My Chai/linearmotionbearings2008 Experience

[Mystichrome]

I just wanted to share my experience with dealing with Chai/linearmotionbearings2008 as it may be a cautionary tale for others. I know this is going to be long and because of that few people will read it in it's entirety, which is a shame because anyone considering buying ballscrews from Chai/linearmotionbearings2008 should at least know about the dealing I had. The following is very detailed account of the transaction. I touched briefly on this subject in Hoss's thread but decided to wait until the transaction was 100% complete before posting my story. I was planning to attach a PDF of the email exchanges between me and Chai, but before I do, does anyone see a problem with me doing so? Any problem whatsoever, whether it be risk of my personal information, potential legal issues, or a CNCZone policy i'm not aware of. I will be happy to share this PDF with some of the reputable Zone members in the meantime if they want to see the actual conversations. Eventually I'll either post it or offer it to anyone who want's to see. However this post is nearly word for word our email exchanges.

I contacted chai about having some ballscrews made using Hoss's C7 ballscrew prints and I chose to have Chai/linearmotionbearings2008 cut down the X-axis ballnut according to Hoss's specs. This was something new Chai was offering to do. As far as I know, I was the first person he did this for on CNCZone. He didn't say this, but nobody on the zone posted about having it done before I ordered. I did this with the hope that they would do a better job than I could and I had the lesser hope that they would do something a little more precision than grinding. Cutting down the ballnut was a new offering from Chai, so I attempted to confirm that they would cut the ballnut down before the balls were loaded. I asked him twice and neither time did he even acknowledge the question. That should have served as my warning, but I choose to proceed, thinking that they should know what they're doing and know that needs to be done before the balls are loaded. This is my Mistake#1.

Upon receiving the ballscrews I noticed several issues. First off, all three ballscrews were threaded with the wrong threads. The RM1605 ballscrews should have had M10x1.5 threads and the RM2005 ballscrew should have had M12x1.75 threads. Instead they had M10x1.0 and M12x1.0 respectively. At first, I didn't think this was a huge deal, but quickly found that sourcing M12x1.0 jam nuts in the US is an impossible task. Regular hex nuts - yes, jam nuts - no.

The next issue is related to the x-axis ballnut modification. The X-axis ballnut had been ground down with a grinder just like any of us could do, no precision work there(this isn't itself the problem though). Sadly however, I believe that the grinding was performed after the ballnut was packed and that little care was given to avoid overheating the ballnut. I believe this for 2 reasons. First, unlike the other 2 ballnuts, I can wiggle this ballnut on the screw if I grab it and rock my hand. Secondly, upon disassembly of the ballnut there appeared to be some grit inside the screw and the plastic ball returns looked, for lack of a better description, worn out. The edges were rough, they appeared to have some discoloring, seemed slightly deformed,and had what appeared to be some grinding dust on them. They didn't seem crisp and clean like the ball returns in the other ballnuts. You can see some of what I'm talking about in the pictures below. Even the wipers looked worse for wear.

The third issue was that all three ballnuts appeared to be short a ball or two. My reading has lead me to the understanding that the correct amount of balls in these ballnut should be evenly divisible by three because there are three circuits. One RM1605 ballnut had 49 balls and the other had 50 balls. My understanding was that the RM1605 balls should have 51 balls (based on another member's post). Early on, I thought that being short on balls was the problem with my x ballnut having some play. My RM2005 had 59 balls, I assume it should have 60, however Chai did not confirm this.

After all the inspecting and finding these issues, I contacted Chai about it. I explained all the threads were wrong and that the ballnuts were missing balls. At this time, I believed that was the cause of the problems with my X-ballnut having play so I didn't mention that. I did however mention the ball returns being messed up.

