Drilling Randomly Spaced Dowel Pin Holes in an L shape on X and Y Axis

[wannabecnc]

Hey Everyone,
I would like to ask you, Can any of you help me out here? I want to drill/cut randomly spaced holes along the Y and X axis in an L shape down the left-hand side and front edge of my spoil board so I can fit location dowel pins to make my material to sit square.
Have any of you done this type of thing, or do you know anyone that has?
I have Vectric V-Carve Pro 11.5.
I have seen a couple of videos on Youtube, but they only talk about the process of drilling holes or making a spoil board full of holes, which isn't really what I need to do.
I want to be able to set the 8mm diameter holes 50mm in from the edge and then space them at certain points along the Y axis, then the same along the X axis.
As a heads up on my progress from a couple or so months ago when I first came on here, My home built CNC is complete and it actually works well, I have run off three test projects and they turned out quite well, so I'm excited about that, and now I want to make an accurate reference point for the materials that I am going to use in my projects. So yes, I'm still a newbie in the CNC world.
Thank you for any help that you may be able to give that will help me in my quest for this project.
Kind regards,

[ohiolyons]

I have seen a couple of videos on Youtube, but they only talk about the process of drilling holes or making a spoil board full of holes, which isn't really what I need to do.

Same concept, just put the holes where you want them, not everywhere.

Draw a L shaped vector and manually place the holes where you want them.
OR
Draw a L shaped vector and Copy Along Vectors where you want them.

Be advised this type of registration has an issue. Primarily your material has to be cut has to be perfectly square if you are going to any type double side work with this method of registration. I once helped a guy who was cutting multiple fishing lures, double sided. He relied on this method and couldn't understand why on some blanks the cuts were off. His wood wasn't square.

A lot of people do their registration this way, I'm just not a fan.

To take maximum advantage of this you should register your work from the lower left hand corner (assuming the lower left hand corner is your L pivot point) in your drawings too. again not a fan of this, I always use the center. Centering your work has its advantages when drawing vectors. Of course you could always draw them centered and convert to lower left hand corner as a final step.

[martin54]

As ohiolyons has already said it is the same process as you have seen but you just have to position the holes where you want them, I have a whole spoilboard full of 20mm holes in an MFT configuration which works for me
Set your material size at the size you want & then draw an L shaped vector, you can draw it at the position you want it (50mm x & y) or just draw it & move it to X50 Y50 once it is drawn, then just draw the 8mm diameter circle & centre it on the line, dot them about where you wish them to be
If you want them to be in precise locations then you can move them using the move tool

[wannabecnc]

Hi OhioLyons and Martin54,

Thank you for your valued input previously regarding drilling holes etc. I managed to sort out the setup for the holes and the file etc, but it seems that the 8 mm diameter isn't 8 mm. Is there a particular way to get the size accurate the first time?
Thank you

Kind regards

[Adrian]

Assuming your machine is properly calibrated the most common cause of undersized parts is bit deflection or deflection in the machine itself.

What toolpath are you using for the holes?

[martin54]

Have you accurately measured both the bit that you used & the dowels ? Bit's are not always the size stated & dowels aren't always the stated size either

[wannabecnc]

Hi Adrian and Martin54,

Thank you for your comments. I used the profile tool path and I was using a 4 mm end mill to cut the 8 mm hole and I did a spiral set-up.
I'm still waiting for the dowels to arrive, but I tried an 8 mm drill bit to see if it would fit in the hole, but to no avail. The holes were cut into a test piece while I am waiting for the dowels so that when I actually do the holes I actually want, I should by then just be able to run the file.
I used callipers to measure the holes and they are under the 8 mm mark.
7.8 and 7.9 mm. I cut four holes, 8.01 8.02 8.03 and 8.05 mm.
The 8.05 hole is almost the right size for the drill bit, but the drill bit is slightly undersized and not exactly 8 mm according to my callipers.

Thank you

[ElevationCreations]

Just be aware that wood dowel pins will swell and change dimension with humidity variances. I use fluted 8mm dowel pins for alignment on double sided jobs and just make an 8mm pocket in the spoil board. I figure the fluted dowels will be centered enough when driven into the pocket and it holds the material rather well. If it's a one-off operation I can just glue the dowel pin in the pocket and surface it flush with the spoil board when finished.

For my X-Y reference I use aluminum TSO Dogs with tight tolerance for the Festool MFT. That way I only have one wear item - the spoil board - which I can cut MDF plugs, glue in, and make new pockets when the tolerances are off due to wear. With the dogs being aluminum I have less chance damaging the end mills when they make contact.

For my X-Y referencing, I typically use a 3-point system for reference. 2 Dogs along the Y- Axis and one on the X-axis. If the stock is not square it typically isn't an issue for most of my work, unless I am doing inlays on squared up stock, then will go to more reference points if needed.

[wannabecnc]

Hi ElevationCreations,

Thank you for the comment, much appreciated. The dowels I am going to use are alloy, so as you say, the holes in the MDF can be plugged and trimmed off when necessary and re-drilled.
With the material, Unless accuracy in being square is paramount, then as long as one edge is against the pins, then it will be fine.
I do have several woodwork machines, so I can cut, plane sand and square where necessary.
One of my original questions was regarding the software accepting the 8 mm size in my set-up details, but the actual hole isn't 8 mm.
Once the pins arrive, I will try them in the four test holes I have prepared to see if any of them fit, and if so, which one fits the best, then run with that for the actual set-up holes that I will machine into the spoil board.
Hopefully, all will work out okay.
Kind regards

[martin54]

If you are using a profile cut cutting inside the line then the error is most likely to be machine calibration, the 4mm bit you are using not being 4mm or tool deflection,

If you are sure the machine is calibrated correctly then measure the cutting bit, you can also try slowing the feedrate down which can help with tool deflection
Just be aware that an 8mm pin will not fit in an 8mm hole (unless you have a hammer)

[wannabecnc]

Hi Martin54,

Thank you for your comments. I will check the diameter of the bit to see if it is, or how much it is out from 4 mm. It certainly makes sense, that if the software thinks the bit is 4 mm it will cut what it thinks is the 8 mm hole, obviously if it's less then the hole will not be as expected.
I feel sure the machine is calibrated correctly.
Yes, I had in my mind that an 8 mm pin won't want to go into an 8 mm hole, ( without a hammer ) it would certainly be snug.
Once I get the pins and have checked the bit diameter, I will reassess and adjust whatever is necessary.

Kind regards

[martin54]

After you calibrated all 3 axis & trammed the spindle did you carry out any test cuts to make sure the machine was cutting accurately?

Once your pins arrive then measure them before doing anything else, these things often have a nominal size so may not be exactly 8mm

[wannabecnc]

Hi Guys,

Just a quick question, I have made a file to cut the holes at the required size, If I need to adjust the size either way, Is there a way in the finished file to adjust the circle diameter without starting again?
Hi Martin54, My Father was in The Black Watch many years ago and was in Korea, Kenya and Aden, so as kids we were like Nomads, from one place to another.

Thank you so kindly

[ohiolyons]

What do you mean start over?

If you are using Pocketing or Profile toolpaths then Allowance Offset.

Drilling toolpath then start over.

[martin54]

You can change the circle size using the set size tool, select all the circles, select scale objects individually, make sure link xy is checked & then enter the new size. After you have done that make sure you recalculate the toolpath. Or you can use the same sized holes & the allowance offset in the toolpath if profile cutting inside the line as has been mentioned
The drilling toolpath doesn't know what size bit is being used & will drill the hole with whatever size bit you put in as far as I know, I don't use the drilling toolpath very much as I generally use a profile cut inside the line for holes.