Author Topic: Accurate Drilling - centering microscope, USB cam, optical punch?  (Read 28319 times)

Offline raynerd

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One of the things I`ve always struggled with the accurately drilling holes in sheet metal, where I want them!! As most of you know, I`ve been playing at building a clock and feel I`m getting there slowly in terms of the skills needed but of course drilling pivot holes exactly where they are marked is critical! Also, these holes are drilled sequentially as the back plate is built up as and when the wheels are made and so it would be sole destroying to muck up the drilling of a later hole, and mess the plate up for the rest of the holes drilled! I need to come up with a better more reliable method of spotting and drilling holes very accurately on sheet brass.

I`m currently accurately marking out, punching and then drilling. Firstly, my punch mark isn`t always perfect (do I need an optical punch), if I do punch accurately, the next issue is aligning that punch hole up to be drilled on the mill (do I need a centering microscope).

I often find that my holes a little out of the centre ligns marked when I look back at the drilled spot. This doesn`t really matter at present but soon when I get to drill out for pivot holes I`ll need to be "spot on!"

I`ve been thinking about an optical centering microscope for a while as hemingway sells a kit for £100 but I have also seen these USB webcams with this free software:  http://www.miketreth.mistral.co.uk/centrecam.htm

There seems to be lots on the web about people building these USB cams and using CentreCam but all the posts seem to be between 2006-2009 and nothing more recent! I can`t seem to find any more recent USB cam developments but this looks to be a serious consideration.

Any advice or info welcome!

Offline John Stevenson

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Re: Accurate Drilling - centering microscope, USB cam, optical punch?
« Reply #1 on: June 26, 2011, 06:34:13 AM »
If you are drilling on the mill why not use the dials / DRO [ if fitted] to lay the holes out ?

John S.
John Stevenson

Offline modeldozer

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Re: Accurate Drilling - centering microscope, USB cam, optical punch?
« Reply #2 on: June 26, 2011, 06:39:19 AM »
Hi Chris,

Something like this?




If you want I can search for my build pics and plans, it uses one of the Logitec VGA webcams.

Abraham

Offline HS93

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Re: Accurate Drilling - centering microscope, USB cam, optical punch?
« Reply #3 on: June 26, 2011, 07:08:43 AM »
yes Please

Peter
I am usless at metalwork, Oh and cannot spell either . failure

Offline PekkaNF

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Re: Accurate Drilling - centering microscope, USB cam, optical punch?
« Reply #4 on: June 26, 2011, 07:25:42 AM »
I struggling with accurate placed and geometricly true as well.

I don't know what size of holes you do, but I imagine small. It makes a difference. I usually work bigger than about 1 mm. Most often between 3 to 12 mm.

I had a lot of trouble popping the centre mark and then getting the hole there. I only work either markking and I read no dials, or marks first hole and then there are only permanet marker crosses to eliminate complete mistakes if I use dials.

1) Drawing the line. I found out that I'm better off scribing the lines straight and holding the scriber straight, note that this will require some off set from the rule, if you are using it. Canted scribe line does not "crab" the punch to correct location. Something to do with the burr or something, hard to imagine that slighty inclined groove would send it on the other side.
2) Popping the mark on the right place: a) Use small sharp 60 decree to get the punch on the right place. b) Locating the intersection: I'll draw the punch on the line until I'll feel the "intersection", you probably want to draw the line you draw last, othervice you'll bump the "wall" of the other line. c) Punch absolutelu upright and LIGHT tap to get very small pip.
3) Inspection: mark can be driven with a gentle taps close the final location. If driven or uneven burr, I always file the surface smooth, the uneven wall will play havoc
4) If the hole is large I finaly pop centre with larger 90 decree punch and check it again
5) I aim that punch visually, larger drills will pull light objects centre, when gently touched with a drill, but wiggler works also for me.
6) I have found that using spotting drills will put the hole exactly where aimed. Pop rivet drills come close second, but I have no luck with normal drills, they wander all over. There are many different types of drills, many will drill happily after they have good centre to start, but on thin drills only spotting drills seem to get the start right (I use 3 mm quite often).

