Knee rebuild order of operations question

Fibonacci · May 22, 2016

I am working on a older (1965) j head machine and am stalled out waiting for some help. I am wondering if I can keep going or if that is going to be a problem later.

Details:

When I got it, the knee was frozen hard, the gib was snapped off, and there was a mildly terrifying amount of gook in all the ways. Long story short, I got the gib pieces out. Here is a picture of the largest one for reference:

Clearly the machine had not been getting the love and care that it needed. I ended up tearing the knee all the way down, cleaned, stripped, and repainted it, put in a new lift nut and screw, and picked up a new gib.

As we all know, the new gib needs fitting. I don't have the skills for that yet, but I am working with someone to get some help doing it. The issue is that their schedule is booked up for a couple months. I am wondering if I can keep going on getting it put back together (saddle, leadscrews, new bearings, etc) in the meantime, or if I need to get that gib fitted before I put anything else on.

At the moment, I have it sitting on the lead screw with the gib lubed up and inserted far enough to keep the knee from rocking. My concern with putting the saddle back on and continue assembly is that the added weight might mess up the gib fitting process. On the other hand, if putting that weight on affects the geometry or loading of the gib that much, then maybe I need to get it back together before the fitting.

Anyone have advice on this?

FTF Engineering · May 23, 2016

Fibonacci is asking about the sequence? How ironic is that?

JRIowa · May 24, 2016

Fibonacci said:
I am wondering if I can keep going or if that is going to be a problem later.

Did you "save this" from a junkyard? If the gib looks like that, the column and the knee probably look the same. IOW, the mill is junk.
JR

stephen thomas · May 24, 2016

Don't do any re-assembling until someone who knows (if you don't) whether to scrape the column ways and the the other side knee way, as well as the flat way on the gib side. That gib is not just a little rusty, it is corroded & exfoliated like the mill might have spent time as a saltwater boat anchor. The column ways can't be much better.

smt

JRIowa · May 24, 2016

Stephen,

Just to try to explain how twisted my mind is, I saw "exfoliated", and I thought; take it to a beauty shop. Then I though make it pretty, which led to lipstick. Then connected to "Lipstick on a pig".

Which leads to the end~ "It's still a Pig"!
JR

Fibonacci · May 24, 2016

The other sides of the ways cleaned up reasonable well.

It is in need of a full scraping, but I am not in a position to do that right now and honestly, I don't need sub thou precision for what I am going to use the mill for.

The mill was used for wafer grinding with a water based lubricant. The wipers were gone when I got it and I suspect it had been used that way for a long time as all of the surfaces were coated with it. The lubrication channels were all gummed up and I am honestly surprised that anything moved at all.

I picked it up for scrap and I am rebuilding it because I want to and as a learning exercise. I realize that it is not worth the effort from a time/money standpoint, but my son and I are doing it together because it is fun. I am working on learning to scrape and planning on tearing it apart again in a few years to give it a proper scraping then. For now, I just want to get it up and running so I can make cleaner parts than I have been doing by hand.

I have more pictures and a description of the ongoing progress over in the reconditioning forum: http://www.practicalmachinist.com/v...ies-1-j-head-rebuilding-major-gotchas-316585/

rons · May 24, 2016

Fibonacci said:
I have more pictures and a description of the ongoing progress over in the reconditioning forum: http://www.practicalmachinist.com/v...ies-1-j-head-rebuilding-major-gotchas-316585/

The pictures look good. The High Quality Tools catalog sells a saddle/table gib #1156. You can start with that.

Fibonacci · May 24, 2016

The gibs in the saddle (saddle/table and saddle/knee) were both in much, much better shape. Getting them and the saddle cleaned up is my next project.

My suspicion is that the knee gib/ways just got ignored because they almost always left the knee at the same height.

rons · May 24, 2016

Fibonacci said:
The gibs in the saddle (saddle/table and saddle/knee) were both in much, much better shape. Getting them and the saddle cleaned up is my next project.

My suspicion is that the knee gib/ways just got ignored because they almost always left the knee at the same height.

That's right. I was typing in a hurry. The High Quality Tool part number for the Knee/Column Gib is #1158.

Fibonacci · May 24, 2016

You can't see it very well in the pictures, but I have the new gib already. It is just too big for the slot (as expected).

My question is if I can put the weight of the table on the knee while I wait for some help to get the new gib fitted, or if that is going to make the fitting more difficult/impossible. I would like to keep working on it in the meantime, but not if that means that I am going to cause problems later.

Just inserting it until the knee moves smoothly leaves 3.5" sticking out the top and the bottom 1.5" of the knee unsupported. I am inclined to cut 2" off the top, cut a new slot for the adjusting screw, and start the fitting from there. That would reduce the amount of material that has to be removed by a bit more than half while still supporting the whole knee.

JRIowa · May 24, 2016

Fibonacci said:
The gibs in the saddle (saddle/table and saddle/knee) were both in much, much better shape. Getting them and the saddle cleaned up is my next project.