He repsonds that they made the threads M10x1.0 and M12x1.0 and that he'll send me some balls for the ballnuts and some new ball returns. He also mentions that that locknuts for the threads he put on the ballscrews were included in my original shipment. This is true, he included some weird, square nuts that had set screws. He listed these in his original quote to me apparently, though I had no idea what they were for. I didn't ask for them, but they were in his quote. I assumed that since I didn't ask for them, they were somehow needed because he included them. Maybe I missed seeing them in other people's threads I thought. I wasn't sure, but they were relatively inexpensive, so I just rolled with it when I purchased everything. Mistake #2 for me, never pay for things when you don't know what they are. Always ask, regardless of how cheap. Remember this for later, it comes up again. He also states that the grinding of the x ballnut was done before assembly.

I respond by questioning why the threads were changed. I state that it's a problem for me since I already purchased hardware with the threads I requested and I had already threaded parts for those threads (I confused myself somewhere and thought the z-axis oldham needed to be threaded for the z-axis ballscrew like it does in Hoss's phase 1 direct drive plans, realized my mistake later). I explain that I'm not trying to be difficult, but i'm upset that what I ordered is not what I recieved. I also explain that finding M12x1.0 jam nuts in the states is basically impossible. At least without having to by $50 worth. I explain that I think that the RM2005 ballscrew should be remade with the correct threads and that I should receive a discount for the RM1605 ballscrews since they were not made to the specification I provided. Admittedly, I should have approached this differently as I stated I thought I should receive a large discount. I only phrased it that way because I knew if I just said a discount, he would offer me a few measly dollars. I wasn't looking for $100 or anything, but I think around $30 would have been reasonable considering they were made with the wrong threads and I had purchased about $15 worth of hardware from Mcmaster for the threads I requested that was now useless. Not to mention that I would have to buy new hardware for the RM1605 screws (another $15 or so, because you have to buy in specific quantities and I was using stainless). I should have specified a dollar amount for the discount. I explain that I think a discount is fair since I did not get what I paid for.

He responds by Asking me what I want. He states that he changed the thread but matching locknuts were included. He says he made this thread for all his customers with no problem. He asks "Do you also want M10*1 and M12*1 locknuts(thin ones?)".

I respond that I just want what I paid for. I tell him that I requested the threads that I did, because that's what I needed, that's what I was setup for. I now have useless hardware that I purchased. I state that if he can provide actual Jam nuts in the correct thread we can work this out. However, I still feel a discount is in order. Again I phrased this differently than I should have. Again, because I figured he'd offer me a whopping couple bucks. I reiterate that I requested specific threads for a reason. I state that the threads that I requested are what I paid for. I then state a response to his, what do I want question. I state that I want (8) M10X1.0 and (4) M12x1.0 jam nuts. Why 8 and 4? Because it would be nice to have a couple spares for the the future, particularly the M12x1.0 because those are impossible to find in the United States. They should be actual Jam nuts, 6mm thick or less and stainless or zinc coated. If he cannot provide that, the RM2005 ballscrew should be remade and I should get a discount on the RM1605 ballscrews.

He repsonds that shipping the ballscrews back would be expensive (clearly expecting me to pay return shipping). He says he will make the jam nuts out of stainless for me. He admits they should have machined them to the specs I provided.

I respond that I should still receive a discount on the RM1605 ballscrews since they're wrong and I purchased hardware already. I reiterate that I think this is fair.

He then responds "how is this fair to me?" He then says that if I had purchased hardware already, why did I accept the locknuts in his quote? He then tells me to resort to paypal customer support to resolve this problem. He did say "God bless you" at the end. That was nice. That almost makes everything ok. [/end sarcasm]

I then respond by asking him how any of this is fair to me? I tell him I PAID for the ballscrews to be machined to the specs that I PROVIDED. He did not machine them to MY specifications. How is that fair to me I ask? I tell him that I accepted the nuts in his quote for the reasons I stated earlier in this post. Since this is his job, I assumed he knew something I didn't, that these nuts were somehow needed. I never asked for them, they were just included in my quote, I assumed for a reason. Maybe they were part of the ballnut, I didn't know (again, I should have asked, but they weren't expensive.) Had I realized they were just nuts for the ends, I would have told him I didn't need them. *Too anyone else ordering from him, you DON'T need the locknuts in his quote unless you want to use them. If you already have the correct threaded jam nuts, his locknuts are unnecessary.* I tried using examples to explain to him that I did not get what I paid for. Is it unfair for me to expect him to fix that? I ask him what he thinks is fair, but to put himself in my shoes. If he didn't get what he paid for, what would be the fair solution? I explain that nobody likes paying for mistakes, but how is it fair for the customer to suffer for your mistake.

