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How to tap metal

Old 07-01-2008, 11:22 PM
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MetallicaJunkie
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Default How to tap metal

is there a tutorial that shows what i need in order to successfully tap my motor mount so i can screw my motor to my metal motor mount.....ive seen them all the time when i go to hardware stores, id like to know what i need....... i have a drill with many drill bits to stat off............... the cowl is not removable ,that why i need to know how to do this
Old 07-01-2008, 11:30 PM
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combatpigg
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Default RE: How to tap metal

It pays to start out with quality taps that cost much more than the junk you will find at most retail outfits. I have had decent luck with DUBRO tap / drill sets, but you can do much better than that through McMaster-Carr. You will improve your chances of success with cutting fluid, too.
If you plan on doing it freehand, it pays to make a little drill guide to keep the bit perpendicular. For this you will either need a drill press or a very good eye, much better than mine [8D].
Old 07-02-2008, 12:38 AM
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Default RE: How to tap metal

thats helped a bit, thanks...... i do have a drill press, its not a floor standing one, just a bench top one...... ill ask one of the hardware store guys, for a little walkthrough.... they ought to know more than i do.... the good thing is i have a couple of old heavy metal mounts i can practice on.
Old 07-02-2008, 12:45 AM
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Default RE: How to tap metal

Dittos to what CP said but do realize that there will be a specific tap drill size for every tap and you must use that tap drill size for that tap or your threads will be a failure. When bought in indivudual size packageing each tap will include the proper tap drill. When you buy tap sets often you must look up the proper tap drill size and provide it yourself. When locating the holes suggest you use the GP hole locator as taped holes must be accurate unlike drilled through or self tapping screws in glass filled mounts.

Also purchase a good tap handle, This you must have to accurately tap the hole by feel. Don,t attempt to use any other type tool. When performing the tap do not just continue to screw in but keep backing off a turn for every quarter turn you turn in. In this way the shavings are cleanly delivered to the flutes of the tap.

Also you can consider the glass filled nylon mounts and use the sheet metal screws that you drill a specific tap drill size and the screw does their own tapping. These work very well indeed and are easier to do.

John
Old 07-02-2008, 05:38 AM
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Default RE: How to tap metal

Why do you want to drill and tap your mount... with the possibility that the screw can vibrate loose.....Wouldn't be safer to drill through the mount use a longer screw and a lock nut...
Old 07-02-2008, 07:11 AM
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Default RE: How to tap metal

I also recommend just using the nylon locknuts for engine mounting. You can tap the engine mount and screw through it, but you'll still want the security of the nylon locknut. And not having tapped holes will make the engine easier to mount.

Brad
Old 07-02-2008, 07:55 AM
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Default RE: How to tap metal

Many of the old metal mounts and some of the glass filled mounts do not work well with through drilling and nuts with the bottom side of the beams at a substancial angle. Through drilling is only practical when the mount has paralell top and bottom surfaces to the beams. This angle will put side loads on the bolt from the nut not properly seating and the bolt will fail.

Steps can ground on the bottom of the beam to provide a flat nut surface however this severly compromises the beam/mount strength.

John
Old 07-02-2008, 08:13 AM
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Default RE: How to tap metal

Good advise so far, but I'll elaborate on the procedure.

Drill the hole with the proper size drill

Place a drop of oil in the hole. Cutting oil is recommended, but anything from WD-40 to cooking oil will work. Put a little on the tap as well.

I don't bother with any gauges to keep it straight, but I have a good eye. Keep looking at it from several angles at first to make sure you're going straight. Once you've got it going straight, you don't need to keep checking - it will follow the hole.

The next thing is - after the first few turns, back off far enough so that the flutes break the chip behind it. Continue to cut, but back-off to break the chip about every half-turn.

If at any time it becomes hard to turn STOP and turn the tap completely out. Clear the hole, re-oil and start again.

If it gets really hard to get out, STOP and screw it back in slightly and try to knock some of the chips out of the hole.

