Surface grind table

[slow-poke]

The 8x30" table is off my at the moment, the surface is not brutal (no drill holes), but there are a few end mill impressions and the top right corner looks like it was used as a base to center punch about 50 points in 20 gauge aluminum. I might live with it, but I'm a bit of a fussy character so want to weigh dropping it at a machine shop to have the top surface cleaned up. Minimum shop cost might be the deal breaker.

Anyone do this?
How long does a job like that take?
Cost, low, high, fair?

Anything I should know, note or specify if I do bring it in?

Suggestions for a shop in Ottawa?

Thanks

 

[Dabbler]

It's pretty expensive here in Calgary. There are 2 shops that can do this, and I wonder if Moore is still taking external work. Modern Tool here will regrind a table, but it'll take the better part of a grand to do it. That seems high, but it would require a minimum of a 12" X 36" grinder to do it. Modern uses a gantry grinder, but that's even bigger. (it's not even located in town, so there's also transportation to pay for).

One alternative is to fly cut the table, but you had better be sure your tram is perfect.


The pecker marks can be safely stoned out. the mill cutter marks might be best left alone, IMO.

 

[Former Member]

Old school. Large flat surface, glue down a large sheet of abrasive paper, flip table over and drag in different directions till smooth to your liking.

This method is still used to redo cylinder heads and the like. For the tolerances that we can achieve in real life more than accurate enough.

 

[Susquatch]

I might live with it, but I'm a bit of a fussy character so want to weigh dropping it at a machine shop to have the top surface cleaned up. Minimum shop cost might be the deal breaker.

In my opinion, the biggest problem with this is NOT finding a shop to do it or the minimum charge. It is finding a shop that can do it PROPERLY. Maintaining tram to the ways is imperative, costly, and requires skills and equipment that the vast majority of shops simply don't have. And I sure as heck wouldn't take their word for it. I'd want reliable feedback from fussy customers who have been happy with work they have done on mill tables.

@Rauce had to take his lathe bed to the USA to do it right. Mind you, he was grinding his ways and you are machining your bed. But it's exactly the same principle.

Quite simply, a bed that has pecker marks in it will work just fine and do perfect work. But a clean beautiful table that isn't PERFECTLY level to the ways will never work right. I know lots of outstanding machine shops. I'd never let any of them touch my mill table. To be honest with you, I'd be getting a new mill before I'd machine the bed.

I have no problem with a little stone work or even light full table sanding on a flat reference to remove the high spots. But that won't get rid of the pecker marks themselves. For that, I'd simply fill them with steel epoxy, and then scrape and stone them flush, or even leave them a little low.

If you do like most of us, you are going to put protective covers on your table so you will never see the marks anyway.

When I first got my mill, I had big plans to fix the pecker marks. After I added covers, I lost all interest in that project.

 

[slow-poke]

Enough said, I will clean it up, can you recommend a suitable stone, I don't have one.

Good advice as always, thanks.

 

[Susquatch]

This is what I have used to date.

Norton 547-61463685545 Ib64 4X1 Round India Comb Bench Stone https://a.co/d/eJG3jjt

However, a while back someone on here posted a much better stone purpose made for removing high spots on a Mill table. I just can't find it. Maybe someone else can jump in.

A few pointers. Circular motions only and only till the high spot is gone. It's easy and obvious to know when that is.

Dedicate your stone to this single purpose and NEVER use it for anything else. A little stone oil can help but some say to never oil. I oil. I think it keeps the cast iron particles from clogging up the stone.

I'll come back and post again if I find that stone. I think maybe it was at KBC Tools.

 

[Rauce]

You’ll probably have better luck finding a place that can grind a table than I did finding someone to grind my lathe bed.

Grinding a lathe bed with multiple surfaces, some on angles, that need to be parallel to each other is a job most places likely wouldn’t have done before and would be unlikely to attempt. Making a single surface flat and parallel to the bottom surface (the ways) is trivial by comparison.

 

[Dabbler]

Perhaps this is something to think about...

 

[Susquatch]

@slow-poke - lots of good info above for you. But don't forget that your stated goal was to get rid of the pecker marks. So another issue you will need to accept is a thinner, weaker bed by whatever the depth of the deepest pecker mark is.

