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Cracked Gib!

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Izzy

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#1
Hey guys, i asked this in another thread but got no response figured i should start a new thread for this. i found a cracked gib in my compound slide when i was taking my lathe apart for thorough inside and out cleaning! its a tapered gib and the crack runs about half way down the gib. i dont have any pics currently but i can get some next weekend when im at the machine. my question is can i fix this or will i have to make my own? i dont think ill be able to find a replacement as its vintage lathe and the manufacturer no longer exists... heres a link the original thread i asked the question in if anyone was wondering...
http://www.hobby-machinist.com/threads/new-to-me-mckenzie-lathe.52122/#post-436421
 

brino

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#2
Hi Izzy,

I am now "watching" both this thread and the previous one......somehow I missed the previous one.

I know I have seen a discussion here about replacing gibs, I'll see if I can re-find it.

-brino
 

Ulma Doctor

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#4
if you have a longitudinal crack in the gib, replacement is the best option.
cast iron or hard bronze would make excellent gibs
 

4gsr

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#5
Is this a tapered gib? Or is it straight or has parallel sides with a parallelogram shape?
 

Izzy

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#6
Izzy,

Sounds like a good project for that new mill of yours :)

Ted
I think so too! I had to get some work done to the motor and winter just hit here pretty hard! So things are being put on hold for while but I'm doing what I can in the mean time!
if you have a longitudinal crack in the gib, replacement is the best option.
cast iron or hard bronze would make excellent gibs
I'd probably have to go bronze as I don't think I could get cast iron square stock? How would I go abouts doing a cast iron gib?

Is this a tapered gib? Or is it straight or has parallel sides with a parallelogram shape?
its tapered and has keyway along the top of the non tapered edge I'll have to get a picture next time I'm at the machine.
 

Ulma Doctor

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#7
http://www.speedymetals.com/c-8389-category.aspx

i'd also like to see the picture of the broken gib, i can only speculate without a body .

you can duplicate the gib easier if you have a milling machine.
...but somebody, sometime did it with a hacksaw and a file.
if the gib is short enough you may be able to mill it in a lathe
 
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ch2co

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#8
Possibly silver solder it first and see if that works before making a new one??

Just the rantings of
CHuck the grumpy old guy
 

Tony Wells

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#9
Might work fine if is were silver-brazed, plus you could get some more accurate dimensions off it if you're careful with the repair. Silver-brazing is good for many things. And I mean the good stuff. BAg-1 (45% Ag) would be good to keep around the shop, along with the proper flux.
 

Izzy

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#10
I wouldn't mind giving brazing a shot I mean I really don't have anything to lose. What would cause a gib to crack anyways? The gib adjustment screw is stripped so I have a good feeling it was just over tightened but there was also paper jammed in there I dunno if that coulda caused that too.
 

4gsr

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#11
....snip......

its tapered and has keyway along the top of the non tapered edge I'll have to get a picture next time I'm at the machine.
I'll do looking in my collection of gibs. I may have one close enough that you maybe able to modify to fit.

Please post some pictures, sure help on getting you fixed up.

Ken
 

Izzy

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#12
I'll get some pics up as soon as I can I just got impatient and figured id make a thread :p maybe I can get someone to send me some pics as I live in a different city from where the machines are :(
 

chips&more

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#13
Is the gib still in one piece? If so, maybe just leave it alone. Maybe drill a stop crack hole in it and use it as-is. Replacing a tapered gib is NOT just buying an off the shelf gib and swapping it out. It won’t happen that way…nada. You will have to make it or modify one. And I just made one out of 12L14 (I think the lead in it will help) for a Levin cross slide. Works like a champ. It would be a REALLY good thing to have a surface grinder for this job…Dave
 
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4gsr

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#14
Back in the days of machine tool repair, we had a shop make our gibs for us. They would buy a slab of cast iron of a determine thickness, usually about two foot square and about 1" to 2" thick. In fact, they kept several thicknesses of cast iron plate on hand just for gib making. They had a smaller openside planer in house that they used for this so they didn't tie up the "beast" for real planning jobs. Took a part off tool and would rip off pieces of varying thicknesses with a taper that matched closely with the original. Once that was done, they set up a angle fixture that was a magnetic chuck and start working the angles until the gib shape was made. Next it went to the machine component the gib was made for and the master scrapers fitted the gib to the slide. Last, the gib was cut to the necessary length and gib screws fitted to the gib and slide.

Just from my own experience, if you use a surface grinder, you will have a problem with the gib warping on you. It takes lots of flipping from one side to opposite side, doing this many times taking only a thousandth or less to keep warpage to a minimum. I find it easier to set up on the mill with a fly cutter or inserted face mill that uses a high positive insert to mill the faces of the gib. You still have to leave material and take same amounts from opposite sides to get the warpage to go away. But with the face mill it tends not warp as bad as it will on a surface grinder. Making a gib out of steel is common, but I prefer cast iron. It's much easier to scrap than steel is. And don't use brass or bronze for a gib. Ken
 

Izzy

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#15
Is the gib still in one piece?
Yes it's still one piece but just barely I thought about stop crack drilling it but didn't know if that was acceptable on this part maybe I could do that along with Brazing to get me by until I can get/make a new one!
@4gsr the only machine tools I have is my birdgeport mill and my McKenzie lathe I do know some places locally that could do surface grinding if it was absolutely necessary and I've been really curious about the scraping process maybe this would be a good starting point for me to learn? Start small and work your way up right? :)
 

chips&more

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#16
Brazing it IMHO does not sound like a good idea. It will take a lot of heat to do that. And so you could warp the part with all that heat. And then your gib would be just about useless. Or need to be reworked. It’s a chance I would not take. I would stop the crack and just use it. How did it crack in the first place? Did it crack on its own? Maybe from internal stresses? What do you think all that heat would do to those existing internal stresses?….Dave
 
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4gsr

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#18
Izzy,

I found a gib that matches your description stated earlier. It's probably much bigger than the gib you have on hand. About 5/8"- 11/16" thick, 1" wide at the biggest end and about 12" long. If you want it, pay the pay the postage and it's yours.