The most important thing to avoid is breaking the tap in the hole - do that and you're screwed.
Old 07-02-2008, 08:50 AM
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Default RE: How to tap metal

Ahhh I see and I have had some of those mounts...I would never weaken the mount by filing or grinding the mount..I have made a spacer cut at an angle and used a coulpe of washers and a lock nut...being in full scale aviation I have a hard time with free running nuts and screws...however if you safety wire the heads of the screws in the mount you'd be golden
Old 07-02-2008, 09:20 AM
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Default RE: How to tap metal


ORIGINAL: MetallicaJunkie
the cowl is not removable ,that why i need to know how to do this


This the most likely reason Metallica wants to tap since he has no access to the bottom of the engine and beams to hold nuts.

This type of cowl at one time was common for many RC Sport planes, controlline stunt airplanes and virtually all RC pattern planes. his cowl is likely similar to the one in this airplane with no bottom side access.

Actually my preferance for this are Specifically Dave Brown mount like this one round at the firewall requires much less space, far easier to install than the so called adjustables and the included sheet metal screws work very well with less tendency to work out of the glass filled nylon than threaded metal where thread lock is a good idea.

John
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Old 07-02-2008, 11:24 AM
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Rodney
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Default RE: How to tap metal

When tapping into aluminum, bar soap works quite well as a cutting aid, just coat the tap with soap. The soap hold the chips so that you can easily remove the tap every turn or so and clean off the chips. Aluminum (when tapping very small sizes like #2 or #4 seems to be more critical for binding during the tapping process than iron or steel does. As an aside, I definitely do NOT recommend that you use WD40 as a cutting oil. WD40 is not a lubricant, it is a water dispersant fluid and a very poor lubricant. Plain old motor oil is a much better fluid if you do not have cutting fluid.
Old 07-02-2008, 12:13 PM
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Default RE: How to tap metal

I like to drill and tap all my engine mounts and put fiber nuts one them plus lock washers. I generaly find the size allen bolt the just fits into the engine lug holes and use that bolt. I get a long drill that will go along side the engine and start drilling the first hole with the engine in the locantion I want it. After starting the first hole, I remove the engine and finish drilling and then taping the mount for the first screw. I then mount the engine with the first screw and then start the next three holes. Remove the engine and drill and tap the final holes. Try and drill the holes as stright as possable, and when you tap you must run the tap stright with the hole even if the hole is cocked a little. Be carfull with the tap they break easy, don't use a old dull tap. If you can't use fiber nuts use good quality lock washers and lock tight. If you use the red lock tight , they will never come out. The blue should work, I would check them once in awhile though. If you figure out what bolt you want to use let me know and I will give you the drill and tap size , you need to get.

oh Ya, do use some kind of oil when taping and don't try and tap all the way though the holes one shot, back the tap all the way out about half way through and clean the plastic or metal off the tap and then finish taping the holes.
Old 07-02-2008, 03:20 PM
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MetallicaJunkie
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Default RE: How to tap metal

ORIGINAL: bkdavy

I also recommend just using the nylon locknuts for engine mounting. You can tap the engine mount and screw through it, but you'll still want the security of the nylon locknut. And not having tapped holes will make the engine easier to mount.

Brad

ORIGINAL: jetmech05

Why do you want to drill and tap your mount... with the possibility that the screw can vibrate loose.....Wouldn't be safer to drill through the mount use a longer screw and a lock nut...

that usually the way i do it, but i purchased an ultra sport from a man, its a kit version, the cowl doesnt come off, so putting nuts of any kind is not really an option, with out havin to butcher my permanent cowl....as of now tapping is my only option.... i bought the kit, and with my drill press and some wd 40 as lube i will attempt to make some threaded holes in my mount


thankyou for all the replies!!
Old 07-02-2008, 03:21 PM
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Default RE: How to tap metal

Metallica,
You've gotten some good advice here.
Especially from Minnflyer - as usual.

I like to use my bench mounted drill press to tap my mounts.
Make sure the top of the mount is exactly 90 degrees to the drill.
Drill the required pilot hole.
Unplug the drill press, remove the drill, mount the tap in the chuck.
Move the tap down to the hole and start hand cranking the tap into the hole (this may require a helper).
I don't have MinnFlyers eye for making sure I am aligned properly so I use this method.
Follow Minn's instructions for backing out and cleaning.
Once you get enough depth to insure alignment you may want to finish it by hand.

I learned this from my Father who used to be a machinest.
I taught it to my mentor who was a retired HS shop instructor - he liked it.

