First Time Scraping/Gib Fitting - Advice Needed!

I am working on some minor refurbishing of a J-head Bridgeport with an original Prototrak rig. This machine sat mostly unused and neglected for a good 10 years in a high school shop, being used mostly for the occasional manual operation or as a drill press. No lubrication or maintenance. Ball screw lube pump is broken.

I work with the school's robotics team and we've generally been the main source of maintenance. Last year we got serious about figuring out the Prototrak and had a great season making some good parts on it. However, we noticed the y-axis screw has play (self-test says ~.020 slop, the y-axis often "floats", etc) and began experiencing binding issues in the x-axis (total servo stall). Machine had been greased before and had reached the inevitable bind-up point. We bought a new Bijur pump (traded to the school for some nice, big steel stock) and decided to tear down the table, parts wash, plumb all the zerk fittings to the Bijur, and generally rehab it.

We found the x-axis gib screw notch was busted out possibly explaining some of the binding issue. Ordered a replacement. Did notice that they are sold oversize before buying Sales rep was impressed that this didn't come as a surprise to me (common complaint, apparently).....rebuilding is new to me but I do try to pay attention! Now we have to hand fit.

I spent the better part of the past week reading up and watching every video I could find on scraping. I got a copy of Machine Tool Reconditioning and read through it several times. I think I have a good handle on how this process works but admit I've got no experience with it. Myself and several other team mentors have experience with other types of precision machinery...this is just a new area for us.

This is where we're at right now and a summary of how I'm going to proceed. I'd appreciate any advice and comments from you all!

Forgot to take a picture, but following Connelly's chapter on scrapers we made one out of a file and it seemed to cut cast iron pretty well. I thought to pick up a real Arkansas stone and boy, was that a great investment!

Initial insertion of new gib and firmly hammered home with a brass rod for initial fit. Stick out is 2.207"



Other side....recessed 0.406"



I believe the process I want is to mill off enough to get the short end to just stick out, then scrap to fit. I figure to move it right about .500" I need to take just about 10 thou off the straight face.

I realized that I could also calculate what cut would get the pre-made adjustment slot in the right place, but I think I would rather keep my face cut as small possible to reduce possible chatter issues (this thing looks like a bear to fixture) and then cut a new screw slot wherever it ends up. Does this sound logical?

I need to figure out how to fixture this thing... I know many guys talk about putting it vertical and milling with the side of a end mill, but I don't trust the table on the other even more whupped manual machine to give me the precision I need. My thought was to fixture it flat and face cut it after indicating all along the length?

My thought was to set the new gib onto the old gib and hold it down at the ends?



For the scraping process, I was going to follow Connolley's "Method 1" given in Chapter 17 in which you spot and scrape both faces of the gib to avoid possible warping issues that may arise from doing one then the other.

So yeah, any advice on the above is welcome.

My other question is about the wear on the saddle ways carrying the table. Here are the four corners. Do these look whupped enough that you would recommend scraping the convexity out of it? My gut reaction is no?









Thanks again for any input!

First thing, don't hammer in the gib. it should be pushed in by hand pressure only. When fitted, you should be able to get a .002"-.003" feeler gage inserted between the gib and the way surface for normal running.

But before marking and cutting the notch, you must scrape and fit the gib first. There is plenty of subject matter on the scraping on the forum.

Once it is scraped and fitted, then you can mark it with a scribe so you will know where to put the slot. Mill the slot square to the face of the gib. While you are at it, cut a second notch for later on when you run out of travel with the first notch. And do not cut off the gib after fitting. Leave that extra on there for later in life rebuilding.