Sometimes I'll locate first hole with a wiggler and then work from there a dial indicator, works only a very small distance, but with very good accuracy.

Biggest improvements I had was to learn to make the punch right, most of the time I'll file the "crater" even and the correct drill will make or break it.

I'm not sure if this helps, but when I drilled PC boards and such, learnt little about drils.

Pekka

Offline Jasonb

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Re: Accurate Drilling - centering microscope, USB cam, optical punch?
« Reply #5 on: June 26, 2011, 08:05:52 AM »
If you are drilling on the mill why not use the dials / DRO [ if fitted] to lay the holes out ?

John S.

As he says the holes are drilled sequentially I would thing that a depthing tool is being used to get the mesh correct rather than just laying out the holes. But yes iff a DRO is available its more accurate than marking out.

Chris what type of punch are you using. First you should lightly use a dot punch and inspect the mark, if its off then it can be "moved by slightly tipping the punch and tapping again. Once you are happy with the dot position follow up with a centre punch.

Another option if you are using a depthing tool is to drill the size hole you need in a bit of scrap steel, use the depthing tool to set this where you need the hole, clamp to the workpiece and then you have a correctly positioned drill guide.
The small optical punches work quite well, I have the Veritas one.

J

Offline raynerd

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Re: Accurate Drilling - centering microscope, USB cam, optical punch?
« Reply #6 on: June 26, 2011, 08:17:24 AM »
Thanks for the info so far. Modelozer, yes I would definitely like to see your pics and plans! what software do you use with it?

John, I could use my dro and I sometimes do but I'll soon be using a depthing tool to mark out the position of gears and so this wouldn't be useful. Also, holes are often drilled in relation to one another and so I still need to find my position from another hole, which I need to centre on. I do agree, dro should be used more but ontop of that I don't always trust my cheap Asian made scales.

Jason, I'm not going to lie, I'm just using one of my three from my punch set!!!! I also have one of those self hammering ones which is no use at all for getting aligned!! I will investigate with the intent to purchase some punches this afternoon.
Chris

Offline Jasonb

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Re: Accurate Drilling - centering microscope, USB cam, optical punch?
« Reply #7 on: June 26, 2011, 09:03:11 AM »
If you have three in a set then just grind one to a 60deg point and use that as the dot punch.

J

Offline DaveH

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Re: Accurate Drilling - centering microscope, USB cam, optical punch?
« Reply #8 on: June 26, 2011, 09:55:22 AM »
Chris,

You don't really need to punch, if it is marked use your mill with a "pointy" bit in the chuck. Align it all up.
Use a small centre drill or spotting drill, and you are away. :D

 :beer:

DaveH
(Ex Leicester, Thurmaston, Ashby De La Zouch.)

Offline kwackers

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Re: Accurate Drilling - centering microscope, USB cam, optical punch?
« Reply #9 on: June 26, 2011, 11:17:59 AM »
If you're simply lining up to an existing mark - say from your depthing gauge. I doubt you really need that much accuracy.

I use one of the cheap pointy tools that you put in the drill, spin up and touch with a pencil to centre. Using that and my eyeball I can easily get within about a thou, probably way more accurate than you need (remember - engineers make bad clocks! "If it rattles, it'll run!").

Offline dvbydt

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Re: Accurate Drilling - centering microscope, USB cam, optical punch?
« Reply #10 on: June 26, 2011, 11:23:16 AM »
Another vote for throwing out the centre punch. Edge find or centre find, use DRO or the dials and use a spotting drill. If the job is too big to fit on the table in one go then mark out only and use a sharp point in the chuck to find the intersection. Like these :-



I bought a box years ago, they are hardened and ground. Also useful for making scribers or very small spade or spotting drills. My version of DaveH's "pointy" bit.

