Hillbilly Scraping

[PeterT]

@Mcgyver cover your eyes & don't judge me! Haha. I'm back on my tool cutter grinder 'kit', making improvements, machining new parts. There are so many things that need attention its hard to know where to start, but I'm committed now. I'll document it better once I get some time, but thought I'd throw this out.

This dovetail block holds the indexing head on top & traverses laterally on a leadscrew which I've re-made. I'm drawing up new gib strips because the stock ones are so pathetic & what I assumed were contributing to the poor fit & jammy motion. But once I removed them altogether I could detect the block itself was rocking on the underlying (reasonably flat) casting surface. Turns out the 2 horizontal dovetail surfaces, which should be coplanar, are about 0.015" different elevation & the high one is tilted. For some reason they decided to fully harden this block, which I don't understand. Its like a piece of glass, a file wont touch it. Maybe it warped in the quench but even that seems doubtful. It has some other ugly machining & dimensional issues so I considered re-making it altogether. But that's a bit of work too. So I figured, try & salvage it.

I felt penned the face & just started going at it with my Dremel stone, trying for equal-ish material removal. Then dress the face with a diamond file & flat stone with oil, rinse & repeat. Its actually hard to do much damage with the Dremel because the material is so hard. About 15 cycles later its getting close dimensionally & the hill worked out. This thing only moves +/-10mm & gets parked into position, so as long as its reasonably smooth & doesn't buzz under power. Now the other surface looks ugly by comparison, but I'll deal with that later. Hopefully the gib retrofit will helps things a bit more. The battle continues.

So this 'Dremel Scraping' could be a big thing. I'm thinking... YouTube videos, international classes, sponsorhip, books, podcasts, my own line of stones, T-shirts, special swag.... HaHa
Sorry I'm too busy to take orders on your lathe bed until I hire some staff.

 

[6.5 Fan]

Looks good. Get some good video footage and you will be a U-tube star.

 

[Susquatch]

So this 'Dremel Scraping' could be a big thing. I'm thinking... YouTube videos, international classes, sponsorhip, books, podcasts, my own line of stones, T-shirts, special swag.... HaHa
Sorry I'm too busy to take orders on your lathe bed until I hire some staff.

You can go broke much better and much faster farming if you ask me. If you have any left, put me on your list for an XXL T-shirt at the liquidation sale.

 

[Bandit]

Buy a t-shirt first and delay the going belly up a bit longer. Trying to figure out the next "toaster" that every one will want is the hard thing.
I am not sure around here about going broke farming, some seem to be doing well even with the lack of rain the last number of years, but as I don't know the ins and outs of everyone in the area, really hard to say. Though it is always the same old, a wrong move, bad timing, or no timing, trying to buy land on credit, new equipment prices, and so on, it's all known to them that know. I got out of the small farming when I left B.C. Couldn't see how to keep it going without a regular job to support it. Was to small for the land that I could really farm on where I was. Rock piles and no water.
Strange thing is, many of the small town/ community's have a golf course around here.

 

[Bandit]

That looks like an interesting job there @PeterT. The point of the dove tail could be interesting to deal with, and as you have said the mating parts surface is out too by a bit makes it all the more interesting. But that may be the easy one to deal with if it's not very hard, a little lapping compound may tune it up fast.
I think @Susquatch may have "some stones" you could get a good deal on, " fresh from the field". Help a poor dirt farmer out!

 

[historicalarms]

The Dremel tool....commonly called the "OHHH $HIT" tool in the gunsmith trade. I couldn't be without one, on my fourth one now i think

 

[Susquatch]

The Dremel tool....commonly called the "OHHH $HIT" tool in the gunsmith trade. I couldn't be without one, on my fourth one now i think

Someplace I'm sure I've talked about my Dremel Stylus. God I miss that tool....... Some bean counter at Dremel prolly killed it cuz it made too much sense.

 

[Dabbler]

I couldn't be without one, on my fourth one now i think

@historicalarms you might try a Foredom tool. They are much more robust.

