Machine shop screwed up - who fixes?

[carlnpa]

I took a Nook precision ballscrew to the local machine shop to have ends machined for K2 machine. I provided the new ballscrew and asked them to duplicate the old ballscrew. Picked it up today and the ballscrew is slightly bent, the ends where the bearings mount are 0.010 eccentric on both ends , (it turns like a crankshaft) and 0.006 oversize, it was cut long (fixed by cutting a spacer washer).
I can't use the ballscrew as it is, should the shop replace the ballscrew? Or is this my problem for providing the ballscrew?
Any advice appreciated.

[HuFlungDung]

Man, that is sad. Obviously they do not have the skills to do the job, and they should know that they do not have the necessary skills and should have passed on the job. They should replace the ballscrew for you, or fix it in a satisfactory manner. I am imagining that you would want to take it elsewhere, even to fix it up, and have them agree to pay the damages.

[Ken_Shea]

The fact that they were willing to give it back and charge you may say a great deal about their ethics and willingness to make it right.
Personally, if that was something I did I would fess up and make it right before even handing it back to you.

Too bad carlnpa

[gmfoster]

Originally Posted by carlnpa I took a Nook precision ballscrew to the local machine shop to have ends machined for K2 machine. I provided the new ballscrew and asked them to duplicate the old ballscrew. Picked it up today and the ballscrew is slightly bent, the ends where the bearings mount are 0.010 eccentric on both ends , (it turns like a crankshaft) and 0.006 oversize, it was cut long (fixed by cutting a spacer washer). I can't use the ballscrew as it is, should the shop replace the ballscrew? Or is this my problem for providing the ballscrew? Any advice appreciated.

Well the bend can probably be straightened if you are carfulll. And your best bet is to find some one to turn the shafts down a little more and then put some shrink fit bushings over them and turn them down properly. I would ask the shop for some money back but I am not sure I would trust them to do any work. The only thing I would add is that if you didn't give them tolerances then you might think about iit the next time. What did they charge you for this work. If you do go back make sure you see the owner or top dog supervisor. Someone that is intrested in the reputatuion of the shop.
Garry

[miljnor]

I agree they should make it right in what ever manner seams fair to both parties.

that being said, In CA you are responsible for only as much as was charged. Ie if you were going to pay 10.00 for said work the shop is only responsible for 10.00 AND the refund.

This sounds totaly unfair at first glance, but, I think the lawyer that quoted me said its to protect the shop from incurring charges well above what is expected. In my instance, an anodizer screwed the pooch on some 3000.00 dollar parts, and you cant expect a 50.00 process to cover 3000.00 dollars (or in the case of an associated shop a 34,000.00 magneesium part).

I guess its the risk of doing business. But in most cases (unless its going to put them out of business) the reputable shops will fix or replace the ballscrew. When I was a job shop I wouldn't take work in unless the price supported a 10% loss on the job and still make money, its just too risky.

[carlnpa]

Thanks for the replies.
I'll try to get them to rework the ballscrew.

[DareBee]

This is an ongoing debate.
A shop can't possibly stay in business if it is as crappy as you say the job was.
On the other hand people make mistakes and we are all human (this is a VERY inherant attribute in custom work - every job is new and our machines are versitile for everything not specifically designed to do any 1 job exceptionally).
IMO the shop should do everything they can to make your unit operable. I feel they should not have to replace your components - think about it - how many shops do mould or die repair on components worth 10s of thousands of dollars, if every slip or broken cutter cost the amount of the tool nobody would be in business.
Customers of mine that ask for specific machining on their own parts get told that if there is a problem the machining or remachining will be free but the component is theirs to supply.
NOW if you had gone to that shop and just ordered a ballscrew complete then they should be 100% liable - just leave it there and walk away untill they call you with a proper unit.

Anyway - ballscrew manufacturers provide custom end machining to eleviate issues such as this. Their machines are built specifically to do only that job.

[Kookaburra]

I have never trusted a general machine shop to machine my ball screws. Here in the Aus, if you supply it it is your risk, the machine shop quotes the job and you authorize them to go ahead, if they stuff up they are obliged to rectify the problem with the original piece of material ie: straighten and rework the journals, or , not charge you for the job. I always ask the supplier of the ball screw to have the journals machined, yes it is a little more expensive, but, when you order the whole thing finished from one supplier, then, you can take it back and tell them you want another one or your money back if there is a problem.

[carlnpa]

I took it back to the shop early this morning after talking to the shop foreman on the phone, he couldn't believe it was that bad. We miked it together, it was as I described above. They are going to weld in new material and remachine. The shop was decent about it.
I have used this shop for almost 20 years but have always dealt with the owner (who is out rehabbing for months) before.
We all can have bad days, but I did learn a valuable lesson. The ballscrew was small money, but it needs to be clear who is responsible if there is a problem with customer furnished material.

[HuFlungDung]

That is great. I hope they do a good job of the fix. That reinstates my faith in them if they do that.

[DareBee]

Originally Posted by carlnpa but it needs to be clear who is responsible if there is a problem with customer furnished material.

"Clear" is the key word there.
In most shops it isn't usually thought of untill the first time it happens then all of a sudden you gotta add a new policy

[rustyolddo]

It's a good idea to discuss the process that they will use ahead of time to rework your part. A shop that makes manhole covers will have a +/- .25" tolerance verse one that makes areospace parts @ .0001". I would hope that they would at minimum turn it in a collet lathe and ideally use a toolpost grinder. Most ballscrew suppliers will turn the ends to your spec for an addtl fee.