Surface grinding a damaged Kurt vise

Hello all -
I have a very well used Kurt D688 with pitted ways. I have never personally done any surface grinding myself and trying to figure out the magnitude of this as a potential refurbishment project.

I live in LA so there are quite a few shops around, but I wanted to educate myself a little before calling. The big question is trying to see if it is financially reasonable to re-grind the bottom and bed (it does not have to match any other vise). The movable jaw most likely needs a fresh surface as well. I have no idea how big of a job this is or if it is worth bothering.

Does anyone with some experience know how long it would take to grind about .005 or so off the bed and bottom and verify they are parallel? Is that a quick and easy or a fiddly, time consuming project that only a good shop can pull off? What would you charge?

Thank you for any advice.

You say pitted? Is this just cosmetic or is it actually swaybacked?

Time wise you are looking at somewhere between minimum to 2ish hours for an experienced grinding hand.
That works out to probably $60-200.

How much do you love this vice?

rx8pilot said:

Hello all -
I have a very well used Kurt D688 with pitted ways. I have never personally done any surface grinding myself and trying to figure out the magnitude of this as a potential refurbishment project.

I live in LA so there are quite a few shops around, but I wanted to educate myself a little before calling. The big question is trying to see if it is financially reasonable to re-grind the bottom and bed (it does not have to match any other vise). The movable jaw most likely needs a fresh surface as well. I have no idea how big of a job this is or if it is worth bothering.

Does anyone with some experience know how long it would take to grind about .005 or so off the bed and bottom and verify they are parallel? Is that a quick and easy or a fiddly, time consuming project that only a good shop can pull off? What would you charge?

Thank you for any advice.

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If you disassemble the vise 75.00 would be fair.Its just flat grinding

Hazzert said:

You say pitted? Is this just cosmetic or is it actually swaybacked?

Time wise you are looking at somewhere between minimum to 2ish hours for an experienced grinding hand.
That works out to probably $60-200.

How much do you love this vice?

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I have no emotional attachement, that is for sure. This vise is a random acquisition with a bundle of other things. A brand new DX6 is only $585 - so it makes no sense to go too crazy to save this one.

The pits look like the previous owner let is rust - perhaps bad coolant? A ran a stone over it for a bit which revealed the pits even more. An eyeball guess is around .005" deep or so. Lemme see if I can capture an image - that should be helpful.

cmccull166 said:

If you disassemble the vise 75.00 would be fair.Its just flat grinding

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That would totally be worth it - maybe even go further and grind the movable jaw too. I won't know how bad it is until I disassemble it.

If the bed is just lightly pitted and no high spots I would not worry about that.The bottom takes the real beating.

Dale Derry just went through a grinding project on a Chinese vise on his youtube channel(Build Something Cool):

China vs Usa controversy machine vise - YouTube

Interesting to watch the procedure, but it was still a Chinese vise when he was done.

wheels17 said:

Dale Derry just went through a grinding project on a Chinese vise on his youtube channel(Build Something Cool):

China vs Usa controversy machine vise - YouTube

Interesting to watch the procedure, but it was still a Chinese vise when he was done.

Click to expand...

I watched that a couple of days ago - it was really interesting to see up close how flawed it was. Even after, as you mentioned - it was still a rotten piece of equipment. I ordered 3 of the Kurt 3400V's that will be my primary vises. This 6" D688 will be an occational use vise for making 1-off parts and fixtures that wil not fit in the 4" vises. I need it to be in reasonably good shape - but no need for absolute perfection like a brand new vise.

The left side I stoned for a bit to knock off the high spots. It looks a little better, but most ot the load bearing surface is history.

Looks simply enough....this guy has a great video.

So it is just pitted? Don't worry about it then, consider it flaking to hold oil.

rx8pilot said:

Hello all -
I have a very well used Kurt D688 with pitted ways. I have never personally done any surface grinding myself and trying to figure out the magnitude of this as a potential refurbishment project.

I live in LA so there are quite a few shops around, but I wanted to educate myself a little before calling. The big question is trying to see if it is financially reasonable to re-grind the bottom and bed (it does not have to match any other vise). The movable jaw most likely needs a fresh surface as well. I have no idea how big of a job this is or if it is worth bothering.

