop nut drill press style striking a suitable strong point attached to the machine. Slider on a rod is easier to do than a screw but not so precise.

Very different machine but this picture shows the sort of layout with an arm on the quill and a slider on a rod with a simple wing headed bolt to set position. (Original was a floppy threaded rod thing with a knob at the bottom. Imprecise, slow and fairly useless.) You'd need to put the rod and stop at the side rather than in front but its not completely impractical. Probably no need for a scale with your built in readout. Will need to touch the job with the drill to set zero position then move everything to one side to set the stop for whatever depth you need.

depth stop.jpg

You will loose a bit of quill travel due to the solid arm stopping full retraction but probably acceptable. Ignore the square tube between arm and body. That goes over to mount the reader on a DRO, 1" less travel being an acceptable, to me trade off for a DRO.

Bodge method is to add an extra return spring to hook on when you need things accurate.

Clive.

Edited By Clive Foster on 15/06/2017 14:48:24

Edited By Clive Foster on 15/06/2017 14:48:54

Ian P15/06/2017 14:49:16
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2537 forum posts
102 photos

I suppose your problem is related to the quill return spring location. On some machines the quill relies on the clock spring on the pinion shaft whereas some other have a spring acting directly on the quill itself.

Depending on the fit of the quill, its weight and the friction involved, its possible that backlash between the pinion and the rack might allow the quill to drop dependent on what method you use to take up the slack when setting the depth.

IanP

Michael Gilligan15/06/2017 16:48:00
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Posted by Gary Wooding on 15/06/2017 12:04:48:

I noticed the problem when I needed to drill a 0.6mm blind hole, 1.8mm deep, in a piece of precious metal 2.3mm thick.

.

Gary,

Given your concerns, and the fact that you are working with precious metals ... I think you might be happier using a 'sensitive' drill ... The design by Geo. H. Thomas [as part of the Universal Pillar Tool] is excellent, and need not be slavishly followed; it's the operating principle that matters.

Here's a very nice example, for inspiration: **LINK**

https://pennyfarthingtools.co.uk/geo-h-thomas-sensitive-drill/2017/02/09/

MichaelG.

Gary Wooding16/06/2017 10:45:46
909 forum posts
233 photos
Posted by John Stevenson on 15/06/2017 12:23:26:
Sorry Gary, still don't follow you.
Set your drill on top of the work. Drill down 1.8mm using the DRO then turn the graduated ring until it stops. This is now a dead stop and the drill cannot drop or go any further.
Retract drill, move to next hole an drill until it stops and that will be your preset 1.8mm

Edited By John Stevenson on 15/06/2017 12:24:11

The DRO tells me the position of the quill but, because of the play I cannot control that position. I can set the depth stop but that only controls where the rack pinion stops, not where the quill stops. With the pinion locked it is possible to move the quill up by about 1mm. If I set the DRO to zero with the drill touching the workpiece and the backlash taken up, then I have to be very careful when the DRO gets to 1.8mm 'cos I can't rely on the drill not getting sucked in further because of the backlash.

Gary Wooding16/06/2017 10:51:37
909 forum posts
233 photos
Posted by 12 Bore on 15/06/2017 12:02:29:

Your Chester Micro Mill appears to be similar to the Arceurotrade Micro Mill, probably same manufacturer, if you go on the Arc website, look under milling machines and at the Micro Mill, there is an exploded view available which should show all you need.

Dave

It certainly looks like the same mill, but I couldn't find the exploded view you mentioned.

mgnbuk16/06/2017 14:09:39
1057 forum posts
70 photos

**LINK**

Is it this one ?

This came from the link on this page : **LINK**

HTH

Nigel B

Gary Wooding16/06/2017 15:01:59
909 forum posts
233 photos

Thanks Nigel B,

That's the one.

Ketan Swali16/06/2017 17:37:35
1384 forum posts
119 photos

Hi Gary,

You mention 'precious metal'. Are you a jeweller, watch or clock maker?..