Ken
 

Izzy

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That would be awesome! Could you send me a picture? Also I'll be at the machine on Christmas (yea I know not so convenient for everyone else) I'll be able to get pictures of mine at that point.
 

4gsr

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#20
I'll take some pictures and post

Sent from my SAMSUNG-SM-G920A using Tapatalk
 

4gsr

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#21
Here's some pics. This is a steel gib made from some form of 1018-1026 steel. If interested in it send me a PM with your shipping address and I'll get a shipping rate for you. Just let know. Ken

It would help if I would attach the pictures.

Oh, before I forget, this gib was design to fit on the left hand side of the cross slide. May not work for you as machined. Ken
 

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Bob Korves

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#22
Is the gib still in one piece? If so, maybe just leave it alone. Maybe drill a stop crack hole in it and use it as-is. Replacing a tapered gib is NOT just buying an off the shelf gib and swapping it out. It won’t happen that way…nada. You will have to make it or modify one. And I just made one out of 12L14 (I think the lead in it will help) for a Levin cross slide. Works like a champ. It would be a REALLY good thing to have a surface grinder for this job…Dave
Not the surface grinder, but rather the surface grinder magnetic chuck to hold the gib while you scrape it in...
 

chips&more

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#23
Not the surface grinder, but rather the surface grinder magnetic chuck to hold the gib while you scrape it in...
Hi Bob, there are so many sizes and shapes of gibs! I do apologize for not being clearer! But, I will stand on my statement of using a surface grinder on making that gib. Because in my statement above, I said it was for a Levin cross slide. The gib was 2” long. And I made it out of 12L14. Warping was not an issue because of size and material, period! The size and material will judge what procedure to manufacture a gib in question as best as possible. To say using a surface grinder is the wrong technique is NOT TRUE. For me, it was the BEST machine/process to use, period. And I will continue to use my SG again and again if the same job comes up. For me, it is the definitive set-up, period…Dave
 
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Bob Korves

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#24
Hi Bob, there are so many sizes and shapes of gibs! I do apologize for not being clearer! But, I will stand on my statement of using a surface grinder on making that gib. Because in my statement above, I said it was for a Levin cross slide. The gib was 2” long. And I made it out of 12L14. Warping was not an issue because of size and material, period! The size and material will judge what procedure to manufacture a gib in question as best as possible. To say using a surface grinder is the wrong technique is NOT TRUE. For me, it was the BEST machine/process to use, period. And I will continue to use my SG again and again if the same job comes up. For me, it is the definitive set-up, period…Dave
Skinnier gibs like for a compound rest could well be a problem using the surface grinder where they are thin and more likely to be steel. Bigger ones not so much, but I suppose you would also need a sine plate or some other way of matching the angles, none of which are parallel on some gibs, while also holding the gib down. I do not like scraping steel after surface grinding it, it is ugly until you get under the ground surface. I have not tried scraping cast iron after surface grinding it, does anyone know how that goes? You are certainly correct when you say that making a gib is much more difficult than it appears. I have never made a gib, but have finished the job the factory should have done on a couple gibs.
 

Izzy

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#25
Wish I had a surface grinder :p maybe one day I'm only just beggining to gather my machine tools and tooling :) but for now I'm young and willing to take on a challenge! :)
 
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chips&more

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Skinnier gibs like for a compound rest could well be a problem using the surface grinder where they are thin and more likely to be steel. Bigger ones not so much, but I suppose you would also need a sine plate or some other way of matching the angles, none of which are parallel on some gibs, while also holding the gib down. I do not like scraping steel after surface grinding it, it is ugly until you get under the ground surface. I have not tried scraping cast iron after surface grinding it, does anyone know how that goes? You are certainly correct when you say that making a gib is much more difficult than it appears. I have never made a gib, but have finished the job the factory should have done on a couple gibs.
Not every gib has a taper. The one I made was parallel and about 2” X 3/8” X 0.o90”, see pic. Using my SG was the easiest way.
gib.JPG
 
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Izzy

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#27
Also @4gsr that looks just like my gib! I'm from London Ontario lemme know what shipping is gonna look like and we'll go from there :)
 

Bob Korves

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#28
Dave, I understand that there are pretty simple gibs, but most still have angles and such. How did you set up the angle for the gib you just posted? (Newbie surface grinder hand...)
 

chips&more

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#29
It did not have any taper, it was parallel. Yes, the sides were angled, but only for fitting. And I did that in a two vise set-up. The one Kurt milling vise that’s bolted to the milling table. And a smaller second vise with straight sides is held in the first vise at 30° to give me that angle you see. If I needed to make a tapered gib, I have a magnetic sine plate.
 
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