Hello,
I use positioning pins to mill 2 opposites faces, works fine. Now i’m wondering what would be the best approach to mill a 2nd face that is not opposite of the 1st?
I cut some small objects like boats cleats out 80cm longs pieces of oak. If you are lazy like me, you’ll want the router to make those holes and rounded edges on the 2nd face. I try yo make them in batches of about 10.
For that i need a good way to accurately mill (0.1-0.2mm) a 2nd face that is not opposite of the 1st.
The width of the wood goes from 6cm to 12cm, so my idea was to first get those strips of wood to some perfectly known dimensions and use a guide.
I am not very happy with that because i sometime use some hardwood kitchentop that ppl tend to leave in the street around me from time to time. That wood can’t really be cut in long strips, it’ll break at the joints.
Still not quite sure what you’re trying to do, but think it has to do with doing a double-sided carving of a piece that has already been cutout from a previous operation. If so, I would recommend a jig to hold the pieces that need the additional 2-sided carving steps. I would index (set 0,0) off of a known place of the jig and not the individual workpieces.
As far as accuracy/precision, I have no problem asking for and receiving a 0.1mm or 0.2mm resolution from my Onefinity. A second decimal place to the right may be challenging, but when I do things like trying to size a hole for something else to insert, adjusting 100 microns at a time is more than noticeable. The trick is how you set your 0,0 and the amount of shifting of the piece that happens after you flip it. I think there’s always going to be variance after flipping and I do test (air) carvings to make sure everything is lined up before turning on the router.
To make 2 sided parts with a precise thickness I will zero off the top of the material for the first side, then zero off the waste board or the second side which after flipping the part is the same face I zeroed off the for the first side. I also leave material around or at the ends of the part with tabs for this to work, you mentioned locating pins so I imagine you are doing something similar.
@ [WaywardWoodworker] Yes that is more or less what i do when i mill 2 faces that are opposite.
Just to clarify take that item
I have 2 ways to make them :
(1.1) i cut a bunch of them (10-12) in a piece of oak of 80cm long
(1.2) i cut them one by one in oak that i found in the street.
(2) Then i round the edges with the sander and the holes with the drill press.
I’d like to find a way to be accurate enough to have the cnc do the (2) part for me. But as you noticed, the 2 faces that i want to mill are not opposite one of the other. 0.1mm precision is totally fine.
I have made a first jig that i am not happy with.
I was thinking that maybe, if i only use the (1.1) method, i could start by having the OF do the holes and the rounded edges, 90°flip and then cut it keeping tabs somewhere…
I would make a template with recessed rectangles for the foot to go into, and screw down strips of wood to hold them down by the feet so to speak. Then drill the holes and if needed, insert screws into the holes for additional strength before routing the corners out. Easier to picture it in my head than in words
While Corbin machines opposite sides, hopefully you can see how his jig technique on a curved opposite side could be used to do a non-opposite side too How to CNC a Bowl - Two Sided Machining … It is like what @Tuvix72 draws, but in video form.
As an aside, you may wish to make the jig but use it in a drill press. From my optic, the setup time for doing a few with the CNC would outweigh the automation. I am not sure how many I would need to be doing to have the CNC drill holes for me.
For clarity, I’m going to call the concave surface with the counterbored holes the “top”of the part. Then I presume that the “sides” are parallel to one another, and that you currently mill the side profiles first on your CNC. If that’s correct, then some sort of vise that grips a blanked-out part by its sides would seem to be a good workholding solution for the secondary operations (counterbored holes and corner rounding).
To do the secondary operations on a CNC, I’d make a “ganged vise” fixture that can hold a bunch of the blanked-out profiles. I’d use rectangular pockets (with corner relief) to position the “feet” of the workpieces. I’d leave one side of each pocket open, and use a slender wedge there to close the pocket and clamp the workpiece in place with side pressure.
So the fixture I have i mind is basically a linear gang of little wedge-actuated vises, with the wedges being the only moving parts. It should be pretty darn easy to make on a CNC.
That is the point where i confess i made a naive jig to try and see and it was a failure but also made me want to get it to work properly.
To see the machine doing everything is kind of a pleasure to me.
The idea was similar to what has been drawn before, a pocket where the item go in an some pin on the size to hold them.
It failed because
1pine wood was a bad choice and/or too thin
2the wooden bars to hold my item need to be tight but then it s quite a pain to put them…
I like the vise idea and i ll try that.
I also want to try the negative shape like on the bowl video but i fear that s a bit more work
Honestly it s more about building up xp on what can or not be done rather than saving time. Instead of writing that msg i could have drilled 10 of them…
Thanks for the help
Ganging the workpieces like that is exactly what I had in mind.
It just dawned on me that the side pressure from the wedges will try to bow the base of the fixture. So I’d keep it pretty thick. You’ll probably need to tap the wedges with a hammer to knock them loose, so I’m thinking that putting a hammering flat on the skinny ends, and letting them pass all the way through the fixture, is probably the simplest design.
