Series 1 knee removal w/ minimal other effort?

Mark Winsor · Jul 26, 2016

I purchased a machine with the knee-column gib removed, because the gib was broken in the classic spot, adjusting screw groove. I have directions for fixing that, but my question is in regards to cleaning.
There are years of chips/storage dust/etc in the gib hole that I'm having a hard time removing, and also probably some in the ways. The machine sat with this gib removed for years.

I'd like to think I could remove the knee (just enough for 100% cleaning) with a simple method
-rotate ram
-remove Z axis travel limiter (is it the large pin I see between the column dovetail?)
-disconnect oil lines
-raise knee to top of travel with manual feed
- lift knee off dovetail using overhead gantry/fork truck

I have searched, and it seems most people remove the table first, and usually only do this as part of a complete teardown. I'd rather not get into that, if possible to take a shortcut.

Or, is there a good way to clean? I haven't tried compressed air yet, for fear it will dislodge more chips and possibly relocate them to worse places, do more harm than good.

The machine has X and Y prototrak MX2 if that matters.

Thanks!

kpotter · Jul 26, 2016

You are a brave man. I have fixed enough stuck gib mills to know that it sucks bad. I would just blast it out with air and solvent then figure out how you are going to get another gib fit to a worn mill. It is not easy but it sounds like you got that covered. I wouldnt take the knee off that is such a pain clean it up good and call it a day.

Derek Smalls · Jul 26, 2016

I would take it completely apart and clean everything. Otherwise, you are going through the trouble of repairing the gib and leaving who knows what other problems to fester. With all kinds of crud in the slides, you will never get the gibs adjusted as well as they could be.
The main reason I say strip it down, it that it's so easily and quickly done. The first time I did it, it only took me a couple of hours, and that included all the fumbling around because I didn't know exactly what I was doing! The only time consuming part is cleaning all the parts before reassembly, other wise, it's a piece of cake. One machine had been being pumped full of grease for years before I got to it, so it was a filthy mess, took forever to clean up. One shot oiler machines are a lot cleaner by comparison.
I'm not sure of what you mean by the z axis travel limiter. All BP's have that pin between the ways, but I don't recall ever having to mess with it to lift the knee off. To my memory, the knee clears it and lifts right off, but it's been a while.

Mark Winsor · Jul 26, 2016

It's very possible that that pin has nothing to do with it, I didn't look closely yet.

To clarify, the gib is not stuck, just broken, and will be repaired by milling the fractured surface square, drill + tap for 2 #10 screws, then make a new piece to bolt on where the original piece fell off (must countersink for new bolts). The idea came from H&W machine repair, I like it, as there is no need to be precise as long as the new gib piece is low relative to the ways and touches nothing but the adjustment screw. So much easier than making a new gib fit correctly.

So is it possible to remove the knee without touching the table? I'd really like to avoid dealing with the Prototrak parts.

Derek Smalls · Jul 26, 2016

Mark Winsor said:
So is it possible to remove the knee without touching the table? I'd really like to avoid dealing with the Prototrak parts.

I'm sure it is, even though in practice it will probably be way more of a pain in the ass than it's worth. I don't see it really saving you much.
Another point, I don't have too much experience with prototrak machines myself, but I've been around them enough to know that those readers need to be removed and cleaned periodically ANYWAY. Places I've worked have had them start "skipping" after a while. If they are the type I'm picturing (kinda like a Trav-a-dial type roller on the table surface) and if the machine has been sitting, and is encased in dirt, they probably will need a good cleaning, tune-up and calibration. Now, or in short order.

Mark Winsor · Jul 26, 2016

I hear you, just concerned about the Prototrak parts because they're currently working, and I don't have any experience with setting them up again in case something goes wrong. I'll do some more looking tomorrow and proceed with caution. Thanks for the input

bsg · Jul 27, 2016

Mark Winsor said:
I purchased a machine with the knee-column gib removed, because the gib was broken in the classic spot, adjusting screw groove. I have directions for fixing that, but my question is in regards to cleaning.
There are years of chips/storage dust/etc in the gib hole that I'm having a hard time removing, and also probably some in the ways. The machine sat with this gib removed for years.

I'd like to think I could remove the knee (just enough for 100% cleaning) with a simple method
-rotate ram
-remove Z axis travel limiter (is it the large pin I see between the column dovetail?)
-disconnect oil lines
-raise knee to top of travel with manual feed
- lift knee off dovetail using overhead gantry/fork truck

I have searched, and it seems most people remove the table first, and usually only do this as part of a complete teardown. I'd rather not get into that, if possible to take a shortcut.

Or, is there a good way to clean? I haven't tried compressed air yet, for fear it will dislodge more chips and possibly relocate them to worse places, do more harm than good.