 

[buckbrush]

There are video’s on YOUTUBE of machinists power scraping machine tool ways with angle grinders. (In Russia I believe) There is always more than one way to skin a cat.

 

[Susquatch]

There is always more than one way to skin a cat.

There is also no shortage of idiots out there. I'm no expert at scraping, but it seems to me that using a power tool like that is just a faster way to ruin a machine. I wonder what @Mcgyver would say about it.

 

[buckbrush]

Scraping teacher Richard King has stated he has used an angle grinder to rough in some large machines. I think he stated this on the ‘Practical Machinist’ machine tool rebuilding forum.

 

[Dabbler]

Richard is an advocate of the 'power scraping only' approach. He has paid lip service to hand scraping, but then belittles anyone doing it.

With care, using a very fine stone or a fine flap disk, a person can get 'close'. This could be valuable where the setup to using a milling machine is too difficult or large, or when the amount to be removed is very large (> 15 thou, for instance)

I have nothing against power scraping, but I think a variety of approaches and more tools in the mental toolbox makes for better results in optimal setups or time to complete.

To respond to @Susquatch - A person new to bluing and scraping is bound to make mistakes. With a hand scraping, the mistakes are minor. With a power scraper, they can be more serious. With an angle grinder, a very bad result is likely.

 

[Mcgyver]

There is also no shortage of idiots out there. I'm no expert at scraping, but it seems to me that using a power tool like that is just a faster way to ruin a machine. I wonder what @Mcgyver would say about it.

Mcgyver says ..... that and $0.50 will get you a cup of coffee. Or three dollars and fifty cents

IMO, correct evaluation of an approach depends on understanding the objective ...... which, in the case of precision machine tools, is get two mating bearing surfaces flat with the smallest possible deviation between highs and lows. From reading tribology books (its a charmed life I lead) its clear that the ultimate plain bearing surface is a perfectly smooth plane. Some advocate hollows for oil, however I've not heard a good engineering/science case for this and suspect its a bit "because me pappy did so". How could oil come out of these pockets? It'd leave a vacuum. There is no controlled experiment I've seen that supports this, and there only seems to lore. Not that its BS, maybe its correct .... I just have some doubts based upon what tribology science has to say. Two perfectly flat planes with oil in between would be a the best bearing surface.

Regardless, you need enough of the area (ideally all of it) with the difference between the highs and lows so small that neither break through the oil. i.e. the thing wedge things ride on. With this ideal condition, there isn't wear because there is no metal on metal contact. This is clear on super precision plane bearings where you can take one that's 125 years old and its still perfect (linear or radial plain bearing its the same principles at work). There is no wear; e.g. watch makers lathes. (provided some bonehead didn't get a hold of it and run it without oil.

These highs and lows are called asperities, kind of like stalagmites and stalactites. When they are more pronounced than the oil layer is thick, you get metal on metal contact and hence wear.

With careful scraping you get to 1/2 tenths difference between high and low. Easily proven by taking a piece of cast iron and in short order a tenths indicator does not fluxuate. THIS is why there is good reason to be suspect of other techniques. You cannot easily control the DOC with a die grinder and can't possibly do so with an angle grinder. If you can't keep the variance to less than a tenth its producing an inferior fit compared to scraping. If it can, thats awesome and you've got a new way to skin the cat.

Its also why the best approach with hardened pieces is grind the hardened part (e.g. the lathe bed), then scrape the mating parts. Tons of quality machine tools were done this way (and casual observer, not seeing the scraping underside of the mating components, thinks its all ground)

There is also good enough is good enough. Something may not be as good as scraping but still be good enough .... making it a perfectly valid approach in that situation.

I had an accounting prof once who would joke that "you know, you can come home, pull shades and dim the lights, and make up a balance sheet that doesn't even balance!" What goes on the privacy of ones workshop is their business. However you can't scoff at or dismiss the logic and rational behind how things are "properly done". Sometimes there is a breakthrough like wheels on suitcases, but mostly there is good reason behind things being a certain way.

