Had my Longmill 1 year. Basically never made anything with it. Feeds and Speeds and Machine troubles

Hey everyone.

I’ve had my Longmill 30 for a year and suffice to say I am less than impressed with how this year has been.

When I got my Longmill I was excited to start learning how to use it and cutting. I assumed I would break some endmills here and there but I’ve broken more than I’ve expected and I don’t think I am really know what is wrong with what I am doing. I compare my machine to how other people run their routers, or how I’d even run my own hand router and nothing seems to work! The only things I have been able to make have been with me 1" surfacing bit using it with adaptive clearing to make a tool for work which was just a circle with a ring on top, and an Ohio flag with 2mm grooves for a friend. Cutting out the contour was a pain and had to be done in 2mm passes as well at 40 IPM.

So the start of my problems: I put everything together and the Y axis had grinding noises and would stop up on its rapids. After adjusting the backlash nuts and ending up replacing the whole bolt that came with it because it caused clearance issues with the Y travel at the end I solved the problem. It was because the backlash nut was to tight to the gantry - not the lead screw.

Afterwards countless hours ensued trying to level the gantries out. The V Wheel with eccentric nut system seems all nice, but even on a level surface that mine was mounted to the eccentric nuts just don’t allow enough travel to have everything evenly clamped. I’ve gotten it the best it can be, but it’s just not a good system in my opinion. Furthermore the V Wheels on the XZ axis carriage is a massive rigidity problem, as when cutting forces are applied it equals leverage to the whole XZ axis. The V-Wheels are not a rigid way to mount the Z axis at all, and I notice mine easily flexes just by pushing on it with one finger without even having a spindle mounted - worse when the spindle is mounted. 0/10 if anything in this system needs to be put on linear rails it’s the XZ axis. I’ve tried tightening the wheels, it only adjusts for so much before it will cause too much force to move the axis at all.

The Z Axis motor is underpowered for any spindle that is not the Makita router, and the mounting bracket is just bad. Only 2 points of contact to mount on a thin bracket. It flexes by sneezing on it. I had to modify my Z plate to fit a thicker spindle mount with 4 bolt holes in both X and Z directions because my spindle would just flex.

Squaring the spindle is an absolute nightmare. Spent forever trying to get mine square enough to use to surface anything. You can pretty much forget about it when it comes to the spindle bracket that comes with the machine. You can shim for adjustments needing made in the Y axis but when it comes to the X axis you’re just out of luck unless you enlarge the mounting holes. This would be a system that would benefit so much from an eccentric nut, or a set screw that would raise / lower the bracket on one side. The only way to do it now is to adjust the V wheels on the axis rails which changes the clamping force and leveling of everything else and it’s just a miserable experience. I fixed with the modification to mount the other spindle bracket and oversized the holes slightly to allow for alignment.

Some of my problems come from having a heavier spindle on it - but the core of the problem comes from the lack of rigidity in the XZ axis.

Moving on to now. I have it working well enough despite the Z axis not being able to make accurate movements. I’ve spent dozens of hours trying to just get good chips with a the 1/8" 2 flute endmills I have.

I just can’t get them to work.

Using the recommended settings from the wiki snapped my end mills and started fires.

I’ve tried running it at so many RPM ranges and feed rates that I can’t even remember. None of them work “well” unless I am taking basically a depth of cut that doesn’t mean anything. Any time I try and do a depth of cut that is larger than 2mm it will just either burn or break the endmill, flex the axis, etc.

No matter what RPM there is and feed rate.

I’ve tried mainly working with pine and I cannot get this to work for anything.

Pictures of the spindle bracket modification with the spindle:

Sweet, you started a fire! I haven’t done that yet.
Take a breath
Looks like we need to break this down to the steps you pointed out.
I just put the Longmill together per instructions and didn’t worry too much about Machinist accuracy right away. Someone else will have to chime in on those issues. I do use the Makita router. It is very light…
I would put the 1/8" bit away and start with a 1/4" bit on some cheap 2x4 material. You can surface with a 1/4" bit also. I use number 4 (not sure what that is on a spindle) on the Makita for speed and 120 IPM for feed with a 1/4" bit with at least a .0625" (usually 0.125") cut depth. Practice with the 1/4" bit a couple of times with surfacing an see how it works.


You have taken a machine that the company has done pain stacking engineering on with 1000’s of hours of beta testing on top of that. Then added a spindle to it that is much heavier than the router it is designed for plus a heavier attachment point. That alone is possibly exceeding the constraints of the machine. It would put excess wear on the V wheels plus bind them up as the machine moves back in forth in all directions. That isn’t the machines fault.

I had my machine set up new and didn’t once tram it only squared the machine during set up with the process of making sure it was square with the plywood and the gantry to the side rails. The machine ran perfect. I suspect you over loaded it. Plain and Simple. Now I don’t know the specs on your spindle so I can’t say for sure. What you said in your post that what it sounds like to me.


@thunderingdragon - Please don’t be too quick to jump on @GregsReinventions. Greg is correct in his statement. Granted there is not much info on Sienci’s web site but they do state that they are not recommended due to their weight. This information is stated in the Resources pages under “Router/Spindles”. As for the 80mm spindle mount it is for one of the Bosch routers that is recommended, not specifically for a spindle. They do not state anywhere that you can not use one but it is definitely not recommended. That means to me that you do so at your own risk. I, like others, would love to use a spindle but due to the info about the weight I won’t be pursuing that with the original LongMill.