Ian

Offline Lew_Merrick_PE

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Re: Accurate Drilling - centering microscope, USB cam, optical punch?
« Reply #11 on: June 26, 2011, 11:53:28 AM »
Bry,

1) If you have laid out your sheetmetal well, you will add "index edges" that allow you to establish a "zero" with an edge finder or some other reasonably accurate means.  There are several ways to control your axis moves very accurately (dials and DRO's are fine, but they have errors associated with them that gauge blocks and stops overcome).  You can also use the method known as "3 disk alignment" or "tool buttons" -- both of which are documented in Machinery's Handbook.

2) There used to be a type of drill specific to sheetmetal.  They have disappeared from the commercial market over the past four decades or so, but they look like the drilling portion of a "UniBit" in that the flute is straight and leaves (about) 75% of the periphery in bearing as the drill cuts.  They are much more rigid than a twist drill and will actually produce round holes in sheetmetal!  Larger bits (say 3/16 or 4.5 mm) are fairly easy to make by turning a (say) 135° included point on a piece of properly sized drill rod (silver steel on your side of the pond), milling out a (just over center) 90° slot, hardening and tempering it (draw to straw), stoning it, and stoning a relief for the point.  Smaller bits are easier to grind from pre-hardened and tempered stock.  Grind the tip (relieve it later) and mount the "bit" in a block steel such that you can press it into a drilled & reamed hole located very near the corner of the block and grind out the very slightly over center 90° flute with a die grinder mounted to the spindle of your mill.  That way you don't get your work ruined during quenching.

I bought a set of sheetmetal drill bits back in the late-1960's.  In those days they were a common product in tool & die supply houses.  They cost about the same as a set of twist drills in those days.  I only have the odd sizes left and was quite surprised a few years ago when people in the tool & die supply business looked at me strangely when I tried to buy replacements.  I guess this is what happens when you get old....

Offline Jasonb

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Re: Accurate Drilling - centering microscope, USB cam, optical punch?
« Reply #12 on: June 26, 2011, 12:30:25 PM »
Lew surely the whole problem that Chris has using a depthing gauge is that he does not know how far to wind in the dial or read off the DRO so there is little point in establishing a zero.

At best the hole will be located a set distance from one edge and at its intersection with an arc, at worse it will be at the intersection of two arcs so you can't use co-ordinates to position the hole.

As for round holes when clock making isn't that what they make broaches for, bit like a reamer but produces a round hole in sheet material.

J

Edit, is this the type of drill bit?

Offline modeldozer

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Re: Accurate Drilling - centering microscope, USB cam, optical punch?
« Reply #13 on: June 26, 2011, 01:45:21 PM »
Will get them together and maybe to a seperate post under tools. Plans in pdf OK?

Chris, Centrecam mostly and the video plugin for Mach3.

Abraham

Offline picclock

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Re: Accurate Drilling - centering microscope, USB cam, optical punch?
« Reply #14 on: June 26, 2011, 02:46:11 PM »
Hi craynerd

IMHO best way is to use DRO's. Its a low cost solution which will get you to within a thou. Just mount on the X and Y table axis and read off the display directly. To locate the work clamp to the table with mdf or similar underneath, and then use an edge finder. I use a starett one on everything except aluminium. The work should have 1 straight edge which you can pick up on with a dti to make it square to the table. Then just use the edgefinder and zero the dro's after taking off the edgefinder radius.

I use a cheepy 6" one for the y and a 300mm one for the X, overall cost <£40. Only thing is must be covered with acrylic/plastic or similar to stop swarf, lubricant etc. Works really well with amazing repeatability. My starett finder has a point the other end which you can use to centre on an existing hole within a thou or two.

