Here is a list of all the postings gerry madden has made in our forums. Click on a thread name to jump to the thread.
|Thread: guideway surfaces regrind|
I probably couldn't afford new ones but I would be interested to know who might sell such things. Do you have any names old mart ?
Tony I think you were right. I did some flatness checks with a micron DI on a surface plate and although the guides were surprisingly accurately ground it was quite obvious a 5um cut would leave some areas not cleaned up. This was the last thing I wanted. I therefore used the corners of a small V-block and some carbide papers to clean up the surfaces.
I didn't manage to remove the brinells completely (which I measured to be about 5um deep) but removed enough metal to take away the rims around the craters, and the corrosion pitting and staining. This should make the things smoother.
As I need to make new ball-spacer bars, I'll produce the new ones with the ball spacing slightly different to the originals. This will ensure that all the balls don't fall into what remains of ruts at the same time, hopefully further improving the smoothness of travel.
Thanks all for your inputs.
|Thread: Digital readings|
Yep all correct !
|Thread: Optimum products?|
Ian B's comment above is correct but I would add that how/where that metal is placed is equally important. Good machine manufacturers should have the benefit FEA these days and should be able look at the structural stiffness of their designs and identify deflection 'hotspots'. This should allow them to move the metal to where its most effective and create a more efficient structure for no extra money.
More and more machines come with geometric inspection documents for flatness, straightness etc. We like this don't we ?!" It really wouldn't be a significant jump for the makers to put a mandrill in the spindle and do a two or three load~deflection checks too. In fact, they wouldn't need to do this to every machine they assemble. Its not going to change unless the structure changes. So a measurement of the prototype would be fine.
Apologies, were we talking only about bench drills ? The original thread was about Optimum products in general which includes mills lathes etc
...."negligible" I'm not sure what that is either Michael !
Perhaps if we all started measuring these things we could begin to sort out the sheep from the goats. Perhaps Ketan, a dedicated and progressive supplier if ever there was one, can start the ball rolling on his product range ?
Lee, 'like a twig in the wind' ... It would be good if we could quantify such important things in a better way. Is there any chance you could slip a spring balance onto the the end of the spindle of your optimum and measure its load-deflection relative to the table in the X and Y directions ?
|Thread: guideway surfaces regrind|
Thanks all for your comments.
Michael, your link was an interesting one - how do you find these things so quickly ?! Anyhow I've sent them a mail and asked for a quote. I think it will be expensive, but as you say its a baseline.
Tony - As I thought about it more last night I concluded that the best way might be to drop the bars into V-blocks and skim each flank using a surface grinder. (The side of the wheel should clear the other flank due to the undercut at the root.) Assuming the guides are already precision machined, most of the error 'could' be in the heights of the V-blocks so some shimming might be required here to get the guide perfectly parallel with the table. I'm by no means an expert in such a field so I would be very interested in your thoughts as to why 0.005mm would be a challenge.
Lapping proposers - yes this went through my mind too. I was worried by two things. Firstly straightness is important. Unless the lap is equally straight, as long and rigid as the guideway itself, would I be at risk of producing small undulations along its length? My second concern was to do with the width of the surface. Its only about 5mm wide so I was thinking the lap would be a little unstable and i would probably end up converting the flat into a camber. Have I got the wrong idea here ? Sorry Blowlamp - I have just re-read your post and I see you are proposing a 90 deg block, presumably to do both flanks at the same time. Yes this solves my stability concern.
Ian P - unfortunately the guides are dowelled and bolted to flat surfaces so it wouldn't be easy to allow for a smaller or larger ball without a lot of argy bargy.
My microscope X-Y table guideways might need a regrind. They have a little wear but it's the brinelling and corrosion pitting that's the real problem as this affects the smoothness of operation.
I think the regrind would need to be a precision job with no more than say 5um taken off each of the surfaces of the 45 deg. flanks. At the same time I cannot risk having any part of the 250mm length of the guide not cleaned up or that might introduce some other problems.
Do you think this is a feasible operation ?
If so does anyone happen to know anyone within say 50 miles of Milton Keynes that might be capable of this ?
The reason I need to keep cut depth to a max of 5um is because I have to compensate for the machining with some oversize balls to avoid introducing play into the system. I think the largest oversize 1/2inch balls are about +10um.
Your thoughts are welcome.
|Thread: Baty gauge repair|
Just so happens John I did one last week. If I remember mine only had three screws and I could get away with removing two for dismantling. However when in came to reassembly I took out the third one too as as it made it easier to get the dial and everything else in the right place with an even compression.
|Thread: Bleeding hydraulics|
Hydraulic systems in wind energy equipment are also 'self bleeding' You "just run them" and the air comes out I was told.
If the whitening is calcium carbonate and its heated to 'cherry red' it will turn into calcium oxide. Isn't this a bit caustic to touch ?
|Thread: OMT microscope|
Hi All. My restoration project of the OMT microscope is progressing but I have just seen that another one has come up for sale on an industrial auction site. If it happens to be anyone on here who's bidding for it, and you are also planning to carry out a restoration, I would just like to give you some advice.
