Used BP, Y Axis must by worn out in the center

[Wade]

OK, I'm the kind of guy that walks in to a Dodgers Beer Garden and cusses the Dodgers, just so I can get my azz kicked. So, feel free to get it out of your system. I've done enough reading to fully understand everyone's emotional attraction to this subject. Yes I searched for this.

Bought a J head for nearly nothing. I tore down it down. Everything was dirty, so I pulled off the table and acme screws, and Y axis slide (whatever you call it), and yoke. Cleaned it all up, not too shiny, but a lot better than the last 4 years of non-use had left for me.

So, putting it back together I put the Y axis slide back together without a drive screw, and pushed it back and forth by hand. Tightened the gib (?), until it didn't move right or left and moved smoothly, cool. But, when I push the slide all the way towards the turret, it binds pretty bad, and when I pull it towards the front it binds. Obviously, it has dished out in the center, fairly bad but not too bad. (BTW, if I loosen the gib to where it will move throughout the entire Y axis, it flops around a little in the center, didn't measure it, the difference is obvious.

So, It's a nearly free machine. I'm not going to dump a lot of money into it, and have it professional done. One of the reasons for buying it, was to learn how to fix it, I'm crazy that way.

My idea was by a granite straight edge on Ebay, there's one that claims +/-50 millionths, (over what I don't know)
http://cgi.ebay.com/BLACK-GRANITE-ST...item3ef2ecdb74

Buy a scraper, and a book, and try to get the ways flat towards the ends. How crazy does this sound? Should I replace the gib key first? Or, is that a waste of time? Something like this http://www.machinerepair.com/Orders.html

Then, I was going to see if that helps the Y axis move, and then figure out what to do about the dovetails, if anything. I understand the blue ink transfer, but have no clue how you blue a dovetail.

I'm not shooting for tenths accuracy here, I want the axis to not bind. I'm even willing to over scrape the ends a few thousand, to keep from having to touch the dove tails. I do plan on putting servos on it soon. and, I'm sure the X axis will have some problems too. If I totally screw it up, I'll part out the machine and buy another one, so I'm not scared too try this.

OK, unleash the dogs.

[machintek]

First question: Are the ways chromed?

George

[Wade]

Originally Posted by machintek First question: Are the ways chromed? George

Thanks for responding.

Nope. Don't appear to be, their pretty rough towards the back, looks like a million little projects where dropped on it over the years. And, it looks like the Y axis has never been back there. When I bought it, the owner, had never hooked it up, just sat in his barn. He was told, a shop used to own it, and the Y was locked in one position mostly for 20 years.

[jmelson]

Originally Posted by Wade My idea was by a granite straight edge on Ebay, there's one that claims +/-50 millionths, (over what I don't know)

Well, the surface plate will only allow you to spot the underside of the saddle. That will be necessary, as it is now worn convex. But, the other problem is the valleys worn in the top of the knee and possibly the inside of the dovetails. You won't be able to spot these on the surface plate. So, you need a dovetail straightedge to get inside the corners of the dovetail. Michael Morgan sold some castings for this at one time, but I don't know if he still is doing this. You might get lucky and find one on eBay.

As for the eBay surface plate, much better to get one on sale at the local MSC, Enco, KBC, J&L, etc. and go and pick it up. The UPS charges on these will be huge. (But, watch out for your back, you can really pop a disc trying to move one of these. Don't ask how I know this!)

The eBay item you linked to has the same problem as an ordinary surface plate, it can't get inside the dovetail. also, it is too heavy for proper use in spotting.

