Was watching a video............

[cybor462]

Had some time while waiting for docs to print so I threw in The Professional Machine course on DVD to see if I could renew my waning memory on the mill.

One strange thing Darrel Holland said was when mounting your Kurt or other mill vise be careful to always mount it in the center of your mill table each and eveyr time unless you have an odd job that requires it in another location.
He even used a tape measure and made sure it was dead on.

Wow now I am not a very good mill operator but in my reading and BBS dealings and other video courses I watched (since I am new to mills) all said make sure you position your vise in a different place all the time to keep from wearing your table out or actually spreading the t slots from underneath towards the table top.

This makes sense but Darrel who seems to be a top notch machinist was very clear on this.

Common sense tells me to use the whole table to keep wear to a minimum.

Ok lets hear what other have to say.

Is it one place all the time or move it around every time you lock her down.... GET ER DONE!

[sch]

Several POV here.
1) Mounting the vise off center will tend
to bend the table at some fraction of the same rate as the
center T slots will bulge upward. Although the vise will be
centered the table overhang will result in the table sagging
downward, so you end up with both ends sagging after a
few years.
2) Screw wear will be concentrated under the vise
so moving the vise about will move the screw wear around
and tend to even it out.
3) The bottom of the vise mount tangs will extrude into the
T slots making dents in the table.
4) None of the above is likely.

[TGTool]

I would guess that he's trying to reduce uneven way wear but I think he's kidding himself about being that carefully centered making any discernable difference.

If it did, what about making sure you always take a same length cut traversing left for every cut you take going right. For a variety of reasons I expect my ways to wear unevenly but that will just be one thing to deal with if and when this machine is rebuilt. I know absolutely and for a fact that I'll find barrel and hourglass wear simply because movement isn't always balanced, and having a table overhung from the saddle is just a feature of the design of the mill. The additional work required to correcty asymmetric wear pales in comparison to the years of inconvenience and high blood pressure from trying to eliminate the possibility.

I'd class that one with just some of the folklore everyone maintains inescapably. I know that some of the things I "know" to be true really aren't. If I knew exactly which things those were I'd correct them now. The problem is, I don't, so I just have to stay open to weigh what I see and hear and change my mind when it seems warranted. Maybe that's mental gene repair.

[wierdscience]

Doesn't matter one bit.Me I like mine in the middle as the table covers I have are cut to fit with the vise in the middle.

As far as defelcting the table with dog bolts and studs,they shold never bottom out in the slots in the firt place,a dot of mig weld at the bottom of the T-nut threds will prevent that.As long as the base of the vise is flat,clampng a vise down won't deflect the table,if it does then something is wrong.This makes an argument for properly fitted table keys even thou some think the table key slots are just there for looks.

[Carld]

it's statements like that from supposedly "expert machinists" that make me roll my eyes in disbelief.

1- unless your vise only touches the table at the front and rear of the table bolting it down will not distort the table. You are pulling the vise against the table and all surfaces are flat.

2- it make no difference where the vise is on the table except for the weight of the table as an overhang that may cause a mill with loose ways to cut unevenly.

3- if you have to go to extremes such as that you have never been a professional machinist working for a living or you worked for someone that didn't have to make a profit on work performed and was satisfied to run a shop at a loss.

I visited a Tool and Die machinist that retired from the GE appliance company in Lou. Ky. He asked me to stop and recommend how to pull a seal from a tractor. He showed me a sleeve he was boring out for a shrink fit and asked what fit I recommended. I looked at his set up he was using a brazed 1/2" turning tool with a chiped and rounded cutting edge without enough clearance on the bottom of the tool to clear the bore. He said he was getting a tapered bore. I explained how the tool had to be razor sharp and clearance on the tool for the bore. I then noticed that the compound and the crossfeed ways had about 1/8" side slop as I pulled them from side to side. He said he had rebuilt the crossslide and compound and could not get them any tighter. I found the gib end broken off of one and the other needed a shim to tighten it correctly.

I remind you that he is a retired tool and die machinist of 30 years at GE. I bit my tounge and did not make any rude comments as I suggested the corrections he may want to try.

What I am trying to say and make the point of is, don't think a person is an expert just because he or others claim he is. I have found many so called "experts" to be far from it. I don't know of the person that made the video but when he made that statement he exposed his ignorance to me. Anyone can make a video and claim to be an expert.

If these statements makes anyone mad then it's your problem, not mine.