Good Luck,
KW_Counter
Old 07-02-2008, 07:58 PM
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The Toolman
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Default RE: How to tap metal

Kerosene works the best for alum if you don't have the factory type fluids like aluma-tap


Ronnie-The Toolman
Old 07-02-2008, 11:33 PM
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Default RE: How to tap metal

I would rap the mount first and listen to it. If it rings like a bell, it should be easy to tap. But if it had a dull sound, watch out.
Old 07-02-2008, 11:47 PM
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Default RE: How to tap metal

One thing no-one has commented on is that you need a starter tap. You will notice on some taps that the threads start part way up the flutes. This is to help start the tap into the hole and automatically square it to the hole.

The other taps are called bottom taps or plug taps and the threads start nearer to the end of the tap. You shoulden't need one of these as you will probably drill all the way through your mounts.

The recommended drill size is usually marked on the side of the tap allong with the thread size.

Use a small tap handle. You really do need to feel what the tap is doing inside the hole.

It is also a good idea to use cutting fluid when you drill the holes as well as when you tap the threads. The primary purpose of cutting fluid is to pull the heat away from the cutting edges.

Don't forget to debur the hole before you run the tap in. You can use a drill bit that is larger than the hole and using your fingers, twist it on the bur to cut it off.
Old 07-03-2008, 12:38 AM
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MetallicaJunkie
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Default RE: How to tap metal

thankyou minnflyer and everyone else [sm=thumbs_up.gif], i took bits and peices from everyone's advice, and it came out OK, i dint think it would go as smooth with one exception, the drill tip broke in one of the holes, there was no way i could get it out, its deep inside where no tool can get.... thankfully i had another 1/8"er on hand to finish the job...

i should be ok with 3 screws right? i used red pacer threadlock

#edit... the tap i used was tapered.... it worked like a charm
Old 07-03-2008, 04:35 AM
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Default RE: How to tap metal

3 screws? on a mount where you can't use lock nuts....I wouldn't do it....but that's me...
Old 07-03-2008, 07:17 AM
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Default RE: How to tap metal

Try drilling the hole with the broken drill from the other end. Even if the holes don't line up perfectly, you should be able to get close enough to knock the broken drill tip out from the other side.

Once you've done that, finish drilling the hole from the top and tap it. It may not be perfect, but it will be better than not having a screw there at all.
Old 07-03-2008, 09:28 AM
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Default RE: How to tap metal


ORIGINAL: MinnFlyer

Try drilling the hole with the broken drill from the other end. Even if the holes don't line up perfectly, you should be able to get close enough to knock the broken drill tip out from the other side.

Once you've done that, finish drilling the hole from the top and tap it. It may not be perfect, but it will be better than not having a screw there at all.

good idea!
Old 07-03-2008, 04:02 PM
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Default RE: How to tap metal

Try using the same size drill inthe original hole, but run it in reverse[backwards] turn drill very slow with moderate infeed.This will sometimes back the broken piece out[sometimes not]. Kerosene has been the reccommended cutting fluid for aluminum.Sharp drills perform with fewer problems.
fredsedno
Old 07-03-2008, 07:11 PM
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Default RE: How to tap metal

When drilling, even on a drill press, lock the work down. Some times you can get by with just clamping it in a vise and skooting the vise arond so it's lined up and drill. Most of the time though, if the work can move, you are likely to snap a drill. Same for the tap. The tip above about using the drill press to start the tap is good advise. Drill the hole and then tap it. move the setup for the next hole and drill and then tap.

Short cuts will get you every time.

Drilling is a drill and peck operation. Going through an aluminum motor mount, It would be a minimum of four steps. Drill down about 1 1/2 times the diameter of the drill and then lift it to clear the swarf. anothe drop of fluid woudl be good here. 1 1/2 times again and lift and clear again.

A lot was mentioned about tap fluid, It serves two purposes. Lubercation was the first, but it is also a coolant. It keeps the drill from heating up and siezing in the hole. Same for Taps.

