Best way to enlarge hole in cast-iron clamp?

Hi all,

I recently picked up three large (7") cast iron 3/4" pipe clamps for a buck each. Second hand, but never used, and I think I know why now: the two holes on the threaded side of the clamp don't match up very well. See a pic of the clamp at:

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It's too difficult to even get the thread started for two of the three clamps. On the one that I can actually thread (as long as the clamp bolt is completely extended), it is impossible to rotate the the clamp bolt back to the open position. All because the two holes don't align well.

Anyway, I'm thinking that the only way to salvage these is to bore out one side of the non-threaded hole until it is parallel with the threaded hole--removing about 1/4" of material by my estimation. The hole is 1" dia., 3" deep, cast iron.

What's the easiest way to remove the metal? I struggled with a round file for half hour and barely made headway (maybe 1/64"). I have a die grinder (but not the proper bit): is that the best way? Any other suggestions?

Thanks, H.

Reply to
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It sounds like the hole in the moveable jaw was bored slightly tilted. If you open up the upper part of the hole on the front side and the lower part of the hole on the back side of the moveable jaw, it may work easily. Much less material to remove.

As to how: I have a huge rat tailed file, 3/4" > Hi all,

Reply to
Roy J

Consider it "a learning experience". By now you've learned why they were marked down to a buck each.

If a file isn't cutting it well, chances are the cast iron contains Gawd knows what other scrap metals, and/or the hot castings were cooled by tossing them in a bucket of water and became "chilled cast iron".

Sounds like grinding with a cylindrical or cone shaped stone is the way to go, on the "tight sides" of the pipe hole as Roy suggested.

Other thoughts...

If the sliding parts can be easily separated from the clamp screw part, you might try putting them in a roaring wood fire and leaving it in the ashes until the whole pile cools down. That might soften them enough to let you file them easier.

From a bit of Googling, it appears that Jet clamps are distributed in the USA by "WMH":

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You might try pinging them and telling them a sob story about how you got your clamps as holiday gifts from your mother-in-law and SWMBO will kill you if her mom learns they're no good. Explain what's wrong with them and see if some customer service twit there identifies with your stated dilemma sympathises with you and ships you free good clamps.

My bride and I have a prearranged routine which we pull if I get pulled over for some minor traffic infraction; i.e. failing to notice a right turn only arrow painted on the pavement. As soon as the officer walks up and I roll down my car window she starts loudly berating me about how I never pay attention to what I'm doing and how even her mother thinks I'm a lousy driver and keeps telling her she shouldn't have married me if the first place, etc.

It's worked fine for us three or four times in the last ten years, so help me.

(Of course if you tell anyone I said that I'll have to kill you.)


Reply to
Jeff Wisnia

A mill or lathe would make pretty quick work of that.

A carbide burr for your die grinder would do it as well and is probably a lot cheaper than buying a mill or lathe :-)


Reply to
Paul Amaranth

Hey Jeff (and Roy above),

Thanks for the suggestions. I may try a larger rat-tail than I did (3/4"!!, that's nice....)

Won't a rotary burr work better than grinding stones in the die grinder?

If it still won't come off easier then I'll try the heating/softening route--that's a clever suggestion

Otherwise, I guess I'm left with sob stories. You've got some good one, I must admit. Had to laugh at your ticket scenario. And you did intend the pun in "It's worked fine for us...", right?

Thanks aga>

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Reply to
Bob Engelhardt

I had some cheap pipe clamps like this from the local Oriental Emporium. Damn things wouldn't thread onto the pipe. Brazed them on in the end - a lot easier although it did damage the cheezy paint job. Geoff

Reply to
geoff merryweather

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