Surface Grinder refurb

[Tony RayParticipant @tonyray65007]

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

[Pete RimmerParticipant @peterimmer30576]

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.

[Steve355Participant @steve355]

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

[Mark Davison 1Participant @markdavison1]

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.

[Michael GilliganParticipant @michaelgilligan61133]

Posted by Steve355 on 29/09/2022 22:34:13:

[…]

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.

[…]

.

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.

.

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

[Tony RayParticipant @tonyray65007]

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.

[Mark RandParticipant @markrand96270]

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.

[Steve355Participant @steve355]

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.

[Tony RayParticipant @tonyray65007]

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.

[Pete RimmerParticipant @peterimmer30576]

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.

[Steve355Participant @steve355]

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.

[Mark RandParticipant @markrand96270]

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.

[Pete RimmerParticipant @peterimmer30576]

Posted by Steve355 on 01/10/2022 07:31:55:

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.

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.

[Andrew TinsleyParticipant @andrewtinsley63637]

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.

[Andrew TinsleyParticipant @andrewtinsley63637]

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

[Pete RimmerParticipant @peterimmer30576]

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

[Andrew TinsleyParticipant @andrewtinsley63637]

Thanks Pete,

Just what I needed.

Andrew.

[Andrew TinsleyParticipant @andrewtinsley63637]

Double post again!

Edited By Andrew Tinsley on 02/10/2022 12:41:26

[Steve355Participant @steve355]

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.

[Tony RayParticipant @tonyray65007]

I think your scraping is improving, it looks a more consistent on your last image. I hope I didn’t send you down that power scraper rabbit hole; I have been working on mine on and off for months, it’s Makita based as I can get parts for it relatively cheaply. The main issue is balance as the scraping gubbins is heavier that the saw blade & clamp. I have increased the counter weight but need to do more testing. It can produce a nice even pattern so I think it will at least  do for initial roughing. There is an alternative design on the Tube base on what looks like a windscreen wiper motor, the design is good but it’s more of a scratch build but I am tempted.

I think your lack of depth of scraping at least in part due to the sharpness of your blade. You also said you are having trouble aiming the blade; join the club, some put a sharpie mark down the centreline of the blade to help. I found it took me a few months until I started to get the hang of it, unlike a chisel where you have a wide contact, with the radius on the blade it’s tricky to get that centre on the desired spot. I would suggest slowing down, place the blade on the spot then look to see where you have placed the blade before making the scrape The difference between a hit and a miss is quite small.

Out of interest where are you based?

Edited By Tony Ray on 03/10/2022 00:42:55

[Kiwi BlokeParticipant @kiwibloke62605]

One of the advantages of using hand/fingers to apply the oil-based blue is that you can sense the film thickness by the quality of the drag felt by the fingers. I'd imagine that, with a bit of practice, you could get a pretty even, thin film with your eyes shut. I've no experience of rollers or water-based media, so things might be easier, or at least different with them.

I assume you've come across the idea of pushing the scraper with your body, the handle having a suitably-shaped 'mushroom' load-spreading end. Most folk aren't strong enough to push hard enough, for long enough, with arms alone, on a job like your column's front face. For roughing, at least, where you need to hog off quite a bit of material, you can afford to, indeed need to, push downwards and forwards hard, creating deep furrows. It's hard work! This not only removes material, getting you towards the desired level, but it also breaks up the area of 'too high' material into smaller bits, which are than easier to scrape off.

Take heart – aiming is initially difficult, but it's a skill, and acquiring skills requires practice.

Sharpening has been mentioned. Different people have advocated different tip shapes. This suggests it's not critical, and, in any case, you will alter the contact geometry by the angle of attack you choose. The easiest way, I believe, is to hold the scraper vertically over the sharpening medium. Try to hold the handle's extreme end still between finger and thumb, fixed in space, but allow it to pivot, and then swing the blade sideways across the medium, from side to side (ie plane of swing is the plane of the blade). This will automagically produce a tip radius that is reasonably 'correct' for the handle length (but don't get too hung up on geometry). Carbide tips are wonderful, but the edge readily breaks down (in use and also when sharpening) into almost microscopic roughness, which causes scratches on the workpiece. A fine diamond plate works well, but not one of the 'perforated' ones – these can chip the edge. Check the edge with a 10X loupe.

