Surface Grinder refurb

Hi all

My new surface plate turned up yesterday at last, so I can get on with my surface grinder refurb project. It’s 25 inches long, and already I can see what a tremendous benefit it will be. Unbelievably heavy though.

I will post progress on this thread for advice and moral support and also it may be useful,to others attempting a similar project.

Looking at the Connelly machine tool reconditioning book, he is clear that one should start with the headstock and spindle, and work around the machine to the table. If one starts at the table, it’s possible to get everything square in relation to the table, only to find the spindle is pointing off around the room somewhere, with not much that can be done about it. So that’s what I did.

Connelly gives the following tolerances for the spindle:

Perpendicularity to the vertical axis of the machine - 0.0004” (I got 0.0001)

Runout at the spindle - 0.0004” (surprising high I thought) - I measured 0.0004

So I am on the tolerance, and the headstock and spindle is acceptable. Does that sound right?

I put my pillar drill vise on the headstock to keep it steady. It didn’t seem to wobble, but I was getting inconsistent readings until I did that. Also there was paint on the bottom reference surface of the headstock, which I had to remove. But I think as long as I can accept 0.0004 runout, the spindle assembly is good.

Next it’s the column. I noticed the column seems to have some reference surfaces on the back, painted over, but look like the they were put there for measuring purposes (red arrows).

So checking the flatness of the column is next.

Any thoughts welcome.

Steve

Seeing your photo with your new surface plate mounted on
on bits of plywood , would be worth looking on here

https://www.starrett.com/precision-granite/precision-granite-faq

for the correct way to install and mount a surface plate.

John

I have no doubt you are right, the problem is I can’t handle it. The plywood base is actually part of the box it came in. I had to use a block and tackle to get it on the bench. I need to find a permanent place for it, when I do I will buy/make a stand and get the correct jacks for it. Once I’m done with it on the bench I will put the lid of the box back on and use the block and tackle again to get it off the bench. It seems like that’s the best way to avoid damaging it at the moment.

Am I missing something? How does the spindle alignment with the table matter on a surface grinder? Surely all you need is rigid to the vertical slide, alignment coming when you dress the wheel?

I have just replaced the vertical slide on mine with linear rails and a stepper. Precision was not high on my agenda, have I gone terribly wrong? (As usual)

Robin

Intuitively, I’d think you are right, but See P485 of Connelly, apparently it’s about surface finish.

In fact, I got the procedure for the spindle from the horizontal mill section of the book, because it reflects better the architecture of my machine, Whatever, it does no harm to make sure that all the components of the machine are reasonably accurate.

Column… stuck already, help!

On my column there are some ground “lugs” on the back of the column, which I was hoping were for the purpose of supporting the column square on a surface plate for inspection purposes. I am sure I was right, but they seem to have been knocked about over the years and it seems to be not quite accurate using these as reference surfaces.

I am trying to 1) check that the ways are perpendicular to the surface that mates with the headstock and 2) indicate the ways to check for “co-flatness” (I read that word somewhere) so I can make a plan for scraping.

1) with the column on the surface plate the headstock surface is about 0.001” out of square with the surface plate (if I place a 0.002” feeler gauge under the other end of the column. That’s the closest I could get it.

2) the far way surface is about 0.002” lower than the near way. I am certain that this is because of the position of the shim rather than a genuine error

3) about 2/3 of the way along the ways I get a roughly 0.001” dip, looking like some wear on the ways, in the area where the knee usually operates. Not too bad.

but I can’t get really reliable, repeatable measurements like this. Possible solutions

1) shim like crazy and try to get the column aligned with the surface plate better - hard and not easily repeatable

2) mess around with a precision level

3) get a pair of meaty parallels, turn the column ways-down and take measurements from the bottom

Any thoughts or advice appreciated

Steve

I may not have fully understood your intended approach, and thus your problem. However, here are some thoughts on what my approach to the task would be. There are, of course, other approaches: I'm not claiming mine is the best.

I would start by scraping what can become a 'local reference' plane, by scraping it to the (blued) surface plate. In this case, it would be the front face of the column. I'd try to remove roughly equal amounts from the unworn ends (and try not to think about what a sacrifice it is to remove pristine, unworn surfaces...). A made-up fixture or gauge would be used to try to ensure that the dovetail angles remained reasonably symmetrical - avoid lowering one side of the front face more than the other. No need to get too hung up about the dovetail surfaces yet, you're going to scrape them later. No measurement has been required yet, other than to warn you about the magnitude of the task. And if you think about that, you'll never start!

