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Fix Wallowed Hole for roll spring pin in thin cast iron?

catalytic

Cast Iron
Joined
Feb 4, 2010
Location
Boston, Los Angeles, and Cleveland
The pics show a cast iron gib for a small Rusnok milling machine. It is retained in place only by a roll spring pin. The hole for the pin has wallowed out, esp. towards the non-bearing side.

What would you do to it before reinstalling? My tentative plan was to reinstall the gib/pin, then use a punch at a 45° angle to punch the wallowed parts into the pin.

Since the pin is the only thing retaining the gib, I have seen a few machines where the pin slips out, then the gib slides out as someone moves the x-axis. It appears to be a design flaw.

The gib is 0.125" thick. Pliers in pics for scale. The second, non-wallowed gib shows the correct size hole, but it's hard to see as it has not been deburred/countersunk like the wallowed one has.

Pic of wallowed side:
IMG-0039_2.jpg


Pic of non-wallowed side (lower gib in picture -- top one is brand new steel one but not deburred and I don't want to use it)
IMG-0033_2.jpg

IMG-0035_2.jpg
 
Drill a new hole in gib and table a half inch or so to the side of the worn out hole. Don't be hammering with a punch on precision surfaces.

In particular, don't hammer on cast iron, especially with a punch. Cast iron will break.

I have some precision slides where the gib is retained with a single pin, sort of like your machine. In mine, the pin is solid steel, a press fit into the body and the hole in the gib is a slip fit. It is easy to remove and reinstall the gib and the pin never has to be disturbed unless a new gib is being made.

On other slides I have, the adjusting screws have dog points that engage shallow milled pockets in the gib.

Larry
 
Thanks for the replies, and glad I asked before punching the cast iron. I knew this, having both snapped cast iron and peened it to bend it in other situations, and yet I was obviously not thinking clearly today.

The gib hole is wallowed enough that it's more than a slip fit -- there's noticeable side-to-side wiggle when I test fit it onto the pin.

I don't mind modifying the gib, but I'd prefer NOT to modify the machine (i.e. by drilling/installing a larger hole/pin or a new hole/pin location).

Could the hole in the gib maybe be filled with something and re-drilled to the correct size?
 
The hole is closer to one end of the gib. Can you drill a new hole at the other end of the gib, and just put the gib in backwards?
 
Many machines that use a straight gib the factory spot faced or also drilled a shallow hole so the set screws also held the gib from left to right and for clearance. not knowing your skill level, but if your very careful to install the gib with the old pin and hole and put in 2 screws to snug gib to machine way. Then resharpen a drill so it is flatter and that is the clearance of the threaded hole and spot a flat spot on the gib. Then screw in set screws in those holes and finish up the other holes. That way you will make the machine better. Be sure to use dog point set screws long enough so you can have a jam nut on the outside. Rich
 
If the gib is just really a parallel cast iron strip I'd be inclined to do what another poster suggested and drill another hole and reverse the strip. I'd fill the existing hole with something like " Araldite " though.

Regards Tyrone.
 
<Snip>

I don't mind modifying the gib, but I'd prefer NOT to modify the machine (i.e. by drilling/installing a larger hole/pin or a new hole/pin location).

Could the hole in the gib maybe be filled with something and re-drilled to the correct size?

I think it would be pretty easy to just bore out the existing hole to pretty much (would not have to be perfectly) clean up. Then make a moderately hardened O-1 bushing turned to fill the hole and accept the pin. It could be quite thin and still do the job and hold up well—-much better than the original hole.. Loctite it in place. Done.

I’d torch harden the O1 and temper it purple so that it would machine pretty easily.

Denis

Added: I suggest O1 as a more or less ideal material and method for this purpose. But if O1 is not easily available or unfamiliar, almost any stelel would serve. Perhaps a SHCS would provide modestly hard machinable stock not requiring any heat treat, for instance.
 
http://www.lathes.co.uk/rusnok/

After seeing what the machine looks like and re-reading the title (duh on my part) Cast Iron, I see it's a small machine with box ways. Seeing the gib has hold downs under it and can't drift down like the ones I have seen on dovetail ways just drill the hole bigger and use a bigger spring pin as there is enough beef in that gib to go a size or 2 bigger.

Also, what dgfoster suggests drill a bigger hole and bush the gib it would be a bit more complicated. If the gib surface riding against the box way isn't scraped then end for end and drilling a new hole seems like a good alternative too. You could slide it in and lock in in place with the sets screws and spot face the gib drilling though the original pin hole in the casting. Just spot it and take it out and drill a through hole in a drill press.

Another idea is to position the gib in the machine with pin in the gib and slide the table on instead of trying to pound the pin into the gib afterwards. Rich

PS: I'm not sure how thick the epoxy would be to adhere to the gib. If you use epoxy be sure to wear gloves. Then spot face it in the machine but don't drill through in the machine.
 
Better than JB-Weld for this use.

BROWNELLS STEEL BED KIT | Brownells

Hint: Punch holes in masking tape with a paper punch and there will be less epoxy to scrape off near the hole after curing. Also, I would suggest running a fine thread tap through the hole that just lightly grooves the inside of the hole. This gives the epoxy more surface area to bond to.
 
I'd avoid a larger spring pin for this application given they tend to have the ends pretty tapered and thinned out, plus the
actual split does reduce the bearing area.

I much prefer the turned, stepped, steel pin solution that's been mentioned.
 
Pick up hole location. Straighten hole with end mill. Drill or ream hole to nominal size. Make bushing from nominal size drill rod. Super glue/epoxy/Loctite bushing in hole. End of report......Bob
 
We just rebuilt my cold saw this fall, it had a snapped pin, and the matching hole was wallowed out. We tig welded it with silicon bronze filler rod, then rebored. This was in cast iron, worked fine. I have also used nickel rod to tig cast iron, it is tougher to machine than the silly bronze, but also sticks nicely to cast iron, without pre and post heat.
 








 
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