So I’ finally start cutting my first real project (a custom built poker table with a super-ellipse shape), and I ran into a big problem.
I am cutting some very precisely located holes in two separate sheets of plywood that need to line up perfectly with each other. A great application for a CNC machine.
I started with a set of 1/8" pilot holes, using a 1/8" drill bit in my Sienci Labs 1/8" Makita collet, and it all went perfectly.
Next I enlarged the holes to the desired final size using a 1/4" drill bit in the 1/4" collet that came with my Vevor 0700C router. This is where things went horribly awry…
The 1/4" bit ended up cutting a hole that was 27/64" (just a shade under 7/16").
I double checked the g-code and all looked right, so I started checking and found that instead of rotating axially along the centerline, the bit was actually rotating in a circle around the axis.
As the 1/8" collet doesn’t seem to have the same degree of runout (I checked with a long 1/8" drill bit), I am guessing that the 1/4" collet is crap. I’ve ordered a new Makita collet from Amazon, so we’ll try again when it arrives.
Anyone have any other explanation for this excessive runout?
Do you have a dial indicator or anything like that? That’s the standard way to check for runout. You’d chuck something straight and precise like drill rod and check the drill rod at both the edge of the collet and as far away as possible. You’d be looking for both to show minimal variation as it turns, ideally. It’s also worth checking the inside face of the cone that the collet fits into with the collet removed.
If the cone face varies then there’s a bearing or bent spindle issue. If both the close and far measurement of the rod vary then the collet is machined with the bore off-center. If one is good and one is bad, then the bore is machined out of true or there’s something stuck in it.
If you don’t have a dial indicator then you might be able to take a bit of dowel or something and rubber band it so that it’s sitting against the rod and pivoting close to the rod. That way it’ll amplify any movement and you can see it against a ruler or something.
With my previous spindle it originally looked good because there was very little variation close to the nut. When I added something longer then it was suddenly terrible. I thought it was cheap crappy collets but eventually figured out the entire thing was ground to that it wasn’t running in line with the rotation of the spindle, or the spindle itself was bent. That’ll make things look ok with short tools but with longer tools or drills it’ll get nasty.
That’s a ton of runout in the video, way more than should be reasonable. Have you tried sanity checking that drill in another battery drill or something? It could be that it’s bent at the shank in a way that looks straight if you roll it? Never mind, I see you tried another 1/4" bit… That’s pretty weird. Same manufacturer and same batch, potentially? Seems unlikely compared to the chance of a damaged spindle, guess.
Many thanks @jono for your troubleshooting suggestions
I put it into my drill press, and it is pretty straight and true there (maybe .001-.002" runout at the bottom of the bit)
There is zero variation when measuring against the cone face and rotating the shaft. This is good, as it means that the router shaft is not bent, and I don’t have to replace the router itself.
This isn’t the case, as far as I can tell. There is very slight variation (a few thousandths of an inch) at a point about 8mm below the nut face, and almost 2mm at the bottom of the bit 3 inches lower
As mentioned above, the variation increases greatly the further from the collet. There doesn’t seem to be anything stuck or obstructing the collet or the bit, so it seems that the collet is machined out of true (not parallel to the centerline axis).
It seems likely that the Vevor (Makita clone) collets are not machined very precisely. I’m hoping that the Makita brand collet that I ordered is machined to better tolerances.
Another thing you can do is to mark the collet face and the cone/spindle nose and try it in a few different rotations. If the wobble follows the collet you can be confident it’s the collet. If the wobble stays with the cone/spindle nose then it would be an issue with how the cone is ground.
Edit: You can also ‘index’ the cutting tool to the wobble in some cases, although I can’t think how that’d work for a drill… That’s about the only way I could get my 0-flute 1/8" cutter to cut cleanly on my old questionable spindle.
I was not able to search and see the rest of your build.
