Old surface grinder table: Scrape to improve action?

[Doc Nickel]

Okay, the purists will likely want to shoot me, but please, hear me out.

I've been putting the finishing touches on a rebuild of an older Covel surface grinder, a model from back when they had flat mill-table like ways, rather than roller bearings. The table motion is relatively smooth, but kind of stiff, taking notably more effort than my later-model roller-ways-equipped grinder.

Now, I know the older version will never be quite as smooth and effortless as the roller ways, but I'm wondering:

The machine has had enough miles on it, there's measurable wear on the ways. The factory flaking/scraping is but a shadow of it's former self.

While I would have loved to be able to regrind everything or rescrape everything back to 100%, I simply don't have the time or equipment for the task. What I am wondering, however, is since the ways have been essentially "smoothed down", if that's not causing a lot of extra "stiction".

What if I were to pop the table off, and give a light, relatively sparse scraping pattern to the ways? In other words, just hit it with a sharp scraper (I have a homebrew carbide one that works quite well) to the tune of anywhere from 6 to 12 or so marks per square inch. Not enough to even remotely affect what alignment it has, just enough to, in effect, roughen the surface to help reduce the stiction of the oil film. And, it shouldn't be enough to prevent a later scrape or regrind, either.

Yes, it would be nice to completely scrape or grind the machine, but in this case, it ain't happening. I have way too many other projects to divide my time.

So, yea or nay? Or just switch to a lighter way oil? (I'm using Vactra #2 now.)

Doc.

[Joe Rogers]

Is The loss of flaking due to wear the probable cause of the stiction? What is the condition of the lube system? Is there any galling in the worn areas? Just spitballing here.
Joe

[JoeLee]

Loss of flaking comes first due to wear and then things start to stick.

At this point if your careful it can't hurt to put down a flaking pattern to reduce the stick / slip that your feeling.
I did it to my lathe saddle and it helped. I didn't scrape the saddle to try to get an accuracy out of the machine, only to break up the surface contact.

This is what I did with my lathe saddle, I'm no expert scraper, some say it's looks pretty bad but it worked.
I also cut the oil grooves while I was at it.





JL...............

[J Tiers]

Quite possible. Some scraping / flaking may help. A lighter oil may also help.

[nc5a]

Doc,

Spot your bearing surfaces first then selectively flake or lightly scrape to breakup the stiction. If you would like a little help let me know.

Ron

[Doc Nickel]

Is The loss of flaking due to wear the probable cause of the stiction?

-I don't know, that's part of the question. The ways are worn nearly smooth, with only a shadow of the original scraping or flaking left, and what little I know of scraping is that supposedly the in-effect "rough" surface helps reduce stiction due to the oil film.

What is the condition of the lube system?

-In this case, the 'lube system" for the reciprocating ways is simply a reservoir cast into the saddle. In each reservoir (one per way, there's one flat way and one "vee" way) there's a spring-loaded "wheel" that carries oil up from the reservoir onto the way. I have no reason to believe these wheels are not working, the ways seem well lubed during use.

Is there any galling in the worn areas?

-No. There's actually surprisingly little grooving or gouges on the ways. They're worn "smooth" rather than damaged. I suspect thanks to the fact the machine may be as old as the late 30s (Covel type 15) and probably never really used coolant or had a proper vacuum system, so the abrasive dust in the air would get on the ways, which just "lapped" each other smooth over the years.

Doc.

[Doc Nickel]

Loss of flaking comes first due to wear and then things start to stick.
[snip]
I didn't scrape the saddle to try to get an accuracy out of the machine, only to break up the surface contact.

-Thanks Joe, that's pretty much exactly what I had in mind. Did it help, noticeably?

A lighter oil may also help.

-Any recommendations? I'm using Vactra #2, which is pretty much given as "the standard", but I have no idea if there's a "Vactra #1" or a "Vactra #3" that's thinner and lighter. Doesn't help that technically Vactra #2, I'm told, has been more or less discontinued and you're supposed to use an "equivalent" now...

I was thinking I might just grab a bottle of a thin motor oil, like straight 20 weight, and try that. It's relatively easy to pop the table off, wipe the ways down, mop out the reservoirs with a turkey baster or something, and try a different oil.

Also, in looking around, I see that a too-thick oil on something like this (a relatively fast-moving table, like a planer, which is not solidly retained [it's just set on the ways]) can 'ride up" on the oil, changing the dimensions of the part.

