- Thread starter minimutly
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Scraping is an interesting, rewarding, theraputic and, if you're reconditioning machines, an essential tool. It's also likely to drive you nuts, because part of the skill is earning to read the flatness of something you had previously machined, and thought would be flat.. this, ultimately leads you to look at your machine, and it's ways, with thoughts of how to fix it.....Wow I thought my projects where big , Intresting stuff this and good use of scraping seems like I black art worth knowing
@pressbrake1 is the man to talk to, when he does his next course. He has a lot to answer for.....
One thing I noticed last night whilst sniffing around the knee and carriage, the rhs dovetail is being held slightly off by the leadscrew. I had thought about the vertical difference (this was cancelled out by machining the whole bottom face) - but of course as the carriage drops, the dovetail moves away - by the sin of the angle times the drop or something like that. Anyway, it seems the lead screw nut holder needs to be able to move sideways, so will need to elongate the holes sideways...
Table is upside down on the Fritz Werner tonight. Started scraping the flat ways - 2 thou low in the middle. Scraping, scraping, lots of scraping....
I confess to having thoughts of flycutting it, but I'm frit...
Question for @pressbrake1 here - do the cast iron tables "droop" over time? I dropped the table, face down on the Fritz Werner to scrape in the underside, and noticed, but didn't check, that the thing swivelled at its centre. The underside had a 2 thou dip in the middle. Now, back to the question - is this the table drooping over time? There is a substantial motor and gearbox hanging off one end, and the table is no more than 2 inches thick, with another inch of dovetail.
pressbrake1
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You can get sag and long term stress relief.
Also if it’s had a animal over tighten tee bolts some tee slot planishing can occur
You can planish the other side and get the curve out sometimes.
Also if it’s had a animal over tighten tee bolts some tee slot planishing can occur
You can planish the other side and get the curve out sometimes.
So scrape top and bottom then....
pressbrake1
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How big is the bow
Correct that man - but I assumed when I picked up the scraper and set to that the bow underneath was wear (which is what you would expect given the wear everywhere else). Since them I started wondering about the whole thing drooping, or relieving itself, whatever.A 2 thou dip on the underside is an upward bow on the top
pressbrake1
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Too lazy to read!A 2 thou dip on the underside is an upward bow on the top
pressbrake1
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A trip to Essex and shove it on the grinder
It's a long day out though....
Tempting as it is, and there are my clamps to reclaim....
I am seriously impressed with this. Years ago i acquired a big dankaert circular saw that had been ripped out of the ground by a Jcb still bolted to a large slab of concrete a foot thick. The cast table was broken in two & all the mounting lugs broken. I fixed it by fishplating the underside with steel plates set down on p38 bodyfiller to take up the unevenness of the casting, Allen bolts held it together, New lugs were welded up & affixed the same way. That old saw served me well for 15 years.
Nowhere near this level of fit & finish though!
Nowhere near this level of fit & finish though!
Well, thanks for the offer @pressbrake1 , but I spent most of a day scraping the deck. It's close enough for now, and anyway - it doesn't need to be perfect, you should clock everything before machining anyway?
So, surface and both undersides scraped.
Been checking them together, a bit more to do.
So I have a question - the underside of the table has been scraped - it was 2 thou worn in the middle, I don't recall how much I scraped off the top of the carriage. Lets say another 2 thou. So the lead screw will be misaligned by 4 thou. So what to do about it? Both ends have dowelled castings, so I guess I could make some offset dowels, and offset the screw holes?
And then there is this:-
This is the nut holder thing that sits under the carriage. Again it will need moving. Anyone got a suggestion how to offset the holes by 20 thou or so? (Guess there from me)..
So, surface and both undersides scraped.
Been checking them together, a bit more to do.
So I have a question - the underside of the table has been scraped - it was 2 thou worn in the middle, I don't recall how much I scraped off the top of the carriage. Lets say another 2 thou. So the lead screw will be misaligned by 4 thou. So what to do about it? Both ends have dowelled castings, so I guess I could make some offset dowels, and offset the screw holes?
And then there is this:-
RobCox
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If there's not enough clearance in the nut, you could skim some off the top mounting face of the nut holder. If you overdo it, you can always add some shim.
Where's the 20 thou come from? You said 2 + 2 thou above, which if the screw and nut are worn you might get away with. Also, losing 4 thou off the top of that nut casting wont ruin it.
Where's the 20 thou come from? You said 2 + 2 thou above, which if the screw and nut are worn you might get away with. Also, losing 4 thou off the top of that nut casting wont ruin it.
You missed the bit that said "and then there is this". Fair enough my badly worded post didn't help.
First things first, the table lead screw. That has bearings, handwheel (one end), gearbox and another handwheel the other end. The movement on this will be what I scraped off the underside of the table and the top of the carriage - flat ways. 4 to 5 thou.
The nut holder sits under the carriage - has the in/out lead screw going through it. As far as height is concerned, there will have been a couple or three thou scraped off the top of the knee, and a bit more from under the carriage, but this has been compensated for. So just the 3 though might need to come off its mounting face. However, this same nut has to deal with what's happened as a consequence of all this scraping - namely that the dovetails from the knee and carriage have moved together, so the carriage has moved left as well as down. So the holes for the (vertical) mounting bolts need elongating to allow this.
I suppose I could drill them oversize and then move the counterbores along slightly? Bit of a bodge though?
I need to calculate it properly first.
First things first, the table lead screw. That has bearings, handwheel (one end), gearbox and another handwheel the other end. The movement on this will be what I scraped off the underside of the table and the top of the carriage - flat ways. 4 to 5 thou.
The nut holder sits under the carriage - has the in/out lead screw going through it. As far as height is concerned, there will have been a couple or three thou scraped off the top of the knee, and a bit more from under the carriage, but this has been compensated for. So just the 3 though might need to come off its mounting face. However, this same nut has to deal with what's happened as a consequence of all this scraping - namely that the dovetails from the knee and carriage have moved together, so the carriage has moved left as well as down. So the holes for the (vertical) mounting bolts need elongating to allow this.
I suppose I could drill them oversize and then move the counterbores along slightly? Bit of a bodge though?
I need to calculate it properly first.
Here's what I mean when I say dovetails moved together..
So just left of centre, the top of the knee and underside of the carriage dovetails. The in/out lead screw is underneath them. The nut holder is out of sight under the carriage. It's this that will need moving left.
Oops, right...
Bumping this because I don't have an answer to shifting the mounting holes in the nut holder. Any suggestions? Yes I know I need to do some calcs, maybe have a look at that now.
Best I can come up with is to drill oversize and make up a pair of offset inserts - hell of a faff about though?
Best I can come up with is to drill oversize and make up a pair of offset inserts - hell of a faff about though?
