View Full Version : Distributing wear evenly
12-13-2010, 04:28 PM
Does anyone here consciously use different parts of their machines to distribute the wear pattern over the movement range of their mill/grinder tables? For instance, by mounting the chuck on their mill table towards either end instead of always in the center? Is it something that's worthwhile or does it make no difference?
Obviously it's difficult or impossible to do in a lathe since the chuck is in a fixed position but I was just wondering if anyone deliberately does it when milling to reduce wear in one spot.
12-13-2010, 04:37 PM
I get the theory but don't bother. Home shop duty cycles mean it will last several generations as it is.....put that effort and attention into keeping it clean and oiled and it'll add multiples to the lifespan, far more so than moving the vise around imo
12-13-2010, 04:43 PM
I keep the vise approximately centered on the table and try to remember to return the table to the middle of its travel to limit the table's sag due to lack of support at the end.
That being said, I agree with Mcgyver.
12-13-2010, 05:33 PM
I offer up a small apology to the god of machine tools, and to my machine in particular, and then I have at it.
Usually I don't have much choice. Having the table balanced and not forcing the gibs to deal with out of balance forces is just as important.
However, I try to make my mill table, with an motor hanging off one end, look balanced before I shut down for the night. Don't ask me why !
12-13-2010, 05:48 PM
I do. I generally leave my vise at about 1/3 of the table either left or right, usually right because the obstructions around my mill are less obstructive that way. I figure it can't hurt.
The more useful reason I do this is so I can use the table surface opposite the vise without moving the vise.
I also wind up the engine on my pickup truck every once in a while. Used to be "blow the carbon out" but that doesn't apply with modern engine controls. I figure the pistons travel a little further up the bore due to component deflection (rod stretch for example) at high speed. I'm sure many have heard stories of the engine pulled from granny's sedan, dropped in a race car, and promptly grenaded. I have a theory that the cylinder bore wear ridge at the top ring travel was created entirely at low engine speed. Then when reved up in the race car the top ring crashed into the ridge and broke the piston. True? I don't know.
12-13-2010, 06:15 PM
I set my vice to one side or the other a bit but as a newly converted CNC machine I can tell that is wearing in a little now that it spends a lot more time moving around. I have tried to move the vice around a little to keep from hitting sticky areas by letting it wear in all over the length of the dovetails.
You can tell though on a small mill with a long table that having a heavy milling vice way out on one side definately has some other effects.
12-13-2010, 06:16 PM
On a mill, I try to put the vise as far to either side as conveniently possible. Not for wear purposes, but to allow the use of an angle plate for plate work or an open area for drilling on the other portion of the table.
Sometimes switch the sides when the mood strikes you or if there is long work to be done..
This way, the vise is always square and you can do other stuff too.
With this, it is the equivalent of having two mills.
You can increase both the versatility of the machine and
spread the wear of the table.
12-13-2010, 08:58 PM
It might be an OK idea on a brand spankin' new machine. But with the old used machines most home users have, it too late to be much concerned now. Off-setting your tooling to even out the wear on older machines generally will just make things harder to do.
12-13-2010, 11:38 PM
I have a mill-drill, and I don't leave the head dead on straight....I rotate it a bit over to one side or the other or in the center (without thinking about it too much).
That way the vise stays pretty much in one spot but the ways get wear in more than one spot.
I don't have any formal training so when I watched one of Rudy's videos and he said to change it's position when you re-mount the vise after a job it kind of made sense...I just don't ever have the need to remove my vise so this is another way to skin that cat.
12-14-2010, 04:11 AM
Many times I have the vise on one side while the RT is on the other - if not then I keep one of them offset *most of the time, from the lead screws to the tables surface and dovetails I like to distribute the wear --- it's not a must do - its just a personal choice, I don't worry about the Y axis at all -- different projects work it at its fore and aft positioning enough so for the most part the ram stays put unless I run out of travel.
It takes quite a few years but a mill that's strictly ran in the center will definitely wear its leads progressive - the way to test for this is to check the free play at the handle in dead center and then at both ends, if you have variation and you do have to do procedures in long parts then the deviations will be transferred unless you have DRO.
The other thing is the table - not just the top surface but the dove tails and load surface - a table ran in dead center all the time will relax its running surfaces and start to develop clearance, this is normal - you can take some of the clearance out by adjusting the gibs but you are limited due to the fact that some of the wear is on the table itself - so you have to leave it a little sloppy or on the rare occasions where you do have to use the tables ends they will bind --- I run a very tight mill in just about every direction (not binding tight - but tight) - it helps keep me in tune with it if ever I start wearing surfaces unevenly.
12-14-2010, 01:52 PM
I have a theory that the cylinder bore wear ridge at the top ring travel was created entirely at low engine speed. Then when reved up in the race car the top ring crashed into the ridge and broke the piston.
Cool theory, but I bet the rings will take up that extra bit of deflection, which I imagine isn't more than a few thou.
12-14-2010, 09:26 PM
It's more than a theory - its fact,,, what it does take is an engine that has been totally babied its entire life, then its not just some mild ridge - its a sharp one, the rings have no place to go and due to not having any kind of a taper on the ridge (because its never seen even the occasional rev) its a total stuff and they do crack --- However - its pretty rare nowadays with the amazing materials and compatibility and lubes, I really haven't seen a good ridge in a cylinder bore since I was a kid and that was always on a big domestic V/8,,, Heck - I can remember they even had a tool that was called a ridge reamer! there's no way that iv seen anything like that since - if a cylinder bore need's its ridge reamed then it most likely needs a re-bore.
All the honda's and toyota's that I pull down have factory crosshatch up and down the bore's and that's even @ a quarter million +...