Pipe clamp - cleaning black iron

[Justin Choi]

I have to clamp a ~50" workpiece so I broke down and bought my first pipe clamps. It sounds like black iron pipe was the way to go, so I bought that. I used mineral spirits to clean the pipe of excess sticky residue, but it looks like I'm beginning to strip off the black coating completely in some areas. I don't know how, I only had paper towels. The worst part is, the pipe still transfers stuff to my hands.

This is probably basic, but am I supposed to strip the black off or did I somehow overdo it? If I overdid it, what should I have done differently? Is there a way to salvage this or do I need to get new pipe? I've got oil-based primer, oil-based enamel, and high heat black spraypaint. All rustoleum if it makes a difference.

[Al Launier]

Alternatives:
Mineral spirits should evaporate leaving "some" of the paint. When it dries you could sand it thoughly even risking getting down to base metal in places.
Sand it down completely removing all paint risking pipe rust over time.
Prime & paint after sanding.
Use galvanized pipe instead of black pipe.


If you leave "tacky" paint on the pipes you risk contact & smearing your workpiece or finish.

[ian maybury]

I looked at pipe clamps years ago, but didn't follow through so my recollection regarding choice of pipe type is hazy Justin - but since you have no other answers. There may be fans of both types of pipe about (black and galvanised), but I suspect galavanised pipe is less inclined to mark wood if this matters in your situation.

I've have a feeling depending on the piping schedule that your black pipe finish could be a chemical pickle with maybe a film of oil or something to prevent rust, or else a cheap sprayed lacquer of some sort. If the black is washing or falling off it might be the latter - finishes on pipe are likely pretty basic.

Either way you can probably clean, remove anything loose or oily, and then paint it. Try whatever paint you fancy, and wash it off if it reacts with the original black - and try something else if needed.

The potential problem is probably the combination of clamps and paint. They may scrape your paint off again, or even be inclined to slip on it. If trying paint i'd go for something as thin and tough as possible - but galvanised pipe would again likely be more robust.

I don't speak American and so am a bit hazy on the topic, but have some recollection that the schedule system of pipe types can be a bit odd. Depending on exactly which one you get it could be that there are differences in the outside diameter of different specs of pipe - which might given the wrong one mess with the action of the clamps.

Do i remember some (might be best to go for one of the better ones) clamp suppliers offering stock pre-threaded lengths of galvanised pipe with their clamps? Might it be one way of making sure to get the right type of pipe?

[Peter Quinn]

Just clean them as well as you can with your solvent of choice to remove dripping oil, perhaps a coat of clear sealer or a spray sealer like boshield etc, that's about all I've ever done. The raw iron staining is pervasive, the key to gluing up is not to let the pipes touch the wood. I use 1/4" rips of plywood or drops from milling layed perpendicular to the clamp direction, usually long thin strips cut the length of the glue up, these keep the pipes from interacting with the wood. The issue is many species have some degree of tannins, add water from the glue and you get iron tannate.....or ugly black stains at each point where the pipe touches glue. It's basically the same thing as the steel wool and vinegar stain used to age wood, but just in a few little blotches. These can go deep enough to be very difficult to sand or scrape out, but they are easily eliminated with proper use of stand-offs.

PS......don't ever buy galvanized pipe thinking it's the solution. The galvanized coating is slippery, and the ratchet mechanism of the clamps has trouble making purchase on the pipe, so the clamps slip rather than lock and tighten. I've been there too many times, every shop I've worked in had at least a few galvi pipes laying in the corner unused, and they are way more expensive, still leave marks on the wood too! So skip that pain.

[Cody Colston]

I have a bunch of 4' pipe clamps that I use for clamping long pieces. I used 3/4" black pipe from the borg and wiped them down with MS on a rag to clean them initially. I don't get any residue on my hands but they will turn the wood black if they contact it during clamping. Some wax paper underneath the pipe solves that issue. I found the adjustable end of the clamp didn't slide well on galvanized pipe so I went with the black stuff. YMMV

[Max Neu]

I agree about not using galvanized pipes, they just don't make good clamps.I have a pile of them I only use in emergencies.

[Alan Bienlein]

There isn't anything wrong with galvanized pipe for pipe clamps if you get the correct type. I use 3/4" ridgid conduit for my pipe clamps and I never have to worry about black stains from glue touching the pipe and the panel and I can crank down as hard as I want with out fear of slipping.

Some times you just need to think outside the box and go to the electrical section to get your pipe.

