Gib advice?

[DPittman]

Hi,

I think I should line up some material to make some new gibs for my bench lathe. The original ones are of a steel material and it appears they were machined by a rat and then screw dib points were made by a drunk man with a hand drill (OK I'm exaggerating a bit) .

I think I will hopefully find some brass for this.

Any suggestions or tips? It seems like a fairly straight forward thing but so has many other things that ended up being very complex and involved! I suspect a few of you that have rebuilt machines knows a thing or two about gibs? (I'm not even sure if it's gibs or gibbs?)

 

[RobinHood]

Gibs are typically made from cast iron. It is easy to machine and scrapes very well with hand tools to get the final fit. It also retains oil better than brass. Look for it under “ductile iron”.

 

[PeterT]

Good overview of remedy options pros & cons, ultimately making a new one from CI.

 

[PeterT]

Rudy have you ever done Turcite application?

 

[RobinHood]

No, I have not.

 

[DPittman]

Thanks for the info. It does sound like it is more involved and precise than what I was hoping . I might have to leave that project for another time as I do not have a mill or surface grinder. In the meantime I will start looking out for cast iron stock. My gibs are small things maybe 1/4" thick? I would have thought cast iron that thin would just snap?

 

[RobinHood]

Do you have a picture of your existing gib? From your description it sounds like it could use some TLC. It is not broken, correct?

You can make your own hand scraper and using some Prussian Blue you could do a print of your existing set-up and scrape what you have for a better fit. Even careful sanding of any high spots will improve it.

 

[DPittman]

Do you have a picture of your existing gib? From your description it sounds like it could use some TLC. It is not broken, correct?

You can make your own hand scraper and using some Prussian Blue you could do a print of your existing set-up and scrape what you have for a better fit. Even careful sanding of any high spots will improve it.

Yes I should take it out again and have a look. I do remember when I first got this lathe I did do some hand file/stoning work to improve it but I think it could be improved. No I don't have a picture of it.

 

[John Conroy]

If the gibs or ways are worn a little you can use shim stock to add to the thickness of the gib. Cut a strip the same width as the gib long enough to fold over the gib at each end so it can be held in place by the adjusting screws. You can put the shim on the non wearing side of the gib. I did this on my old mill and it has worked fine. I bought a roll of .003" and one of .006" brass shim stock from KBC. I wound up using the .006"

 

[Dabbler]

You can work on your existing gibb, to put oil ways (these may be seem as poor machining on the surface) and to straighten the gibb if it has worn unevenly. This can be done with hand tools, but it will be a project (and because you are new to this) it will take a lot of hours. Hours without your lathe.

You might consider using the lathe the way it is and sourcing stock for a new gib, and when you are ready, making a new one. As John says above, the old one can be shimmed - and that will keep you going a long time.

 

[DPittman]

Yes all good advice I will take in, thank you. I have a couple of tight spots in my carriage movement and I suspect that is mostly due to the gibs but it may also be due to the ways themselves. I also suspect I have tightened and ran the gibs up too much in the past in an attempt to reduce slop.

 

[Dabbler]

You can 'touch' up the gibb by scraping by using very little in tooling (an offshore surface plate, some watercolour paste, and a cheap braze-on carbide tool)

The ways would require a 60 degree straight edge, which would cost well over a hundred bucks, but then you could touch up that too. For a touch up, there is little risk and technique can be learned by watching youtube and self-discovery.

It's dimensioning and holding to an angle or scraping for parallel that things get much harder very quickly.

 

[PeterT]

Cut a strip the same width as the gib long enough to fold over the gib at each end so it can be held in place by the adjusting screws.

I always wondered about how the shim was held in place in those cases. I guess if its trapped between the screws & same width as the dovetail segment, it cant curl or go anywhere.

The reason I asked about Turcite is looking at the the manufacturer & end user installations, they use an epoxy adhesive between the CI & strip material. After bonding & trimming the Turcite might be further scraped in, or sometimes that's it depending on the installation. Obviously epoxy adhesive is more than strong enough in this application, there is very little shear on the joint itself. To remove one day I guess they just use a heat gun & off it comes. So I bet you could borrow this technique & glue metal shim stock too.

I dont see Moglice used in this manner on the face of gib strips, usually only saddles & ways. Maybe there is higher risk of inadvertently permanently the components together if the epoxy drain flows out or releasing agent isn't just right. I've seen my fair share of that action with composite molds haha

 

[Dabbler]

So A guy I know rebuilt 5 punch presses for a truss company in town. He rescraped the ways to true, squared the machine and then bonded normal .030 teflon to the ways using epoxy. Until then the presses needed service every 800K-1M punches. After the teflon, they went 20M and still were going strong when I lost touch with the production manager.