Surface Grinder refurb

Hi Mark,

I adapted one of these.**LINK**

but I paid £30 for it. I copied Lookcreations on the tube. The worm drive that provides the speed reduction to the whetstone is really poor so I would not go down this route again. Instead I would copy Stefan Gotteswinter and us a 24v dc geared motor, there is lots of choice on eBay. DC motor speed controllers are also readily available if needed.

The good news….

Of the bearing surfaces I’ve now scraped the column, the table (top and ways) and the knee (horizontal and vertical surfaces). All seems to be reasonably flat and square: I’m now starting on the carriage between the knee and the table.

The not so good news….

Measuring parallelism of the column dovetails, it looks like about 0.009 of wear.

Column dovetail

I reckon I need the straight edge for this, which hasn’t turned up yet, despite chasing. Even then it’s a significant job.

If you have bought an HR Lamb straight edge from Clive be prepared to be patient ! It will be worth the wait when it arrives.

I kind of expected it, he’s clearly very busy, and he obviously doesn’t make any profit out of straight edges.

Even when it turns up, obviously I have to scrape it flat! Although I expect it will be pretty close to flat when it arrives.

I’m kind of thinking that once I finish these last few small surfaces, if I don’t have a straight edge, I’ll put it back together and treat the dovetails as a second project.

That’s not a bad idea, you may be pleasantly surprised how good it is without that last bit of work.

I can’t help thinking though that with such a big dip that the table will “flop” in that area. It’s easy to see why it happens, there’s a lot of weight pulling against the dovetail around there, if it’s scraped it will surely hold oil much better.

Taking 9 thou off is a lot - and the wear area is quite small, maybe 1/4 of the length of the dovetail. That’s a lot of scraping.I’ll have a look and see if the bulk can be removed with a file.

Update…. I have finished the scraping of the main services to a reasonable level, obviously some could be better, but I could probably keep at it for weeks. The problem is still the dovetails. Despite assurances, I still haven’t got the straight edge. so I have started putting it back together to see how it works, despite the 0.008 wear on the vertical dovetails.

I have been pleasantly surprised by the squareness of the knee with the column, it’s pretty much bang on. However, predictably, adjusting the gibs on the knee doesn’t really work very well due to the wear. If I tighten up the gibs while the knee is in the wear area, when I lower the knee, it gets stiff and interferes with the gear that is raising and lowering the knee, potentially causing it to come loose.

given that I know this, I can work around it, in practice for any particular job the amount of vertical movement I need is very small. But at some point those dovetails need to be sorted out. I am tempted to carry on and put the machine back together this weekend carefully, measuring and checking everything as I go.

Stupid question no doubt, but what are these oil reservoirs called/how do they work? Do I need a wick of some sort?

Steve

Edited By Steve355 on 12/11/2022 10:33:01

Those reservoirs should have a losenge-shaped felt pad in them. They are just a giant oil wick that lubricates the table as it slides over.

The absence of your straight edge is bothersome.. What length did you say the column dovetail is? At least you’ll be working on a narrower surface so metal removal will go faster. I think the knee ways are poorly designed, that’s why they have worn excessively. I would suggest putting in some oil grooves on the moving knee surface ( less work than doing the column like diagonal zig zags. Those grooves should stop before the ends and I would install way wipers at least on the top side; you can make them out of the felt you’ll need for the lozenges.

Hi Tony. Well, I put it all back together yesterday for tests today. It is most annoying but to be honest I could do with a break from it. I have plenty of other projects to get on with, and I really want to get it to something usable.

It has the oil grooves you mention on the gibs and opposite dovetail of the table. So I can see what you mean.

One question, I’m guessing I need a special oil gun to fill the reservoirs from the oil nipples. Any idea what type? I’ve never come across this before in my very limited experience,

Steve

I had to make my oil gun from an old grease gun. I cut it in half, turned a heavy cap to serve as a base and welded it on. Cut the handle down to 6" long and filled it with way oil.

I understand the need for a break and you can tweak the gibs to suit whatever part of the height range you are using.

Oiling these old machines, in fact any machine seems to me much harder than it needs to be. I have machines that have nipples that it looks like they are made for grease gun attachment ( but require oil), some that look like a nipple some that are the flat ball oilers. I dislike all of them I have recently put a piece or 6mm id PVC tubing on the end of an oil can; that has helped greatly with the second type and I expect it to work on the grease nipples type as well.

If you have room I would look at fitting lidded oil cups where you can, that's a job that I need to get around to myself.

Update….

It’s all back together now and I’m running some tests. I didn’t scrape the dovetails as my SE (still) hasn’t turned up. It worked almost very well, see pic. It’s flat and thicknessed to +/- a few tenths, except at one end. At that end (right in the pic) the surface finish changes slightly and the thickness is about 0.004” less. I’d bet that that occurs when it crosses the centre of gravity of the table.

Problem 2 is the table gibs. If I tighten them enough to ensure there is absolutely no lateral movement of the table, then if I wind the table to either end of its travel, it gets very stiff. I’ve messed with it for ages trying to find a sweet spot, but to no avail. I have a nasty feeling that it is caused by dovetail wear.

Any thoughts welcome.

Steve

I'd guess at dovetail wear going by the way mine behaved.
My Centec is similar, particularly as I have a large(ish) single phase motor at one end of the table to provide the power feed. At far right extension, the table certainly leans a little.
In practice, I keep a universal dividing head bolted down at the other end to help balance it up.

Bill