Thread: Scraping Projects

Ewan,
go back to Mike's thread and you'll find how to get it for free - I just did. (Hint: you have to scroll to the bottom of the page)

Originally Posted by Ueee

Why not put it on the surface plate and use your V block and an indicator to check the heights of each end of the ways? any twist or height error should show up immediately and repeatably. As you have scraped the ways flat the middles should be fine, mind you, you should be able to reach a fair way off each with the indicator to check them.

I did actually try that, problem is it has to be jacked up to the same position that it was ground in...

Just plonking it on the plate on what I thought was the reference spots did not work, it was a bit like a table with one short leg...

Originally Posted by .RC.

Have made up a jig to measure the doube inverted V's on the grinder saddle that I just scraped...

Double V's are much more complicated then a plain V and flat... A V and flat you only have to worry about them being in the same horizontal plane...

A double V has to be parallel in horizontal and the vertical plain... I take my hat off to people who can scrape them efficiently from worn to parallel..

Luckily for me, these had minimal wear, at least some of the original grinding marks were visible all along the ways, in some areas more then others... So it was just a matter of enhancing the spotting to full length... In most cases it only took two passes to get good coverage and a few more passes to refine the bearing.. I did most of it by hand...

To measure it to confirm parallel in two planes I used a jig I have used before, with some enhancements... Ways are 400mm apart with a huge obstruction in the middle... I also scraped up a V Block from the TC grinder project to fit these V's... The V block confirmed the V's were in fact all formed at the same angle..

Sitting the V block on one of the V ways, with a roll sitting in the small V on top of the V block, Then on the other side I had the jig that the magnetic level sticks to and a long arm that sits on the roll.....

Zero the level as best as possible then slide along... Do that a hundred times and take the average...Mine are looking pretty good.... I think one end is every so slightly higher then the other, but hard to say as it is a very intolerant procedure to inconsistency... I found even pushing the jig at different speeds yielded different results... Consistency is the key... That test does the horizontal plane.

The vertical plane I used the same setup without the level but instead a dial test indicator was placed on the side of the V-Block... Any divergence from parallel should show up on the indicator.

That test went quite smoothly and was well within what I thought OK.... I used the Bestest 0.002mm indicator and it read 0.003mm or so... Not very much...

Next is to use the saddle as a master to scrape the main casting ways (they are shorter) then use the table to scrape the top of the saddle...

Fantastic work on the double Vee's. Even thinking about that gives me a headache, parallel both ways, square,90 degrees, twist, bend, ouch ouch ouch,.....

-J

Just dawned on me why the shorter cross slide ways show wear on the ends and not the middle so much...

Richard King over on PM or HSM mentioned that he always relieves the middle section of shorter ways by a small amount... Logic behind this is the ends always wear first, with the middle relieved, the ends wear down a bit first then contact is made along the whole length, then the ends wear down a bit more and you get less and less contact, then time for a rescrape...

So you relieve the middle to get more life out of the machine between rescrapes... Not that many machines get rescraped these days...

Does that make sense?

Originally Posted by .RC.

Does that make sense?

Yeap thats all makes sense........ means you have to go back over yours now

Stuart

Originally Posted by Stustoys

Yeap thats all makes sense........ means you have to go back over yours now

Stuart

Nope, have not scraped the short ways yet... double

OK the double V's are done.The middle third has been relieved to the point that there is some minor touching going on there, but very little, as the ends wear, if they ever do it will touch more and more....

Just the top of the saddle where the table runs to do..... Preliminary assessments seem to indicate very little needs to be done to them...

Just for kicks I put the starret level on the saddle to make sure there was not going to be any rise droops as I moved the saddle across...

###? the level moved 3/4 a graduation when moving the saddle across.... Much thought went into it...

Then many hours later in the day while doing normal work it dawned on me.... The grinder sits on rubber pads, three of them... To test the theory, set the level up again and sure enough if I pull the saddle towards me, the bubble will rise to the back and vice versa...

If I put my weight on the base casting the bubble moves again..

Lesson there is that your machine has to be solid if depending on levels for alignments...

Also have to wait on some 3/8 chromed rod a PM member has kindly offered to post me, that is for the table hydraulic ram.... Au prices were out of this world, $300/m.. Guess they thought they had a captive market...

Have new way wipers, new piston rings and new seals.... Will be splitting the atom hopefully before the month is out.

Love your work .RC.
Just stop making it sound so easy.

Phil

Nice work.

Our grinder sits on 5 iron levelling pads (~150mm dia) so it does not rock going front to back or left to right, the levelling procedure is real pain due to the shifting centre of mass. Get it level in one configuration, move to next, level again, rinse and repeat until the pressure on all 5 pads is just right.

I'll find a pic if your interested

-J

Originally Posted by .RC.

###? the level moved 3/4 a graduation when moving the saddle across.... Much thought went into it...

Then many hours later in the day while doing normal work it dawned on me.... The grinder sits on rubber pads, three of them... To test the theory, set the level up again and sure enough if I pull the saddle towards me, the bubble will rise to the back and vice versa...

If I put my weight on the base casting the bubble moves again..

Lesson there is that your machine has to be solid if depending on levels for alignments...

Nice work as always.

I went through the same process with my surface plate stand, it was flexing enough to move the bubble as I put things around the plate. Quite frustrating.

I scraped in the saddle to the table this evening, all the scraping should be done now, unless I scrape the top where the mag chuck sits.. Some say to scrape this, others say to grind it... Or I leave it alone lest touching it will warp the table..

Now I need to work out, do I flake the short ways or leave them alone?

I do have photo's of the finished saddle, but I cannot seem to take photo's of the blue spots, they just wash out in the flash making the blue areas look very sparse...

Good work RC.

I'd like to see BT doing some scraping and taking some pictures of his spotting...no doubt it will come out fine for him! Trying to photograph the spots is real hard. I was trying to take pics to compare spots from one round to the next, it ended up a useless effort.

Looks great RC

All the ways a pressure fed aren't they? Surely if they had been flaked you'd be able to see it? I vote for copying what they've done.(of course if someone turns up that knows what they are talking about I may choose to change my vote lol)

I find single pictures of blue can be pretty useless for anyone else (doesnt mean I dont like to look at them anyway) but I take a picture of each spotting as close to the same way and distance as is easily done. Flipping through them seeing how its going helps me see I'm getting somewhere...........

Stuart

Well gents it is back together, ground the table top a bit, with my fingers crossed that taking a smidgen off the table will not warp it.... then put on the chuck and ground it in...

Did the 4 bits of steel in each corner and one in the centre, grind them, then invert them and swap them to the opposite corners.. Grind again, then measure....

And the error was..... Well I dunno, maybe 2 microns over a 6X12" area, I am not a good grinder and need to hold my tongue in the right area to get the right results... Plus I find it exceedingly difficult to measure sub 5 micron amounts...

I am pretty happy with those results though... Big thumbs up to Phil and Marko for teaching me the finer points of scraping at the scraping class..