Is a hand scraper pulled or pushed?

I have got scrapers, many collected from auctions and both flat with a slight curve on the end, triangular with relief between the corners and curved again with relief between the edges.

I never was able to get them to do anything.

Reading old ME's I cam across an article about some pne scraping a flat surface and said get an old file, grind the teeth off the end, slightly curve then, then bang the tang into a wooden chair leg so it would fit over your shoulder.

There are endless articles on the web about scraping, but so far I have not come across one that tells you that you PUSH the scraper, or PULL it!

This is only for flat surfaces, such as fettling a lathe saddle, for bearings then you use the triangular and curved ones and PUSH them.

What do the experts say? It could be that my scrapers are too small, blade about 8" long, handle similar, but nowhere near the 24" chair leg.

I have only seen it done, not done it, but I am sure the answer is push, like wood chisel.

have you tried Youtube?

I think it largely depends where in the world you come from.

My former machine tool fitter colleagues based in Halifax (UK) all used the push method. I have seen videos of German / Swiss fitters using a different type of scraper designed to be pulled. I have not seen this technique used in the UK. My collegues were trained at the likes of Asquiths, Butlers, Churchill Redman, Stirks & Crawford Swift (when Halifax was awash with machine tool builders), though on a visit to Bridgeports in Leicester their fitters used the same technique. The patterns left by the two techniques are different - pushing while "rolling" the scraper gives a longer, curved mark, while German / Swiss machines show short, straight strokes.

Scrapers need to be sharp to do anything. I am by no means a scraping expert, but I "test" scrapers for sharpness by lightly scraping against my thumb nail (what remains of it - nibbler !). A sharp scraper takes a light shaving with no effort - a blunt one just skates off the surface. My former colleagues had a bench oil stone along side them when using a steel bladed scraper & regularly rubbed the flat side against the stone to maintain the edge. Carbide insert scrapers were usually hand ground on the face on a fine green grit wheel, though by rights they should be diamond lapped to a fine finish for best results. Power scraper (Biax) carbide inserts were taken to the Biax agent (who was conveniently local) for diamond lapping. The end face is ground with a slight curve across the width to a negative cutting angle from both sides to give two cutting edges.

Carbide scrapers were prefered for cast iron & steel scrapers (usually old flat files re-purposed) were prefered for steel. Three square (triangular) or curved blades were used for bore scraping - something done rarely for us, as we got very few plain bearings requiring scraping in.

I have a couple of different length commercial (probably Chinese) steel scrapers & find that they don't hold an edge long. I use the longest I can get in on the job in hand - more leverage with a long blade. I use a small three-square for deburring & have a 12" or so long holder + file handle I made up to hold a carbide blade. I have only seen Sandvik carbide scraper blades & they also used to make handles/holders for them in a variety of widths. Mine is about 25/30mm wide from memory. They are also expensive - £25 / £30 each for the inserts some 20 years ago.

You don't take much material off with a scraper - my colleagues used to reckon on 3 scrapes across a surface to take off a thousands of an inch. I am limp-wristed, scrat about & am probably nearer 5 scapes to the thou !

HTH

Nigel B.

Bob

on Youtube, if you search for 'lookcreations' you can watch Matt Look scraping no end of things including the ram on his Elliot shaper, beam straight edges and various parts of his Holbrook lathe whilst being renovated.

HTH

Dave

Scrapers are pushed but need to have a very sharp edge. As an apprentice I had to make my own, which I still have.

the largest scrapers would only be around 18" inches long overall and small one could be down to 8" inches.

They were used to get cast iron surfaces flat and bronze bearing halves to the correct size to fit crankshafts etc.

The test for sharpness was to hold the scaper against a thumbnail, if it slipped then it wasn't sharp enough.

Brian

There are push scrapers and pull scrapers. The majority will be push scrapers. Push scraping tends to remove more material. Pull scrapers should be easy to spot since they will hold the cutting tip vertically, but it's not a rule.

I spent a good proportion of lockdown pushing a couple of homemade ones; I'm certainly no expert, and had never really tried scraping before.


This was the setup I used for sharpening them on a 3000 grit diamond lap; They really do need to be sharp to cut without too much effort.

As I learned to my cost, the grade of carbide is quite important too; the smaller one worked well and held an edge OK, whereas the left hand one in the top photo is a carbide milling insert, which took an edge OK, but didn't hold it for long at all.
I later made a 3rd one using the same type of carbide blade as the right hand one, but cut in half and silver soldered across the end of a piece of stainless bar, to give a 25mm, rather than a 10mm cutting edge.

The rest of the album is HERE
Bill

p.s. Here's quite a good video of the basics

Edited By peak4 on 21/08/2020 22:06:21

Bill, use a 1500 grit disc at 400rpm or less. You'll get a great cutting edge. your 3000 grit disc is too fine and the 1500 will give a huge improvement IMO.

Cheers Pete, I was running about 350rpm from what I remember.
I'd used a 1500 grit to shape it originally and then swapped to the 3000 for a final finish and to touch up/re-hone the edge.
Genuine question, as I'm very much learning, but why are you suggesting a 1500 for the final finish?
I'd actually read elsewhere to lap even finer after 3000 with diamond paste to a mirror finish.

Cheers

Bill

Possibly preempting a reply from Pete, but I've always been told that the vertical edge needs to be slightly rough to 'bite', but the bottom face can/should be honed as fine as you can.

Rob

It's down to the amount you grind off. The 3000 grit in the photo is already done - I have a pile of them like that. The amount you'll blunt the edge by is more than the amount you'll be grinding off so you can't bring the edge back truly sharp. Also you're very sensitive to the angle you are grinding at - just like the novice HSS tool grinder who produces a beautiful facet but neglects the cutting edge.

