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M250cnc
09-01-2011, 02:22 PM
You draw your part in CAD then create a Gcode file using a CAM program

The attached pic is drawn in the lower R/H corner this is X Plus Y Minus

The piece is 100 mm square and you want to put a 20mm hole in the centre

This assume your machine is perfectly set up, no backlash etc

You only have simple equipment no edge finders of any type

You will hold this in a vice clamped to the table with the back edge running perfectly parallel to the X axis

Have the part stick out say 10mm on the left hand side

You can use a dowel of 6mm dia or a cutter mounted in your collet upside down

Bring the dowel up on the left hand side so it is just touching you can use a feeler gauge to do this but you have to add the feeler gauge thickness to the DRO's setting

Once you have TOUCHED OFF set the DRO to the correct dimension then raise the Z and move the table to Zero it should be obvious if the dowel looks correctly on the centreline

Then you repeat for the other axis

Using this method you should be able to be accurate to 0.02mm

You could also have other holes, recesses shapes in the plate but the edge finding is the same



HTH
Phil

i2i
09-01-2011, 05:27 PM
I get a piece of paper and hold it between the cutter and the job, then gently move the cutter to the job until the paper is just trapped. You can do this on the edge of the cutter and the face, for x,y, and z.

M250cnc
09-01-2011, 05:34 PM
I get a piece of paper and hold it between the cutter and the job, then gently move the cutter to the job until the paper is just trapped. You can do this on the edge of the cutter and the face, for x,y, and z.

Yes i used to use a cigarette paper .001" with the spindle running, the trouble is that is very dangerous and i didn't want anyone to think i was in Jonathan & Blackburn Marks gang. :rofl:

So this is a non dangerous way of doing the same.:lol:

Phil

Jonathan
09-01-2011, 05:36 PM
I get a piece of paper and hold it between the cutter and the job, then gently move the cutter to the job until the paper is just trapped. You can do this on the edge of the cutter and the face, for x,y, and z.

I do that too, adding 0.1mm for the thickness of the paper. Or get the cutter close, put the spindle on and move it so that you just hear it brushing.

i2i
09-01-2011, 05:46 PM
Yes i used to use a cigarette paper .001" with the spindle running, the trouble is that is very dangerous and i didn't want anyone to think i was in Jonathan & Blackburn Marks gang. :rofl:

So this is a non dangerous way of doing the same.:lol:

Philobviously without the spindle running.:lol:

blackburn mark
09-01-2011, 05:47 PM
your all pussies !!!! i use one of my eye lashes.... while its still attached to my face :)

i2i
09-01-2011, 05:49 PM
i used to wet a piece of paper and nudge the tool onto it but sometimes you get a fine witness mark on the job if you're a bit heavy handed. With a dry piece of paper and the spindle off you can feel the connection.

M250cnc
09-01-2011, 05:55 PM
your all pussies !!!! i use one of my eye lashes.... while its still attached to my face :)

True but we are not missing any bodily parts.:wink:

Phil

i2i
09-01-2011, 05:57 PM
and we can still see, those bionic eyes aren't all they're cracked up to be.

m_c
09-01-2011, 08:56 PM
Edge finders aren't that expensive - http://www.arceurotrade.co.uk/Catalogue/Measurement/Edge-Finders

However, I've always used an edge finder, then if I need critical height, a bit wet paper, or just wind down/up until the tool just starts to mark the workpiece, depending on what I'm doing.

blackburn mark
09-01-2011, 09:13 PM
iv been using a video edge finder with some success (a modified webcam 5) needs a bit more tuning, its off to one side so its really easy to use with the tool still in
i just nick the surface in the z and back off a couple of steps
ill use a rizzler if im feeling fussy

h4ppy-chris
10-01-2011, 02:01 PM
thanks Phil that helped me


You draw your part in CAD then create a Gcode file using a CAM program

The attached pic is drawn in the lower R/H corner this is X Plus Y Minus

The piece is 100 mm square and you want to put a 20mm hole in the centre

This assume your machine is perfectly set up, no backlash etc

You only have simple equipment no edge finders of any type

You will hold this in a vice clamped to the table with the back edge running perfectly parallel to the X axis

Have the part stick out say 10mm on the left hand side

You can use a dowel of 6mm dia or a cutter mounted in your collet upside down

Bring the dowel up on the left hand side so it is just touching you can use a feeler gauge to do this but you have to add the feeler gauge thickness to the DRO's setting

Once you have TOUCHED OFF set the DRO to the correct dimension then raise the Z and move the table to Zero it should be obvious if the dowel looks correctly on the centreline

Then you repeat for the other axis

Using this method you should be able to be accurate to 0.02mm

You could also have other holes, recesses shapes in the plate but the edge finding is the same



HTH
Phil

Phil Gravett
10-01-2011, 02:06 PM
Traditional tool makers used a sticky pin. This is a dressmaking pin held in a bit of plastacine (blue tac or chewing gum works but not as good) put on the cutter or drill. With spindle running, you press on side of tip of pin till it runs true. This could be done with a lolly stick or something like. You now have a fine point that is true with centre of cutter and can be lined up with edges, scribed lines and centre dots/pops.
A wobbler set is a sophisticated version but although I use a set on lathes and mill I have always found a "Sticky Pin" most useful and quick. Wobblers are useful for edge finding but you do need height.

h4ppy-chris
10-01-2011, 03:15 PM
fanatic idea thanks for sharing :)


Traditional tool makers used a sticky pin. This is a dressmaking pin held in a bit of plastacine (blue tac or chewing gum works but not as good) put on the cutter or drill. With spindle running, you press on side of tip of pin till it runs true. This could be done with a lolly stick or something like. You now have a fine point that is true with centre of cutter and can be lined up with edges, scribed lines and centre dots/pops.
A wobbler set is a sophisticated version but although I use a set on lathes and mill I have always found a "Sticky Pin" most useful and quick. Wobblers are useful for edge finding but you do need height.

Lee Roberts
01-03-2011, 10:55 AM
There are some other choices as well:


http://www.youtube.com/watch?v=Oc-9gTFj-y4

and also


http://www.youtube.com/watch?v=KOXY4O0UkRM

Below is one i made earlier :lol:

3805