The machine has X and Y prototrak MX2 if that matters.

Thanks!

Just pull the whole assembly off, do your repairs and clean everything up, makes it easy to clean inside the knee.

I have had to do this so as not to disturb digital readout scales........one nice thing about taking it off in one big lump is you can move the table to balance the assembly, it will make it easier when trying to reinstall.

There is a bolt to limit travel for the knee so it doesn't come out of the screw.

One other thing to consider, I have seen the nut for the knee elevation damaged by having to much pressure on the last thread, pull the nut with the assembly, it will make it go a lot smoother.

Make sure to have a plate or something bolted to the table for your pickup point, don't rely on just one t nut, and make sure the assembly is balanced before removing!

Good luck and please post pictures..........

Kevin

conant · Jul 27, 2016

Second that regarding caution with winding the screw out of the nut. They can strip out.

comstockfriend · Jul 27, 2016

I'd pull the table, it's so easy. I pulled mine with the scales on, I'd take them off the next time. Saddle is easy as well, then you can get to the knee. Much easier to get the crap out if it's not on the column.

My knee gib has the same repair.

John

Dave K2 · Jul 28, 2016

If the gib is removed, the knee will clear the safety limit screw - it only works when the gib is in and adjusted as there is enough slack when it's out to allow the knee past it.

bsg · Jul 28, 2016

Dave K2 said:
If the gib is removed, the knee will clear the safety limit screw - it only works when the gib is in and adjusted as there is enough slack when it's out to allow the knee past it.

It just may but why? It is only one bolt and could cause complications when lifting the assembly off the machine if not aligned just right?

When I mentioned removing the elevating nut I should have said remove the whole casting that holds the nut...........

Kevin

Dave K2 · Jul 28, 2016

each to their own i guess, with the gib out, that bolt does nothing at all, i have just stripped and reassembled my bp with the screw in and it was easy but the gib has to be all the way out of course.

yes, i would remove the screw-pedestal or at least release the nut when doing this.

Mark Winsor · Jul 29, 2016

It was a piece of cake, thanks everyone
File_.jpeg - Google Drive
File_2.jpeg - Google Drive
File_3.jpeg - Google Drive
File_1.jpeg - Google Drive

conant · Jul 29, 2016

I guess if it worked, so be it.
I would never put that much strain on the table dovetails, the weight of knee, apron etc.
Glad it worked for you.

Mark Winsor · Jul 30, 2016

I will report back after setting the machine up w/ an indicator, after the gib repair is complete. If something was bent, I expect to find out then. The way I'm wishfully thinking about this, the weight was distributed on a large dovetail area. It seems like the chain would snap before over-stressing any machine component, but I'm judging based on what I can see from the outside, haven't taken the X and Y axes apart yet.

Anyone else done it like this and confirmed no bent parts afterwards?

Dave K2 · Jul 30, 2016

You won't bend it

It's cast iron so it just fractures and bits drop off.

captain-trumpet · Jul 30, 2016

Mark, just in case. Sooner or later you`ll take the table off. There`s absolutely no need to be alarmed. Removing the tabel is a piece of cake. The booklet "A guide to renovating the Bridgeport Mill" is cheap and helped an absolute beginner (me) to manage it all by myselves in 2hrs without a crane but only with a table on the left. With some pipes I rolled the milling-table off the knee. Same with the saddle. This machine is so simple it`s hard to believe.

rainer

bsg · Jul 30, 2016

conant said:
I guess if it worked, so be it.
I would never put that much strain on the table dovetails, the weight of knee, apron etc.
Glad it worked for you.

What about the dovetail in the ram which supports the whole machine when lifting.....seems to be ok to lift it by that dovetail?

I'm sure there is way more load on the table dovetails when moved to the travel extremes!

Kevin

Mark Winsor · Jul 30, 2016

A couple more pictures just for fun:
File_1.jpeg - Google Drive
File_.jpeg - Google Drive

I'm in a catch 22 situation with the broken gib, because I need the gib to use the mill (it's my only one), and need the mill to fix the gib. The solution, a temporary oak gib, which I sawed with approximately a 0.5 degree angle and gently tapped in there while rocking the table around to seat it. As long as the knee is in the right position during "installation", it seems to work well, leaving all Z travel to the quill and keeping the table surprisingly rigid. Gib removal is easy, lower the knee and pull/wiggle on the wood with channel locks. This will be good enough to finish the real gib repair.

Apologies for my continued trouble posting pictures. I have tried to link from google drive and imgur, neither is working out using the "Insert Image" button. ?

What about the dovetail in the ram which supports the whole machine when lifting

I was thinking the same, but those ones are significantly bigger. So far, no signs of trouble, although I've only indicated a vise, not the full table yet.

Series 1 knee removal w/ minimal other effort?

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