Ken

I guess when I do gibs I find I can't get a good marking without tapping it in lightly with a hammer and brass punch. Scraping gibs generates lots of smearing and false bearing when your marking up, due to the fact they are flexible and usually bent, also as you slide it into the pocket it rubs and picks up blue where it don't belong. First thing I do is check for warp on a surface plate and most of the time they can be lightly tweaked by hand, they don't need to be perfectly flat, if your pinky can press it flat it's good enough. I usually place an indicator over the hump and squash the gib to measure it .001 - .003 warp is ok on a gib that long IMO. When I insert the gib I first push it in by hand until it wedges then I try to wiggle each end to see where it's pivoting, and only scrape the tight end until it has even drag on both sides, kind of like how richard king says to hinge a straight edge to find the high spot. Also alternate between scraping to a surface plate to cover the end hanging out of the saddle. As far as milling goes, gibs are a PITA, .005 off one side and it curls like a banana. The best I've ever done is use Lo-Melt alloy, and mold it into a tray so I can put it on the surface grinder. I could give a detailed description of the process if you want, (we did this ALOT in a past shop) otherwise I would say be careful with the milling, sounds like you know what your doing. Good luck

I can't offer much in the way of useful input, it sounds to me like you're going about it in a very logical and intelligent way. I would be grateful however if you could continue to put up the process here as you go about it. Your photos are very well taken, and it's always nice to see others go through the process from start to finish and how it worked out, and what they may do differently next time.

Just an opinion, but I don't think that wear looks bad to me.

In so far as scraping, I'll suggest that scraping per se isn't too difficult, but scraping to alignment in multiple planes can be a lot more difficult, especially at first. Just a suggestion, but I think it would be time well spent to scratch around the workshop and find suitable crash test dummies to scrape, then scrape them to a specific alignment instead of just making a hunk of cast iron flat. That will allow you to better judge how much material you're removing with each pass etc so as to know in which direction the surface you're scraping should be moving and by how much. Books are great, but all the theory in the world won't tell you when you've had a false print and so on, and a few days of specific practice scraping to alignment of non-critical parts could save a considerable amount of time and effort chasing your own tail needlessly on the target machine.

You wrote "My other question is about the wear on the saddle ways carrying the table. Here are the four corners. Do these look whupped enough that you would recommend scraping the convexity out of it? My gut reaction is no?"

The ways are chrome plated and can't be scraped. The wear on the outside is do to the table being bent (thank you Archie, I finally believe your right plus the dirt gets in on the ends) because the top of the table stretches when tightening the Tee Nuts. Take a look at the Kansas City scraping class thread and I explain how we peened the BP table straight. I like the double notch gib trick Ken Presents...Learn something new every day. I mount a mag base on both ends of the table and put the dial indicator on the end of the saddle and "shake" the table back and forth to check the gibs taper to see if it is the same. I like to scrape the gib with a method I call step scraping if it is out. I also scrape the gib .0005 to .001" low in the center 40% after I get both ends .0002" same shake. but leaving the gib loose when checking ..say .0022. If it is to tight you will get a false reading as German says. Rich

PS: The old new gib also looks like it is to high in the one picture. might not slide in as its hitting the top and bottom and the corners. That is easy to thin f you black it in on a surface grinder table.

I would definitely _not_ start by milling. Too little to take off, and as Ironsmith notes, you don't even know where it hinges yet. Milling it to the old bowed gib (as Richard notes) won't necessarily give the new geometry you want.

Find the hinge points and get it rough scraped so it hits all over. Then, if it does not yet stick out far enough, (my guess is it will, by the time it is properly fit) and you have a sine or tilt chuck big enough, you can take a little off the back side on a surface grinder. As has also been noted by others, when you are scraping a taper gib, there is a certain amount of back-n-forth from face to face in keeping it flat and well fitted without hinging (high point). But the non-sliding face does not need very many points per inch. Ironsmith gives a very good description.

smt

Guys....thanks so much for the input. Its late, but I wanted to reply after my first night of scraping.