Does anyone with some experience know how long it would take to grind about .005 or so off the bed and bottom and verify they are parallel? Is that a quick and easy or a fiddly, time consuming project that only a good shop can pull off? What would you charge?

Thank you for any advice.

Click to expand...

.
most modern larger cnc mills in good condition can mill surfaces flat to .0003", its been that way for over 30 years
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sometimes its shiny and far more mirror like than grinding but even dull finish is often same tolerance. there is a waviness to surface of .0003" TIR and the high parts of the waves can often be .0002 or less
.
i clean rust pitted worn surfaces on machine slides often. often its only .001 or .002", takes longer to setup than to actually mill. if you are a big shop you can just have bigger cnc mill do it
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modern insert facemills can leave a good accurate finished surface. actually its often hand scraped not for accuracy but to put in a oil retention pattern. debatable often whether you really need the scrapped in oil retention pattern. basically when scrapped they are putting .001" deep gouges in it in a regular repeating pattern

If you don't have flat diamond ground stones, buy or do that before you go nuts stoning the bed of anything.

There is a thread and youtube video about grinding stones.
PRECISION GROUND TOOLROOM STONES - YouTube

The point is, whatever your stoning will appreciate having been stoned with a very flat stone. very flat stones will not gouge the surface and it will make determining what needs ground a lot easier.

Your vise has very bad but still just cosmetic pitting. It looks like shit but has plenty of good flat area to carry the very minimal load of the moving jaw.

IMHO 2 hours tops doing all the relevant way surfaces on a grinder would have it right to at least one decimal place better than toms machining. Probably nearer 1 hour to do.

Getting rid of the pitting will stop it filling with shit and make it a lot easier to keep clean which is essential as beds of machine vices are key datums and need to be accurate to there bases, i too agree that’s classic corrosion. Take 4-5 thou off that and its going to look great!

adama said:

IMHO 2 hours tops doing all the relevant way surfaces on a grinder would have it right to at least one decimal place better than toms machining. Probably nearer 1 hour to do.

Getting rid of the pitting will stop it filling with shit and make it a lot easier to keep clean which is essential as beds of machine vices are key datums and need to be accurate to there bases, i too agree that’s classic corrosion. Take 4-5 thou off that and its going to look great!

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It may look ugly but there looks like plenty of original material to hold true.

Just use it.

Any material removed will need to be compensated for which is additional work and possible introduction of error.

As already mentioned the pockets can hold oil...Just keep it clean and for 1 off it will work just fine as it is.

If you wish to remove pitting some epoxy can be used but that smacks of effort...
Sent from my SAMSUNG-SGH-I337Z using Tapatalk

Seems like a ready-made excuse to buy a surface grinder, which seem to be a dime a dozen these days. I use mine about ten times more than I ever thought I would, often for "clean-up" projects very similar to that.

adama said:

IMHO 2 hours tops doing all the relevant way surfaces on a grinder would have it right to at least one decimal place better than toms machining. Probably nearer 1 hour to do.

Getting rid of the pitting will stop it filling with shit and make it a lot easier to keep clean which is essential as beds of machine vices are key datums and need to be accurate to there bases, i too agree that’s classic corrosion. Take 4-5 thou off that and its going to look great!

Click to expand...

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milling to .0002" flatness overall with waviness of .0003 TIR max is acceptable to most places. its only a milling vice. i can almost guarantee whatever you set your vice down on in the milling machine you want to use it in is not that accurate. most milling machine tables are wavy not flat to <.0003 at least none i have worked on.

I have an older Kurt and a trio of clones. About a dozen years ago, broke a clone using it as a forming press. So brazed it up and re-ground the whole thing on my DoALL 1030.

A grinder with more cross travel (Z) than the typical 6-18 is necessary to do the bottom of the base. The rest could be done on a 618, if you wanted to work that hard.

Do the underside of the ways need addressed?
Other than that it is straight forward. The key thickness will probably need ground a bit. The bolt heads may or may not need skimmed, or the bolts shortened (for fixed jaw). You wouldn't think so for mere 10 or dozen .001's, (stack/cumulative) but ISTR there was some very minor issue there.