This completely takes out the centre punch and manual alignment. I use a small BS1 centre on super accurate stuff to set the start position. Other thing is your eyes only have to be good enough to see the numbers   :thumbup:

Best Regards

picclock
Engaged in the art of turning large pieces of useful material into ever smaller pieces of (s)crap. (Ferndown, Dorset)

Offline Jasonb

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Re: Accurate Drilling - centering microscope, USB cam, optical punch?
« Reply #15 on: June 26, 2011, 04:06:16 PM »
Hi craynerd

 Just mount on the X and Y table axis and read off the display directly.

As I said above if you don't know one or both of the x & y dimensions this method is no use. Chris is using a depthing gauge to mark the centre not a given dimension :doh:

Offline Troutsqueezer

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Re: Accurate Drilling - centering microscope, USB cam, optical punch?
« Reply #16 on: June 26, 2011, 04:18:10 PM »
Before I added DRO's to my X2, my method was to mark the hole locations using blue Dykem and a scribe (calipers drug along the edge usually). Then with the part mounted in the mill, I would use a spotting drill and eyeball it (using magnifiers) and then, with the motor turned off, gently lower the spindle and very lightly dimple a small dot in the Dykem. Then it was easy to see if I needed to move the table slightly to get the dimple directly over the cross scribes.

-Trout
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Offline bp

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Re: Accurate Drilling - centering microscope, USB cam, optical punch?
« Reply #17 on: June 27, 2011, 01:08:55 AM »
A couple of months ago I got an imported centering 'scope from Enco in the US, it was "on special", I happened to notice the other day that the same thing was still on sale, something like US$190 plus freight which wasn't too bad to Australia.  I've used it a huge amount since, not only for centering on the mill, but also for getting lathe tools absolutely spot on center height.  As it happens I've just finished making an engine mounting plate, which had 12 accurate holes marked out with a height gauge and they are all spot on.
No doubt others will decry them, but as far as I'm concerned it was one of the best bits of kit that I've got, and not just single function!!
cheers
bp

Offline picclock

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Re: Accurate Drilling - centering microscope, USB cam, optical punch?
« Reply #18 on: June 27, 2011, 03:45:28 AM »
@JasonB

OK now I understand. I never realised that in clockmaking you adjusted the hole distance to get the gear fit. Also I had never heard of a depthing gauge - which seems like the ultimate in bodging it. Having said that its been done this way for many years so it's obviously the method to use.

Needless to say I have never attempted to make a clock .. .

picclock

 

Engaged in the art of turning large pieces of useful material into ever smaller pieces of (s)crap. (Ferndown, Dorset)

Offline John Hill

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Re: Accurate Drilling - centering microscope, USB cam, optical punch?
« Reply #19 on: June 27, 2011, 05:22:46 AM »
If I understand correctly the function of the depthing gauge is to accurately determine the required distance between two pivot points?

So, my suggestion, figure out some way of accurately measuring the setting of your depthing gauge, maybe micrometer across the two shafts minus the diameter of one shaft.  Armed with that information you can move your mill using the DRO. :scratch:
From the den of The Artful Bodger

Offline kwackers

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Re: Accurate Drilling - centering microscope, USB cam, optical punch?
« Reply #20 on: June 27, 2011, 05:49:07 AM »
There are two points of note with a depthing gauge.

First it lets you run two gears together until you're happy they're meshing correctly - at that point the points on the guage are correct for marking the clock plates.

Second - and more important from a marking out point of view, they behave like a compass. So you start from your reference and mark the next gear, then set up for the next and mark an arc and so on using the intersections of arcs to correctly place all the gears.
It's this method of marking out that means you can't use the DRO easily. You'd need a DRO that you could give multiple arcs to and it would calculate the intersections.

What you could do I guess it put them into a CAD package and read off the absolute positions, but that somehow seems harder than simply marking out the positions of the gears...

Offline John Hill

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Re: Accurate Drilling - centering microscope, USB cam, optical punch?
« Reply #21 on: June 27, 2011, 06:19:15 AM »
There are two points of note with a depthing gauge.

First it lets you run two gears together until you're happy they're meshing correctly - at that point the points on the guage are correct for marking the clock plates.