Progress to date:

I spent quite a bit of time fixturing the gib (using the old one) and finally got it indicating within a thou or so across its entire length and width. Cut half of it and had to break down due to time constraints (its tough when you've only got 3hrs per week in the shop and you're also helping lead a class). Used my new $85 Grizzly 2.5" face mill and was very impressed....granted, taking 10 thou off of cast iron is no good test, but it cut quietly.



While checking elevation with the indicator, I did test for warping. My gib was dead flat....even after taking the center cut. Pressing on it with the dial indicator over the center showed no movement. Guess I got lucky...

This past weekend I had time to re-fixture it in another mill and finish the ~10tho cut. I didn't see Stephen's advice until tonight but I think I'm ok despite starting with milling (I've seen other start with milling so I know that's a subject of debate). Long story short, I got ~10 thou off the gib's tapered face.

Tonight I assembled the table and saddle (Lightly lubed the horizontal ways and rear dovetail with Vactra and removed the inner half of the oil on the front horizontal ways to avoid getting oil squeezed onto the gib but allow everything to slide together). Used a 3lb maul and block of wood to firmly hammer the table against the rear dovetail, blued up the gib, inserted it, and gave it a few blows through a brass rod. Pulled it out and had almost no indication except at small end of the gib. Started scraping.

Houston, we have honest chips!

z

My fixturing setup was just a light clamping to the table using the old gib as a shim and with some masking tape under the jaw of the hold-down. Worked just fine. I gave the table a few raps with the sledge/bock of wood before each fitting to make sure it was seated.



Second spotting....binding at the small end still.



Scraped it down...



One or two iterations in....started getting high spots at other points. Seems like we're headed in the right direction!



This was the first very encouraging spotting. I was seeing the few high spots merge into a line. From my newbie understanding, this is a strong indication that my scraping work is heading in a productive direction and not just chasing random high spots.



And how I scraped it down. I'm sure a pro would take issue with the quality here, but I am pretty happy with my novice efforts! A finger detected no imperfections and it looks kinda like a pro finish? Not bad for a newb.



A few more iterations in and I finally got a nearly dead-straight line of high spots along the whole length of the gib. Even more encouraging, there was a matching line of contact near the lower edge on the reverse side! This tells me that the gib is beginning to bear equally along its length but not in rotation about that same axis....something easily corrected. I'm making positive improvements!

I also noticed that when tapping the gib out after spotting (I was using multiple tap in, tap out cycles to get a good spot) it was starting to give gradually instead of all at once....indicating, again, that it was truly starting to bear at more than a couple of points!



Another shot of the good chips I was getting....guess my rookie scraper isn't half bad on cast iron!



The result of the most recent scraping. This is an unreasonable amount of fun!



So hopefully I'll be back at it again soon. Any comments or criticisms are welcome....I think I'm going in the right direction but if anyone thinks I'm just well on my way to making a $40 piece of scrap iron please let me know!

Looks like your gettin 'er figured out! Always good to hear when somebody is having fun learning something new. What kind of blue are you using on the gib, looks like the drying layout blue. I would recommend a non drying medium like Dykem Hi Spot or canode. You may have trouble seeing the lesser hi spots with that blue. In other words only the very tightest points will rub through, and it's often helpful to see the points that are "getting close" so you can stay ahead of the game. I personally like the way richard teaches using the yellow canode on the work and blue on the master (gib pocket here). It gives pretty sensitive readings and any smearing or false bearing is easily distinguishable. Before I started using canode I used a white oil paint on the work, applied thick and wiped off almost entirely to leave a frosty haze, and Hi Spot was used on the master. This was before I knew canode existed, I'm not old enough to know about red lead, (sigh of relief) lol. And perhaps your method works better than I expect, just thought I'd chime in, best of luck!

I need a cutter...but just the name Grizzly makes me cringe......

I hope the cutter is better then their machinery....plus i think we are not suppose to mention that name on here...oops

Richard King said:

I need a cutter...but just the name Grizzly makes me cringe......