Scraping an entire machine is a formidable task. As I get older, I'm increasingly aware that time is running out more quickly than is money (thanks to pensions…). My arthritic hands and wrists already limit some activities, and are only going to get worse, and I have a number of machines waiting to be restored. To hell with the expense – I feel a Biax coming on!

[Steve355Participant @steve355]

Posted by Tony Ray on 03/10/2022 00:39:48:

I think your scraping is improving, it looks a more consistent on your last image. I hope I didn’t send you down that power scraper rabbit hole; I have been working on mine on and off for months, it’s Makita based as I can get parts for it relatively cheaply. The main issue is balance as the scraping gubbins is heavier that the saw blade & clamp. I have increased the counter weight but need to do more testing. It can produce a nice even pattern so I think it will at least do for initial roughing. There is an alternative design on the Tube base on what looks like a windscreen wiper motor, the design is good but it’s more of a scratch build but I am tempted.

I think your lack of depth of scraping at least in part due to the sharpness of your blade. You also said you are having trouble aiming the blade; join the club, some put a sharpie mark down the centreline of the blade to help. I found it took me a few months until I started to get the hang of it, unlike a chisel where you have a wide contact, with the radius on the blade it’s tricky to get that centre on the desired spot. I would suggest slowing down, place the blade on the spot then look to see where you have placed the blade before making the scrape The difference between a hit and a miss is quite small.

Out of interest where are you based?

Edited By Tony Ray on 03/10/2022 00:42:55

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

[peak4Participant @peak4]

Posted by Tony Ray on 03/10/2022 00:39:48:

I think your scraping is improving, it looks a more consistent on your last image. I hope I didn’t send you down that power scraper rabbit hole; I have been working on mine on and off for months, it’s Makita based as I can get parts for it relatively cheaply. The main issue is balance as the scraping gubbins is heavier that the saw blade & clamp. I have increased the counter weight but need to do more testing. It can produce a nice even pattern so I think it will at least do for initial roughing. There is an alternative design on the Tube base on what looks like a windscreen wiper motor, the design is good but it’s more of a scratch build but I am tempted.

………………..

Edited By Tony Ray on 03/10/2022 00:42:55

That's interesting, I picked up a Makita one myself, specially for that attempt at a conversion, but haven't started yet, as I was struggling to come up with an easy way to vary the stroke length due to the internal design.
How did you address that?

Bill

[Tony RayParticipant @tonyray65007]

Bill,

Mine's a Makita JR3050. I machined off the counterweight on the large bevel gear (it was pretty hard definitely a job for carbide) and machined a deeper counterweight incorporating a sliding dovetail which carries the crankpin. To accomodate the increase in height I have added some spacers between the two halves of the aluminium castings. The dovetail is locked with a couple of grub screws. I have to remove the a cover to adjust it. As designed radial play in the reciprocating shaft is limited by a crude bent metal U shape and the amount of play was unacceptable so I machined a sturdier block and fitted bronze wear strips and surface ground the 'ears' on the reciprocating shaft. I'll put some pics in my album this eve when I get home. As I said balance is the main issue meaning that it vibrates excessively. I intend to measure this and empirically add weight to the recip. shaft to see if it is reduced – if it is it means the counterweight mass is too high and I can reduce it, if not it means the counterweight is insufficient so I'll drill out some areas and fill the voids with lead. I'm using a PWM speed controller and the stroke length is limited to 20mm. I'm using the saw upside down compared to it normal use as the shape is better and I am working on a Biax like bulge to fit on the flat-ish area. I have ditch the Makita handle and intend to 3D print a shorter cover which will hold the speed controller. I am working on other projects so it hasn't had a lot of attention recently.

[peak4Participant @peak4]

Tony, Thanks, I'll not hi-jack Steve's thread any further.
Bill

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