It is straight forward work, but you will still have a few hours in it, to do right.

Base, top of base (ways) bottom of moving jaw, top of both jaws to same height.

Then check jaw faces and verify parallel to key, and slight lean inward/square to bottom.

Kurt types are easily rebuildable, at least the first time. But it's not trivial to do it right.



How it was broken,



It's still in service. Maybe time to re-grind it again, the tops of the ways have a lot of rash.

smt

Grinding larger than the surface grinders travels is easy enough, especially with the above kinda vice base were you can do the ways then just hang it over one way then the other. If the chuck is true and you rough both sides the final finish and blending the 2 together well enough not to even tickle a tenths indicator is no harder than keeping everything clean IME.

Tomb you might be lucky and your errors cancel, here they always seam to add up, getting rid of any makes life easier for me. Have ground plenty of milled parts for a range of people from a pretty wide range of sources, have yet to see any clean up in just a few tenths, milling sucks for accuracy at these levels grinders win! Milling to a few tenths is hard, grinding to that level is trivial, its harder measuring it than it is removing it. I don't think its a lie to say for a given operator input - skill level grinding gets you a good 10-100 times better accuracy than milling. For me hitting a few tenths on the surface grinder takes no more effort than hitting a +- 10 thou tolerance milling. You should try it some time, you may well find you get more done faster and get a better result - end product!

As to a surface grinder, me it was more a want, but these days i would not be with out it, customers know ground = accurate and most love and pay happily for shinier things too. Its with out doubt the least used big tool i have, but its so low effort and makes prescion so easy i wish i had got it sooner! FYI i think i have about £2K total into the grinding side of what i do surface grinders are cheap, whats more for simple flats, set the stops and just walk away, im only ever stuck as a operator to mine when im doing fiddly crap like sharpening die chasers, were grind times seconds and set-ups a couple of minutes! Don't think i will ever make that £2K back on chargeable grinding time, but grinding bits of jobs and the cutters it lets me sharpen easily has paid for its self several times over each year i have had it. IE its more like a measuring instrument than a mill or a lathe to me were its a accessory to processing parts, not a direct billing centre - source if that makes sense.

milling to flat .0003 spec requires specific parameters. i often mill taking only .001 or .0005" depth passes and when magic marker red marks go semi transparent its taking roughly .0002"
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true you aint going to mill flat using a little bridgeport and a end mill. picture showing mirror finish of milled surfaces which is typically better than what a typical grinder does.
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a hand scrapped surface has basically .001" deep scraping marks in surface to hold oil, that is example of a .001" wavy surface where top of waves can be flat to .0002", many consider the waves not bad but deliberately seek to put them in a surface
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it is a science milling flat to replace grinding or scraping surfaces been done well over 30 years that way. still hand scraped oil retention pattern still added to milled surfaces. many want that wavy oil retention pattern. sometimes you get 2 extremely flat parts they stick together like gage blocks. thats often not wanted.
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on a printing press i often had rollers 12" dia by 6 foot long and surface too shiny and i have to make a cross hatch pattern with 220 grit emery cloth. it helped retain some solvent in surface and actually ran better that way and when the cross hatch pattern wore off i had to sand it again. many times you want some waviness or a rougher surface
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it can help so vise slides on table easier, too smooth it can stick at times and be hard to move. majority of milling machine tables have waviness in surface. it helps. take .0001 indicator and measure milling machine table. never saw one flatter than .0003" often they are .0005 to .0010 wavy

ground plenty of milled parts for a range of people from a pretty wide range of sources, have yet to see any clean up in just a few tenths

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What he said^^^^^.

There will be more than .001 warp in the base casting. Maybe a couple.

If you have a $2K grinder that you have not re-scraped and are grinding near the extremes of travel, print some of that large work in faint blue on a surface plate and see how flat it really is. Not saying inadequate for a vise, just "informative"

The other problem with 618 size grinders is the tiny wheel. You spend more time dressing than cutting. Well, not really, but it is a serious nuisance factor.

However, as has been said including by me, it is do-able on a 618. What I usually do (& did for the vise) is grind the base, print it, selectively scrape it, and then grind and build up from there.

smt