So both the scraping and maybe the oil change may be required.

Doc.

[Doc Nickel]

Spot your bearing surfaces first then selectively flake or lightly scrape to breakup the stiction. If you would like a little help let me know.

-I have no equipment beyond a homebrew scraper in which to do so.

Doc.

[JoeLee]

-Thanks Joe, that's pretty much exactly what I had in mind. Did it help, noticeably?



-Any recommendations? I'm using Vactra #2, which is pretty much given as "the standard", but I have no idea if there's a "Vactra #1" or a "Vactra #3" that's thinner and lighter. Doesn't help that technically Vactra #2, I'm told, has been more or less discontinued and you're supposed to use an "equivalent" now...

I was thinking I might just grab a bottle of a thin motor oil, like straight 20 weight, and try that. It's relatively easy to pop the table off, wipe the ways down, mop out the reservoirs with a turkey baster or something, and try a different oil.

Also, in looking around, I see that a too-thick oil on something like this (a relatively fast-moving table, like a planer, which is not solidly retained [it's just set on the ways]) can 'ride up" on the oil, changing the dimensions of the part.

So both the scraping and maybe the oil change may be required.

Doc.

It helped at first. but there is still some sticking now. If I oil up the ways and run the saddle back and forth it glides pretty smooth but will eventually start to feel sticky again.
I've always used True Edge way oil. I just got a gallon of Mobil Vactra No.2. I don't expect anything magic to happen using the Mobil oil, it has the same properties as the True Edge.

JL..................

[Axkiker]

Dont they make roller bearing conversion kits

[Doc Nickel]

Here's a photo that shows the saddle ways:



I believe there used to be flaking/scraping on these ways, but it has since been "lapped" smooth in the intervening possibly-as-many-as-eighty years.

The ways on the table still show a ghost of flaking/scraping. My plan is to simply scrape a coarse pattern, of perhaps only as many as 6 to 12 marks per square inch on the table ways. I don't know how to flake or frost, and likely don't have a suitable tool for it anyway.

Would it be better to do both surfaces of each way?

Doc.

[Mark Rand]

There is a Vactra 1, also Vacuoline 1405, which is the 'original' Vactra 1. Both are ISO32 way oils.

32 weight way oils are avaiable from online sellers (presumably as expensive as everything in the frozen North...). If you can't find any, cut the Vactra 2 with 75% 32 weight hydraulic oil.

It wouldn't hurt to re-scrape the ways for flatness and alignment if you are grinding anything other than very thin, flexible stuff.

[BCRider]

You might find that a thicker oil aids in reducing the stiction. The thick mixture I use on my lathe bed really keeps the tailstock gliding freely for quite some time.

[TGTool]

Here's a photo that shows the saddle ways:

Would it be better to do both surfaces of each way?

Doc.

No. If you were scraping for flatness and alignment you would do both. In this case, since you're treating the work as oil retention pockets of uncertain depth, flake only the shorter surfaces. This would be the saddle on the surface grinder. The theory behind that is that these surfaces are never exposed to open air the way their opposing surfaces are and so are less likely to be repositories for grit and chips.

[Doc Nickel]

32 weight way oils are avaiable from online sellers (presumably as expensive as everything in the frozen North...). If you can't find any, cut the Vactra 2 with 75% 32 weight hydraulic oil.

-That's an idea, I hadn't thought of something like that. Yes, specialty lubes like way oils are hard to find up here, basically only being available by mail order.

It wouldn't hurt to re-scrape the ways for flatness and alignment if you are grinding anything other than very thin, flexible stuff.

-Again, I'd love to, but as I said, I have neither the time nor the equipment.

You might find that a thicker oil aids in reducing the stiction. The thick mixture I use on my lathe bed really keeps the tailstock gliding freely for quite some time.

-With this setup, I have to worry about the table "riding up" on the oil, as well. Too much of that and it can throw off the grinding tolerances.

No. If you were scraping for flatness and alignment you would do both. In this case, since you're treating the work as oil retention pockets of uncertain depth, flake only the shorter surfaces. This would be the saddle on the surface grinder. The theory behind that is that these surfaces are never exposed to open air the way their opposing surfaces are and so are less likely to be repositories for grit and chips.

-I can see the logic in that.

Doc