PDA

View Full Version : Advice wanted how to refurb Atlas Shaper cross rail?



brozier
03-15-2011, 05:04 AM
Hi Folks,

I've been looking at adjusting my Atlas 7B shaper for the last week or so after noticing oil pulsing out out from between the plates and their corrsponding ways.

The vertical ways (knee) seem okay I've removed a layer of shim on one side and seems to have removed any rocking.

The horizontal axis is causing me more issues. As the Top way surfaces on the Cross-Rail are worn more in the middle than at the ends.

Using feeler gauges between the clamp plates and the way I get a gap of 4thou in the middle and about 1.5thou at the ends.

Using a 1" and 5" Micrometer I measured the width of the top way (2 thou difference) and the distance from the top edge of the top way to the bottom edge of the bottom way (4thou difference) . The top way seems to have worn in both planes.

Wear seems to be in the 2-4 thou region so probably a bit much to scrape out - has anyone had to deal with this before? What did you try to cure it?

I think I may be able to get the cross rail onto my Raglan small vertical mill so that is possibly an option.

I also have a granite surface plate and Micrometer blue and some scrapers but no straight edges. I wouldn't class myself as an expert scraperer either! :D

Is is safe to assume most or all of the wear will be on the top rail?

Cheers
Bryan

Mcgyver
03-15-2011, 10:14 AM
should have been a law that shapers must operate in a full submerged vat of oil.

I don't think there's an easy answer for you...when a machine tool's worn, properly correcting it is a bunch of work; good news is its doable and doable in the home shop. Another part of the challenge is if its that worn there, are you going to be satisfied doing all that work on one set of bearing surfaces only to have the rest sloppy? This could be how you spend most the next year of hobby time :)

Start by doing a detailed study on exactly what is worn where. The parts are small enough that this probably can be done the surface plate with an indicator, mics etc. There's a chance all the wear is on the surface against the cap plate, in which case carefully milling this, scraping and then milling down the table where the cap bolts on (if necessary) will do the trick....but you never want to start removing material, especially from a casting until you are absolutely sure of whats wrong and how to correct it. This maybe where all the wear is but probably not; perhaps if enough of the wear is concentrated there maybe it is a 'good enough' solution.

I would suspect most of the wear is on the top, but you can't just indiscriminately modify the top - the bottom then won't line up. There are five or six surfaces on the cross rail (can't remember if the bottom horizontal one is bearing). You've got to develop a mental picture of where they need to be parallel, coplanar and square to each other as well as square and parallel to bearing surfaces on the same part to the vertical movement. You can't usually remove material from one with affecting the others, hence machine tool reconditioning is usually about planning how to restore all of these relationships.

Scraping is fairly easy, albeit time consuming. The complexity comes in maintaining and creating parallelism, squareness, coplanar surfaces etc. The pieces are small so it is doable. If its out several thou and you can get it on a mill, fine, but be VERY careful. Milling to a thou is high precision stuff so it would be easy to go too far. If not, you scrape - not that bad for 2-4 thou but you'll wish you had a Biax :D. For a small project like this you don't need to buy a straightedge, get a piece of durabar and make one - how long is that part, maybe a foot? In fact you'll probably have to make one anyway to fit in the recessed part of the box way.

brozier
03-15-2011, 12:04 PM
Hi McGyver,

Thanks for your response, you haven't seen how oily mine is now :eek: , mind you 7B doesn't have a cover for the cross-slide which doesn't help!

There doesn't seem to be any noticeable rock in the ram or the knee so I'll try and keep focussed on just the cross slide but I know what you mean about projects taking over. :D

I've started to survey the cross-slide - I think it's bad enough to warrant taking it off and getting it on the surface plate.

It's 6 surfaces as the gib runs on the bottom edge. I'm hoping the large wide front surfaces are good enough to act as a reference.

The recessed part is only 1/4"-1/2" wide is it possible to get a straight edge that thin without it going banana shaped?

Cheers
Bryan

Mcgyver
03-15-2011, 03:22 PM
The recessed part is only 1/4"-1/2" wide is it possible to get a straight edge that thin without it going banana shaped?


thats a good question! I've scraped gibs that long and thin and they hold their shape, at least well enough during the scraping operation. you'd use cast iron of course. I might do it that way or you could make an L shaped spotting tool that would bear against the top and spot the side....more work no doubt, but you'd probably end up scraping a small square to get in there anyway.

otoh maybe you just mill it after scraping (or not if its perfect) the front surface. Set it up on mill super accurately, indicated the front surface (either after scraping or not if its good) and take a very light light pass; couple of thou. The surface won't be as perfect as a scraped but may well be serviceable; lots of mini mills etc are sold with milled bearing surfaces and this is not a heavy use area.

It could well be the the wear is concentrated there as it is a much narrower bearing surface that probably didn't get oil as well as the broader surfaces bearing against he table itself. I guess I'm conditioned to expect the worse.... but there's no point in a making a job bigger than it needs to be. As you note, next steps are a more detailed survey. The movement of truth will be setting the cross rail on a surface plate and measuring where the wear is.

brozier
03-22-2011, 06:20 AM
Despite not wanting this to become a project I ended up buying a 24" x 18" Grade 00 granite surface plate and ordering several books on machine recondioning! :eek:

I've made a start of the survey of my shaper.

I've been concentrating on the cross-slide casting. I can't use the front (horizontal ways) as a reference plane as it rocks quite badly so ended up using the rear vertical ways as a reference, these still show the milling marks so are not as worn and no discernible rocking when balanced on two parallels.

The bottom shear front edge has 2thou of wear in the middle and zero at the ends as I was expecting.
The Top shear front edge is more worn ranging from 1.6thou at one end to 2 thou at the other. I think this is why the casting rocks on the front face.

My question is this do shapers try to tilt the table slightly to compensate for drooping? and would this explain the top shear being at least 1.6 thou below the bottom shear?

The top edge of the Top shear shows wear I'd expect 0 at the ends and 3.6 thou nearer the middle.

The bottom edge of the bottom shear seems to be worn more on one side thatn the other.

I haven't measured the thickness of the shears yet.

The cross slide will fit on my vertical mill I'm assuming that 3.6 and 2 thou max wear is too big to be scraped out in a sensible amount of time?

Cheers
Bryan