Cutting bolt with minimal heat

wrote: (clip) After the epoxy is cured I cut the bolts with the angle grinder and grind what is left of it down until it´s surface is flush with the plate. (clip) ^^^^^^^^^^^^^^^^^^^^ If I've got this right, you drill and tap a hole, and then you plug the hole so you are back where you started. Why?

Since you don't put any torque on the bolt when you screw it in, why not saw most of the way through it before you screw it in? After the epoxy sets, break it off or finish sawing, and then grind off smooth.

Well, indeed, without the context this sounds pretty strange :) I=B4ll explain it. The metal plate is actually the deck of my boat, which was covered with teak wood. All these strips of teak were fastened to the deck with screws. After removing the teak (because it become really rusty underneath) I ended up with 800 holes, 5 mm. Which have to be closed. At first I wanted to weld them, no worries about corrosion or waterproofness. But on the inside there is sprayed-on foam which makes the welding unsafe. To remove the foam all the ceilings have to come out of the boat and to do that a lot of cupboards need to come out as well. Unfortunately the boatbuilder used nails on a lot of places, so it is really hard to remove interior parts without damage. Filling the holes with some epoxy based filler would have been easy, but after that it is impossible to sand blast, which is really necessary looking at the condition of the deck.

So, therefore I figured out this method with drilling, tapping and glueing bolts.

I thought about something like this too. Only I tried to do it with the angle grinder. Problem was that this made the bolt so hot that the zinc plating started looking strange and I had doubts whether the epoxy would still adhere to it.

What you suggest, using a saw, would not be hot. But I don=B4t know if it is possible to do this quickly for all the 800 bolts. I also live on this boat. Well actually we are sailing around with it and have a working break now. But I don=B4t have many nice tools. Handsawing this quantity of bolts seems not very attractive to me. Maybe mounting the jigsaw upside down? How would you do it?

Why not buy socket head grub screws? You could epoxy them in flush then fill the socket with epoxy. Job done, no grinding required.

Tom

wrote: (clip) Handsawing this quantity of bolts seems not very attractive to me. (clip) ^^^^^^^^^^^^^^^^^ I would use a portable, hand-held band saw like a Portaband or a Milwaukee. (A cheapo from Harbor Freight might work, but I don't know whether it would last through the whole job.) Hold each bolt in a vise, and cut it until it is easy to break.

Another way would be to use a Saws-all to finish the cuts--the blade is flexible, so it can cut flush while the saw is held at an angle.

If you can afford a boat, I would think you could easily handle the cost of a saw. If you don't feel like adding to your toolchest, you could rent a saw and easily cut the bolts in half a day. Is there a shop where your boat is docked? Maybe they would cut them for you for a fee.

Buy socket head setscrews about 1/4" long. Dip them in epoxy and screw them in. Since you will undoubtedly use both filler and High Build primer after you sand blast, before the finish paint, it will add little to your work.

Bruce-in-Bangkok (Note:remove underscores from address for reply)

Buy a couple boxes of set screws from an indistrial supplier.

Clean the hole with a brush on a cordless drill, install each set screw wet with epoxy, and fill the slot or hex head on the screw with the same on installation. You can use stainless set screws, if that works.

Cheers Trevor Jones

800 holes!! Yikes. If you can't sandblast after filling with epoxy, could you sandblast first, then fill with epoxy? The holes are only 5mm and if the blast stream isn't exactly perpendicular, there should be very little penetration of sand into the hole.

If you rule that out, the Sawzall (reciprocating saw) with a bimetal blade is the way to go. Faster even than the abrasive cut-off wheel. If you don't have one, it would be worth the investment just for this job.

Bob

BTW - in case you don't already know this, to do the tapping, use a spiral-point tap in a drill. 6mm should be small enough to not slip in the jaws. (800 holes!!)

I'd buy a bunch of all thread to make your own flush screws, dip in loctite red and screw in using a sharp carbide scriber to as close to flush as possible. Finish off with angle grinder or belt sander.

Good luck with your project.

wes

To this I would add that the setscrews should be degreased before use by washing in solvent. The standard approach is three tubs of solvent and one basket. Tub 1 has the newest, cleanest solvent. Swish basket full of screws first in tub 3 (dirtyest solvent), shake excess off. Then swish in tub 2, and shake excess off. Then tub 1, shake excess, allow to dry.

As tub 1 gets dirty, dispose of the solvent in tub 3, fill with new, clean solvent, and renumber the tubs: old 3 is new 1, old 1 is new 2, and old 2, is new 3. Repeat as needed.

Solvents. I would use acetone.

If you have access to a vapor degreaser, use it and skip the tub dance.

Joe Gwinn

Get block of steel perhaps 50 mm square x 25mm thick. Drill and tap a hole in the center of the square side.

Screw 6mm allthread thru the block and into the plate so the block is snug or tight to the plate. Use Loctite rather than epoxy. Keep Loctite off the block and out of its threads.

Strike block smartly sideways with a maul. This will easily shear off the 6mm mild steel allthread flush to the plate. Only very light, if any, grinding will be necessary to make the surface smooth.

I would fill the holes with 3M 5200 sealant. It remains flexible, so sandblasting will have little effect on it.

You don't have to hog it off in 2 seconds...blip it with the cutoff wheel in time increments to reduce the heat. Grind flush the same way. Clamp a vice grip to the top of the bolt to help sink the heat. JR Dweller in the cellar

snipped-for-privacy@gmail.com wrote:

If it was me, I'd install the screws with epoxy.

To remove the extra length of bolt above the deck, a cold chisel and hammer, or sawzall.

To finish, a belt sander, but not dwelling in one place, keep moving. Or if all you have is a body grinder, get a wet or dry sanding disk,. Since you don't have much patience, that can be run wet. DJ

On Wed, 19 Dec 2007 10:52:50 -0500, with neither quill nor qualm, "Chas Hurst" quickly quoth:

If he's just going to fill and seal them anyway, why not just NOT drill and tap those holes in the first place? What a timesaver!

-- Seen on a bumper sticker: ARM THE HOMELESS

Spend 2 seconds on each, then go to the next one.

Get lengths of nylon threaded rod, goop-up the end, thread it in, cut it off with a hot-knife...next!

See if you can find stainless steel blind pop rivets. Coat the deck with waterproof material and it is done. Since you are just trying to plug the holes, why not a plastic or rubber plug?

Bob

TSP!