Author Topic: Accurate Drilling - centering microscope, USB cam, optical punch?  (Read 28326 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.

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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.