From what I see in the pictures, there is a lot of pitting on the column ways. That's the bad news. Pitting hold dirt and swarf which drag on the opposite surface.

You can put it back together, but movement will just produce scratches which will just have to be removed. Clean it best you can, wipe it with a little oil and send to Richard King and ask him.

That mill needs a lot of work!
JR

Fibonacci · May 24, 2016

If I have learned anything in my time here, it is that Mr. King has more than enough to do and does not need my projects/problems too.

Having it done up properly by an expert would be awesome, but also fairly expensive. Since this is not my day job, I have a hard time justifying that kind of cost.

JRIowa · May 25, 2016

That should have been "send a picture". My mistake. Other things on my mind.

There are others that do the sraping and rebuilding, the trouble is that there are none close to you that I know of. Idaho is not exactly a Meca for machine rebuilders.

If I was going to rebuild a BP, I'd send to John Fahnestock for the scraping.
http://www.practicalmachinist.com/v...s-and-lathes/like-new-bridgeport-ohio-303666/
JR

Fibonacci · May 25, 2016

That makes more sense.

I did have him take a look at some pics and his recommendation was the same. Load it up on a pallet and ship it off to A&D Machine Rebuilding in WI and pay them to do it. I am all in favor of the concept, but the round trip shipping cost alone is non-trivial, let alone paying an actual expert for the work.

As you can see from the pics, it does have a significant amount of pitting and such, esp. on the top of the knee, so a large amount of material needs to be removed to refinish it correctly. I plan to do that down the road, but not until I have appropriate skills.

The upside to the depth of those gouges (in my mind) is that any additional wear I put on it from not doing a great job fitting the gib will still be less than those gouges, so it won't add extra work to the full rebuild later.

JRIowa · May 26, 2016

It's you mill. I don't think you want advice, you want confirmation of what you've decided to do.
JR

Fibonacci · May 26, 2016

I have priced out having it done, and that is outside my budget.

What I am looking for is if there is something I am missing or don't understand about it that will come back to be a bigger problem later. I have tried to lay out my logic for why I don't think this is going to cause more long term problems, but I am aware that I am not an expert and I could be wrong.

I know that having 40thou ground off the make everything flush again, then a full scrape job is the ideal solution, and I am not ruling that out down the road.

Fibonacci · May 26, 2016

I will amend my earlier statement a bit.

As I read the various replies, I am perceiving two answers (I could be missing something, which is why I am being very specific here):

1. The mill is junk and should be scrapped and replaced with a better one.
2. The complete and correct fix to get it back into perfect working order is to ship it off to a re-builder and have all of the imperfections ground out, then a fresh scrape job over the whole thing.

In a perfect world, I agree. That is the complete and correct solution. If I were running a shop where I needed this machine 100% reliable and 100% accurate (or as close as possible, nothing is ever truly perfect), then those would be the valid choices. In that situation I would also have significantly more resources available. In my case, neither is feasible right now. My goal is to get it functioning at a moderate level in a way that will not cause more damage under light use over the next couple of years so that it can be properly rebuilt then. That was the question I asked here, not how to do a full repair.

Perhaps this is the wrong place to ask because the general opinion is a full fix or no fix. If so, I apologize for wasting your time.

Dave K2 · May 26, 2016

Personally, I think that one is dead.

I am in the same sort of position financially so i can see where you are coming from, but, these machines are very common, even over here in the UK.

It will be very hard to get a decent motion on those ways, it will likely be a source of frustration. Even a worn mill will yield decent results but rusted and pitted is just the end of the road I think.

Don't scrap it though as it has value as a parts source - strip it and sell the bits.

rons · May 26, 2016

Fibonacci said:
I will amend my earlier statement a bit.
My goal is to get it functioning at a moderate level in a way that will not cause more damage under light use over the next couple of years so that it can be properly rebuilt then. That was the question I asked here, not how to do a full repair.

You should have just cleaned up the rust and lubed whatever needed it. Then seen how the mill works.

Instead, you are surfacing and painting the castings. And when you put everything back together you hope that you
can have something that works to some acceptable level. Maybe it will work out for you.

JRIowa · May 26, 2016

Fibonacci said:
My goal is to get it functioning at a moderate level in a way that will not cause more damage under light use over the next couple of years so that it can be properly rebuilt then. That was the question I asked here, not how to do a full repair.

OK, then why are you bothering to strip it all down and paint it then?
Also, If you have to take .040" off any of the ways to clean them up, that machine is beyond rebuild. You've been told this by several people yet you want justification. Well, go ahead and put it back together. It's junk now, it won't be any more junk in a couple of years.

Just don't go trying to tell people that you "rebuilt" it.
JR

Knee rebuild order of operations question

Aluminum

Hot Rolled

Diamond

Diamond

Diamond

Aluminum

Diamond

Aluminum

Diamond

Aluminum

Diamond

Aluminum

Diamond

Aluminum

Diamond

Aluminum

Aluminum

Stainless

Diamond

Diamond

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