I hope the cutter is better then their machinery....plus i think we are not suppose to mention that name on here...oops

Click to expand...

I'm not familiar with their other products, so I certainly won't defend things I don't know about!

This particular one is made in the USA and seemed to have good reviews among folks looking for an inexpensive entry level insert face mill. I will definitely report (on another thread) when I finally get a chance to use it on some aluminum or steel. There's been a few discussions on other PM threads about this model and the consensus seemed to be "Its not a pro grade tool, but it gets the job done pretty well."

I won't buy anything from China if I can help it though!

ironsmith89 said:

Looks like your gettin 'er figured out! Always good to hear when somebody is having fun learning something new. What kind of blue are you using on the gib, looks like the drying layout blue. I would recommend a non drying medium like Dykem Hi Spot or canode. You may have trouble seeing the lesser hi spots with that blue. In other words only the very tightest points will rub through, and it's often helpful to see the points that are "getting close" so you can stay ahead of the game. I personally like the way richard teaches using the yellow canode on the work and blue on the master (gib pocket here). It gives pretty sensitive readings and any smearing or false bearing is easily distinguishable. Before I started using canode I used a white oil paint on the work, applied thick and wiped off almost entirely to leave a frosty haze, and Hi Spot was used on the master. This was before I knew canode existed, I'm not old enough to know about red lead, (sigh of relief) lol. And perhaps your method works better than I expect, just thought I'd chime in, best of luck!

Click to expand...

That was my first thought as I started out and got very little indication....if doing it wet would help. I have regular Dykem but it takes long enough to dry that I might be able to do that?

I did think to get red Dykem to try the contrast-agent technique as I got close.

For right now, this method seems to be working well as I'm still getting limited high spots (that are responding) with high contact pressure. I'm sure this method won't produce good marks as I get close...and that was when I was planning to put red on the gib and blue in the pocket.

What should I be looking for for bearing? I have heard that the tapered side isn't crucial for bearing as long as it is true and showing even contact over its surface. I was told that the dovetail face should be ~10 spots per inch? Being a whupped school machine and seeing little use, I wasn't planning on going crazy with it.....

Thanks for the input!

For a gib I'd say 15-20 on the sliding side and 10 on the non sliding side. Apply flaking to the running side and don't forget to drill the oil hole! Most tapered gibs have a slot on the backside say 1/4" wide by .030 deep milled about 1" long starting at the oil hole and running towards the fat end of the gib. That way when you adjust for wear in the future it's still transferring oil.

JB Wrote:

"I'm still getting limited high spots (that are responding) with high contact pressure. I'm sure this method won't produce good marks as I get close...and that was when I was planning to put red on the gib and blue in the pocket."

I don't want to sound like I am picking on you, but there is a reason for using a paste bluing over dry. Dry will pull up a gall or scratch when you apply high contact pressure.

JB, you have to remember several of us are professional scrapers / rebuilders and we have been scraping for years and not weeks or days. It's not our first rodeo like it sounds it is for you. We want to save you and the other readers headaches and hope you will benefit from our experience.

You need to buy some paste bluing because if you continue to use the dry inks you will screw up either the gib, but the table dovetail and will put s scratch or gall. Wet bluing is slippery and won't gall under high pressure.

Over the years I have seen many scores in ways in the center of the long way, no sign that a chip worked its way in there from the edge. The reason there is a scratch in there is because no oil could reach it and the metal in there welded together and galled up. A 8 once bottle of Canode costs around $15.00 for the blue and yellow. If you prefer red or orange you can buy it too. A .55 once of Dykem High Spot blue costs $9.00, I see the spray can of Dykem dry is $15.00 and paint on is $8.00. Clean-up for Canode is so easy compared to the other methods too.. Windex.

I use the dry stuff for Lay-out or down in the corner of a dovetail if I can't find a high spot in there that rubs. Happy scraping. Rich

PS: I scrape the back of a gib to approx 2 to 5 PPI

You got grease in my oil !!!