Second - and more important from a marking out point of view, they behave like a compass. So you start from your reference and mark the next gear, then set up for the next and mark an arc and so on using the intersections of arcs to correctly place all the gears.
It's this method of marking out that means you can't use the DRO easily. You'd need a DRO that you could give multiple arcs to and it would calculate the intersections.

What you could do I guess it put them into a CAD package and read off the absolute positions, but that somehow seems harder than simply marking out the positions of the gears...


Marking out the positions is only a step along the way, it is not easy and neither is it necessary.  Much easier to use the DRO to move from one drill position to the next.  For example, first draw the positions of the required holes after accurately determining the distance between positions.  You will need to solve some very simple right triangles to get the required DRO coordinates, using a protractor to get the angles from your paper drawing.
From the den of The Artful Bodger

Offline kwackers

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Re: Accurate Drilling - centering microscope, USB cam, optical punch?
« Reply #22 on: June 27, 2011, 06:50:22 AM »
Marking out the positions is only a step along the way, it is not easy and neither is it necessary.  Much easier to use the DRO to move from one drill position to the next.  For example, first draw the positions of the required holes after accurately determining the distance between positions.  You will need to solve some very simple right triangles to get the required DRO coordinates, using a protractor to get the angles from your paper drawing.
I don't follow, where did the paper drawing come from? Did you draw it yourself? If so how's that easier than simply marking out using a depthing gauge?

I think people are getting carried away here, marking out clock wheels using a depthing gauge and then drilling the points isn't a big issue. It doesn't need to be super accurate on a per hole basis but it does need to allow for accumulated error.
The system of using a depthing gauge and drawing arcs fits those parameters perfectly. As soon as you start measuring and calculating you accumulate errors and risk the whole thing going pear shaped.

Offline spuddevans

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Re: Accurate Drilling - centering microscope, USB cam, optical punch?
« Reply #23 on: June 27, 2011, 07:14:58 AM »
Another reason to use a depthing gauge is that it allows you to set, very precisely, the spacing and thus the depth of engagement of the two gears. The importance of this is realised when you consider the effects of not meshing the gears well will result in greater friction, a thing most undesirable in a clock train, and will also result in premature wearing of the gears.

So when you add home made gears into the equation, which most likely will not be precisely the diameter called for in the plans, the need for meshing the gears on a depthing gauge prior to marking those positions on the frame of the clock becomes essential for the smooth running, and therefore the accuracy of the clock.

Tim
Measure with a micrometer, mark with chalk, cut with an axe  -  MI0TME

Offline Jonny

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Re: Accurate Drilling - centering microscope, USB cam, optical punch?
« Reply #24 on: June 27, 2011, 08:15:38 AM »
these holes are drilled sequentially as the back plate is built up as and when the wheels are made

Issues such as runout i wont go into.
Since as stated holes drilled sequentially with the actual wheel to be used, this is quite easy. Nothing more than basic equipment such as a drill press.

Used to do this all the time on irreplaceable one offs of significant value.
Offer up the wheel and position where required. Then you could clamp but i never did and drill through the offered up wheel and in doing so marking the plate. By some chance if it veeres off may need a centre drill in centre of hole that was started, it should self centre.
Works even if a smaller hole is required in the plate such as a tapped hole.

Could show a piccy of a one off built up in similar fashion assembled product done in such a way but may not go down to well out of the ballistics section.

Used to use dividers all the time the trick is to catch the light right and get the point of a punch exactly where you want it.

Offline Lew_Merrick_PE

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Re: Accurate Drilling - centering microscope, USB cam, optical punch?
« Reply #25 on: June 27, 2011, 11:02:49 AM »
Lew surely the whole problem that Chris has using a depthing gauge is that he does not know how far to wind in the dial or read off the DRO so there is little point in establishing a zero.

At best the hole will be located a set distance from one edge and at its intersection with an arc, at worse it will be at the intersection of two arcs so you can't use co-ordinates to position the hole.