Thank you Sir. I was a Beta Tester and I know what these machines can do and take the gantry can twist with too much weight on them. They are not meant to take a spindle that are much heavier than a few ounces more than a trim router. I was there in the shop during some of the design and trouble shooting . 1000’s of these things are in the market place and very few if any have encountered problems as severe as this. I don’t believe my statement was harsh or even mean just truthful and factual. If thats not what you want to hear that isn’t my fault. If you have broke your machine because of this then I do not represent Sienci Labs or anyone there but I seriously doubt will cover it in any kind warranty. Sorry


I know it has been a while but I took a break from the router entirely for a while.

Removing the spindle and putting an indicator to the gantry, I can flex it 0.005" in either direction twisting the X axis with a few fingers and even with the V wheels tightened completely the Y axis tilt under any kind of load is greater than .005" in either direction. The machine is just flimsy due to the nature of its construction on V Wheels.

When sticking a regular trim router on and simulating a cutting force with just a finger I can twist the gantry upwards of .010".

I’m not very happy with this after so much time and I think I may end up putting it up for sale second hand and find a different option at this point. I didn’t know much about CNC routers back when I purchased this and it seemed like a wonderful option due to being the only lead screw driven one in its price range, so at least I’ve learned a lot.

@Blunderpunk I assume that you have contacted Sienci tech support with your issues. Did they help at all?

One thing that you may not have already checked is the dimensions of your V wheels. There was a Sienci blog post some time ago about a batch of wheels that they received that were not in spec. They were too small. Some of these got out to customers before Sienci found it out. With these wheels, it was impossible to get the adjustment right. This may be old news to you, and it’s more than likely that, when you contacted Sienci tech support, they asked you to measure your wheels, but I thought that I would throw it out there anyway.

I’ve not checked that, but at this point I’ve already committed to converting it to linear rails and am just reusing the electrical components and Z axis and moving to steel square tubes that will bolt directly to the table.

All in all I am debating reselling the whole unit and just completely building my own because I find the V wheels to be an incredibly impractical system.

@Blunderpunk You’ve certainly had more than your share of problems with the Mill. I’ll be interested to see your linear guide setup. I’ve looked at the guides, but I am not competent to re-design the Mill to use them. Good luck.

Depending on how things go I may be completely on my own designing a new CNC router entirely.

The lead screws are aligned with the center of the angle iron so I cannot just weld a plate to cover it for a flat surface for linear rails.

I may have to replace them with steel square tubes to have a surface the linear rails can mount to, and then there’s the issue of the anti-backlash nut being difficult to reach and adjust. The anti-backlash nut can have a spacer made when attaching it to align it properly, but adjusting it would prove to be difficult.

Alternatively I could just upgade to ball screws as well, but I am getting to the point where I am so far away from what the Longmill is it’s basically its own thing, so I am debating the best method of doing this still.

So the tricky part is finding linear rails that are small enough in width to fit 2 per each side where there is enough room to allow the anti-backlash nut to be attached - or the ball screw nut. Whatever I decide on going with.

I’m still baffled by anyone’s success with this. The machine is impossible square the spindle from the factory. You can adjust hose eccentric nuts all you want but that messes with the clamping force available. It is a constant battle between clamping down and being aligned, and if its too tight the carriage just stalls the motors.

@Blunderpunk FWIW, if I were looking to make the kind of changes that you are, I would either start from scratch or find a CNC that already has the features that I want. I’ve done a lot of “thing” modifying over the years, and while some have turned out OK, most have been a lesson in futility, costing more in time and money than the results warranted. That said, I can only base my decisions on my resources. Yours are clearly much different.

In terms of “bafflement”, I guess that I am more baffled by your lack of success than by the success of thousands of others. I mean no offence, but let’s face it, you are somewhat the odd man out here. The Long Mill and many other hobbyist machines use components like adjustable delrin wheels and they seem to work well for many, many users over years of operation. I don’t particularly like them, either, but my research before buying the LM showed them in use by many makers and they did not seem to provoke screaming reactions. My experience has been the norm. I find them finicky, but I am able to do quite intricate projects with my LM. My issues have never been the lack of precision brought about by the wheels.

I have no idea of your background. I came into this with a fair background in woodworking, and a peripheral knowledge of commercial woodworking CNC use. My expectations of the LM were based on that. Some here seem to be criticizing the LM based on a machinist’s eye for precision that is simply not possible on a CNC machine of this calibre. Nor are those expectations reasonable when working in wood - a material that moves more during a long carve than any lack of precision in the Mill will cause. I have some experience with a $150,000 woodworking CNC and it is not capable of achieving the one ten thousandth of a inch precision that some owners here seem to expect of the Mill. With respect, I believe your expectations are out of line with what these type of machines can deliver. That is not the “fault” of the machine nor of you. It is, in my view, simply the reality of the situation.

I sincerely wish you luck in your pursuit of a CNC router that you can enjoy using. If this is a hobby for you, it should, after all is said and done, be fun. If it is to be a business, it needs to be a machine from which you can earn a profit. While those two criteria are not mutually exclusive, they are somewhat contrary to one another. So, choosing or building your next machine needs, first and foremost I believe, to be influenced by what you are going use it for.

Here endeth the epistle. :grinning: