Member postings for Steve355

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.

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.

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.

Hi Tony, thanks for asking My wife doesn’t care about my project.

l’ve been going a bit slower for the last week due to half term and work etc. But I have been making some progress with the knee nearly done. I have a fairly clear weekend so I’m hoping to get some hours in… this scraping is a really time consuming business. But hopefully I’ll get the column and knee back on the machine this weekend.

One thing that did turn up in the post is a level that I got on eBay. This seems to be a very well made and useful tool, given its very smooth and stable adjustment mechanism. At least, it has helped me double check my measurements. It has 1 in 10,000 divisions, so at 8 inches long, 1 division is 0.0008”. So indeed my table is flat to < 0.0005, probably 0.0002 in most places. Not perfect for a surface grinder but way better than the 0.004 I started with and probably good enough for anything I will do with the machine.

BTW I have switched over to the carbide scraper, with a little skinny blade I made to get into dovetails. I’ve been sharpening it with a diamond hone. I think the diamond disc I was sharpening with before was no good and the diamond coating had come off. I really could do with a diamond wheel of some sort.

No sign of the straight edge yet

More later this weekend, I have some dovetail measurement questions that I know will come up.

Steve

Update….

well, I spent the entire weekend on the ways of the table, in the end I made decent progress.I realised that I could measure the top of the table (already scraped) with a depth gauge. I was getting decent consistent measurements that way. I ended up with the table corners within 0.0005. Which will have to do.

i dealt with the ways, which don’t quite fit on the surface plate, by carefully scraping not too much so as not to overshoot and end up with a scooped or bowed middle, it’s not 12ppi everywhere by any means, but again, it will have to do and it’s now all flat to 0.0004 rather than 0.004. So ten times flatter than it was.

Now I’m onto the knee.I’ve started with the easiest surface, which has some well defined wear in the middle.

I have also blued up the vertical surface of the knee. The question here is, am I seeing this pattern because of.wear (i think that’s where I would expect wear) or poor printing due to the weight distribution of the knee, or both?!

Slow progress, but progress. Tony’s idea of having a couple of days off was a good one.

Edited By Steve355 on 17/10/2022 23:57:03

Edited By Steve355 on 17/10/2022 23:58:08

The work and workpiece is on a surface plate.

The scraping looks horrible because on the ”0” side I have 0.001 to remove across about 12 inches so I was just going at it and roughing it out, I will clean it up as it gets nearer to the target height. That was the idea anyway.

Yes I have checked it with a micrometer, but to take the measurements shown I used a small V block on its side to try to measure the general thickness for roughing it to approximately the correct height before using the surface plate to print it and get the surface flat. What I found after a while was that one of the ways has lateral wear of about 0.001, this was really not helping with accurate measurements.

The surface plate is 24” (same as the straight edge I’ve ordered) and the ways are 32”. Not ideal at all but I can’t justify a bigger plate or straight edge for this one surface. 24” is plenty for everything else I’m likely to do. So I was focussing on one end of the ways and taking it carefully, I am not sure how the straight edge will help?

The top of the table is flat at about 12ppi. There are some areas that aren’t quite 12 ppi but I had to stop somewhere.

If I had a really good way of measuring it that I trusted I think it would work out fine. But when the blue doesn’t agree with the dti which doesn’t agree with the micrometer, it gets tricky!

Getting disillusioned now

I took the table to my local machine shop and they told me to go away. Said they didn’t have time to do it and it was too big for their machines anyway.

So I carry on trying to flatten the ways myself. It’s mostly within about 0.001, up to 0.002 in places. But of course I can get it flat, but it needs to be flat and co-planar with the top of the table on the other side. Looking at the blue patch between 5 and 10, the blue says it’s a high spot. But the DTI says it’s a low! I’m very reluctant to keep scraping away at it unless I know what I’m doing is right.

Hi Tony

What I tried to do was to use my Burke horizontal mill to skim the last quarter or so of the bed. The wear was all in the middle, so skimming those sections bright the ends in. It wasn’t altogether unsuccessful. In general, there’s about 0.001 of variation now, a little more in places.. The extremities were a lot more difficult to do, so one is high and one is low. The high one can be scraped, and the low extremity probably doesn’t really matter.