Not to change the subject of the OP but when dealing with the lube system pay close attention to the fittings and lines on the Bijur system. Recently started tearing into the carriage and apron on our 40 something Warner Swasey 2A turret lathe.
Some well meaning citizen had put grease in all the zerks AKA we now have a lot clogged filters, lines & metering devices. Make sure all your lines and passage are clean while you have her apart, visit the Bijur site, they have lots of info on lube systems. You really have to pay attention to the orientation of fittings and values on metering devices.

I realize from the OPs opening statement that he and a lot of others are more than likely aware of this. Just thought I would mention it for those who are not quite to that point yet. I have noticed that most shops have a grease gun, have not too many oil guns though, tells one something.

So for all you well meaning souls that automatically reach for the grease when you see a zerk, stop and consult the manual or lubrication instruction placard on the machine.

BTW Very informative info prior to my post thanks for sharing your activities and documenting with nice photos.

Richard King said:

JB Wrote:

"I'm still getting limited high spots (that are responding) with high contact pressure. I'm sure this method won't produce good marks as I get close...and that was when I was planning to put red on the gib and blue in the pocket."

I don't want to sound like I am picking on you, but there is a reason for using a paste bluing over dry. Dry will pull up a gall or scratch when you apply high contact pressure.

JB, you have to remember several of us are professional scrapers / rebuilders and we have been scraping for years and not weeks or days. It's not our first rodeo like it sounds it is for you. We want to save you and the other readers headaches and hope you will benefit from our experience.

You need to buy some paste bluing because if you continue to use the dry inks you will screw up either the gib, but the table dovetail and will put s scratch or gall. Wet bluing is slippery and won't gall under high pressure.

Click to expand...

I don't feel like you are picking in the slightest. I appreciate the advice on paste bluing. As a novice, I hadn't understood that when a scraper talks about "bluing" he is almost always referring to paste not the normal dry bluing that everyone else means. I will definitely get some paste and work with it. As a newbie, I don't know what I don't know! This is why I'm glad for input like this.

How do you deal with smearing? Aside from being a world-class player at the old "Operation" board game, how do you extract a gib with paste bluing from the slot without ruining the spotting on both sides? Do you work one side at a time (and let the other smear) or do you just be so damn careful that you maintain the spots while you move the gib out?

Richard King said:

JB Wrote:

"I'm still getting limited high spots (that are responding) with high contact pressure. I'm sure this method won't produce good marks as I get close...and that was when I was planning to put red on the gib and blue in the pocket."

I don't want to sound like I am picking on you, but there is a reason for using a paste bluing over dry. Dry will pull up a gall or scratch when you apply high contact pressure.

JB, you have to remember several of us are professional scrapers / rebuilders and we have been scraping for years and not weeks or days. It's not our first rodeo like it sounds it is for you. We want to save you and the other readers headaches and hope you will benefit from our experience.

You need to buy some paste bluing because if you continue to use the dry inks you will screw up either the gib, but the table dovetail and will put s scratch or gall. Wet bluing is slippery and won't gall under high pressure.

Over the years I have seen many scores in ways in the center of the long way, no sign that a chip worked its way in there from the edge. The reason there is a scratch in there is because no oil could reach it and the metal in there welded together and galled up. A 8 once bottle of Canode costs around $15.00 for the blue and yellow. If you prefer red or orange you can buy it too. A .55 once of Dykem High Spot blue costs $9.00, I see the spray can of Dykem dry is $15.00 and paint on is $8.00. Clean-up for Canode is so easy compared to the other methods too.. Windex.

I use the dry stuff for Lay-out or down in the corner of a dovetail if I can't find a high spot in there that rubs. Happy scraping. Rich

PS: I scrape the back of a gib to approx 2 to 5 PPI

Click to expand...

Who supplies "Canode" thanks.