If I understand you used your cnc to drill 1/8 holes with a Makita collet, then change to a Venor 1/4" collet. Did you also use the Venor collet nut? What is the router on your cnc? Mixing Collets and Nuts seldom work out. Keep in mind that the router shaft, collet and Nut all must have the same tapers. That much runout indicates you have a mismach of the collet and Nut
The nut and 1/4" collet were both supplied with the purchased router, so I’m pretty sure that they aren’t mismatched, or if they are, they came that way from the factory.
Yes, I used the same nut for both the 1/4" (original) and 1/8" (Sienci Labs) collets.
The 1/8" collet has very little runout, even using the original nut that came with the 1/4" collet. The original 1/4" collet has a ton of runout with the original nut. It doesn’t seem to be an issue with incompatible taper or mismatch between the collet and nut, as far as I can tell. I’m thinking that It seems to be a defective 1/4" collet. I’m getting a new collet next week, so I’ll be able to report back then itf it fixes the problem
Hi, i would say something about the 1/4" collet: try a 1/4 inch enmill and see if the runout still there.
That will give you something to try until delivery
I’m wondering if the shaft of the drill bit is really 1/4, just because the ‘head of the bit it doesn’t mean the shaft has to be - drill bits don’t need to be that precise as a 3 joe chuck is self centering. My makita router came with a 1/4” AND 6mm collet and they might look the same and bits fit but they’re different enough to cause issues.
Yes, the 1/4" end mill also has some noticeable runout (smaller, because it is shorter)
Thanks for the response.
The bit shaft is just a tiny bit smaller (0.2465" 6.26mm) than the end mill (0.2500" 6.35mm). The end mill is a pretty snug fit into the collet, the drill is not quite snug, but certainly isn’t loose, and only requires a very light turn of the nut to tighten it snugly.
0.014" 0.35mm (6.00mm 0.2360" vs 6.35mm 0.2500") would be noticeable for sure. Not sure if 0.0035" 0.09mm is enough to make a difference.
Given that the end mill also has some noticeable runout, I’m still leaning toward bad collet. Once the new collet arrives, hopefully we will know for sure.
Just to follow up and close out this topic, I received a new Makita collet from Amazon.
I found that it still had a bit of runout at the end of the drill bit, but that seemed to depend on how the collet was installed into the holder. Even at its worst, there was a LOT less runout than the best I could get from the original collet. By rotating the collet in the holder, I was able to get it down to the point that I couldn’t notice any runout with my eye.
I drilled a test hole with the 1/4” drill bit installed, and the hole ended up at around 21/64”. While that was a big improvement over the 29/64” with the original collet, it still isn’t precise enough for my application. I think that trying to use a palm router with a fairly flexible and fairly long drill bit is just allowing too much deflection.
So I drilled all of my holes using a short 1/8:” bit to make pilot holes, and then I bought a drill block to help me to with making perpendicular cuts with the larger bits using a handheld drill.
I use a mill smaller then the hole i am going for and pocket the hole size and depth i need. Diamater can be adjusted with setting in the pocket allowance. I have never tryied it to be ultra precise but do a lot of cribbage boards with odd peg requests.
I had a combination of 1/8”, 1/4” 3/8” and 1/2” holes that needed to be cut fully through 3/4” plywood. I found when doing some test cuts in a different piece of plywood, that the 1/8” mill was getting burnt when cutting the 1/8” holes (basically plunging straight through the 3/4” ply).
So I decided to use a drill bit for the 1/8” holes instead of an end mill. For some reason I got it in my mind that I could/should also use drill bits for the other holes as well. In retrospect, I should have used the 1/8” drill bit for the 1/8” holes, and used a 1/8” end mill to cut all of the larger holes with an angled ramp.
Too late now to go that route for this job, but I continue to learn from my mistakes…
Easy to get blinded by science in this case in reverse the length of the drills would cause me problems. I started drilling all my cribbage boards that is tedious and even longer than milling.
the length of the drills would cause me problems. I started drilling all my cribbage boards that is tedious and even longer than milling.