Experience / Tips on scraping Harder materials

I started working on a project (lathe) which involves scraping the ways. However soft in the end surfaces they are rather hard in the actual "runways", a bit set-back when discovered but need to push through anyway due to the present wear.
For fun I attached a 3d representation of the ways. Deviations are magnified 1000x

Had I the possibility to have it ground - I would have.

It is scrapable, sort of. But for sure - any harder and it would be a no-go. Material removal rate is Slow and blades dull quickly, covering 50"x2" one pass calls for a touch up on the 1500 or 3000 grit diamond disc. Dull blades don´t need to bother.

So far I´ve concluded best concept to be Biax blades with +5° positive angle 75% speed and approx 10-12 mm stroke length.

Any of you guys who dealt with harder material, do you have any tips on best approach to negotiate this kind of challenge?

We've rebuilt several machine with hard ways by spot grinding with a disk grinder and die grinder with a cutoff wheel (use side of wheel) it's not ideal but it works. If the scraping is getting you there I would stick with it, also use alcohol as a coolant on the surface you are scraping.

Thanks,

I´ll get some cut off discs for the die grinder and try, at least for the bulk.

I tried a bit with angle grinder (115mm / 4,5" disc) while removing the "bulk volume" but I found it a bit.. Let´s say it requires a high degree of control.

I'd use a handheld grinder to rough-in with then finish with the biax

I'm no Pro so ......

Push it down the biax real hard
Perhaps a bit shorter on the stroke You have to keep it cutting

Peter

Lumber jack emailed me about this and I told him using a BIAX for this is not recommended and he needed to grind the bed or lap it. I completely forgot about the hand grinder method.
here s a link to a thread we did a few years ago. If You look on You Tube, PM member Ironsmith (something like that) is Chris Johnson who is another pro on here and on You Tube his name is CG Precis.ion shows grinding a hard way. One of the English guys did a Hardinge bed that way too. I have used that way too.... Demon over in UK has done a bang up job doing it too

http://www.practicalmachinist.com/v...ardened-bed-ways-video-your-amuzement-299334/

Turret slide way and the grinder disc I used
Slide was .020 taper got it down to. 002 ish in a afternoon

Downwash77 said:

We've rebuilt several machine with hard ways by spot grinding with a disk grinder and die grinder with a cutoff wheel (use side of wheel) it's not ideal but it works. If the scraping is getting you there I would stick with it, also use alcohol as a coolant on the surface you are scraping.

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Yeay' great advise...single malt works great, my fav is Macallan 12y or better. Nothing else, after a few you give a damn.

Or did you meant to pour it on the ways? for that i am not that certain .

I also heard that 60 grit round 3/4" die grinder is a good way to go as well. Go easy. and slow.

dee
;-D

Thanks guys for your input.

I´ll keep pushing through, this is really testing ones grit...

Richard, I´m sorry I didn´t see your reply. I´ll have another look in the mail and read it through. Been too long.

Now it´s late evening and time to apply some of that alcohol - either way

Cheers!

Keep in mind the grinding cuts may be to deep to scrape out if your not carefull.

A little update on the progress.

I´ve swapped to grinding until further on, minimum for roughing and semifinish. I´ll decide in a later stage if I try to add some refinement by scraping but right now I doubt that as the result is coming rather ok.

The rear flat way is done geometry wise, it´s flat and in location, was very careful as to grind as "straight down" as possible and ended up with a minor tilt which was basically within stoning territory. It looks a bit crappy so I might return to it for "cosmetics".

I have now moved on to the outer surface of the front V-way. Picture shows one of the first passes, as you can see I segmented the surface in three "rows" top/middle/and bottom with 90° shift, later I went to only two -top and bottom half. This is just to reduce risk of loosing control of the surface. Remember I´m doing this in my home workshop on my spare time, On the job one would need to push the bulk away faster. Maybe with a larger disc and higher speed.

The tool I´m using is a straight cut-off grinder with 3" disc.

