Upgrade to spindle or not?

I currently have a Pro XXL with the Carbide router. Lately I have been running into limitations with the feed rate I can run a 1/4 endmill without running into the bit slipping down and messing up the depth.
I realize I need to dial back on my feed rate (and have done so).

The question is, if I upgrade to a spindle set up (either the Carbide 3D one or the one offered by PwnCNC) will I be able to increase my feed rate while using a 1/4 shank or will I need something that can handle a larger shank size?

I know there is a lot that goes into feeds and speeds, but I am specifically looking for information on the capabilities of the collets gripping / retention strength between platforms and shank sizes.

Thank you for your time.


First, your bit should not be slipping no matter how hard you push the machine. In my opinion you should be stalling steppers or the router before that happens. Every time you switch out a tool, be sure to clean out all the chips and dust in the router and collet. Make sure you fully tighten the collet nut using 2 wrenches. Not so tight that you can’t get the nut off again but pretty tight. If you still have slipping problems, replace the collet. Carbide 3D makes some nice ones. Elair Corp is another good source.

Second, a spindle is a nice upgrade but not necessary. I think you are unlikely to see a major performance difference between the router and a spindle when using a 1/4 tool in wood. The spindle gets you better bearings which can improve surface finish, less noise (if it is a water cooled version, not sure about the air cooled) and automatic speed control.


ER-11 collets are a nicety, but they shouldn’t be necessary to get the tool securely in place to cut. The big reason to get them is if one is using metric tooling, or tooling in a variety of diameters.

This was rather thoroughly explored in the thread:

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Thank you for your thorough reply. I’m going to try to make sure I answer all your points. I’m not trying to be short or disagreeable, but I suck at typed communication without coming off as jerk :slight_smile:

  1. I agree completely that a bit shouldn’t be slipping based on feed rates. I can visualize getting chatter, scorch marks, excessive wear or worst case a bent / broken bit. However, I have trolled the forum for old posts and I have found mention of it being an issue. I’m not an expert and have to take it into account as a possibility.
  2. I’ve made sure all the dust and chips are clear before any tool swap.
  3. The collet is tight… probably too tight by how hard it was to remove.
  4. That’s pretty much what I was thinking concerning the spindle. It has been on my long term upgrade list. I just wasn’t sure if moving it up would actually help me with this problem.

It’s looking like I will be getting some new collets at the very least.

I cannot advise on spindle, however I have had the same issue and found that after putting calipers on my collet that it in fact I did wollow out the inside. I specifically remember stalling out the router and losing steps to the point the wood was smoking, then having the slippage consistently after that happened. I replaced the collets which I ordered from Carbide and havent had the issue since.

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I’ll mention that checking both your collet inside dimension and the exact bit diameter makes a huge difference.

Most of the bits tend to slip in my experience. I have had C3D send me replacement collets with no help.

So at the end of the day, what to do? I tighten most all bits where I almost cannot remove them.
This shouldn’t be the case, just because all the collets I have are oversize and the bit will fall out. Some even tightening then are not really being held tight.

I have R8 collets on my bridgeport mills that just do their job and tighten down on the end mill.

It becomes a pick and choose for pairing collet with end mill diameter. So if you only have 1 of each your stuck.

I am thinking it’s the nature of the beast and we are using something that was never really meant to be used in a cnc?

Your not alone. Maybe there is a solution (make collets that are the right inside diameter)

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I’m not sure what to say other than I ran the Carbide 3D router for a couple years doing nothing but pushing hard in aluminum and never had a tool slip. I used both the precision collets from Carbide 3D and some metric ones from Elair. My employees also use these kinds of routers in hand form all the time and we have no issue with tool slip. The loads that a Shapeoko can put on the router can be quite a bit less than what you can do with a profile router bit by hand. I have seen someone stall a makita router like this using a profile bit with a 1/4" shank by hand.

There is definitely something wrong. I don’t know your experience and knowledge level so don’t take this wrong if you have already checked this stuff. There are people ranging from never seen a CNC before a Shapeoko to aerospace/medical machinist as a day job on this forum.