There are two basic kinds of taps and several variations of each. The common taps we get from Dubro and the hardware strore are hand taps. The will have either 2, 3, or 4 straight flutes and come in a starter, long taper, a plug, short taper, and a bottom tap. The hand taps cut the threads and the chipps pile up in the flutes. If you turn in to much with out backing up to break the chips you can jam up the tap. A good rule it two to three turns when first starting the hole and then back up 1/2 turn. The I recomend 1 tunn in and a 1/2 to break the chip. If you feel the tap starting to get really hard to turn, take it all the way back out and clean the flutes, blow the chips out of the hole and go again.

The other style of tap is a sprial point tap which is designed to push the chips through the hole, rather than pull them into the flutes. As you can guess, you need a through drilled hole, they won't work in a blind hole. With the sprial point taps, you don't back them up, other than to remove them from the hole when you are finished. These taps also have only two flutes and are quite a bit stronger than a hand tap.

My recomendations for motormouns is to drill and tap. Use the exact size hole at the motor lugs. IE a 52 magnum four stroke, or an O.S. 52 both use a #6 screw. The 70 and 92 four strokes use a #8 screw. If you then use a socket head cap screw with a proper split ring lock washer, you will never have trouble with loose screws, providing that you tighten them down properly to start. I use thes on the composit mount, like the Dave Brown also. Withe that style mount, the front holes will usually show a little thread just before the bottom of the lug. This is not a problem as you will have at least 10 to 15 turns of screw in the hole which is more than enough.

One place where I use a nut on the motor mountig screws is if I need to add weight up front. I cut a strip of 1/8" lead sheeting about 1/2 to 5/8" wide, and make it long enough to span the mount lugs and loop under the engine. I form it in the shape of a U with ears and then clearance drill. I use extra long front engine screws, long enough to clear the bottom of the lug and then a couple sheets of the lead, a flat washer and a nut. You will add about 1 1/2 oz of very effective nose weight like this. Just make sure to use thread lock on the nuts as the lead will deform something awful.

Don
Old 07-03-2008, 07:29 PM
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Default RE: How to tap metal


ORIGINAL: fredsedno

Try using the same size drill inthe original hole, but run it in reverse[backwards] turn drill very slow with moderate infeed.This will sometimes back the broken piece out[sometimes not]. Kerosene has been the reccommended cutting fluid for aluminum.Sharp drills perform with fewer problems.
fredsedno

If your motor mount is aluminum, or composit. you can soak it n a pan of alum mixed with water. Use a strong mix. THe alum will desolve the steel bit. Needles to say, this wont work getting a broken drill or tap out of steel. It has to be a non ferious mount as the alum will attack any ferious metal.

Another tip. If you are using the aluminum mounts. and you kind of miss getting the alignment correct on a hole. there is an easy fix. Tap the hole out to one size larger than the screw size you are using, but don't tap it all the way through, just enough for the tip of the tap to come through about 1 turn. We are going to put the taper to work. Get a short piece of aluminum round the size of the hole you just tapped. Thread it for a long enough length to go through the mount lug. Now, this is extreamly important, use soap, water, and the acohol and clean every last bit of oil from both the hole and the treaded aluminum rod. Now put the threaded rod in your drill press and the mount in a vise that is locked down well make sure the thread are started clean by screwing the rod in about 1 turn maximum. Holding a bit of down pressure on the drill press, turn it on. It will screw in the aluminum and snap of the end of the rod at the top of the mount lug. File it smooth, top and bottom and it's like the off center hole was never started.

Aluminum has a nasty habbit of self welding to another piece of aluminum if there is not lubercation. This habbit though is put to use here because what you have just done is to pressuer weld the threaded rod into the motor mount. This won't work with anything other than aluminun. It turns out that this is how they weld together those flat aluminum plates in the freezer of your refrigerator. They form two plates with the 1/2 the tubing and place the plates face to face and use a pressure roller to tracet the edge of the tubing. Just the pressure is all that is needed to weld them together. Works on motor mounts very well also.

I have one that I missed the hole by 1/2 diameter. I did this fix and was very leary that the 1/2 thread would hold up to tapping and then multiple screws run and out of it. Worked like a charm.

Don

Old 07-03-2008, 08:39 PM
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Default RE: How to tap metal

thank you for the wonderful advice, and suggestions, ill try the drill bit backwards idea, if not ill try drilling it from the other side.... i dont have alum, or know what it is....

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