Some key properties of the process as I´ve learned so far is:
RPM controls material removal rate.
Angle (disc-work piece) control depth of cut and size.
Motion - constant speed - no start or stop on the workpiece - and a swinging motion soft in / soft out.
Force - constant - no more than what can be maintained constant and controlled over the entire surface.

All-in-all pretty basic stuff and the handscraping basics really apply.
This is not "Angle Grinding" but should be thought more of as precision grinding.
Note on rpm, too high rpm can be counter-productive as it tends to cause the disc to jump when touching the surface, to mitigate this one need more force which is difficult to maintain over the full pass and even more so - several passes.

The disc I´ve been using so far has no marking on it... But looks coarse and comparing visually against know ones would indicate it´s likely a 24 grit disc. I found and ordered 60 grit 2mm thick (1/12"?) that I hope will improve finish.
Finish is actually more a concern in terms that it leaves marks which are similar to scraping chatter marks which are not appreciated. Top of high spots do get stoned and I will try use some plastic polish brush wheel just to try and knock of / soften as much burrs as possible.
If the 60 grit wheel is a major improvement I´ll go over the rear flat way just for touch up as even I would like a nicer appearence, but it was learning curve there. I just didn´t have any similar hard cast material to practise on.

This is by no means any "teaching" but just a update and I´m sure I´ll discover more as the work progresses. I´ve taken some more videos, and I´ll try to get some better pics also esp after the 60 grit disc.

I suppose those little grind marks could be called oil pockets. I forgot several years ago , way before I ground the beds with a air angle grinder with those push and turn 2" dia. sanding disks. We used a electric belt sander on hardened bed ways of a Lucas Boring machine. Those ways were 8" wide by apprx. 12' long. 4 of them. I was thinking I wonder if you used one of the 1/2 wide air belt sander. So you could blend in the surface ground look. I forgot what those small ones are called now. All in All your attempt looks good...As you said cosmetically could look better. As long as what you have now is shallow, not abrasive to the saddle and tailstock. Plus the wipers can clean out the straight shallow flaking. Go for it! :-)

Lumberjack said:

A little update on the progress.


The disc I´ve been using so far has no marking on it... But looks coarse and comparing visually against know ones would indicate it´s likely a 24 grit disc. I found and ordered 60 grit 2mm thick (1/12"?) that I hope will improve finish.
Finish is actually more a concern in terms that it leaves marks which are similar to scraping chatter marks which are not appreciated. Top of high spots do get stoned and I will try use some plastic polish brush wheel just to try and knock of / soften as much burrs as possible.
If the 60 grit wheel is a major improvement I´ll go over the rear flat way just for touch up as even I would like a nicer appearence, but it was learning curve there. I just didn´t have any similar hard cast material to practise on.

This is by no means any "teaching" but just a update and I´m sure I´ll discover more as the work progresses. I´ve taken some more videos, and I´ll try to get some better pics also esp after the 60 grit disc.

View attachment 221092View attachment 221093

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Just my 100% unproven gut feeling but I would really really prefer small angled die grinder with roloc disks.
You can adjust the aggressiveness easily with grit size as these are available from 36 grit to 400 or even finer.

Or 5" 36 grit Cubitron disk if you need to remove large unconrolled asmounts of metal.

There has been some more votes for this set-up with Roloc / Kvick type discs.
I might need to get some and test out, good reason enough to buy a "die angle grinder", I have no doubt they will be handy to have around in general, both grinder and discs. Could of course test with a straight one.. Hmmm..
My thinking and feeling has been that the cutting really takes place along the edge hence this type of disc will wear out too fast, otoh they are not very expensive.
But I´d be more than happy to find there´s a better way, or combination!

Otherwise it´s been a slow week with to much other things going on. I did get the 60 grit discs and tried them, that was interesting. Norton Bluefire, I think I could just have sliced the whole bed into little cake pieces just by accident. By that I mean they CUT like a samurai.. I was bit surprised at first but my guess is those discs that came along with the grinder are some cheap shit that actually doesn´t cut very good however in this particular case - beneficial. I might try some more but they moved material Fast.