He responds that he has done everything to meet my requests but that I'll still ask for a refund(FYI, I don't know if he means a complete refund or not, but I never asked for a complete refund. Just don't want anyone to be confused). He offers to make the jam nuts out of copper(yeah, completely the same as the stainless or zinc coated I asked for earlier) and refund me $18 for the ballscrew machining. He states he's taking a loss to do this.

At this point he's already told me to deal with paypal once, so I'm kind of stuck. I don't want to end up with parts that I cannot use. I contacted paypal out of curiousisty (I didn't file anything, just got some info on procedure) and I would have to pay the return shipping to return the ballscrews in order to get a refund. Paypal's policy apparently. I've shipped internationally before, that would be at the absolute cheapest $40. I'd end up $40 in the hole and have nothing to show for it. Not to mention the money I already spent on jam nuts for the threads I asked for. That's unacceptable to me. I hate deviating from my principles, but I just can't throw away $40. I wanted so badly to send them back just so he'd be stuck with these custom things he couldn't get rid of, but I realized he would just screw somebody else with them. It's at this time that I also realize that the X ballnut is warped or something. I borrowed the missing balls for the X nut from the Y nut. Even with the correct amount of balls, the play is still there. I can only assume the ballnut warped from the heat of grinding. His $18 refund offer would actually have satisfied me at this point, but the problem is I also needed another ballnut now, to replace the ground one. Given how little he's been willing to accomodate, I know he's not gonna give me the $18, make the jam nuts, and a give me a new ballnut. Honestly, I don't hold him totally responsible for the ballnut anyway, I requested he modify it, that's something they hadn't done in the past, there was bound to be risk. I'm not unreasonable, I accept that. Moral of that part of the story is that I should have modified the ballnut myself.

At this point I still feel like I'm getting the short end of the stick in this whole transaction since I'm not the party that made the mistake. But, I email him back and agree to the $18 refund, jam nuts, and some ballnut balls(to make up for the missing ones) with the condition of us splitting the price of another ballnut. Again, I didn't want to end up with pile of useless parts, so that is why I agreed. He wasn't going to budge any more. If I pushed, he would have told me to go to paypal again.

He agrees to my condidtion, stating the price of a ballnut is $24, so half is $12. So in the end after all this, I basically got a $6 refund for having all of my ballscrews made with incorrect threads and I'm out about $15 in hardware I already purchased. $15 in hardware - $6 refund = $9 in the hole. So I essentially paid $9 extra to have my ballscrews made incorrectly. Not a bad deal. I'm sure most people are willing to pay an extra $9$ to have something made the wrong way as opposed to the right way. So that's a new option for anyone considering getting ballscrews soon. For less than $10 extra, Chai will make your ballscrews to the specifications he chooses. [/end sarcasm]

Ok, yes I'm still angry over all this. In the end, did I end up with parts that I'll be able to use? Yes (I think, still have to install). Did I get them much cheaper than the next cheapest source? Yes. So why am I still upset? The parts aren't to the specifications that I paid for. Furthermore, only bandaid offering's were made to compensate for this. It's like ordering a Mustang(car) but when the car comes in it's a Focus. To compensate you, they wave the title fee. Sure it still gets you from point A to Point B, but it's not what you paid for. I don't think it was unreasonable to ask that I either get my parts the way I requested them or to be compensated for them being incorrect. I'm sure there will be people that think I'm being unreasonable. I'm sure there will be people that think I doctored the email text (If I do post it). One email in particular where the text color is different in the separate paragraphs I'm sure will be cause for suspicion. I think it was because I copied part of my message from an email draft I had started earlier, but hadn't sent. If there was a way for me to show the emails where it were impossible for me to have doctored them, I would do it as I really want people to see how this deal really went down.