However, I am very tempted to do as you suggest and see if a local machine shop will do it. They should be able to get it all much flatter that I can prior to scraping. I will ring around on Monday and see what I can find, as you say it’s a simple and quick job for someone with a decent mill.

Re the surface plate, diagonally it is about 2 inch shorter than the full length of the table. This is by far the longest surface on the grinder, and I just couldn’t justify or afford (or move) a bigger plate. But if the table bed is pretty flat (say 0.001) before it is spotted, well I haven’t done the trigonometry but the potential error (1 thou in 32 inches) is incredibly small.

The straight edge that’s coming is sized for the dovetails, so it’s 24 inches long which is the length of the longest dovetail. I don’t think a bigger straight edge would be easy to handle.

I think you are right about the gibs, given they don’t seem to be worn, just slightly warped, they should be fine. As Mark suggested, they seem to have improved since I took them off the machine.

It’s the carbide that came with the scraper. I haven’t had a lot of success with it. I actually prefer my old Eclipse HSS scraper - it’s a better length for me and is dead easy to sharpen, and when sharp it seems to hog off quite a lot of cast iron.

I had an idea to try to use my little horizontal mill for it. It’s far too small for the surface grinder table but I only need to skim a couple of thou off the ends. If I’m careful I can probably do it, I will give it a go tomorrow.

Progress….

I scraped the top of the table to about 12 points. There are a few areas that I’m not totally happy with but I could go on forever.

The sides are parallel to about .005 so I’m not messing around scraping those.

The sides are square in so far as I can’t get a 0.0005” feeler strip between the square and the metal

I’ve started on the bottom. If anything beats me, it will be this. They are quite worn going up at the ends by 0.003. Quite big patches of 0.002. I’ve tried scraping but it’s slow. I have tried a file as recommended by Pete but the two rails (?) are not evenly worn, and if I try to file just one side it’s very easy to end up with a hump in the middle and low at the edges. Ideally I’d fly cut it on a great big mill but obviously I don’t have a mill big enough. My surface plate isn’t quite big enough, but will probably work ok.

It is hard to measure. I’ve tried using a gauge block, perhaps that will help.

I have a feeling that this is going to be very very time-consuming and hard work.

I’ve also been looking at some gibs. They don’t seem to be worn (consistent micrometre measurement along the length), but they are warped, with a hump in the middle of a few thou,

Hi Tony

I think it’s because the scraper is shorter that I can get my weight above it and really dig in, whilst controlling the length of the stroke. And also, I can scrape kind of “backhand” with the back of my hand facing my face (probably makes no sense!) and that’s even easier than a forward scrape, and I don’t need to turn the workpiece. A picture would help explain. I have 2 carbide scrapers, one about 3 foot long from eBay which cost £60, and one I made myself, about 2 foot. I’ve barely used the expensive long one. The home made one is currently superseded by the Eclipse scraper.

For some reason my carbide sharpening hasn’t been working. But whilst the HSS blade needs sharpening more often, when it’s sharp, it’s very sharp.

Problem is, I don’t know anybody locally who is remotely interested in machining, scraping (or plane making and other things I do in my spare time). It’s a bit of a niche passtime!

Edited By Steve355 on 05/10/2022 09:55:28

I had a couple of hours before work this morning, thought I’d have a good look at my blade. Under a magnifier it was clear that it wasn’t really sharp at all. Out of frustration I grabbed an old eclipse scraper I have to see how it performed. It was a total revelation. I found I can get it really sharp in about 15 secs with a simple diamond hone. And being short, I can get my elbow behind it. I was getting the little black piles of cast iron dust at the end of each scrape again. Sure it goes blunt after a pass or two, but it’s so quick to resharpen it isn’t a problem. Just goes to show that hi-tech carbide isn’t necessarily better.

I’m in Hitchin, near Stevenage.

Edited By Steve355 on 03/10/2022 11:48:44

After realising quite how much effort it’s going to take to get this surface grinder scraped, on Sat morning I went out and got a cheap reciprocating saw, having watched a bunch of YouTube vids about making a poor man’s Biax scraper. I did it, and it worked quite well, for about 10 mins, at which point, what SpaceX would call “Rapid Unplanned Disassembly” occurred. I fixed it but it happened again.