[daryl bane]

Probably get flamed for this, but I like to put the vise off of center cause seems like I always have some dinky setup that I can't use the vise. Now I have alittle room to mount my setup,etc without moving the vise.

[cybor462]

Doesn't matter one bit.Me I like mine in the middle as the table covers I have are cut to fit with the vise in the middle.

As far as defelcting the table with dog bolts and studs,they shold never bottom out in the slots in the firt place,a dot of mig weld at the bottom of the T-nut threds will prevent that.As long as the base of the vise is flat,clampng a vise down won't deflect the table,if it does then something is wrong.This makes an argument for properly fitted table keys even thou some think the table key slots are just there for looks.

Wow and I thought I had it down, gotta tell this story....true even...my father had a friend that always said "Do not believe everything you read in the paper" (this was way before internet or video tape) and he was very stern when telling you that. Any person he met would get that statement whenever a discussion about anything took place.

It would not matter whether you felt you were right or wrong he made his point.

One thing I failed to tell you, this guy was totally blind! True story ... but it kinda fits here...

I saw Rudy K (a serious machinist) and a number of other so called experts, all say the same, to avoid excess table wear change mounting locations each time mounting the vise.
But the way you explain it makes the most sense. If the vise is worth anything by tightening down the bolts should not damage anything. On the other hand they may have been eluding to the fact that you would wear the slot out by using the same spot all the time. I can see that happening.
The point of contact were the t nut compresses against the slot could over time effect the table or at least the slot.

What do you think about that? Would you feel that may be a possibility? Not doubting anyone just trying to get a clear understanding of something I have only been part of for a short time.

[Carld]

On the many mills I have used the T slots were abused by the use of worn or damaged T nuts or using a hex head bolt or some such in the slot. The slots are then deformed and a bolt will not slide from end to end. Unless you put extreme tension on a T nut bolt you will not deform the surface of the table if the T nuts are not deformed themselves. Using the T nuts in the same place will not cause deformation unless the flats on the T nuts are not flat and square to the slot. Don't use a T nut with a sloping surface that contacts the underside of the slot.

I did see a fellow worker rip the T slots out at the end of the slots on the table. There was nothing above the T bolt to keep the table from ripping out. The shop owner was very pissed at him. He always overtightened everything he did and tore up and damaged a lot of what he worked on.

A lot of people over tighten things. The two bolts holding the vise down don't need to be as tight as you might imagine. The bolts keeping the compound from turning don't have to be as tight as you may think.

I have machined stuff and when removing the tool bit found I had only lightly snuged it during set up and forgot to tighten it. It cut perfectly.

Overtightening is a serious problem just as under tightening can be. The location of the vise on the table is not important. Put the keys in the bottom of the vise so it is in alignment all the time without indicating it and you can slide it anywhere on the table you want to. That is, if you haven't over tightened the bolts and deformed the slots so the bolts or keys won't slide from end to end anymore.

I don't leave the vise hanging out on one end, I slide it to the center of the quill no matter where the table is so there is not to much hanging weight on one end. I also center the table when I finish the job. Why intentionally warp the table??

I always try to apply common sense and physics to anything mechanical. Almost everyone has personal don'ts that don't ring true, it's just the way they like to do it and they teach it as fact. Hense the expression, don't believe everything you read, hear or see. It may be an illusion, exaggeration, lie, or personal belief.

When someone tells you how they do it or how it has to be done study the practicality and physics of it. Determine the effects of it as they proposed. Determine the value of it and use it as you see fit. Accept nothing at face value, but determine it's value with study and contemplation.

[John Stevenson]

Sorry but I'm in the other camp.
I always make sure my vise is secured to the bed accurately in one position.

When I say accurately I mean to a thou.

I have no idea what that measurement is but rest assured whatever it is it's accurate to a thou.

Not only that, it's also accurate to a thou if I measure it from 'tother end as well.


.

[Carld]

When I was in high school in the late 50's I worked for my uncle in his auto garage/speed shop. He was opinionated and his way was the best and right way always. After a while I started asking him and the other mechanics how they did things. He found out I was asking the others and was pissed. He said, if you don't believe what I tell you why do you ask me? I told him I always ask everyone how they do things so I can find out all I can about a subject. He thought for a bit and said, well, be careful who you listen to as gospel. These were his respected employees and he and they confered all the time but he was still pissed that I asked how they did things even though he was doing the same thing when they discussed the how to's of a new job or ways to do stuff.