Are you new to working with 'cheap' machines?

If combination of the above, then please don't waste your time trying to figure anything out. I say this with the greatest of respect. From experience of selling to professionals as well has amateurs in the above field, I can tell you that professionals buy and modify this machine somehow to meet their precision requirements (don't ask me how as I don't know), and persons who are new in this field (expecting high precision drilling) usually end up disappointed.

The X0 does have a variable amount of end float due to the rack and pinion arrangement on the quill. 1mm movement seems to be a little on the high side, so are you sure this is the case?. It works as it is supposed to, as it was designed, for the purpose of 'drilling' metal. Almost all drilling machines have such end float. It is not designed as a high end precision drill/mill.

Certain people such as Frank Crispin - well known in the hydrological arena have stripped the machine and added bits to it to remove end float, to meet his precision requirement. Otherwise, his words: ' he would have to spend around three to four times as much' to buy a high precision micro drill for his purpose'.

For milling, one would lock the quill by tightening the large socket head screw (which originally used to be the locking handle part 96 on the exploded drawing.).. this would remove the end float for the purpose of milling.

Ian P16/06/2017 19:40:58
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2537 forum posts
102 photos

It does seem as if the play you are seeing is in the rack and pinion so one workaround would be to arrange a spring to pull (or push) the quill upwards. The spring needs to be strong enough for the quill not to be dragged down say, if a drill breaks through when drilling brass. The spring will overcome the backlash problem but its not a perfect solution.

By adding a second spring you will lose some feed sensitivity so you will have to experiment. The diameter of hole you mentioned is best done with a rigid machine designed for the purpose.

IanP

John Stevenson16/06/2017 21:52:45
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There is already a spring fitted. It's part number 15 and is adjustable by removing the three screws behind where the graduated ring goes. Take care when you release the last screw as it will want to unwind. Just wind a bit more tension on it and replace the screws

I'm a bit non plussed why Gary can't set this up. A while ago I got a contract to supply some capillary housings in large quantities in brass

The OD is CNC turned and then they go onto 2 of these Sieg X0's for drilling. These were bought just for this contract and remain set up. The first machine drills a 1.8 mm hole 9.5mm deep the second machine then drills a 0.4mm hole all the way thru which is also 9.5mm deep

The reason for the stepped hole is so two tiny copper pipes can be soldered in. I have done in the low thousands in snatchy brass and never lost a drill or a part yet
Ian P16/06/2017 23:10:05
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2537 forum posts
102 photos

Notwithstanding your good results with the parts you made, the spring (15) acts on the pinion shaft. When the pinion is rotated the leading face of the teeth push the rack downwards. If the quill is a close fit in the casting there is enough friction to keep the same gear faces in contact as the quill travels down and they remain in contact once the drill is in contact with the work. If the quill is a loose fit though, gravity will keep the back of the teeth in contact and they will stay contact until the drill touches, there is then some lost motion as the pinion catches up with the rack.

I think the X1 type mill has the quill return spring acting directly on the quill so does not suffer this particular backlash problem.

That's how I see it anyway.

Ian P

Ketan Swali17/06/2017 06:03:08
1384 forum posts
119 photos

Apologies Gary, I stand corrected to a certain extent by the more helpful comments which followed mine, to deal with your particular requirement. Please don't let my comments discourage you from considering options.

Ketan at Arc.

Mark Rand17/06/2017 12:12:49
1086 forum posts
12 photos

Because the problem is due to slack between the quill rack and the pinion, one solution could be to determine the number of teeth and pitch (presumably metric module) of the pinion, then order an approptiate anti-backlash gear from the likes of HPC gears. Note that this is not a cheap option.

It may also be possible to fit a compression spring between the top of the quill and the bearing seat at the top of the head to pre-load the rack/pinion slightly. Hopefully there would be enough movement available in the quill return spring to be able to increase its tension to counteract the additional spring.

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