Drilling and Tapping new screws

[Solitude25]

Has anyone ever tapped a screw before? I don't know if I'm using the term properly, but I'm trying to secure a piece of new aluminum track onto an existing track (can't get to the bolts holding the old one to the boat). I did some homework and bought a "drill and tapping set", which I'm told is all I need. A drill bit opens up a hole in the old stock, and then the "tap" is screwed into that hole....as it progresses it "gougues" new threads that a machine screw should mate to.

 

[Ross]

You got that part right. Now clean up the chips and thread the screw into the hole.

 

[thereisabelle]

correct! hope you bought a quality set. keep the tap straight, one turn forward then back to clear the chips. the tap will cut the aluminum not gouge. use a lubricant thats light weight. just a drop or two. good luck. jimbob

 

[okawbow]

To TAP A hole for a machine thread screw: First drill the hole with the correct size tap drill. The hole will be slightly smaller than the srew size. Example: the tap drill for a #10-32 machine screw is a number 21 drill.. For a 5/16" x 18 screw: a 1/4" drill is close enough. After drilling the hole, tap the hole with the crrect size tap, using a tap handle. For aluminum, use a little kerosene or WD-40 on the tap for lube/coolant. Be sure the ap starts straight, and back the tap out after a couple turns to clear out the chips if it is a blind hole. Be carefull to turn it straight and avoid side pressure, or,,,snap!

 

[thereisabelle]

light speed is the only thing i can think of how you beat me to that one Ross..
your in Md. and I'm in memphis. I peeked and poked as fast as i could.LOL!

 

[woodster]

you will find in tap sets that there are three different taps to one size ,,,starter tap,,,,,tap,,,and bottoming tap for tapping a hole that is not all the way through your metal and the latter is so you get all the thread you can in the blind hole.....oh and bees wax is a very good lube for aluminium

regards

woody

 

[Maine Sail]

Has anyone ever tapped a screw before? I don't know if I'm using the term properly, but I'm trying to secure a piece of new aluminum track onto an existing track (can't get to the bolts holding the old one to the boat). I did some homework and bought a "drill and tapping set", which I'm told is all I need. A drill bit opens up a hole in the old stock, and then the "tap" is screwed into that hole....as it progresses it "gougues" new threads that a machine screw should mate to.

The problem here is that the "track", which I am assuming is a genny type track, is very thin. You will need to use a bottoming tap other wise it will be necessary to drill clean through the deck something which is not advisable.

You still may not get enough thread bite to hold what ever it is you're using, perhaps a genny, when under load, as the tracks are usually concave on the bottom side to hold sealant and the cross section quite thin for even a bottoming tap. I would consider fabricating cover panels for the area in the boat under the track and opening up access as this is very common practice. The old track may also need to be re-bedded anyway..

 

[Don12364]

Not intending to appear condescending but you do not seem to have much experience in mechanical engineering matters.
If this is the case have you thought about seeking help from someone more experienced as it might well be that they will be able to take the original screws out and save you the trouble of having to make what will be at best a bodge job by piggybacking tracks upon each other?
Wishing you every success.

 

[Solitude25]

No worries about condescension....you're correct that this is new to me. I've had several yard guys take a look at this project, and no one seems able to get to the nuts on the end of the bolts holding the track down (this is the mainsheet track just aft of the companionway on an O'Day 25). Moreover, as one guy put it, "and even if you could get those off, good luck getting new ones ON". The bolts go through the track and then through the fiberglass. They come out in a space between the underside of the cockpit and the bulkhead of the galley....about 2" wide and 2' deep.

I'm going to look at it one more time tomorrow; appreciate everyone's input.

 

[packman]

If the track has a stainless or aluminum backing plate you might be able to drill and tap through the fiberglass and backing plate and omit the nuts entirely. this assumes that you're not reusing the existing track. the old track bolts can be drilled off and removed in sections, allowing you to secure the backing plate in a couple of places to keep it from falling out of position. You should be able to finagle a new track in position, drill and tap new holes through to the backing plate and install new fasteners. Alternatively a rivnut might be used although it's a one shot deal with them and the next guy to work on it might curse you

 

[Ross]

For threaded fasteners to hold the designed load they must engage at least a diameter of the threads. This is why larger nuts are thicker. This means that for the work you are trying to do to succeed whatever you are drilling and tapping should be as thick as the diameter of the screw.

 

[Bill Roosa]

What I found once

My Hunter 37.5 jib tracks did the same thing. Ran through the FG and had bolts on the inside. There where 4 screws that where "blind" however where the track passed over the head bulkhead. Those where (gasp) fiberglassed in. There where no nuts, no metal of any kind just fiberglass threads.
Are you sure you can't get access to the back of the deck?
Also I've heard tell of metal nuts being "cast in place" during construction. That would be great as the nut and backing plate/washers would just stay put and all you would need is a new track and possibly new screws of the right length.

 

[Hermit Scott]

Take a picture and show us. There is ALWAYS a way to get it done.

 

[Solitude25]

Well, it worked (but forgot the camera!). A friend and I tried one more time to get to the backing nuts, but not only would that require an inspection port and some probable cursing, there was no way to assure that we could re-fasten the new track once the old was removed. So, we drilled. Centered the new track lenthwise over the existing, and got lucky - when centered, the holes of the new track were over solid stock and not existing screws.

Drilled the first hole into the existing track with a #10 drillbit, tapped per instructions (used a Kobalt kit with #10 bit and 1/4-20 tap), and fastened with a #10 x 3/4" flathead machine screw. Funny how happy two 40-somethings can get when a screw goes nicely into a hole we just created. So with the first one done and holding the track in place, we proceded down the line until all the holes were drilled, tapped, and mated to their respective screws.

Test #1 - installed the new traveler and pulled with progressive tension to full muscle. No give or bend at all.

Test #2 - sailed in a mild breeze and mission accomplished: excessive friction eliminated, freely moving boom, easily adjustable traveler, and brand new mainsheet.

Regarding the "stacking" issue of one track on top of another, with the cockpit cushions in place you really don't notice. Unfortunately I live 90 minutes from the marina so I definitely will remember to bring a camera and take some pix.

Thanks again to all for the input and thoughts. This has been a real stymie for me and it's like having a new boat. REALLY great having all that spaghetti from PO off the cabin top and out of sight as well.