Use the 1500 and when you grind the initial shape grind it square then do your sharpening at 2-5 degrees negative. That way your first dozen or so sharpens will be grinding a very thin land taking less time and using less diamonds. If you can, clean the wheel with a spritz of brake cleaner on a paper towel or rag.

Pete.

By the way - test your scraper on your thmb nail. If it slides it's not sharp, it should dig in on the edge very readily. Check the middle of the scraper edge then test one side of middle (where you barely use it). If the edge cuts more then the middle you're not sharp.

I self-taught and never knew what a sharp blade really was until I took some instruction.

There are a lot of videos on youtube about scraping. Stefan Gotteswinter has some good ones and there is an excellent one from the war period which is referenced somewhere on this forum (I think I posted the link at some point).

Personally, I've done some scraping, but the results are mixed. I've had some success in scraping in bearings, but properly flat surfaces still elude me, though I've been able to 'improve' my micro mill no end. (not saying much).

Iain

I think Nigel (mgnbuk) gives a very good summary of typical scraper use. I have seen YouTubes of 'pull' scrapers but they are a different (hooked-end) design.

I have a few scrapers - simple straight ones (10 inch?) which are Eclipse brand, triangular bearing scrapers, which are old but very good steel (and worth looking out for) and a longer Sandvik blade with a clip-on carbide insert (for which I can't find replacement inserts btw). I'm not very good at 'fine' surface scraping, probably because I don't have the patience to get really good results and I tend to be satisfied with "better" (rather than "perfect" ).

However, it may be worth mentioning (at the risk of being heretical) that I use my Eclipse scrapers quite regularly for things I probably shouldn't. For instance, having drilled and tapped a plate with multiple holes, it was very quick to make a few passes (at diagonals) over just the hole rims to take the burrs down. Not a perfect cosmetic finish perhaps but quicker than countersinking - and perfectly smooth to the touch. I also found rust 'lumps' under one of my 'shed' surface gauges recently. They were easily (& quickly) removed with a scraper and the surface remained flat - which wasn't checked by blueing - but simply by checking there was no rock with a DTI installed - which is all I required.

You can remove very small amounts of metal with a scraper and in very specific areas - which is not always possible by other means. I think this is worth mentioning, as I think many folk tend to think of scrapers as just being used for surfacing complete areas to very fine limits - but they do have simpler uses too.

Regards,

IanT

Edited By IanT on 22/08/2020 11:06:21

Cheers Pete, that inclined table was actually set at about 4° negative, and I know that the lap shown was past its best. I replaced it shortly afterwards. By coincidence with your comment, I also picked up a gallon of brake cleaner last week, amongst other reasons, to clean the lap(s) before storage, as I've no immediate plans for another scraping project. I've just about got my hands clean from this one.

The thicker 4mm x 25mm insert scraper, I did pre-shape square on the Clarkson and just touched up the edges on the lap, as you describe, though for the little 10mm one, which is only 2mm thick, I just used the lap.
I must find a more appropriate grade of carbide for the larger one before any future job; The proper Sandvik blades are labelled H10 (I can't remember offhand what this one was, but certainly not correct)

The smaller one, and the later 25mm wide silver soldered one used THESE scraper blades if it's of any interest; they seemed to both take, and hold, an edge quite well.

Thanks for the advice.

Bill

Thank you Bill I just bought a pack of those. I'm going to try them out as scrapers for small dovetails, where the larger blades are too cumbersome.

Pete.

No problem, but also no idea what grade of carbide they are, as there's no writing on the box.
I was using them for the dovetails myself.
As you saw, I was screwing them on lengthways, but for a wide one I used ½ a one which silver soldered OK to the stainless shaft with Tenacity No.5

What are you using for bigger lumps of carbide, or did you shell out for the Sandvik scraper inserts?

Bill

Edited By peak4 on 22/08/2020 21:07:28

I've used all sorts of things, some old flat carbide facemill tips that someone had a bunch of, some carbide slips, some carbide that a guy I know got made quite cheaply. They all work to varying degrees but nothing I've used so far had compared to the Sandvik or Biax tips for holding an edge.

I got lucky a while ago and bought a box of 5 tips from eBay America quite cheaply. Those have all gone now, mostly passed on to other budding scrapers so I've just bought another box of 5 which have worked out about £20 each.

THIS PAGE gives a useful comparison of grades.
From what I've seen of web photos of the Sandvik scraper inserts, they are labelled as H10, though you will of course know better than me, as you have some.
It seems like other manufacturers have equivalents, so it's down to finding something equivalent in the right shape.

Bill

As is usual, after posting this, sat down with an ME off the pile to read and an article about scraping, 15 Jan 1988 issue 3817.

Their scraper, made from an old flat file, the end has the teeth removed and then slightly hollow ground. Use the periphery of the grindstone to put a slight hollow right at the very cutting end of the file. Grind the end with a slight curve and finally stone on an oilstone.

In use the description is "The tool is drawn steadily across the work with slight pressure applied to enable the cutting edge to make the cut.". My immediate reaction was 'ah, it is pulled'.

In use the scraper seems to be held at about 45 degrees to the work, so the 90 degree end face is at the same angle to the work if pulled or pushed.

Must say that pulling makes more sense if you have a handle the length of a chair leg, 20" or so, plus the length of the old file, 12" or so. Internal scrapers can only be pushed but they are hollow ground and the trailing edge touching sets the cutting angle.

Another problem solved! Thanks to everyone who read and contributed.