As for round holes when clock making isn't that what they make broaches for, bit like a reamer but produces a round hole in sheet material.

Jason,

The positions you cite (distance from one edge & intersection with an arc or an intersection of two arcs) is geometry that can be calculated in terms of X and Y coordinate values.  Yes, there are many times when transferring geometry is simpler, but it is rarely more accurate -- and accuracy is stated as a concern.  I admit that I have never made a clock.  Travel and test dial indicators, yes.  Clocks, no.  Finding the coordinates of an intersection between an arc and either another arc or a line is the base application for the solution to a Quadratic equation that we all had to memorize at some point in school.  We do it quickly and painlessly today using CAD software.  ???

[/quote]
Edit, is this the type of drill bit?
[/quote]

Those are similar, but they are ground for drilling (burning might be a better descriptions) holes in hardened steel.  If you found one in the proper size, you could regrind the point.  The sheetmetal drill bits of my youth were fairly common -- and I spent more time than rational trying to find a source for them a few years back.  I ended up making a small set of them for a client and they were thrilled.

 .

   Lew

Offline kwackers

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Re: Accurate Drilling - centering microscope, USB cam, optical punch?
« Reply #26 on: June 27, 2011, 04:03:14 PM »
I can't believe people are seriously considering replacing a perfectly simple tool that can obtain the ideal mesh between two gears and transfer those points to a plate with as close to perfect accuracy as it's possible to get with a system that still requires the tool, suitably modified to enable the distance between the two points to be accurately determined and then the numbers crunched in a CAD package before finally being entered into the DRO.

Why make things so complex?

Offline Miner

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Re: Accurate Drilling - centering microscope, USB cam, optical punch?
« Reply #27 on: June 27, 2011, 05:02:39 PM »
I've certainly learned far more about just how clockmakers lay out the holes than I knew before. Since I obviously still know very little about this my comments could be a total waste of space on this thread.

It seems to me that the inaccuracys are mostly due to the prick or center punching as your depending on feel and normal eyesight to get those punch marks aligned at the true center of your layout lines. If the punch marks are even slightly out then the drill will drop into that punch mark and you then have a misaligned hole. I'd delete the punch marking completely since there's no real way to get consistant and accurate results.

As people have mentioned, Those spindle mounted web cams would be your best bet IF you can get a consistant alignment with the cameras cross hairs and the spindle C/L. IMO a dedicated web cam mount like a end mill holder that uses set screws to retain the end mill and fits the mills spindle would be a priority. If your spindle allows rotation of that web cam/end mill holder like a mill with a M/T internal taper would, Then marking both the spindle o.d. and the holder so they always go back into the same position would be a nessisity. Those high end German made 3-D Tasters use the same idea to get accurate and consistant results. The old school clock makers didn't use anything like a web cam and everything was done by hand and eye. But there's no doubt if they had what we do today they would have dumped the hand methods in a second. Other than your absolute need and the requirements to use a depthing tool, For myself I've given up on center punching work that requires accuracy and use the coordinate system. You then start from a referance point. The old school (non cnc) super accurate Moore jig boring and grinding machines used that system, So if it was good enough for them.............

Pete    

Offline John Hill

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Re: Accurate Drilling - centering microscope, USB cam, optical punch?
« Reply #28 on: June 27, 2011, 05:20:19 PM »

I don't follow, where did the paper drawing come from? Did you draw it yourself? If so how's that easier than simply marking out using a depthing gauge?

I think people are getting carried away here, marking out clock wheels using a depthing gauge and then drilling the points isn't a big issue. It doesn't need to be super accurate on a per hole basis but it does need to allow for accumulated error.
The system of using a depthing gauge and drawing arcs fits those parameters perfectly. As soon as you start measuring and calculating you accumulate errors and risk the whole thing going pear shaped.


You need some idea of the layout of the gear train unless you have designed the clock entirely in your head.