Final Judgement
Believe it or not, I'm not trying to talk anyone out of using Chai/linearmotionbearings2008. They're the cheapest game in town by a large margin which is ultimately why I used them. Sure, my spiteful side would feel great if he lost business based on these actions, but ultimately him losing business would do nothing to improve my situation. I will still have incorrectly made parts that I essentially paid extra for. Enjoyment from Spite is short lived. All I really hope to accomplish is to make people aware that if there is a more serious complication than something like your ballnuts being short on balls in your transaction, good luck getting any satisfactory resolution from Chai. I advise people to refrain from having Chai cut down your ballnuts. Over time they could get better at it, but do you want to risk being part of their practice? Also, if you're for sure going to order from him, I'd recommend doing so in the very near future since my transaction will be fresh in his mind and he will likely be more mindful about making sure things go smooth. A few months from now, all bets will be off again. My other piece of advice is that when you email your specs to Chai, be very specific that you need your parts made exactly to your specifications. Obviously you shouldn't have to do that, but the more black and white things are, the less he has to hide behind. Though I suspect it won't change much. He seems unwilling to let his mistakes cost him financially. I don't know about the rest of you, but in the Jobs I've had over the years, I was always expected to fix my mistakes. At least once that meant money out of my pocket. I guess it's different in other parts of the world though.

I've attached some images and I may attach a PDF of my email exchanges with Chai. The first and second Pictures you see are of the inside of the X-axis ballnut (the one they grinded) before I removed the ball returns. The Third Picture is one of the X-axis ball returns removed from the ballnut. Note how worn and ragged it looks. The fouth picture is of the inside of the y-axis ballnut before I removed a ball return. The 5th and last picture is of the y-axis ball return I removed from the ballnut. Notice how much cleaner and crisper it appears.

I do realize how lengthy this post has been, but I wanted to be as thorough as possible. I just want people to see how unreceptive Chai is to correcting larger issues. I want people to understand that this is a possible risk before they commit. Also with this information they can better set the terms of their transaction before money changes hands. I just want people to be able to make an informed decision. I feel it's a real shame things went the way they did, he offers a good product at an incredible price, it's a shame that you're playing russian roulette when you place an order. That's my point of view now anyway.

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[DRock]

I just want to state that I ordered right after you and brought both issues, missing balls and machining, to his attention and he assured me that they now check to make sure all the balls are there. Also, my nut looks like it was milled down on both sides and it has no appreciable backlash when moving by hand. I cannot comment on the change of threads because I got the bdtools mounts and they just specified a "12mm dia thread" at that location. I will update this post with some pictures of my machined x-axis ballnut.

That is unfortunate you had such a bad experience with him though.

[Fastest1]

Mystic, I am sorry to hear of your misfortune. I have now ordered 2 sets of (3) screws from Chai. The first set did have a few issues with 1 screw being miscut. Upon our review of my drawings (actually Billy's from BDtools drawings) he admitted their mistake and rectified the problem very quickly (he made a new screw). Unfortunately all the original screws were destroyed by swimming pool chemical storage issues (not Chai's fault LOL). I ordered another set with a little different dimensions. This time I requested the flange be ground as you requested. I also asked for 2 flats to be ground on the end of all screws (for set screws on the couplers). I also asked for jamb nuts instead of those square nuts with the microscopic allen wrench set screws. He made everything exactly as requested except the jamb nuts. I ended up using regular nuts and they all fit fine. I do not know if he ground the flange on the screw or not. Upon initial installation I am measuring about .008 in backlash. I cant feel it with my hands or see it but I can measure it. Also my understanding on the number of balls in the circuit is more about load carrying than to deal with backlash. The diameter of the ball within the track determines the amount of backlash, the quantity will determine how much force could be applied. I will break in the machine a bit before I really worry about the backlash myself. I do think there is a language barrier and wonder if Chai doesnt use a Google interpreter or similar. Anyway sorry to hear of your misfortune and dealings.

