I have an SO3 with an HDZ. I am trying to make the holes for barrel hinges bigger. They are currently just a little too small. I have been using the offset and choosing the offset and making a pocket tool path. I just want the holes slightly bigger for the barrel hinges to fit in snugly.
My question is what is the inch measurement to get a single step in the X and Y to get these holes slightly bigger. I think I am hitting a rounding error and after about 10 tries the holes are not getting any bigger.
As stated above it is an SO3 with HDZ. I was trying an 0.0008" offset and making a new tool path for the offset and deleting the previous tool path for the pocket. The depth is .432" and that is fine it is the enlargement of the hole that is giving me fits.
Here is a picture of the holes. This will be a ring box using barrel hinges.
Looking back at a few other posts it looks like the default steps/mm for a SO3 is 40. (0.001")
In this case you are concerned with the XY axes.
Did you measure the holes?
What could have happened is, since CC likes to conventional cut, if there was any deflection on the tool on the first cut, it might have made them oversize to begin with. And now that there is no material in the way, your subsequent passes haven’t exceeded the deflection yet and are removing no material.
cut them undersize to begin with, leaving a roughing clearance and making a full-depth finishing pass
if you need a tight fit, measure (or use a go-no go gauge) and adjust the CAM, but take into consideration @Tod1d 's observation on min. move dimension being 1/40th of a mm — that said, the machine will be interpolating/moving on a diagonal for much of this motion, so it’s not like it’s really holding at grid points
One option is to leave the holes undersized and finish w/ a hand-drill or drill press — I did that on the miniature worksurface I made recently.
EDIT: also, if you haven’t calibrated on a belt-drive machine, doing so will ensure holes are round:
When I fit those barrel hinges I just reload the .c2d file, select the holes and increase the radius a couple thousands. Save the adjusted tool path for just the holes and run it
0.0008" is aerospace territory and requires expensive metroligy gear to even measure properly. Good calipers have a margin of error of +/- 0.002".
That said you’re working in wood. It expands and swells that much with a fairly small change of temperature. I worked at Boeing for a decade and the QC rooms there are temperature controlled since a hole in aluminum will vary by 0.0008" going from getting cut in a flood coolant equipped machine to a lab due to temperature. Boring out holes with a +/- 0.0005" tolerance meant I often intentionally slightly overshot the diameter in the machine so that it would measure within tolerance by the time QC got it.
I think Tod had a point with the defection comment. The first cut likely deflected slightly, so with you cutting mostly air in these cuts, it’s not quite hitting the walls and not deflecting. If you require tolerances 0f +/- 0.0008", your going to have to impliment a roughing/finishing strategy to get close. I do that in aluminum in an HDM to get within 0.002" of nominal.
Don’t barrel hinges expand in the hole? I’m sure they have the ability to expand to a much larger degree than a thou.
I cut this project the first time and the holes were slightly too big. So I redesigned and they were just a little too small. So I am trying to sneak up so the barrel hinges get the goldilock effect of just right. Once the barrel hinges are in you tighten a screw and expands the barrel slightly. So the barrel hinge must fit snugly to start with.
@Tod1d Thanks for the measurement. I thought I was likely not moving a whole step so I will try 0.001" and see how that goes with getting the hole slightly larger. The tool path only takes 2 minutes to cut the 4 holes so like @Ed.E I would let that tool path run and then pause and check the hole with a hinge. If it was not lare enough I would stop and go back in CC and edit the file and reload in CM.
There is a fine line between go and no go with these little hinges. Just trying to sneak up on the fit.
Thanks all I will come back when I get the holes just right.
Each hinge is different. So you unscrew the barrel hinge and put it in the hole. The bottom of the barrel hinge is split but not by much. When you tighten the screw it should hold. When you open the box there is a lot is a lot of stress and can pull the barrel hinges out. So you want the barrel hinge to just slip in and then tighten the screw. The ones I have are from Rockler and are 10MM. However a 10MM brad point drill bit makes them just a little too bit big. You can put a drop or two of CA glue but that means you can never remove the hinges. It is not likely to remove them but you never know.
This project is a 2" X 2" X 2" ring box. So the barrel hinges are perfect. I have to round over the back edge of the two halves so the box will open all the way. If I do not round over with a 1/4" bit then the leverage of the top hitting the back can pry the hinges out. So you dont want the two halves to hit each other when the box is open. i have used barrel hinges a few times and the good part is they are hidden when the box is closed. They have a built in stop at about 105-110 degrees. I could have put the holes a little further back but I did not want the material so thin.
One more little thing is the depth of the hole. You do not want the hinges flush with the hole. Just a little bit higher so the box closes in the front completely. For me and these Rockler hinges it is .432". You have to measure the barrel hinge and deduct a few thousands so it is just slightly higher in the back.
So I had to see what these look like and found the ones on Rockler you mentioned (I think). Interestingly enough someone else posted their photo & review and mentioned the same thing about the 10mm Brad Point (or maybe that was you). Anyways, my question is, what is the point of the half screw hole on the side Opposite the side with the full screw)? Is that so you can lock it into the wood?
There is a screw in each half of each hinge. You loosen them and put the barrel hinge in and then tighten the screws. The screws slightly expand the bottom half of each half of the hinges to keep them from pulling out. There is a lot is a lot of stress when you open the box. During final assembly I will put a few drops of medium CA glue to make sure they do not come out. This box I made is quite small but a larger box with more weight could pull them out. So I would only use the barrel hinges on small projects like the ring box.
I got my box finished sanded, a coat of shellac and the hearts painted white. I may put a second coat of paint on it late tonight. I will let it dry until tomorrow and sand off the top, reapply shellac and put about 3 coats of polyurethane on the box halves.