Here is my suggested process in some detail.

1. sketch layout of gear train.
2. use depthing gauge to determine distances between drill points and mark these on your sketch.
3. drill first hole.
4. refer to sketch for distance and direction to next hole.
5. use DRO to position for next hole.
6. drill
7. rinse, lather and repeat.

Note that each position is determined relative to the one before therefore errors do not accumulate.

From the den of The Artful Bodger

Offline PekkaNF

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Re: Accurate Drilling - centering microscope, USB cam, optical punch?
« Reply #29 on: June 28, 2011, 01:37:17 AM »
Really great thread. Like this formum. People from different backgrounds and disiplines tell how AND why they use the method and how it works from them. I never build a clock and have found it hard to understand WHY they do gear train the way they do, but I think it's dawning to me now. In principle, it's not that fundamentaly different from how gear train is build on banjo before thread cutting...

IMHO if centre punching is used, it needs practice. Least for me: I need small and sharp 60 decree punch to find the centre of two scribed scores, held perfectly straight up, then gentle tap and checked with magnifier. Haven't noticed difference between 60/90 decree punch marks when I have used NC-spotting drills, twis drills seems to need 90 decree punch, although I have found out that too big "crater" for the drill size is not a way to go.

Does anybody use a conical wiggler or sticky needle to center spindle to centre punch?

How small holes we are talkking on this thread? I have't found smaller than 3 mm spot drills, but years ago we used PC-board drills to make 0.5 - 1.2 mm holes. They were britle and run very hight rpm, but worked then fine on good drill press.

Pekka

Offline picclock

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Re: Accurate Drilling - centering microscope, USB cam, optical punch?
« Reply #30 on: June 28, 2011, 02:48:09 AM »
The problem as I understand it is to accurately transfer a running gearfit dimension to the plate to be drilled.

As a possible thought, has anyone considered making the chuck on the mill part of the depther. So to get a correct gearfit, utilise a spindle with the gear fitted into the chuck and the meshing gear and spindle fitted to the plate. An additional block may need to be made to ensure that the plate gear spindle is truly vertical, just a block with a long hole on the top to align the spindle, the bottom part of which can be milled away to clear the gear. This method would allow adjustment of the fit to the correct distance, then the spindle in the chuck could be replaced with a centre for making the drill start.

This eliminates the depther and should give far higher accuracy without any need for centre punching or transfer of dimension.

Hope it makes sense.

Best Regards

picclock
Engaged in the art of turning large pieces of useful material into ever smaller pieces of (s)crap. (Ferndown, Dorset)

Offline kwackers

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Re: Accurate Drilling - centering microscope, USB cam, optical punch?
« Reply #31 on: June 28, 2011, 04:32:43 AM »
You need some idea of the layout of the gear train unless you have designed the clock entirely in your head.

Here is my suggested process in some detail.

1. sketch layout of gear train.
2. use depthing gauge to determine distances between drill points and mark these on your sketch.
3. drill first hole.
4. refer to sketch for distance and direction to next hole.
5. use DRO to position for next hole.
6. drill
7. rinse, lather and repeat.

Note that each position is determined relative to the one before therefore errors do not accumulate.

My problem with that is measuring the distance between the points on the depthing tool with any accuracy.
Where you have a train of gears the inaccuracies add up.

Although tbh I think everyone is thinking like engineers and as I said earlier, engineers build poor clocks for the simple reason they make everything an engineering fit...
Clocks aren't made that accurately.

The most important bit is finding the correct mesh between two gears and the distance between them. Once you have that you can happily drill the hole by eye on a pedestal drill - don't even need a mill...
Whilst 10 thou might be a bit poor getting it within one or two isn't an issue - there should be around a thou play in the axle anyway! The holes for the axles are usually tapered too so has to prevent any chance of racking jamming the gear.

The problem Chris (OP) has is he's thinking it all needs to be super accurate, it doesn't. It needs to be free.