  • Is your collet nut in good shape?
  • Is the router taper in good shape?
  • Grasping at straws here. Are you using a 6mm end mill in a 1/4" collet?

No offense taken. I have a technical background (power plant operations) and a eye for tracking trends (audit and surveillance background). However, I have never got into the numbers heavy machine use or crafting. I’m just trying to figure out the problem and move forward.

  1. I haven’t measured yet (will be doing that tomorrow), but no obvious signs of deformation
  2. By “taper” are you referring to the inner bore where the collet seats?
  3. This specific endmill is a 1/4 Compound bit from IDC Woodcraft. I assumed it was a nominal/correct 1/4" shank but I will double check this as well. I haven’t had issues with other bits from IDC in the past.

I plan on measuring my collet and the 1/4 bit in question. I will do a test cut with one of the standard Carbide 1/4" bits that came with the machine as a comparison.

I do have some new collects on order now, should be here by end of next week.

The bit pulling down into the material is usually not an under-powered router issue. The SO4Pro can stall a router, and usually it doesn’t plunge when that happens. Make sure the bit and collet are clean and use a set of calipers to verify the shank isn’t undersize. If you purchased inexpensive endmills, they sinfulness advertize metric as imperial and the result is a shank that might be too small.

That said the C3D VFD Spindle is about perfectly matched to the motion system of the SO4Pro. I think it has a slight bit more power than the motion system… but if so… barely. The weight is not much more than a router (compared to a water cooled 80mm). We have one on our SO4Pro at work and it is so nice to run. I also have one on my SO5 Pro and it works great there too. The ER-11 cooler system does grip better and is an industrial standard.


The router taper and collet quality are definitely worth checking.

On my 2.2kW spindle (random Chinese not Carbide) I found a huge improvement in holding capability at reduced tightening torques by using slightly less crappy ER20 collets than it came with and also polishing up the inside of the taper with some fine scotchbrite to reduce friction as the collet is pushed into the taper. Do not lubricate these, they should be dry but they should also be smooth.


what feeds,speeds,depth of cut? material? I just upgraded my pro to a carbide vfd…very pleased

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Material: 3/4" Finished Europly (higher ply count)
Pass Depth: 0.25"
Speed: 21000 (#4 on router speed control)
Feed: 60 in/min

The actual cuts themselves seem fantastic. Clean edges, no burrs or fuzzies. I don’t hear any indications of strain from the machine. Full disclosure, I just recently bumped it up to this feed / speed combo. It was cutting like I envisioned it would when I made the decision to purchase the machine.

The cuts themselves were basic profile cuts to release the pieces being cut out for later assembly. Mostly straight line with transition to next straight line.
Plunges were ramped in over 2".
Finishing pass and tabs were specified, but I did not allow the cut to progress that far as the bit was running out from the collet.

edit: spelling

I’ve ran harder than that in baltic birch on an SO4 Pro with the C3D Compact Router. So I suspect an issue with the collet itself (they are considered a wear item), dirt/debris/oil on/in the collet, shank diameter, or a dull endmill.

As a torture test I’ve cut cabinet shop baltic birch at 75 IPM plunge (with ramp), 150 IPM feed, 6 on the router dial (had to as it was in the edge of stalling the router), and 0.375" depth of cut. That was with a 1/4" compression endmill. The endmill didn’t move in the collet at all.


I have been cutting 3/4 baltic birch (slotting with PRO XXL) with a 3/16 e.m. roughly the same feeds and speeds. Been using my new carbide vfd. Runs much much smoother and no chatter. I should have purchased a vfd spindle long time ago.


You mention this slipping happening with a particular bit from Woodcraft. Does it happen on other bits? What about the #201 1/4" endmill that shipped with it?

Since you’re on the Carbide router, open a ticket with support to see if they can send you a new collet as a starting point and potentially a new router (could be a defect in the cone in the shank). As other’s have mentioned, a spindle and/or ER-11 collets for your Carbide router are great (I love my spindle from Amazon), but you have a collet, router shank, or bit problem that is solvable.


Hi Matt.
I upgraded to the 1.5KW Huanyang water-cooled spindle and love it. I went through three C3D routers before finally taking the plunge. Trust me, you will not regret this upgrade.


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