Deep hole saw

[JimConlin]

I recollect talk here about hole saws that might go 4" or more.
Do these exist? What's a practical way to make one?

[Draketail]

I've had some luck with using a normal hole saw to define the hole. Then chip out as much waste as possible. Use auger or spade bits to remove more material to final depth. Then use a long top bearing bit in a router to clean up the hole to full depth. The original hole defined by the normal hole saw guides the router bit.

Worked for me to make 4" dia by 5" deep holes for a trebuchet axle....But, as I remember now, I used a fly cutter to define the original hole. Meaning the clean hole was defined only to a depth of 1" or so. The rest of te clean up was done with auger bits and the router. The trebuchet is still firing fine 12 years later..

[JimConlin]

To set the context, I have a glass tube that's buried within a larger composite structure and I want to get it out. Think of an embedded stern tube.

[Gib Etheridge]

A photo would help a lot. In the meantime how about you go as deep as possible with the hole saw, chip away the walls you created, perhaps with a screwdriver or 1/4" chisel, install a longer pilot bit, repeat process?

I found extra long hole saws on the net but they are very expensive.

[Draketail]

Oops... Previous suggestion not applicable... The glass tube sorta ups the ante, now don't it?

Would it be possible to turn a wooden blank to fit inside the glass tube to serve as a guide/center point for a fly cutter?

[Paul Pless]

How deep Jim? Concrete cutting companies commonly use hole saws (core hole bits) that are more than 12 inches deep, perhaps they would be adaptable.

[Mrleft8]

.... So....... What you're really saying here, Jim....... Is that somehow your favorite bong got stuck in a concrete patio sidewalk, and you want to get it out, without breaking it, before your parents get home?......
If you take a piece of steel pipe the diameter that you want, and the length you want, and weld, or bolt it to a 1/2" shank to chuck into a VS drill, then use carborundum powder and cutting oil as an abrasive cutting medium you will get a hole of more or less the desired diameter, and depth.... It may not be pretty though.....

[Chip Chester]

Pure conjecture here... It would be worthwhile to see if a standard home center hole saw is truly hardened throughout, or just near the teeth. If you can cut it in half by saw or thin-wheel grinder, then weld in (and dress the joints) a tube segment to extend it, you would have standard mounting and normal teeth, with a long body in the middle. You could change the 'set' of the teeth if you need a wider kerf for tube/weld clearance.

Plan B -- would the surrounding structure melt without burning? And without killing your tube? (Glass meaning fiberglas, or actual glass?) One could guide a heated ring down the path, and "somehow" remove the goo (drain hole + gravity?) A risky mess, in my book...

If the concrete boring saw exists at a depth that suits you, that would be much easier, of course. Sometimes you can rent those with the drill to run it.

[Jim Mahan]

Thinking the same thing, but cut teeth with a grinder and a file.

[Paul Pless]

To set the context, I have a glass tube that's buried within a larger composite structure and I want to get it out. Think of an embedded stern tube.

Can we file this under the 'epoxy is crap' thread?

[seedy]

Does the tube have to come out intact?

[JimConlin]

To clarify further, it's a fiberglass epoxy composite tube that's buried in a wood/foam/glass composite structure. Inside the tube is the remnant of an aluminum rod that wasn't supposed to corrode, but did. Quite immovable.
The glass composite tube is relatively firmer than the surrounding composite, so it would effectively guide a deep hole saw without a pilot. Cutting an inch or so at a time and chipping/burrowing the core out is not an option.

I'm thinking that the business end of a hole saw, some thin wall steel tubing a shank and some welding might work.

Paul, stick it where you want.

[Paul Pless]

Inside the tube is the remnant of an aluminum rod that wasn't supposed to corrode, but did. Quite immovable.

Hey! Those concrete bits routinely drill through steel rebar in slabs. They may cut straight through that aluminum with out damaging the sleeve. Just a thought. . .

Best of luck!

[potomac]

I've had some luck with using a normal hole saw to define the hole. Then chip out as much waste as possible. Use auger or spade bits to remove more material to final depth. Then use a long top bearing bit in a router to clean up the hole to full depth. The original hole defined by the normal hole saw guides the router bit.

Worked for me to make 4" dia by 5" deep holes for a trebuchet axle....But, as I remember now, I used a fly cutter to define the original hole. Meaning the clean hole was defined only to a depth of 1" or so. The rest of te clean up was done with auger bits and the router. The trebuchet is still firing fine 12 years later..