[Mystichrome]

I just want to state that I ordered right after you and brought both issues, missing balls and machining, to his attention and he assured me that they now check to make sure all the balls are there. Also, my nut looks like it was milled down on both sides and it has no appreciable backlash when moving by hand. I cannot comment on the change of threads because I got the bdtools mounts and they just specified a "12mm dia thread" at that location. I will update this post with some pictures of my machined x-axis ballnut.

That is unfortunate you had such a bad experience with him though.

I'm glad yours turned out ok Drock. I remember you mentioning you had just ordered when I commented on things in Hoss's thread. I was actually wondering about how yours turned out as I was writing my post. Yours definitely looks milled down. Mine was definitely ground. I'll try to remember to take a picture of the grinding job tomorrow. This is the gift that just keeps on giving for me. My replacement ballnut and the jam nuts showed up today, I was waiting to receive them before I made a post about all this. However, I just got home to had a chance to check them. Here's a shocker, the jam nuts don't fit correctly. They screw on about 5 threads and stop. I don't know if they're threaded incorrectly or just weren't opened up enough. Well, I should say the M10x1.0 nuts don't fit, I can't check the Z-axis right now as I have it mocked up on the machine to check fit and make sure I have my mount made correctly. This has just been such an awesome experience.

Mystic, I am sorry to hear of your misfortune. I have now ordered 2 sets of (3) screws from Chai. The first set did have a few issues with 1 screw being miscut. Upon our review of my drawings (actually Billy's from BDtools drawings) he admitted their mistake and rectified the problem very quickly (he made a new screw). Unfortunately all the original screws were destroyed by swimming pool chemical storage issues (not Chai's fault LOL). I ordered another set with a little different dimensions. This time I requested the flange be ground as you requested. I also asked for 2 flats to be ground on the end of all screws (for set screws on the couplers). I also asked for jamb nuts instead of those square nuts with the microscopic allen wrench set screws. He made everything exactly as requested except the jamb nuts. I ended up using regular nuts and they all fit fine. I do not know if he ground the flange on the screw or not. Upon initial installation I am measuring about .008 in backlash. I cant feel it with my hands or see it but I can measure it. Also my understanding on the number of balls in the circuit is more about load carrying than to deal with backlash. The diameter of the ball within the track determines the amount of backlash, the quantity will determine how much force could be applied. I will break in the machine a bit before I really worry about the backlash myself. I do think there is a language barrier and wonder if Chai doesnt use a Google interpreter or similar. Anyway sorry to hear of your misfortune and dealings.

This is what I don't get. He's obviously worked out people's issues in the past, why is it suddenly an issue with me? I shouldn't be surprised I guess, this is the story of my life. If there's one bad one in the bunch, I'll get it. I just don't get why he has been so unwilling to work with me on this. Am I really being unreasonable here?

[DRock]

Yeah I wonder why the sudden switch to milling instead of grinding, I ordered very soon after you did I believe. I have heard of issues with getting the jam nuts to work correctly, mine shipped with the rectangle ones but I am not sure where they actually go on the mill so I am not sure if it is going to be an issue or not.

I commend you for having such a level head through all of this though...I cannot say I would have kept my cool as well as you did. It just sucks to communicate with people sometimes and it can be very very frustrating when you are trying to solve issues.

[doorknob]

Unfortunately all the original screws were destroyed by swimming pool chemical storage issues (not Chai's fault LOL).

Sorry if this is OT, but could you elaborate on this (or point to a thread where you may have explained in more detail)?

[SCzEngrgGroup]

Sorry if this is OT, but could you elaborate on this (or point to a thread where you may have explained in more detail)?

He learned, the hard way, what happens when you store your tools and equipment in a space that is accidentally exposed to Muriatic acid fumes....

Regards,
Ray L.

[Fastest1]

Exactly as Ray said. If you have a pool, store any and all chemicals outside of the building where any tools are kept. Regardless if the pool chemicals have been opened. They were even lightly oiled when placed in the closet. Took less than 2 months to rust everything (ballscrews only).