DONT remove all the paint by grit (bead) blasting. This unfortunately removes the tons of filler that has been applied by the bucket load to the castings. Just make isolated repairs to the paint where its chipped or flaking, otherwise look forward to a lifetime of filling sanding and painting, filling sanding painting etc
DONT use Halfrauds spongy grit pads. They constantly shed grit which keeps reappearing from nowhere when you are on to the fine stuff. It creates big scratches just as you thought you were making progress.
DONT use Halfrauds knifing filler. It starts hardening very quickly so you only get a chance to spread the stuff once or twice before it becomes unworkable. However, even in that short space of time, it will soften up the undercoat that you applied earlier in the day.
DONT bother with Halfrauds 'filler and undercoat'. Its about as much use as cotton buds to an amputee due roughness of the castings.
'Body work' has never been my thing really and I probably don't have the dedication that many others would have to achieve a pristine paint finish. But at least when Im done the paint wont be chipped, flaking and be badly discoloured in places. The final reassembly will be a total pleasure though and I am sure of that.
|Thread: Paint and painting specialists question|
Thanks for all your efforts and advice chaps. I have some acetone on order for other things so will try that. If not I'll probably use new brushes as I appear to have accumulated quite a few in my brush box.
No one commented on the filler for the casting surface. I'll try something from Halfrauds if the popular products are ok to use directly on bead-blasted iron surfaces.
I have an umpteen tin of Fosroc Galvafroid paint that's in good condition so Im using it on some castings in the unseen areas. All is fine except for cleaning the brush afterwards. The tin says 'use Fosroc thinners'. Ive tried white sprit, turps and modern Hammerite thinners. The latter has no effect. The turps and white sprit don't really dissolve the paint, instead they turn it into rubbery lumps which have to be brushed out of the brush.
Does any one know what might be a proper solvent for this paint or an equivalent to the Fosroc thinner ?
My castings have been bead-blasted so all the old surface filler has been removed. I now have to refill and smoothen them. What would be a good filler for this job please ?
|Thread: microscope refurbishment|
Just a quick one if I may. A number of the visible brass parts on the microscope, including the nameplate, are plated with a steely coloured material obviously to match the genuine steel parts. The plating is not too hard as its worn away in many places from just hand rubbing. Would I be correct in assuming the plating will be nickel ?
For those that are interested, Im still stripping the machine down, which is actually a pleasure. There are no chewed up screwheads, nothing overtightened or with mangled threads and a few surprises like this part:
I didn't expect to find this iris in the backlighting tube. The lighting unit already has a rheostat in its circuit so perhaps the purpose of the iris is to allow the colour of the light to be maintained even when you don't want much intensity. I don't know, I'm just guessing.
I've not yet attempted 'storing' of the rotary table or the micrometer heads. When I do I'll let you know what happens.
|Thread: Mystery Inspection Item|
Hi Martin, may I ask who was running this auction ? I keep a list of auction sites for stuff like this but I appeared to have missed this on ! I hate the thought of 'gems' going to a bad homes where they wont be appreciated
|Thread: Cleaning emergency !|
Thanks all for your thoughts and suggestions. I have tried a few more concoctions without even a hint of success so I'm not hopeful, especially after reading about plasticiser migration !
Looks like it might have to be a new floor or a large carpet. Look out for my next post where I ask for advice on how to break the bad news
Hi fonts-of-all-knowledge, I have a bit of challenge. I placed some new tyres directly on the floor of my campervan a couple of weeks ago. When I removed them recently, to the other halves consternation they had left brown rings. I said "don't worry dear, they'll be a piece of cake to remove" …. and I genuinely believed myself.
I'm packing it today and was given strict orders to remove the rings first. To say its not going well would be an understatement. In fact they aren't going at all !!! I've tried acetone, white spirit, bleach, toilet cleaner, all with and without scotchbrite pads. There is no change.
The fact that mild abrasion wont shift them suggests the discolouration in the material (which must be a kind of vinyl) rather than on its surface.
From my school days I recall the chemistry teacher talking about oxidising agents as stain-killers. Is this the secret ?
Any thoughts chaps as to what I can try next ?
|Thread: microscope refurbishment|
I'm in the process of refurbishing a 1940s OMT toolmakers microscope. Its a lovely machine and deserves to be brought back to life. It has no significant damage but cosmetically has deteriorated a lot in some areas and I could do with some thoughts and guidance on a couple of things.
The micrometer heads have unsightly patches corrosion in the knurling. I could remove the rust with a soak in citric acid but I'm worried it might damage, discolour or lift the plating. To be honest I'm not actually sure what the plating is. Is it an unpolished chrome ? Perhaps there is a better/safer way to improve the appearance of the heads ?
The rotary table is very dark and discoloured and has some areas pitting but this isn't too deep. To clean it up it could be very lightly skimmed on a surface grinder. Its 300mm diameter. Alternatively I have seen some examples which have been scrapped. This looks impressive but I can imagine this would be quite challenging to do well, particularly as I'm not versed in the art. May be I could engine turn it instead ? The surface doesn't need to be super flat. Any thoughts on how to clean up this part ?
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