[Jim Dwight]

I have both galvanized and black iron pipe in pipe clamps. I have to swat the pawl on the fixed end with a soft blow hammer (or a regular hammer) to set the jaw on the galvanized. They work fine with the additional step. The black iron don't need that. I didn't do anything to clean the black iron. I remember them being a little sticky for awhile but it went away. If you pull the workpiece from the black iron clamps after an hour or so, I don't see any bad staining. If I leave it overnight, I may.

[Lee Schierer]

I also have galvanized pipe on some of my pipe clamps. They work just fine with the toothed pawl type clamps. The stacked angled plate type clamps don't work well on galvanized pipe.

[ian maybury]

Completely without experience, but i though i saw the view expressed somewhere quite a few years ago that the issue with galvanised pipe experienced by some may be down to the diameter of the pipe being slightly different. Which was why i mentioned that the differing pipe schedules and standards can result in subtle differences in OD for what's nominally say 3/4in pipe.

Don't know if it's true, but it might be worth measuring and comparing. If nothing else pipe clamps are presumably designed to work best on a given diameter of pipe, although i've never seen that specified.....

[Alan Bienlein]

I have both galvanized and black iron pipe in pipe clamps. I have to swat the pawl on the fixed end with a soft blow hammer (or a regular hammer) to set the jaw on the galvanized. They work fine with the additional step. The black iron don't need that. I didn't do anything to clean the black iron. I remember them being a little sticky for awhile but it went away. If you pull the workpiece from the black iron clamps after an hour or so, I don't see any bad staining. If I leave it overnight, I may.



Lee Schierer
I also have galvanized pipe on some of my pipe clamps. They work just fine with the toothed pawl type clamps. The stacked angled plate type clamps don't work well on galvanized pipe.



Now are these from the plumbing section or are they 3/4" Ridgid conduit meant for electrical? All of mine use the stacked angle plates and they have no problems grabbing the the galvanized 3/4" Ridgid conduit. Even my harbor freight clamps grip so good I sometimes need to hit them with a hammer to loosen their grip on the pipe after use.

[Kent A Bathurst]

I'm baffled by the premise: Black Pipe needs to be aggressively cleaned. :confused: :confused:

My big - BIG - collection of 3/4" black pipe clamps are as much as 15 years old, and I used them straight from the store. Every one. If I had them cut and threaded, I used whatever was handy - MS? DNA? - to wipe off the cutting oil, but I didn't get all obsessive about them.

On the marking - yeah, they will mark wood - really nasty if it gets in the glue squeeze out.

Do this - black or galvanized:

Get a short length [couple-three feet] of 1" PVC pipe. Cut it into 1" +/- sections.

Take those to the BS. Cut out a big slice, so that you have left a partial circle that is about 2/3 or less of the original circle.

Snap 2 of these onto the 3/4" pipe, and they provide you a nice offset. Unless you are off on your glue application by a few gallons, the squeeze out will never touch the pipe. The pipe will never touch the wood.

They slide up and down, they come off and on very easily. Screw them to the wall, and they make excellent vertical pipe clamp holders. It slices. It dices. But wait!! Ther.......Ooops, nope, no more.

[John Lankers]

I wipe new black pipe with mineral spirit, let it dry/evaporate and apply a length of blue painters tape where the pipe makes contact with the wood, no issues and the tape lasts a long time. I find that no matter what, black or galvanized pipe will eventually stain the wood.

[Marc Rochkind]

Maybe black pipe has changed over the years. I just bought a few lengths at Home Depot, and they were very gunky. Took off the black stuff 100% with Goof Off, but probably MS would have worked. Not a trace left. Horrible job, but now done. Next time, if there is a next time, I will get galvanized or something else.

[David Ragan]

I cleaned off my black pipes upon purchase. Checked them as the years rolled by, and they are still clean/dry.

I normally just use blue masking tape on all clamping fixtures next to wood; peel it off @ the end of project.

Those bar clamps of any variety don't work so well when glue adheres to the bar.

[ian maybury]

There's seemingly (?) different pipe finishes about depending on the code/spec of what you buy. Chemically pickled and possibly oiled - or alternatively lacquered?

[Myk Rian]

i wipe new black pipe with mineral spirit, let it dry/evaporate and apply a length of blue painters tape where the pipe makes contact with the wood,
^^^^this^^^^

[Tom M King]

I have stacks of them that I'm sure are over 25 years old, and never did anything to the black paint either. I use whatever I can find to block them off the work, especially if there is glue involved. I have three 20 foot long sections that maybe once every 10 years get joined together with couplings to make really long clamps for working on houses. The clamps don't hold well on galvanized pipe if you need to put much force on anything.

[Dave Cav]

I'm baffled by the premise: Black Pipe needs to be aggressively cleaned. :confused: :confused:

My big - BIG - collection of 3/4" black pipe clamps are as much as 15 years old, and I used them straight from the store. Every one. If I had them cut and threaded, I used whatever was handy - MS? DNA? - to wipe off the cutting oil, but I didn't get all obsessive about them.


