Repairing Cracked Drill Press Vise

[JHCC]

On 9/28/2025 at 6:05 PM, Irondragon Forge ClayWorks said:

That vise will turn out just fine

Update: so far, so good. Unfortunately, I cracked the casting at the back corner, but I’m thinking about possible repairs once I’ve finished the cleanup. 

[Frosty]

How'd you crack it? Silver solder repairs cast iron good as new. . . . Almost.

Frosty The Lucky.

[JHCC]

Over-tightened it. 

[Irondragon Forge ClayWorks]

I would probably braze it.

I can’t control the wind. All I can do is adjust my sails. ~Semper Paratus~

[JHCC]

I might, but I've never actually brazed anything before. Could be a good opportunity to give it a try in a less-than-critical application, although I'd worry about throwing the vise out of square and flat.

[Frosty]

Yeah, over tightening drill vises is pretty common, I doubt you were the first to tweak that ear. 

Brazing and silver soldering are both hard solders. There are some pretty good low temp hard solders available and if you git right on a crack like that you can often get a good join without having to grind.

So long as you heat and cool slowly cast iron, especially thick profile cast isn't prone to warping. Heat the entire vise from the bottom side, use the outer flame from a large tip, stay away from the HOT inner cones and keep the flame moving! You want the "bottom" ( the place the crack stops) of the crack a LITTLE hotter than the rest of it and evenly heated on both sides. Lay a piece of self fluxing brazing rod or dust the crack with fine powder flux a GENTLE puff from a distant air hose or a hand bellows will help. Do NOT try blowing it in with the air hose, you do NOT want high velocity grains flying around.

Once fluxed just lay a length of fluxed brazing or silver solder rod on the crack and slowly bring the vise's temperature up till the rod flows into the crack, take the torch away and look at the crack on the torch side. If you see solder/braze it's good just let it cool. If you don't see braze or solder add a half sized piece to the top, if it doesn't flow bring the torch back but keep the heat GENTLE.

Hard solder flows TOWARDS the heat so always apply it at the far point from the torch, iron, etc.

If you've soft soldered before, hard soldering is the same process, just hotter.

Frosty The Lucky.

[BillyBones]

Drill and tap. 

Brazing is just fancy soldering. Same principle applies, heat the metal until it is hot enough for the braze to run. I love brazing, especially forge brazing, something kind of magical when it happens. 

[JHCC]

21 hours ago, Frosty said:

thick profile cast isn't prone to warping

And therein lies the problem: the cast is fairly thin at that point. Maybe 1/4"?

[Gazz]

I have repaired broken iron castings before and have used several methods, Ni rod, braze, silver solder (high temp  - not the stuff that plumbers use) and MIG.  In all methods I would clamp the vise to a heavy piece of steel to keep it flat and another clamp to close the crack up and do the repair while it remains clamped.  Preheat the whole thing with a rosebud and cool slowly when done for all methods.

Ni rod - grind the crack out and have at it with the rod.  Remove the clamps and grind the other side out and weld.  Bury the thing in vermiculite, sand or ash to let it cool slowly and when cool, grind the bottom surface flat.

Braze - grind the crack out and fill with brazing rod with an oxy/acetylene torch.  A small piece of steel can be added to bridge the repair to add more strength as long as it does not interfere with the operation of the tool and braze that in place too.  After cooling, soak in warm water to dissolve the flux.

Silver solder - grind the crack out and lay a steel rod or screw/bolt in the crack, flux and add the silver solder.  The rod or screw serves to reduce the amount of the expensive silver solder required.  Repair parts can be added as above as well.  Clean metal is important when using silver solder.  After cooling, soak the part in warm water to dissolve the flux. (you could probably buy a new vise for less than what the silver solder would cost but what fun is that?)

MIG - grind the crack out and weld as usual.  This method is best for items that do not require great strength such as decorative stuff and seems to work well enough for that.  I have found some cast iron parts do not take the MIG weld very well so it may not work for all things.

I once had to repair a broken casting that was the gear cover for a large mixing machine.  I was about 36" in diameter and I first ground the crack out to a vee and placed the whole thing on a large bed of glowing coals from a fire that I had built for the repair.  Then brazed the vee and covered the whole thing with sand to allow it cool slowly.  No complaints from the customer.

[JHCC]

Any recommendations for brazing flux? I doubt I'll be doing a lot of cast iron brazing, so if I can use anything I already have (homemade anhydrous borax, 20 Mule Team, boric acid (Roach-Prufe), Iron Mountain) and not have to invest in a big can of something new, that would be great.

[Frosty]

Buy self fluxing brazing rod and break some off the rod and grind it to fit. Remember, flux isn't glue, just a LITTLE BIT does the job, especially in such a small gap as crack repair.

I have most of a can of Peterson #1 Blue flux has been my go to flux for forge welding, brazing, silver soldering, mokume gane, and a 1lb. can cost me about $26 at a local welding supply.

I've use a couple other "real" forge welding fluxes and while they work Peterson worked better at less than 1/4$.

If you like powdered iron oxide in your flux I believe Peterson made that too but don't quote me, ask them.

Frosty The Lucky.

[Gazz]

Use the flux coated brazing rods as they are - no need to break any off.   If the brazing rods you have are not coated, use the borax.  I've used that for silver soldering before.  Also as Frosty states, your local welding supply place probably has a can of flux on the shelf.

[JHCC]

So, to wrap up this sad tale, I made a little fish plate out of angle iron, clamped the crack shut, marked the screw hole locations with a transfer punch, drilled and tapped said holes, and bolted the whole thing together with some 8-32 machine screws:

Unfortunately, the tap broke in one of the holes, which is why there are only five screws rather than six. However, I figured the other two screws on that side of the crack would offer enough strength, so I didn't bother extracting the broken tap and finishing that hole.

I also replaced the setscrew that holds the end of the vise screw in the moveable jaw, as the old one was pretty chewed up. I couldn't find my setscrew jar, so I made this one from a small machine screw with the head cut off and a slot cut in the end:

This is shown before it was screwed all the way in; when it's all the way down, the end is flush with the surface of the jaw.

Under all the rust, the working surfaces of the vise turned out to be in excellent condition. Everything is nice and tight, and the jaw moves with very little slop. Mission accomplished.

[Frosty]

Good save John, not as pretty as a nice brazed or silver soldered join  but functional was the mission. And you can always learn hard soldering on test pieces.

Frosty The Lucky.

[Irondragon Forge ClayWorks]

Looks good to me and what is the saying "necessity is the mother of invention".

I can’t control the wind. All I can do is adjust my sails. ~Semper Paratus~