Being that cast iron is cast, that also raises the possibility that taking the deck down will expose other currently hidden voids and then you are further chasing your tail. I don't know how much thinner that will make your T-Slots either. Whatever it is will result in a linear reduction in stiffness and resistance to T-slot tearout. That has to be weighed against the aesthetics of a nice looking bed. In my mind, aesthetics takes a distant back seat to function but not everyone is the same.

So here is a new thought. Set aside the reliability and advisability of such a repair for a moment, and instead take a wild guess at the cost of having the bed recut or reground. Add that to what you paid for the mill and then compare that to the cost of a brand spanking new mill. Then ask yourself which one you would rather have......

You can prolly sell your mill right now for more than you paid for it.......

 

[trevj]

It's pretty expensive here in Calgary. There are 2 shops that can do this, and I wonder if Moore is still taking external work. Modern Tool here will regrind a table, but it'll take the better part of a grand to do it. That seems high, but it would require a minimum of a 12" X 36" grinder to do it. Modern uses a gantry grinder, but that's even bigger. (it's not even located in town, so there's also transportation to pay for).

One alternative is to fly cut the table, but you had better be sure your tram is perfect.


The pecker marks can be safely stoned out. the mill cutter marks might be best left alone, IMO.

Forget perfect tram.

As long as the table travels are capable of reaching the edges of the table, or you have access to a larger mill in decent nick, you simply put in a decent sized end mill (inch, 3/4 inch-ish) you work with a very slightly OUT of Tram head, easy to identify, as it will leave a better surface finish in one direction than the other, and start stepping across the table lengthwise, in say 1/4 to 3/8 inch steps, always in the direction that leaves the lower edge (that leaves the nicer finish behind) trailing as you travel. This will allow the nicest possible results.

This very nearly replicates the Planed surface that was a characteristic of many many milling machine tables. It leaves a series of alternating high and low points, the net result is a flat surface, but without the inherit problem of sliding a vise around, being a battle against stiction, as there is always a little room for some oil and some air under whatever is on the table.

Deep holes, get drilled, tapped, a plug installed and "Oil Here" stamped around them! Then carefully stone down the metal raised by the stamping! Learn how to flatten and use a stone, it goes a long ways toward being able to inspect and fix raised metal displaced by various dings from dropped parts or chip pinched when mounting tooling on the table.

A lot of shops will place a sacrificial tooling plate on the table, so as to not have to deal with (or, look at) the scars of past work accomplished. The down side is, that if any moisture coalesces between the table and the sacrificial plate, it can be a VERY ugly result!

Honestly, I cannot envision anything that is quite as effective, as mounting the vise where it needs to be and placing a couple sections of oily plywood over the remainder of the table, so as to not see the grooves.
For the most part, based upon my experiences around Edmonton trying to find someone to grind a Myford bed, you are money ahead taking the machine to the dump, and buying a different one!

 

[Susquatch]

Honestly, I cannot envision anything that is quite as effective, as mounting the vise where it needs to be and placing a couple sections of oily plywood over the remainder of the table, so as to not see the grooves.
For the most part, based upon my experiences around Edmonton trying to find someone to grind a Myford bed, you are money ahead taking the machine to the dump, and buying a different one!

^^^^ This! +20

Another view of the same advice is that a flawless bed is only flawless if you can see it's flawlessness and it won't be flawless for long if you can!

 

[Dabbler]

This very nearly replicates the Planed surface that was a characteristic of many many milling machine tables. It leaves a series of alternating high and low points, the net result is a flat surface, but without the inherit problem of sliding a vise around, being a battle against stiction, as there is always a little room for some oil and some air under whatever is on the table.

Learn how to flatten and use a stone, it goes a long ways toward being able to inspect and fix raised metal displaced by various dings from dropped parts or chip pinched when mounting tooling on the table.

@trevj We agree 100% on the second point, which I tried to make above.

However, on the first point we must differ. Firstly, the head does not have a ram, so you could use a 2" face mill and still not reach the corners and ends of the table. This is why it HAS to be fly cut. it will need around a 4-5" swing on the fly cutter to reach the corners of the table. That was what I measured when rotating my head with my version of this mill. With a 4" fly cutter you have to take care for the tram, which isn't hard, and is good practice anyways, perhaps even 'best practice'. The step over idea is a great one - but it shouldn't be used as a substitute for tramming your mill.