I'd then work the top and bottom to flatness, using a smaller, liftable(!) surface plate, checking squareness to the front face with a precision square. Get it reasonably flat first, then worry about squareness. The square could either bear on the front face, or the surface plate. The former is easier... Some form of fixture would be needed to check that the two ends were parallel to each other (their separation might be different on each side of the column).

Then the awkward dovetails. A gauge would be made up, to ensure the angle remains correct. Another gauge/fixture is needed to ensure they remain 'parallel' (their separation at top and bottom of column remain equal). The dovetail faces are scraped for flatness to a wide-faced straight-edge.

As you can see, most of the job is done without measurement. Really, that's the great joy of scraping - you can achieve great results with barely any measurement. Of course, there's more to it than this, and measurement can speed things along, but, often, you can think your way around the need for it. If you do get stuck on the idea of, say, plotting a surface's deviation from straightness, you then have to do some maths (spreadsheet!) to re-calculate the deviations from a carefully-chosen reference plane or line i.e. the desired end-point. I favour the lazy option of trying not to have to do this.

Whether the 'lugs' you indicated would be useful reference surfaces, I don't know, but I see no need to use them. The gauges and fixtures I've mentioned are explained by Connelly - it's all there, somewhere!

I suspect you may need to expand your toolkit - you'll need a second, smaller surface plate, a precision square, a straight-edge and made-up gauges.

Kiwi Bloke

Sorry, I’m not explaining myself well. See pic….

So the factory reference surface is the surface the headstock sits on. It is not a wear surface and shouldn’t need scraping. The ways need to be perpendicular to this surface and co-planar. If I just start scraping the ways, I can get them flat, but they will not necessarily be perpendicular to the factory surface. They will likely be in a skewed plane.

I was hoping to use the “lugs” to sit the column on the surface plate, making the plane of the ways perpendicular to the reference surface, and parallel to the surface plate. However, when I do that, the reference surface isn’t quite perpendicular to the surface plate, by about a thou. Which makes it tricky.

Ideally I’d put the reference surface on the plate directly, and take measurements:

but, clearly my reference square and surface gauge are nothing like tall enough for that.

The reason for taking the measurements is (having watched videos by Keith Rucker et al doing this) to get the ways perpendicular to the reference surface and co-planar, they split them into areas of similar height and scrape and measure, scrape and measure etc. to bring it gradually in to a perpendicular and co-planar surface. Then, once pretty close, spot and scrape it dead flat.

Problem is, I can’t quite seem to work out a way to get those measurements accurately and reliably.

Steve

Edited By Steve355 on 25/09/2022 13:09:14

Edited By Steve355 on 25/09/2022 13:10:00

Steve, your explanation is fine; the problem is that we're coming at this from different directions and run the risk of talking at cross purposes. Also, according to my wife, I'm capable of misunderstanding the simplest of things. BTW, I note the nice granite square!

The fundamental difference in our points of view is that I believe your 'factory reference surface' (FRS) is a poor choice for a plane to which everything else must be scraped into alignment. It's unlikely to be 'surface plate' flat, and it sounds like you've already discovered that it's not at right angles to the front face ways. Because it's neither a guidance surface, not subject to wear, it was probably milled or planed, with a less good surface than the ways, and probably never was really well aligned.

If you were to stand the column on the FRS and somehow measure the vertical 'tilt' of the front surface ways, you may then believe that you need to remove say 4 thou from one end of the ways. However, because the FRS is only about a quarter of the length of the ways, this translates to having to remove only 1 thou from one end the FRS - much easier! Also, the dovetails and front face ways, and their alignment to each other, should be pristine at either end of the column, and can act as references, so scraping 'tilt' out of the front face ways messes up the dovetails, more at one end than the other, making their re-alignment more difficult.

So, if you need to bring the worn front face ways flat, try to scrape a surface that effectively remains parallel to the plane passing through the unworn face at the ends of the column. Of course, you destroy this reference as soon as you scrape it, but that matters less than you might think. You can rest the column on the surface plate, on the lugs, if you believe they are - or have made them - reference surfaces, and measure the height of the front face. Or you could rest the column front face down, supported at either end, on parallels, and measure the gap twixt surface plate and face. But then, you have to be careful about keeping the places where the parallels will go parallel to each other. So measurement has its problems.