There are experienced scrapers who will admit to using a die grinder on hardened parts. I've wanted to experiment with this to see how well you could control the DOC based on the grit and rpm. Maybe it has potential. otoh I'm aware that a commercial reconditioner has to get things done quickly, get paid and thats the end of it.... how long it actually lasts is an unknown and likely will always be so because there are too many variables around use and lubrication. In businss you might expect a redone machine (be it a bus or a lathe) to last some fraction of what a new one does.....me otoh scraping for myself, I want the damn thing to be still perfect the last time I use it so maybe i'm fussier.

 

[Susquatch]

Scraping teacher Richard King has stated he has used an angle grinder to rough in some large machines

I believe that. "Roughing in" is a whole different thing than the purpose of scraping which is almost by definition not roughing in.

I cannot in my wildest dreams imagine roughing in by scraping. I can easily imagine roughing in with a power grinder.

I think perhaps it is a matter of definition and interpretive boundaries of the meaning of the term scraping. If the word scraping is used to encompass more than just the use of a scraper then one must ask, what is included and what isn't? Is using a mill part of scraping? Is using a grinder part of scraping? I suppose we can, and probably do, all have different definitions, but my own definition of scraping is the use of a scraping tool with a sharp flat edge that shaves a very thin layer (sub tenths) of the metal off in a scraping movement.

Therefore, in my mind, milling is the first step, grinding is the next, and scraping with a scraper is last.

That's not to say that careful grinding cannot accomplish the same end result as scraping. Many fine machines are built without using a scraper. But in my mind, that's still grinding, not scraping. Similarly, I believe it is possible to use a grinder to recondition a machine, but I think it becomes much harder to do. Not that scraping is all that easy! But my perception is that scraping is a better approach given that large precision grinders are not common or readily available.

@Dabbler - I think the word "power scraping" says it all. In my uneducated clueless opinion, it's a misnomer and the process of power scraping doesn't really exist. Unless of course a machine actually exists that can actually scrape with a blade instead of grind. I suppose that's possible but one has to wonder why and how that would be useful or advantageous.

Interesting discussion.

Edit - seems @Mcgyver posted seconds before I did. Thank God nothing I said conflicts with his much more experienced and knowledgeable thoughts on the matter. If anyone thinks they do, then please disregard mine.

 

[Mcgyver]

Many fine machines are built without using a scraper.

Can you name some? As I understand it, most ground the long geometry then scraping the mating parts to it. It was how SM did 12 or 13 years ago. You wouldn't know they were scraped because all you saw as the shiny ground bed ways. Even then they had three full scrapers scraping the in HS, TS and saddle for bearing and alignment. Its done because its very difficult to grind two mating parts with numerous angles and get them in perfect (to tenth) contact while also keeping things perfect to the spindle axis. Scaping lets you creep up on it and get it perfect.

I think the word "power scraping" says it all. In my uneducated clueless opinion, it's a misnomer and the process of power scraping doesn't really exist. Unless of course a machine actually exists that can actually scrape with a, blade instead of grind.

Sure it exists, scraping with a Biax (and there are others). I've two of them and used them all the time. I generally switch to hand scraping toward the end, it gives more control. Takes longer and maybe a commercial guy can do as a good a job with a Biax, who knows, but imo you do not have the same control for pointing at the end (taking of individual high spots).

btw you do start rough in when scraping. Early on you take heavier cuts, longer strokes and you're doing a criss cross hatch by zones (vs focusing on indivuals spots of blue)

 

[Susquatch]

Can you name some? As I understand it, most ground the long geometry then scraping the mating parts to it.

I guess, it all depends on your definition of "Fine Machine". My grizzly lathe is all I could ever want. It was made in Taiwan and was not scraped. But it isn't the finest machine ever made. Just plenty fine enough for me.

Sure it exists, scraping with a Biax (and there are others). I've two of them and used them all the time.

Learn something every day. Power scraping exists then.

But would you call power grinding power scraping?

 

[Mcgyver]

But would you call power grinding power scraping?

call me anything but don't call me late for dinner.

I guess, it all depends on your definition of "Fine Machine".