Offline John Hill

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Re: Accurate Drilling - centering microscope, USB cam, optical punch?
« Reply #32 on: June 28, 2011, 04:45:16 AM »
Kwackers,  I see little point in explaining further so I and done with this.
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Offline raynerd

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Re: Accurate Drilling - centering microscope, USB cam, optical punch?
« Reply #33 on: June 28, 2011, 05:05:47 AM »
The most important bit is finding the correct mesh between two gears and the distance between them. Once you have that you can happily drill the hole by eye on a pedestal drill - don't even need a mill...
Whilst 10 thou might be a bit poor getting it within one or two isn't an issue - there should be around a thou play in the axle anyway! The holes for the axles are usually tapered too so has to prevent any chance of racking jamming the gear.

The problem Chris (OP) has is he's thinking it all needs to be super accurate, it doesn't. It needs to be free.

Qwackers, I know in Colin Thrones Book - "Clock Building for the Model Engineer" he just explains that the marked out points are then drilled - he doesn`t say how and I presume it is just done by eye. What would be your method, centre pop and then drill ?  The hole I`m drilling is 0.8mm so literally, how would you go about from a marked out point to drilling the small hole?


I`ve been watching every single post made in this thread with interest and I didn`t want to throw in any stupid comments so I have stayed out. My issue does lie as many have said with having a hole with no co-ordinates and therefore just wanting to drill from the marked point hence the suggestion that an optical scope or punch may be needed.

You have all made many very very good suggestions but I would like to consider my options now as if a DRO was not available and just spot drilling to a cross marked position.

 :mmr:   I am kind of pleased that my thread has sparked all this discussion and that my issue is clearly one that can be done in many way as I presumed! I just find when I currently mark out my position and then drill a hole, the hole is not perfectly central to the "cross hairs" mark! A few have suggested a pointed in the chuck/collet - this could possible work well!
Chris

Offline Jasonb

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Re: Accurate Drilling - centering microscope, USB cam, optical punch?
« Reply #34 on: June 28, 2011, 12:13:31 PM »
As I said use a sharp DOT punch not a centre punch. Lean it slightly so you can see the end as you place it on the intersection of your two marked lines, you should be able to feel it sit into the scribed line. Bring it vertical and give a light tap, inspect this punch mark with a magnifying glass, if it is off the punch can be tilted and tapped at an angle to pull the punch mark to where you need it. Once happy with the dot punch mark follow up with a sharp centre punch.

You can then locate the centre punch mark in your drill or mill with a centre finder, the pin type will do and drill your hole.

Jason

Offline kwackers

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Re: Accurate Drilling - centering microscope, USB cam, optical punch?
« Reply #35 on: June 28, 2011, 01:03:09 PM »
For most of my drilling let me just say that I co-ordinate drill using my DRO.

In cases like clock frames though I simply blue and mark using proprietary tools - i.e. a depthing gauge.

The depthing gauge works best if a small centre pop'd mark exists in order to more easily register the point of it's shaft, then I draw the arc, mesh up the next gears and continue.
The centre pop is done as Jason says above. You can feel the intersection of the arcs with it's point, then keep it dead vertical and a light tap - you hardly need to be able to see it.
Inspect it and if necessary you can adjust it slightly but with a bit of practice you won't need to.

Then I put the frame on my mill (I use the mill because it's easy to move the frame accurately).

In your case with a 0.8mm drill I'd be happy to line that up by eye - although I find it much better to do it whilst it's spinning, otherwise the facets of the cutting edges can throw you.

But for most stuff I use a wiggler set - in particular the pointy tool (follow link for an example)
Wiggler Set on Amazone
You put the wiggler in the chuck, spin up the machine and just lightly touch the pointy bit with a pencil, this will make it run true and the very sharp point means that with my now obligatory magnifying goggles I can (according to my DRO) see an error in the order of a couple of tenths - providing I wasn't too heavy handed with the punch...