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Can I shim a machinist vice??

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Alvin Schlitter09/05/2010 00:30:45
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I own a ZAY 7045FG milling machine and have a generic (Chinese) 4" machinist vice installed on the mill. I checked the vice to see if the fixed jaw was parallel across the vice and found that the right side of the jaw was .18mm higher than the top of the left hand side jaw.
I removed the vice and checked the ground bed over a 8" distance where the vice sits and found a difference of only .005mm. This then indicated to me that the vice is not ground correctly. Is it advisable to shim up the vice to get it to somewhat level? I do not have a accurate parallel that I trust to check the  inside base of the vice so I am going by the top of the fixed jaws only.
I hope that this makes sense to you the readers.
Thanks in advance for replies!
Terryd09/05/2010 07:17:02
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Hi There Alvin,
 
Where are you based? Here in the UK the consumer is protected by the Sale of Goods act (1979) as amended, which says that goods must be 'fit for purpose' (among other things) and if not, can be returned for replacement or refund. I would argue that this vice is not 'fit for purpose'  as it cannot be used for it's intended purpose without being modified (shimmed etc).  The retailer is responsible as the consumers contract is with them, not the manufacturer, and it is they who should replace the item for an accurate one.  The act also applies to second hand goods when purchased from a retailer but not private sales.
 
I have several times sent Chinese tools back to retailers when they have faults, quoting the act and the items have been replaced no problem.  (especially Arc Euro) .
 
Most UK residents do not know the degree of protection that the act gives to the consumer both in products and services and are too willing to accept incorrect 'get outs' from retailers.
JasonB09/05/2010 07:35:35
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I seldom reference anything off the top of the vice. You should be checking the bottom of the opening as most work is referenced off this by the use of parallels. If you shim the base you will also alter this face.
 
And how are you measuring this, you don't need a parallel to check the bottom of the opening a dti will be the best thing for the job.
 
Also if the vice comes on a swivel base I would suggest removing that as they are not needed veryoften, this will remove any inaccuracy there and give you more room between vice and spindle nose
 
Jason

Edited By JasonB on 09/05/2010 07:37:40

JasonB09/05/2010 08:14:57
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Just another thought, both jaws are usually bolted to the main body, it may just be a case of loosening the bolts and tapping the high end down or put a small shim under the low end and tighten it back up. Could have just got a knock in transit or put together poorly.
 
Jason
Circlip09/05/2010 10:23:44
1723 forum posts
You summed it up in the first sentence Alvin. "and have a generic (Chinese) 4" machinist vice installed on the mill"
 
  Only way is to get the vise assembly on a surface plate stripped down and check each part as you rebuild it with a DTI ,re-machining as nessesary.
 
  You get what you pay for.
 
  Regards  Ian.
Alvin Schlitter09/05/2010 11:14:19
14 forum posts
Hello Terryd;
I am retired and live in Thailand, you are right that is great protection!
Here everythingis misrepresented and one never gets what they are promised.
 
Regarding the top of the vice, you are right one hardly ever uses to top for anything. It was what I used to check how level the vice was. I intend on using soft jaws for the vice so the top issue is really a none issue.
Removing the swivel base is a good option or trying to mill the inside base if that can be done?
I suppose one could open up the jaws all the ways then check the two ridges that supports the parallels. I do have actually a couple of wide parallels that are right on so this might work as well.
I will start with the parallels and then go from there, and if needed remove the swivel base.
 
Thank you all for the positive feed back and great suggestions.
 
 Regards
 
Al


JasonB09/05/2010 12:37:41
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Why use parallels, take a dti reading off one "ridge" and then the other. At least that way you eliminate any error in the parallels if they came from the same source as the chuck
 
You should not need softjaws on a machine vice, as soon as the soft material deforms under load it will throw any accuracy (or not) out the window.
 
Jason
chris stephens09/05/2010 23:35:36
1049 forum posts
1 photos
Hi Alvin,
I am sure all of the above replies are helpful, some more than others, but if you are  just worried about the top of the jaws, not the rest of the thing, simply mill the top surface (the jaws are not as hard as you might think, the Chinese "hardened" does not seem to mean  the same as in English ). The jaws on my Vertex can easily be milled true with a carbide end mill. If you go down this route do make sure that they are in a repeatable position before milling. By "repeatable" I mean sitting squarely, without muck or swarf interfering with the things. It might also be an idea to clamp a piece of round bar, say 1/4", horizontally in the vice. about half way down, before doing the milling. This will load the jaws to take up any play in the slidey bits.
 
As you will have to take the jaws off to clean things, it might be an idea to mark the rear of the jaws so that they can be always replaced in the correct orientation, i.e top and bottom./ fixed and moving. When you put them back you might even find that the jaws are in an acceptable position.
 
The milling operation can only be done a few times before you run out of jaw, so make sure you get it right first time. 
chriStephens 
Stub Mandrel10/05/2010 21:50:45
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My chinese vice nightmare - I've got one of the camlock ones, 'overtightened' it and with a crack the fixed jaw fell off! There isn't a huge amount of metal in the casting at the base of the fixed jaw...
 
Rather than scrapping it, as the fracrture was clean I 'fixed' it with four long M6 high-tensile bolts and filled the joint with slow setting epoxy before torquing the bolts up tight. For a while I used to treat it very gently, but to be honest it was so long ago I'd forgot I'd done this until I read your thread!
 
Neil
Lawrie Alush-Jaggs11/05/2010 14:01:14
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118 forum posts
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Hi Alvin
 
I have to agree with Jason when he talks about the top of the vice.  You have to measure the bottom and the back jaw.  I do not recommend it be done on the table of the mill.
If you do not have a surface plate, go to a glazier's and get a 450mm square peice of 10mm plate glass.  Mount your DI or DTI in a mag base, place the vice on that and run the DI across it the vice base from front to back and side to side.  Then run it up and down the back jaw.  If you find that the vice is out in this manner then allowing for very minor discrepancies in the glass, the problem is in the vice.  If it all comes up flat and perpendicular then the problem is in the machine table.  One thing to be very aware of when you are performing this type of work is oil and grit.  Because you are making descisions that affect the way you use asimportant a tool as the vice, it is imperative that the base mounting surface of the vice and any surfaces you intend to measure be absolutely free of grit and oil.  You must polish the foot of the vice with a clean cloth and then rub your hand across it before putting it down.  You have to do the same with the base of the mag stand and the glass.  Anything on there will make a difference to the measurements you receive.
I have a Taiwanese mill/drill.  A fortnight ago I found to my great dismay that I had a dip in the table.  I put a straight edge across the table and at the deepest the dip measured just over 0.03mm
I removed the X axis leadscrew, made an arbour to fit an ER collet, put a cup wheel in, let the mill run for three quarters of an hour to warm it up and then ground the top flat.
Once I put the vice back on, I checked the back jaw with a DTI and it read zero from top to bottom.  Then I checked for bottom of the vice with a DI and it too was zero from back to front.

Lawrie Alush-Jaggs11/05/2010 14:10:13
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118 forum posts
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Sorry, it took a little while to work out how to add photos.  Now I know.For an explanation, see my previous post.


KWIL12/05/2010 10:09:46
3681 forum posts
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Follow up on Terryd's Sale of Goods Act, better still is the Distance Selling Regulations, which means that if you buy by phone, internet etc, with goods unseen before delivery, you have the right to return them without question, you may only loose the carriage/postage.  You may choose have have a replacement if you wish, again subject to the same rules.

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