Jon

[Wade]

Originally Posted by jmelson Well, the surface plate will only allow you to spot the underside of the saddle. That will be necessary, as it is now worn convex. But, the other problem is the valleys worn in the top of the knee and possibly the inside of the dovetails. You won't be able to spot these on the surface plate. So, you need a dovetail straightedge to get inside the corners of the dovetail. Michael Morgan sold some castings for this at one time, but I don't know if he still is doing this. You might get lucky and find one on eBay. As for the eBay surface plate, much better to get one on sale at the local MSC, Enco, KBC, J&L, etc. and go and pick it up. The UPS charges on these will be huge. (But, watch out for your back, you can really pop a disc trying to move one of these. Don't ask how I know this!) The eBay item you linked to has the same problem as an ordinary surface plate, it can't get inside the dovetail. also, it is too heavy for proper use in spotting. Jon

Thanks, makes sense.

The site http://www.machinerepair.com/Orders.html
sales a straight edge casting for $220, but it needs to be ground/scraped. I guess a 24"x18" surface granite from Grizzly would allow me to level it. And it appears the casting is setup to get back under a dovetail. Eh?

I know these kind of straight edges exist, but at $4500 whew.
http://www.newmantools.com/busch/6000.htm#6700

[Sparky_NY]

Originally Posted by Wade Thanks for responding. Nope. Don't appear to be, their pretty rough towards the back, looks like a million little projects where dropped on it over the years. And, it looks like the Y axis has never been back there. When I bought it, the owner, had never hooked it up, just sat in his barn. He was told, a shop used to own it, and the Y was locked in one position mostly for 20 years.

Going by the statements above, maybe the Y isn't worn but rather damaged. Dent's etc would have raised edges which would be more than enough to cause the binding. First thing to try is stoning them by hand to knock off any high spots and see if that improves things.

[jmelson]

Originally Posted by Wade Thanks, makes sense. The site http://www.machinerepair.com/Orders.html sales a straight edge casting for $220, but it needs to be ground/scraped. I guess a 24"x18" surface granite from Grizzly would allow me to level it. And it appears the casting is setup to get back under a dovetail. Eh?

Yes, that's Michael Morgan. His book is pretty good. But, be sure you pay by credit card, as it took almost a year for him to deliver the straight edge casting to me.

After rough machining, you need to get the straightedge stress relieved, or it will continue to warp for a year or more after the skin is machined off.

Yes, this casting was designed specifically for spotting under dovetails.

I bought some 1/8 x 1/2 x 1.5" carbide cutting inserts for a couple bucks from a machine shop supplier, and brazed them to steel strips to fit the Anderson scraping handles. MUCH cheaper than the ready-made scraping blades, which can cost $50 each. You will also need a face-type diamond grinding wheel to maintain the scraping blade.

Jon

[Wade]

Originally Posted by Sparky_NY Going by the statements above, maybe the Y isn't worn but rather damaged. Dent's etc would have raised edges which would be more than enough to cause the binding. First thing to try is stoning them by hand to knock off any high spots and see if that improves things.

Yha, I was pondering that, while looking at it the other day. I'll definitely try that first. The only reason I didn't think it was the entire problem; is it binds in the front, and there is no damage their. But, if it will free it up enough to make it not bind, I'm good with that.

[Wade]

Originally Posted by jmelson Yes, that's Michael Morgan. His book is pretty good. But, be sure you pay by credit card, as it took almost a year for him to deliver the straight edge casting to me. After rough machining, you need to get the straightedge stress relieved, or it will continue to warp for a year or more after the skin is machined off. Yes, this casting was designed specifically for spotting under dovetails. I bought some 1/8 x 1/2 x 1.5" carbide cutting inserts for a couple bucks from a machine shop supplier, and brazed them to steel strips to fit the Anderson scraping handles. MUCH cheaper than the ready-made scraping blades, which can cost $50 each. You will also need a face-type diamond grinding wheel to maintain the scraping blade. Jon

Thanks, good info. I kinda thought the carbide price seemed way high. They have used cutting tools for sale here, was considering finding some old carbide lathe tools and making my own tool. I'm also sure someone has placed instructions on how to do this on line somewhere. Most of the books are 50 years old, that I've seen. Get me a bench grinder, and a green stone and make my own.