Heres the video of Chris doing his thing with an air grinder, very nice work imo and hopefully should give you some ideas.

Heres a link to some bits and bobs ive done in the hard stuff. Please ignore posts 26 and 37 as they were just for jokes, although im not sure everyone realised att .

Thanks Demon,

I´ve watched your videos several times.

How would you estimate your end result? surface depth etc.

What kind of disc were you using more specifically? It looks like some thin stiff disc 1,5-2"?


I tried your technique but for me it works better almost the opposite direction, a sweeiping motion towards me touch down on and leaving the bed in constant moving / speed.

All in all it takes some time, patience and grit but the result is actaully better than I expected. Surface depth is reasonable for the intened use, surface is basically within 0,0004.

In the detailed picture is now what I call The Matti Trench ( As the Marianer Trench) as I got hold of some roloc discs on my way home today ;-)
For sure they do remove material and they are nice to work with in general, but I don´t like them for this. I don´t get any "feel" what´s happening and but no, not my thing. Maybe it´s just a question of getting used to but I´ll stick to the grinder. A very grit disc could be used to knock down high spots if one would want as flat as possible but I´m more considering to maybe put in deeper low-spots. However I did also get some soft polishing disc I´ll use to just rub of the surface, just knock any sharp grind mark edges.
The prints in the pictures are a bit to thick, to much canode. But it´s getting there, way different than from the start.

Lumberjack said:

Thanks Demon,

I´ve watched your videos several times.

How would you estimate your end result? surface depth etc.

What kind of disc were you using more specifically? It looks like some thin stiff disc 1,5-2"?


I tried your technique but for me it works better almost the opposite direction, a sweeiping motion towards me touch down on and leaving the bed in constant moving / speed.

All in all it takes some time, patience and grit but the result is actaully better than I expected. Surface depth is reasonable for the intened use, surface is basically within 0,0004.

In the detailed picture is now what I call The Matti Trench ( As the Marianer Trench) as I got hold of some roloc discs on my way home today ;-)
For sure they do remove material and they are nice to work with in general, but I don´t like them for this. I don´t get any "feel" what´s happening and but no, not my thing. Maybe it´s just a question of getting used to but I´ll stick to the grinder. A very grit disc could be used to knock down high spots if one would want as flat as possible but I´m more considering to maybe put in deeper low-spots. However I did also get some soft polishing disc I´ll use to just rub of the surface, just knock any sharp grind mark edges.
The prints in the pictures are a bit to thick, to much canode. But it´s getting there, way different than from the start.


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Ah those videos arnt mine. The guy doing the grinding is Chris German (Ironsmith on here I think).
You can do it any ways you feel comfortable, I did the same as you pulling strokes rather pushing them when roughing the Shou, but I find it easier to push when youre spotting as its easier to see what youre trying to hit.
Re soft or hard discs and depth:- I normally prefer a bit of depth 0.0005" - .001" when im scraping anything, but it depends what youre trying to achieve and to an extent what you believe. Yours looks good to me, nice and straight but no so deep, if you wanted to lap it to resemble a ground finish or prefer a shallow cut then it makes sense. The reason I prefer a hard disc, the sanding pad kinda flattens out and sands an 'area' where as the hard disc grinds a more defined relatively deep groove that more resembles a scrap mark. But honestly thats just my 2c, do whatever you need to do to get the result youre after, and dont be afraid to experiment with different approaches, you can only learn something

But Demon if you recall Chris did the grinding on that mill after he read about doing it on here. You and I were talking about it as you did something over in England on a hard way machine you had. I don't recall what you were doing. It was you right?. Practical Machinist will go down in history as a macca of learning.

Richard King said:

Practical Machinist will go down in history as a macca of learning.

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Mecca a seriously bad standard, actually.

And I have high hopes it never does go down.

Only gets passed-on to another generation of competent minders.

Well to you it means that, I meant it to mean:

"A place regarded as a center for a specified group, activity, or interest"