A man after my own heart. My collection of pipe clamps (55+ and counting) is up to 30 years old, and they're made of any kind of 3/4" pipe I could lay my hands on. I'm way too cheap to buy pipe at the store. I got most of mine at the salvage yard, cut it into appropriate lengths with my (metal) chop saw and threaded the ends. On some of them I threaded both ends and put a coupling on the bottom end so I can connect a couple of them together if I need any longer than 6 feet.

[ian maybury]

C'mon guys, let's get real about this and maybe back off on trying to (subtly) own the sand pile - and on the lobbing in of unqualified assertions. We're heading for page 3 and still going around in circles - and will get nowhere until some hard information on what actually makes pipe clamps work starts to hit the table.

This (with the inconsistent quality of sample clamps) is precisely why years ago when setting up to buy a set of clamps i gave up on trying to bottom these questions and went for various Bessey parallel clamp options instead. There's no point paying out loads for pipe and clamps, putting in the time to clean, cut to length and thread the pipe (which may entail more cost in hiring pipe threading kit) - only to find that the result doesn't work very well.

Some say black pipe is oily. Some say it's dry. Some seems to be pickled, some lacquered. Some say galvanised pipe works perfectly with pipe clamps, some say not. Some say the type/spec of pipe matters a lot, others don't seem to have a clue as to what pipe they use. There's clearly differing brands and maybe models of clamps in use.

The two big variables are pretty clearly the key details of pipe (surface finish, roundness, dimensions, coatings, required wall thickness etc), and the clamp itself. (brand/gripping principle/manufacturing quality/other details) If nothing else some pipe has a welded seam, and depending on the quality may or may not be truly round or smooth. There's also the possibility that technique plays a part. The one thing you can be pretty sure of is that whatever black or galvanised pipe were 20 years ago, they certainly are not the same now - not when bought retail anyway, and not since the box stores ('source it cheap above all else') and Eastern makers got involved.

We have to presume that the various conflicting views are honestly presented, and that differences like the above account for them.

:) Maybe we can with some effort run to ground the 'why' of the issue???

[jack duren]

Personally I wanted galvanized pipe but the shop bought black pipe instead. We wiped everything down with lacquer thinner and put them to work. If there really oily then get them somewhere where they are not.

Galvanized pipe works fine but cost more....

[Prashun Patel]

I am with dave and kent. I never cleaned mine and never had trouble with gunk. I get more headache from the rubber clamping pads leaving oil marks.

anyway if i were concerned about it, i would just wipe with a dry or ms damp cloth, then spray it with shellac or lacquer. Thats what i do with wrought iron cabinet hardware and it works fine.

[John Lankers]

There's seemingly (?) different pipe finishes about depending on the code/spec of what you buy. Chemically pickled and possibly oiled - or alternatively lacquered?


Ian, it is starting to dawn on me that this seems to be the issue.
Galvanized thin wall pipe, black painted heavy wall pipe and black (unpainted but oiled) heavy wall pipe. I don't like the galvanized pipe because it's not rigid enough and water in the glue can react with the zinc and cause black marks. The black painted pipe should be fine. The black, oiled pipe can rust when it comes in contact with water and cause brown rust stains on wood, but it's cheaper.
I like Prashun's suggestion of applying a coat of Shellac or Laquer - good idea.

[Alan Bienlein]

What galvanized thin wall pipe are you talking about? I never get my pipe from the plumbing supply house or the plumbing section of the borgs. Instead I go straight to the electrical supply house or section of the borg and get the 3/4" ridgid conduit.

[Kent A Bathurst]

Just to rail against the rainstorm one last time:

You may be missing a central point:

The blue tape and the shellac/lacquer will prevent the stains. BUT - you are still smearing squeeze out onto the surface. If you have open-pored wood [WO, etc.] you now have glue in those pores and it will not take dye/stain/varnish. You have to plane/sand down through that to get to fresh fiber.

If you enjoy that, carry on.............the real point of the PVC standoffs is to prevent that misery. But then, I do a lot of QSWO and it is very important/advantageous. And, I have been able, over the years, to get to a point where my boards align well enough that just a card scraper finishes the joints. Before that, the glue in the pores did not matter because I had a lot of work to do to get the surface flat, and the glue was gone anyway.

Rant over.

