Surface Grinder refurb

You won't be disappointed with a Lamb straight edge they are easy to scrape and the casting quality is very good. I have an 18" and a 30", plus a 15" square and an unfinished 20x10" master square from him.

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

Your straight edge is an investment and if you need to you can sell it on in the future.

Some hopefully helpful feedback on your scraping;

it's difficult to tell exactly but I wonder if you are applying a little too much blue to your plate? I ask as although you have certainly improved contact, the areas of blue are too contiguous and over blueing can merge one point into another. I would suggest seeing if you can reprint with a thinner application of blue, if the points per inch improve then you'll know. Otherwise I would advise you to now break up the blue areas to improve oil retention.

There is a lot of info on scraping on the 'The Tube' but I think Stefan Gotteswinter covers the basics really well.

Tony

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

Hi Steve,

Its good that you are working it out,. The application method may also depend on what type of blue you are using, I like the Charbonnel water based artists product. I apply it to an area of the plate that I won’t be using for spotting with a rubber roller and rolll it out, that area is heavily blued I then pick up a smaller amount off that area using it a bit like a paint roller tray. I then roll that onto the spotting area and the spend quite a bit of time pushing the blue around until it’s pretty even and I can see the granite flecks though it.

The blue does dry out so I remove it with the typically blue window spray, the Charbonnel does come off my hands pretty well but I do use a barrier cream. In my household scraping is known as Smurfing.

In an earlier post you mentioned runout on your spindle, this isn’t the only factor affecting surface finish, their condition is also important followed by wheel balance and wheel choice. On wheel choice I was advised to use a 46 medium bond and I have found this to meet all of my needs thus far.

looking forward to seeing your progress.

Tony

You definitely have too much blue on there but it's not too bad when you're only roughing. What you will find is that if the part has a lot of sticktion on the blued plate from too much blue it will smear and it will also print heavily around the edges of the part.

The reason Richard says to use your hand is because you will feel any grit on the plate. I rarely use my hand maily because I use an oil based blue, instead I use a rubber ink roller and it picks up a lot of this grit. I roll out a patch on a spearate plate and use that to load the working plate and replenish the roller. To get an ever spread I sometimes skew the roller so it's not rolling straight ahead but skidding and rolling. It gives a nice even coating of blue. If you roll a plate out and find it's too heavily applied, just clean the part and repeat until some of the blue is used up. For blue I use Diamant Tuschierpaste from Germany. For cleaning the parts and the plate I use Scott blue workshop towel and brake cleaner in a pump bottle.

First thing I can tell you from your pics is that your scraper is not nearly sharp enough. The scrapes are thin and long but not deep, they are skating on the surface. Next thing is that you're over-scraping each pass. However wide your scrape is, the next one must be at least that far away from the previous. From where you are at now, you want scrapes about 5mm wide and 10-12mm long with a minimum of 5mm between each one and a bit more won't hurt. go 45 degrees one way then 45 degrees the other and scrap in diagonal rows. Leave a gap between each row of at least 10mm for the above sized scrapes. If you do that and get your scraper good and sharp you'll see a good checker pattern come out right away.

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

I started with you tube and have since been lucky enough to get some coaching from Pete, but am still very new to this. I still suffer the problems that you seem to and find the following to be the main causes;

I am constantly surprised at how much difference a freshly sharpened blade makes. Try touching it up on a diamond lapping disk every few passes, even for carbide. I find it makes a huge difference. Your blade geometry sounds correct.

Rolling out in one area and then transferring to another was the single biggest thing that helped me. As for the roller, I'd been struggling with a cheepy ebay roller until I finally went to the art shop in town and spent £7 on a descent one. That made a big difference too. I actually bought two, a 2" and 4".

When I have the blue on the plate thin enough I find it dries out quite quickly. Im now wiping it clean and starting again much more often than I did initially. I find i need to do this to both plates, not just the one I'm printing from for best results. I use the Stuart's. I've left the top off the tube a few times and some of the oil has separated out so I'm going to buy a new tube.