In fact, you can abandon measurement and just scrape the front face ways to the surface plate. You'll get a good idea of how it's going by the way the blue-marked areas move together (assuming the face is hollow). It's bad enough scraping the front face ways flat, without simultaneously having to worry about their relationship to the FRS all the time. No measurement...

Then, it's time to do the dovetails - always a challenge... That's my main reason for suggesting that the front face ways are worked first, with no real regard to the column ends - try to disrupt front face ways to dovetail surface alignment as little as possible.

Then, use this new, 'local'reference plane to adjust the base surface. That's easy for the 'front-to-back' right angle, but the 'sideways' alignment will require a gauge to be made that bears on the dovetail surfaces. (Sideways tilt doesn't matter so much at the spindle housing end, but, at the base, a Leaning Tower of Pisa looks bad...). When that's done, work the spindle housing end, ensuring the ends remain parallel (or at least the 'front-to-back' right angle). You'll need some sort of improvised gauge.. So, work from the most critical surfaces to the least critical.

Incidentally, for bolting faces, as at the top and bottom of the column, there's no need to scrape for a high density of contact points, and the surface can be relieved in areas away from the bolt holes. Then, for correcting alignment, only small areas need to be scraped.

Hope that's clear and helpful. However, there's no 'right' way to do this, just a vast number of ways to make the job more difficult.

Steve,

You're approaching this problem backwards. Scrape the long ways straight and flat then put the square on the long ways and use it to measure the short ways' perpendicularity with the scraped long ways. For that surface it only needs to be pretty close because you will dress the wheel from the moving cross-slide. What is most imporatant is that the knee and cross table ways are nicely scraped in. That joint barely matters at all.

Hi Pete

Last night, I got fed up with it and started doing precisely that.

I had a good look in Connelly on scraping perpendicular, and frankly he says “use a protractor” or make up a square template (how?!) I’ve Googled around the topic too, and there is a lot of BS about it, but no clear examples of how it’s done There must be a standard approach to it - basically these machine tools are big squares.

Steve

Buy or make something like this.

https://www.judgetool.com/products/suburban-tool-magnetic-cylindrical-square/

John

Should have added this video in previous posting on
usage of cylinder squares.

https://www.youtube.com/watch?v=LOaAMvGjUTk

John

Me again

A deep cut on the surface grinder might be a mm in 20 passes. Cut by hand your tea is stone cold and your cigarette has burnt to nothing in the ashtray. I think your reference square could be a massive overkill albeit very pretty.

Here's a thought... If you ever decide to cut with the side of the wheel verticality suddenly becomes important, but a slight tilt on the spindle means you can dress one side without putting in a shoulder and still go deep

You can probably tell I lie awake at night trying to get my head around this stuff.

Robin

Serious question to the OP! Does your grinder actually need refurbishing, have you tried using it or is this something you just want to do?

Tony

Kiwi bloke

thanks for the effort you have put into responding, I’ve come to the conclusion that you are right. I managed to get the column and square but only by adding a 0.004” at the other end. That’s a lot of scraping. And in fact, if I did want to get the end surface of the column flat, the amount of metal there is pretty minimal, and as you say it will only need to lose a thou.

So I’ve started the spotting and scraping process. Add the spotting is basically mirroring the measurements that I took.

my next question

I will need to address some dovetails before long, and I’m guessing for that I need a straight edge. Here are the lengths of the dovetails:

column 21”

table 25”

knee 16” and 15”

i’ve already been in conversations with Mr Lamb about getting a straight edge. What’s the best size to get? obviously something Long enough for the table, but won’t that be unwieldy for the shorter dovetails, and possibly other small dovetails I want to do in the future? on my lathe etc? I can barely afford one straight edge, let alone too!

Cheers

Steve

Did you ever look at the video series on Youtube about fettling a Herbert, which is what gave me quite a lot of pointers.
I had to adapt methods a bit, as I don't have a large surface table.



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.

Bill

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

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

Sounds good. I'm not familiar with HR Lamb's products. Just a reminder to think ahead: will the straight-edge be suitable to get into the 'female' dovetails, ie has it a bevelled edge? You'll probably end up making small masters for awkward internal dovetail work, unless your muscle development keeps up with your work...

Good luck. By half-way into this project, you'll either have been bitten by the scraping bug, or will vow never to do any more - ever!