Trebuchet you say. Would punkin chunkin be involved and is there a forum for this?
And mention of glass bongs too- this is some kind of thread.

[P.I. Stazzer-Newt]

To clarify further, it's a fiberglass epoxy composite tube that's buried in a wood/foam/glass composite structure. Inside the tube is the remnant of an aluminum rod that wasn't supposed to corrode, but did. Quite immovable.
The glass composite tube is relatively firmer than the surrounding composite, so it would effectively guide a deep hole saw without a pilot. Cutting an inch or so at a time and chipping/burrowing the core out is not an option.

I'm thinking that the business end of a hole saw, some thin wall steel tubing a shank and some welding might work.

Paul, stick it where you want.

I once removed a stuck corroded piece of aluminium by dissolving it out - caustic soda and patience.

[Chip Chester]

Do you really just want the aluminum out, instead of the tube? If so, there are chemical ways to make that happen. I believe mercury, for one (eek!) Lotsa nasties there. But there are chemicals used to dissolve aluminum and leave steel alone, (used in cleaning up cylinder bores with trashed aluminum pistons) that you might test on glass. Do a little research before you commence to chewin'.

Drilling multiple holes thru the already-corroded aluminum could weaken it enough to be "persuaded" out. Chilling with dry ice may break it loose, too. Introduce the dry ice down into your holes in the aluminum.

You might also drill and tap the aluminum, and fabricate a puller to hold the tube, but pull the rod.

Chip

[Leatherneck]

Would it be possible to turn a wooden blank to fit inside the glass tube to serve as a guide/center point for a fly cutter?

I really think Draketail's solution would offer the best final product if the tube is straight and clean enough to serve as a bearing surface for the fly cutter.

TC

[JimConlin]

Do you really just want the aluminum out, instead of the tube? If so, there are chemical ways to make that happen. I believe mercury, for one (eek!) Lotsa nasties there. But there are chemicals used to dissolve aluminum and leave steel alone, (used in cleaning up cylinder bores with trashed aluminum pistons) that you might test on glass. Do a little research before you commence to chewin'.

Drilling multiple holes thru the already-corroded aluminum could weaken it enough to be "persuaded" out. Chilling with dry ice may break it loose, too. Introduce the dry ice down into your holes in the aluminum.

You might also drill and tap the aluminum, and fabricate a puller to hold the tube, but pull the rod.

Chip

To my considerable dismay, the alu corroded, swelled and is beginning to split the tube, which was too light for the job.

Just for more context, on Damfino, the outboard is mounted on a sled, whose nose pivots on a rod that sticks out of the side of the main hull. The first try for the pivot pole was heavy wall 1" 304 stainless tubing. A couple of those were bent when someone stood on them. Second try was a solid alu rod of an alloy (memory fails) that was s'posed to be stiff and corrosion resistant. It corroded and took the tube with it. Third try will be a thick wall 316 stainless tube. Just gotta replace the tube, and go a bit heavier .
I'm pleasantly surprised that this is my biggest engineering problem to date.

[Gib Etheridge]

Grease fittings?

[the_gr8t_waldo]

i'm thinking that you want to preserve the fiberglass tube to maintain it's alinement- with that and the fact that the tube is cracked- the very easyest would be wholesale destruction, and re aline a new tube with a generous wall thickness ( probably work very well with the new shaft in place and shimed to maintane equal distance around the shaft ) . back fill with epoxy,and thickened epoxy.

[Breakaway]

The guys who install bow thrusters use big honking long holesaws. Maybe you could call one of them up and either ask where they source or how they make their saws.

Kevin

[Sailor]

If that guy needs a bow thruster to manoeuvre a boat that size he shouldn't be on the water in the first place. That's just an itty bitty little boat.

[JimConlin]

i'm thinking that you want to preserve the fiberglass tube to maintain it's alinement- ...

I just want all or part of the tube to be gone. I just don't want to leave too big a crater. Aligning the new tube is no problem.

[Gib Etheridge]

How about if you drill out as much of the aluminum as possible and proceed as in post #4?

[Jefe]

See figure 14-25 on page 162
http://www.westsystem.com/ss/assets/...k%20061205.pdf

The end of a hole saw is cut off and welded to a steel tube and ground flush. The end of the tube is welded to a rod (and ground flush).