What I was getting at was you could look at about every top make of lathe and not see scraping. Only the ground bed is visible leading many to erroneously conclude that top lathes aren't scraped and/or grinding is more accurate. In reality they're two different techniques not competitors and there is a very good chance the matting surfaces you can't see were scraped. While the saddle and tailstock may have it worn away, you see it when you pull a headstock

 

[PeterT]

My grizzly lathe is all I could ever want. It was made in Taiwan and was not scraped.

Have you had your tailstock & carriage off to observe the vee & flat underside sliding surfaces? A milled or fly cut surface with no further work would be hit & miss to obtain any kind of decent fit. For sure there are offshore machines that skip this step, but AFAIK most every Taiwan machine has it to some degree. Not a great picture but underside of my tailstock. My late 90's era Taiwan carriage was already blued but for sure you could see corrections. (I'm not talking about lubrication frosting or whatever the proper term is.) Now 'scraping' on my machine is really pushing the limits of what is considered minimum effort. Once I get myself organized I'm going to hand scrape my TS base to kill 2 birds with one stone - better fit & reduce the over height from a couple thou to zero-ish.

Biax power scraper. If you ever see one at a garage sale GRAB IT

 

[Susquatch]

Have you had your tailstock & carriage off to observe the vee & flat underside sliding surfaces? A milled or fly cut surface with no further work would be hit & miss to obtain any kind of decent fit. For sure there are offshore machines that skip this step, but AFAIK most every Taiwan machine has it to some degree.

Boy, this whole thread has been a whole grocery store of humble pie....... I have not had the carriage off in years. I take the tailstock off regularly, but do not remember any signs of scraping. Nonetheless, I took it off just now.... Despite the small marks which suggest fly cutting or milling at some point in the early process, the main surface is clearly ground to a very fine polished finish. And then, plain as the nose on my ugly face, they have been scraped...... Insert giant humble pie here.

My ways are ground to a similar finish and induction hardened but show no sign of scraping. The only visible wear on my entire lathe is at the inboard junction of the removable gap block. Although you can see it, it is very small and totally inconsequential. I cannot measure any movement resulting from it with the metrology I have. And my fingernail doesn't know its there. Only my eyes see the small polish mark. It's the dark spot in the photo. The white spot is a reflection.



I have never removed the gap and never will. Any job that requires it will go elsewhere. I don't know how the setup is done at the factory or how the alignment and flatness was achieved. I would love to see that. Heck, I would even enjoy a YouTube video if there was a credible one out there! A plant tour would be an amazing experience.

Once I get myself organized I'm going to hand scrape my TS base to kill 2 birds with one stone - better fit & reduce the over height from a couple thou to zero-ish.

Mine was delivered at zero, or at least so close to zero that I cannot measure the deviation with my very best metrology. But even if it wasn't, it is somewhat adjustable and can accommodate a 1/2" drive torque wrench for small adjustments. Which I confess I am dubious of because the tailstock nut critically affects the over center position of the lock which affects the required torque. Nonetheless, my lathe doesn't really see any significant work. I purchased it new and I have done a few big jobs with it but still nothing like it would see in a job shop environment. On average, it might get used a few hours a week - maybe less. Therefore it has stayed more or less exactly as received for about 12 years.

I very much admire your determination to improve your tailstock alignment. I'll be watching that thread when you get around to it!

Biax power scraper. If you ever see one at a garage sale GRAB IT

I will. But it would be purchased solely to regift to another member at cost. Scraping, even under power, is way beyond the patience, steady hand, and passion possessed by this hairy old man.

 

[Bandit]

The closest I have come to scraping is a bearing or 2 that needed a slight "tune up". I looked at the tail stock of a crank grinder that had some wear on it one time, thought I would leave it be after blueing it and removing a few ugly burrs. Thought it was working fine,less then 0.001 taper in 24 in. A glazed stone could do a few 0.0001 in 2in. and I could make it a lot worse really fast.
The tail stock and bed can get wear fairly fast as every crank that is a different length needs the tail stock to be moved, while a good wipe down and lots of oil do help, it is grinding grit and gets around!