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Will you accept a suggestion from one with very little experience of scraping, but some background in Ergonomics ?

Try standing on a box

No, I’m not being flippant … If you are already noticing the difficulty then it is pretty significant.

With any work like this, adopting the right posture can make a big difference.

MichaelG.

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Edited By Michael Gilligan on 30/09/2022 07:44:30

I concur with Pete & Mark re blueing and yes my roller was about £7. I can’t stress how much easier the Charbonnel is to use.. sharpening at the 5 degrees is correct. I built a lapfollowing what Matt Look of Look Creations did. the diamond disks do a great job and I have since found the machine great for roughing up carbide inserts.

As scraping is so physical it’s vital imho to get the ergonomics right especially on a big project like yours and a stable workbench means your effort is going into the work and not wobbling the bench around. I found reducing the stroke length hard to do at first but it improved with practise and once I was a bit fitter and able to control the scraper. I am working on a reciprocating saw based power scraper which is showing some early promise.

I have an image of a sheet that Richard King uses in his trading that I screen shotted off one of Kieth Ruckers vids which I’ll put in my album.

The sharp edge needed isn't the angle of the cutting edge, it's the lack of any flat on the edge whatsoever. If you can see the edge, it isn't sharp. My test, after lapping a blade is to gently push it along a thumbnail. It should remove a scraping off the top of the nail rather than sliding along it.

A Workmate can be useful when hand scraping because it's lower than the bench and you can stand on the step of it when the work is still too tall. The work needs to end up close to waist height.

You should find that the blue on the surface plate gets thinner as you go along. Don't add more blue each time, just roll it out to make sure it's even. As the work gets closer to flat, the thinner blue comes into its own.

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.

The blueing looks ok now, but I would say there are relatively large areas not making contact as seen on your second image. It may be helpful to go around the edge of those areas with a marker pen, This will help to visualise them and it’s easy to avoid them on the next scrape. I can also see lines of almost continuous blue along some of the edges also similar lines of non contact near the edges, that suggests that scraping is not being started at the edge. This is to be expected as this is difficult to do and unnecessary as It’s far easier to turn the work and scrape off the edge.

As Pete has suggested you need to shorten your stroke and you should scrape in a regular pattern at 45 degrees. I would do this all over the piece omitting strokes in those marker penned low areas. I would then repeat in the other direction without blueing in between. I trust that you are checking for hingeing and that the surface is flat rather than convex or concave as it is easy to produce a nice looking surface that isn’t flat.

Definitely the result of over-scraping. The good thing is that you have a decent spread of blue across the length . So long as it's hinging nicely you're not far from done. As Tony says, scrape only the blue but not all of the blue. Leave9what you would consider to be) large gaps between scrapes and watch the pattern come in as if by magic.

It certainly sounds like your bench is far too high for comfort. Mine are 900mm off the floor and they could do with being lower. I am just building a lower height bench just for the purpose.

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.

Make another scraper blade with a smaller radius. This'll make it easier and more accurate to do small cuts when trying to even out the coverage in the later passes.

If you are finding that the print pattern moves about every time you scrape, the only thing that can cause that is the difference in height between the last blue pattern and the changed blue pattern is the depth of one scrape or less. If you think about it, this is a good place to be but it does mean that 1. your blue is very thin and 2. your scrapes are very shallow.

You need to increase the depth of your scrapes so that this stops happening. Once you do that your pattern will develop and you'll be able to use slightly heavier blue without it smearing.

This is also a time where having a flat stone can help a lot.

Has anyone got contact details for H R Lamb? Can't seem to find anything apart from a Facebook contact, which I!

don't do.

Andrew.

Has anyone got contact details for H R Lamb? Can't seem to find anything apart from a Facebook contact, which I don't do.

Andrew.

Edited By Andrew Tinsley on 02/10/2022 11:43:19

https://www.lambco-machinery.com/contact