Never mind. A lost day and a few £££. At least I tried. Back to hand scraping today.

Thanks Tony & Pete

Here’s where I got to last night, basically trying to break up the blue areas.. Yes, it is hinging nicely. But I feel I’m going around in circles, each pass doesn’t really seem to improve the pattern, just change it. I am having trouble with making smaller scrapes, and also with accuracy. It’s difficult to predict exactly where along the blade is making contact, so sometimes I miss the target.

In the end I stopped and moved on to roughing the table, which too me at least 1/2 hr for just one pass. I realised quite how much of this I have to do - the whole surface grinder, and the straight edge when it arrives, plus eventually other machines I have. I’m not one for giving up though.

Thanks all for the advice

I went to the local art shop this morning and picked up a new roller. It seems much better than the other one I have.

I like the “Tom Cruise” solution of standing on a box. I have a workmate somewhere, it may be worth trying that also.

I hope I am getting closer with this column, my latest spotting below. It seems like it’s question of breaking up the blue in a few areas and I’ll be there. Does anyone beg to differ?

one thing - the contrast isn’t good. It isn’t easy to see blue patches under the light.

Then tomorrow I can go at the grinder table with the crosshatch pattern and wider spacing Pete was talking about.

Hi Pete

I have a rubber roller, but frankly it’s not very good, or perhaps the blue is too oily for it to work well. I’ve been using the typical Stuart’s blue. As you suggest I tend to use a side to side motion with the roller to move the blue around. I think I’m getting the hang of how thick it needs to be by using the hand application method, basically no excess. I also have a cotton “mop” like a French polish mop that I’ve been using.

I think part of the problem I’m having with the depth of the scraping, is that my bench is a standard height bench but by the time I had on around a foot of column, in fact I am scraping at chest height. So the scraper inevitably hits the metal at quite an oblique angle. For other parts of the grinder that aren’t a foot thick, it should be easier.

for sharpening the scraper, I have been following Connelly, who says that a 5° negative rake angle should be used. I guess that doesn’t really give a sharp edge, more a “corner” that contacts the metal. Is that wrong? I was surprised to read that.

When I get on to the grinder table at the weekend, I’ll do what you say and use wider scrapes, and try to get a decent crosshatch pattern.

Edited By Steve355 on 29/09/2022 22:35:07

Hi Tony

Funnily enough that’s exactly what I’ve been struggling with this morning. Either too much or too little blue, or unevenly applied on the plate, and getting different results. I read a post somewhere by Richard King where he said the best way to apply the blue to the plate is by hand. So I tried that and I have been getting much more consistent results - in particular Stefan G points out the dark rings around high spots in his videos, which I’m now observing.

So a combination of those 2 techniques seems to be helping, And I do look like a Smurf at the end of the scraping session, but it’s a price worth paying.

Steve

Straight edge ordered from H R Lamb. I don’t expect it’ll turn up this week, so I can’t scrape any dovetails for a bit. I wonder, once I’ve finished the ways of the column, what else can I move on to without a straight edge? The top of the table? I want to keep it moving, I have a clear weekend coming up! Don’t want to waste it.

Sounds like Mr Lamb might not be selling camelback straight edges any more soon, which would be a big shame for hobbyist machine rebuilders.

I’ve spent about 8 hours on the column so far I reckon, 4 yesterday and 4 today. When I started this morning it looked like this:

And by this evening it looks like this:

nearly there, surely! Now I need to make sure I don’t go too far and end up chasing my tail.

Steve

dovetail lengths:

column 21”

table 25”

knee 16” and 15”

I am going to ring HR Lamb in the morning and order a 24” straight edge unless someone advises me not to….

Thanks

Hi Bill

Yes, and I’ve been combing your pics for tips on how to do all this!

>>>Also, don't forget that maybe you don't need to scrape the top of the column yet;
It needs to be co-planar with the table, so you can assemble the knee and table, and then use that with a surface gauge and DTI to see how well it all lines up.

Thats a really good point.

Steve