 

[Susquatch]

Btw, I really like @trevj s suggestion to use oiled plywood to cover the table. I was told not to use wood or cardboard by a corrosion specialist because they can both contain corrosive acids. He recommended corrugated plastic.

Your idea to use oiled plywood is much better in my opinion!

 

[PeterT]

I'm using cardboard out of laziness & haven't seen any staining or corrosion underneath. Under the vise is a different story, I am seeing a light stain emerge aligned to the contact footprint. It comes off (with work) with WD40 & synthetic Brillo. I thought plastic would be good too but one attribute is hot chips can actually melt & stick to it making it owee on the hands. I'm going to try 1/4" MDF next because its nice & smooth. Oil just finds its way into it naturally but I don't think the fibers swell & break down like with water. Plywood wood be better but also has a habit of warping. I've seen some guys use like a neoprene rubber sheet which would be good if chips don't embed & stick.

 

[Susquatch]

I'm using cardboard out of laziness & haven't seen any staining or corrosion underneath.

I am too, and I haven't either. I just don't like it when a guy whose whole business is providing corrosion tech support to machine shops in Canada says he has seen it and recommends against it. That Murphy guy just loves to lay in wait for me to take advantage of any minor mistske.

How about oil rubbed cabinet grade plywood?

 

[Dabbler]

Trapping moisture under the plywood/cardboard should be be reduced significantly if your cover has space for air beneath it.

I avoid using soluable oil nowadays, as I found discolouration beneath my vise, despite trying to be careful to mus the minimum, and to wipe away surplus ASAP. I use thinned oil for cooling/cutting, despite the smell and mess, tom avoid the problem with moisture getting under the vise.

I've been thinking about those plastic slot covers, table covers, and other things, and for me the jury is out for now. I'd like it to be easy to clean, so a simple lip will trap swarf too much. I've also thought of a thicker lip that makes a sort of ramp, so that swarf can be swept or vacuumed off the tray.

 

[trevj]

I'll be very clear, I was not suggesting using the plywood as a fastened down cover, rather a couple pieces that served mostly, to prevent having to fiddle around clearing swarf and chips from between the tee slots! Cheap and simple! When done well, about 95% of the mess gets lifted off the table and shaken in to the waste bin.

Use way oil, so if you leave the stuff on the table for long periods undisturbed, the net effect is to leave an oily spot on the table!

 

[Susquatch]

Trapping moisture under the plywood/cardboard should be be reduced significantly if your cover has space for air beneath it.

As I recall, he wasn't concerned about moisture. He was concerned about other chemicals in the cardboard and wood.

I avoid using soluable oil nowadays, as I found discolouration beneath my vise, despite trying to be careful to mus the minimum, and to wipe away surplus ASAP. I use thinned oil for cooling/cutting, despite the smell and mess, tom avoid the problem with moisture getting under the vise.

I avoid soluble oils too. I like regular oils and cutting oils. I don't really give a damn what it smells like.

I've been thinking about those plastic slot covers, table covers, and other things, and for me the jury is out for now. I'd like it to be easy to clean, so a simple lip will trap swarf too much. I've also thought of a thicker lip that makes a sort of ramp, so that swarf can be swept or vacuumed off the tray.

The jury is out for me too. But I do like the oiled plywood idea.

 

[Susquatch]

I'll be very clear, I was not suggesting using the plywood as a fastened down cover, rather a couple pieces that served mostly, to prevent having to fiddle around clearing swarf and chips from between the tee slots! Cheap and simple! When done well, about 95% of the mess gets lifted off the table and shaken in to the waste bin.

I never thought you meant anything else!

Use way oil, so if you leave the stuff on the table for long periods undisturbed, the net effect is to leave an oily spot on the table!

Way oil is too expensive. I have lots of other oils like spindle oil and light gear oil I'd prefer to use.

 

[Janger]

What about using ductwork galvanized sheet? I mean just as a cover. To keep the swarf out. It’s light, shouldn’t rust. Bend to fit and wrap over the edges?