[Chip Chester]

Note: pg. 162 in PDF, pg. 148 in "print". Use 162 to find it. With a 4" diameter needed, the 'weld a threaded rod' technique will need some additional improvisation. Hence my recommendations in post 8. On edit: Since I've never had fiberglassed boats -- only straight "plain" wood or aluminum -- I've never had occasion to visit West's site. The book cited by Jefe above is certainly worth the trip... and looks like there's lots more to see as well. Thanks! Chip

[JimConlin]

I'm contemplating something like that. It might make sense to weld on the 'top' of the hole saw 'cuz it mates with the mandrel, etc.
The trick is in sourcing thin wall steel tube of the right size.
I'm looking for a well-adjusted local welder. Suggestions will be welcomed.

[Chip Chester]

Many online metal dealers will sell short lengths... like onlinemetals (dot) com, for one. I've never used them myself, but heard others mention them as a small quantity, cut-to-length supplier. I'd start by finding your welder first, as he may have certain steel requirements for weldability, and he also might have some sitting around. Regarding wall thickness... if you choose the inside diameter to match your saw, the outside can be easily turned on a lathe. Possible, but not so easy the other way... turning the inside. Best bet to turn before welding. Chip

[Ron Williamson]

I'd think about buying a slightly over-sized hole saw and piece of right-sized steel pipe/tube that just fits inside it.
Using the slots in the hole saw for alignment I'd drill matching holes in the pipe and pass a bolt through the two.
Then I'd file teeth in the other end of the pipe.
When it gets too dull to cut, file again.
IMHO,concrete core bits have the wrong tooth shape and rake for cutting wood/glass efficiently,but renting one and a Kango to drive it ,sounds less painful than getting a weldor to manufacture a custom deep hole saw.
R

[S B]

Not entirely sure of the problem, both rod and tube are toast? Drill the out the center of the rod, increasing bit size till you run out of bits. Tap and insert bolt,apply wrench and heat to bolt, when epoxy softens enough for rod to turn, you are halfway there. Extract using roughly same procedure.

[the_gr8t_waldo]

on the face of it, it sounds ideal to make a small hole for the new tube but, if the hull has any thickness at all, you'll need room to pack the thickend epoxy into (also brush epoxy onto the raw surfaces). and it'll probably be easyest to do it in three or four sittings( to make sure that the new tube isn't moved out of position). when i said "wholesale destruction" i wasn't suggesting you take an axe to the old assembly. i would think you'd be miles ahead by simply renting a diegrinder, and buy two burs and work on the tube, untill the aluminum shaft drops clear....once done you can hand the tool back to the owner.

[Paul Pless]

The book cited by Jefe above is certainly worth the trip... and looks like there's lots more to see as well. Thanks! Chip

I'd be willing to bet that Mr. Conlin considers that book akin to the 'Word of God' with regards to all things epoxy boat related.

[JimConlin]

I found a well-adjusted local welder and supplied him with a minty new hole saw of the appropriate size. His very diverse scrap bin supplied a piece of thin wall bicycle frame tube of about the right size. Slitting it lengthwise allowed a minor adjustment of diameter. Fifteen minutes of cutting the top off the hole saw, welding & grinding produced the needed tool. It did the job. Better still, I made a new friend.

My faith in barnyard ingenuity stands.

[Stiletto]

Good result, well done!

[Paul Pless]

Excellent. Does this mean you can resume sailing?

[Breakaway]

Cool!

[davhill]

The glass composite tube is relatively firmer than the surrounding composite, so it would effectively guide a deep hole saw without a pilot

I'm remembering that the dull tip of a common finish nail can drill a hole in oak....

If the surrounding composite is relatively soft, I venture to say that you don't really need hardened teeth... and your deep hole-saw can consist simply of a pipe section slightly larger than the glass tube. Find the thinnest wall material of suitable diameter .. or even fabricate THAT from sheet steel .. File teeth in the end, and mount a mandrel. Drill away. Even if you have to regrind the teeth a time or two, that's easier than the alternatives.

Dave (who greatly appreciates P.I.S-N's tag line)

[davhill]

<<I'm remembering that the dull tip of a common finish nail can drill a hole in oak.... >>
Errrrr... ok, Excellent. Well done. Please ignore the guy who doesn't read to the end of the thread. Yeah, NEVERMIND...
-Dave