Sorry I found the supply thread. I'm trying to get used to this.

jbrowne said:

I don't feel like you are picking in the slightest. I appreciate the advice on paste bluing. As a novice, I hadn't understood that when a scraper talks about "bluing" he is almost always referring to paste not the normal dry bluing that everyone else means. I will definitely get some paste and work with it. As a newbie, I don't know what I don't know! This is why I'm glad for input like this.

How do you deal with smearing? Aside from being a world-class player at the old "Operation" board game, how do you extract a gib with paste bluing from the slot without ruining the spotting on both sides? Do you work one side at a time (and let the other smear) or do you just be so damn careful that you maintain the spots while you move the gib out?

Click to expand...

As for the smearing, a true high spot develops when lightly seated with a mallet, the high points will rub through the bluing and make metal to metal contact, leaving a shiny plateau surrounded by a bullseye ring of blue. Smears are elongated drag marks of thick blue, it doesn't take long to distinguish between the two. As far as which side first. I usually scrape the back (non sliding) side to a surface plate first, then blue the dovetail of the table and assemble it to the saddle and tap the gib in to take a print, hinging the gib to find which end is binding first. I alternate between a surface plate because the end hanging out of the gib pocket has a tendency to flex away beings it's unsupported by the gib pocket. I'll try to find a pic of true high spots.

In a pinch oil paint works well as a transfer medium.

Hey guys, sorry it's been a while....busy time of the year!

So I located some Canode from American Rotary Tools Co. As far as I could tell, the usual suspects (MSC, McMaster) don't carry it.

Die Spotting Ink - ARTCO - American Rotary Tools Company

Price was reasonable.

I finally got back into the gib today and wow, what a difference the thicker paste bluing makes! A few lessons learned:

From the get-go, I realized that the thickness of application is VERY important. This stuff is quite thick, just like oil paint, as Spyderedge mentioned. The thickness that gives a fairly easy even coating with a brush is much too thick for a good spot. I noticed that the quantity of Canode on the gib made a noticeable difference in how far it would insert with finger force.

I started by putting the bluing on the gib, inserting it, tapping lightly with a mallet and brass rod, and then withdrawing. I worked only one face at a time, allowing me to slide the gib along the other face without smearing the blued face. I got mixed results....even when using fairly light coats of canode. I would get some points of contact and some areas of light blue (yes, pressure is clearly visible with it), but it wasn't as good as I wanted.

I decided to try bluing up the inside surface and inserting a clean gib. Maybe this is obvious to you all, but it was a learning experience for me! Because I was too lazy to get an engine hoist to the location I was working at, I had an obvious problem.....how do I blue the inside surfaces of this pocket when accessing them requires removing and re-installing a 200+ lb table onto the saddle? I ended up cleaning off the gib and applying a thin line of Canode with the bottle tip in a zig-zag pattern on the face I was working with. I would then tap it home firmly, pull it out, and reinsert it with finger pressure several times. Upon withdrawing it, the entire gib had an even coat of blue. Logically, this meant the pocket did as well. I then cleaned off the gib and reinserted with light taps, and pulled it out. It gave some information, but looked like there was too much bluing. I cleaned it off and reinserted. This was the result....and possibly the most useful spotting I had seen yet.



The contact points were clearly identifiable and their interiors showed lighter bluing...indicating pressure. I.e....these were true high spots. This was on the non-sliding side of the gib.

This was the next spotting. The big blobs of contact had started to break up and form two distinct groups on the end of the gib. I wasn't explicitly going for a gib that bore at the ends (I know some prefer that), but at this point in the project, I'm ok with that being the general result.



I realized just now that I apparently forgot to take a picture of the last spotting on the non-sliding side of the gib that showed even more even bearing in wide swaths of both ends. There were easily 10 points of contact per inch.

I switched to the sliding side. This was the first spotting.



Another shot (sorry about the glare)



This was after one or two scrapings....improvement!