[Charles E. Bishop]

Justin;
I've been where you are.. Decades ago, when one bought (or found) black pipe, it had no "coating" other than a "Black Oxide" finish.. Then the pipe companies "cheeped out" and started dunking the pipe into some sort of "Black Tar"... inside and out!! As I do 99.9% mechanic work, I have a 25gal parts washer, so I put the "under 24 inch" length pieces of pipe into it and let them soak (in kerosene) for a few days.. This softens the black coating enough to wipe off, still with some effort. It's an improvement by degrees.. I also have some four and six foot lengths of black pipe.. a couple laid outside in the weather for a few years, the others I had to clean by hand (hard on an arthritic old man!) but those are the only choices that I know of.. I do have a couple of galvanized pipes.. These are NOT good to use with pipe clamps.. the "clamps" tend to slide on the zinc coating (the galvanize).. I've had to use a ball peen hammer to "persuade" the clamps to actually "bite" into the zinc.. Not worth the effort, in my opinion.. So, buy a couple rolls of those blue shop towels (paper) and a gallon of kerosene and spend a few days outside scrubbing black pipe :-( Charles.
PS Do NOT paint the black pipe, the clamp "locks" slide on the paint, until it's scraped off.. ceb

[Mike Schuch]

I have been using galvanized pipe clamps for almost 30 years. I have never had a problem with any of the clamp heads I have, from pony to HF cheapies. I have never had a problem with the jaws slipping.

[Jeff Ramsey]

Kent, nice tip on the PVC that I'll be using next time with my black-iron clamps.

[Phil Thien]

What galvanized thin wall pipe are you talking about? I never get my pipe from the plumbing supply house or the plumbing section of the borgs. Instead I go straight to the electrical supply house or section of the borg and get the 3/4" ridgid conduit.

Don't the pipes thread onto the pipe? How do you get the EMT threaded in the lengths you need, do they perform this in the plumbing sections for you?

[glenn bradley]

I've used galvanized pipe with Jorgensen No. 50 style heads since . . . forever. No stains, no slip. As others have noted, I do keep the pipes off the surface to avoid smearing squeeze-out onto the material when that is worth the effort. That is; when the effort to clean up exceeds the effort to not smear in the first place. An example might be a panel that is close to finished thickness when glued up or a material that likes to hide squeeze out from you until the first coat of finish hits ;-) Just my two cents.

[Alan Bienlein]

Don't the pipes thread onto the pipe? How do you get the EMT threaded in the lengths you need, do they perform this in the plumbing sections for you?

Ridgid conduit for electrical is thick wall just like the galvanized for plumbing. comes in 10 foot lengths that are already threaded on both ends.

EMT is the thin walled conduit that is typically run on the surface and has those slip on connectors that tighten on with a set screw.

[Phil Thien]

Ridgid conduit for electrical is thick wall just like the galvanized for plumbing. comes in 10 foot lengths that are already threaded on both ends.

EMT is the thin walled conduit that is typically run on the surface and has those slip on connectors that tighten on with a set screw.

Oh!!! I know the stuff you're talking about, I only see it used outdoors or where it is partially embedded in concrete.

Thanks for the tip.

[Michael W. Clark]

Ridgid conduit for electrical is thick wall just like the galvanized for plumbing. comes in 10 foot lengths that are already threaded on both ends.

EMT is the thin walled conduit that is typically run on the surface and has those slip on connectors that tighten on with a set screw.

Looks like the rigid conduit is the same OD as pipe and slightly thinner wall (if any thinner) than SCH40 pipe. All "pipe" has the same OD, the ID varies with schedule. I think most of the rigid conduit is galvanized, correct?

[Alan Bienlein]

Looks like the rigid conduit is the same OD as pipe and slightly thinner wall (if any thinner) than SCH40 pipe. All "pipe" has the same OD, the ID varies with schedule. I think most of the rigid conduit is galvanized, correct?

Yes it's galvanized but I don't think the galvanizing is as thick as on the plumbing pipe. As for wall thickness you can bend 3/4" ridgid but you sure don't want to do more than a couple of bends with it. Your better off using a hydraulic bender.

[ian maybury]

Guess there's another variable too - pipes so far as i can remember can be hot dip galvanised, or zinc plated. Both apply a coating of zinc, but the film in the latter case is only a tiny fraction of the thickness of a hot dip coating.

Zinc does it seems have some lubricating properties - it's used all over the place in oil additives, anti seize compunds, and lubricatiing soaps like zinc stearate - the question i guess is whether it's a factor in pipe clamps slipping.

[Alan Bienlein]

The ridgid conduit I use is plated and my clamps do not slip what so ever.

[Myk Rian]

As far as squeeze out is concerned, use Waxilit on the faces before gluing. When dry, just snap the squeeze-out off, and use alcohol to remove the Waxilit.
http://www.sawmillcreek.org/showthread.php?200993-Waxilit