Fabrication Questions (Loren, Others)

[DanStokes]

I've done a fair amount of fabricating and used to be able to pick the brain of the guys in our shop at work but now I AM the local expert (scary, knowing what I don't know). I've been building and fixing stuff for the van and have stumbled across a few question:

1) Rough estimate - how many holes can you tap with a tap before it's shot (dull and/or undersized) and needs to be replaced? I realize that will vary with material being tapped, etc. but just looking for a ballpark. I just tapped 14 1/4X20 holes in aluminum for the running board repair (I'll post pics in the "ME's Van" build thread once complete) and although the screws fit well (so probably was cutting to size) it took WAY more effort to turn the tap than I would have expected. So maybe it's dull?

2) Will soapstone mess up a weld? As I've commented from time to time, I have a heck of a time following the line of a needed weld due to my crappy eyesight (welcome to old age and diabetes). I had the brainwave that I could draw a soapstone line down the area needing welded and then (maybe) I could see it and follow the line. But would there be inclusions in the weld that would significantly weaken the it?

I'll probably think of more but these are a good start.

Dan

[JamesMayberryIII]

did you use cutting fluid?

[squirrel]

Tap Magic....I got some from McMaster Carr. I have a tap I bought in 1977, it still works.

Can you figure out a way to get more light on what you're welding? Halogen work light, or something like that

[nickleone]

You can buy magnifying lenses for welding helmets. Go to the local welding supply.
Nick

[Deaf Bob]

There are all kinds of cutting fluids avaiable now, tranny fluid works pretty good.
As for soapstone.. If it was so bad, wouldn't welders find something else to mark with? Flux and gas is supposed to "wash" soapstone out..
Using lighter lenses is NOT the way to do it.. Get more light into your weld space..

[Huskinhano]

Dan, I use to tap a lot of aluminum brackets with small taps such as 4MM. I've use either plain water or water with just a touch of liquid soap. Never use oil, you might as well use crazy glue. Funny you say that about a tap's life span. I wasn't so concerned abut them being dull as I was about them getting fatigued and snapping.

[squirrel]

I've dulled a few taps, usually by chasing threads in rusty iron. Yeah, I should get some thread chasers instead.

[Loren]

If you bought that tap from the hardware store it may be junk right out of the package. Factories in China sell their good stuff to MSCdirect.com and others who have customers that know their stuff, the garbage goes to TruValue, Sears and whoever else and is passed along to old fools like you or I who worked hard for their money but who are apparently are in their opinion easy suckers. A good $5-10 industrial tap may last hundreds of holes in steel using Tap-Magic as Jim says or even the much-cheaper pipe-threading oil from -yep- the hardware store as a lubricant.

As far as soapstone goes, I think it just floats to the top with other slag.

[tardis454]

It depends on the job and the type of material you're cutting. When I ran Warner & Swasey automatics I'd get 5,000-6,000 pieces out of a 1/2-13 3 flute spiral bottoming tap cutting lead-alloy with standard grade machine oil. On some stainless jobs a tap would last about 500-1000 pieces. Brass jobs I'd get 8,000-10,000 pieces. Hand tapping with Tap-Magic or tranny fluid is a different story. A tap used for hand tapping should last a long time as long as it's centered properly and carefully used. Buying a good quality tap to start with helps too. The place I work at now hand taps everything. They use this stuff called Anchor-Lube, and boy does it work good. I highly recommend it. Anchor-Lube's right up there with Tap-Magic except it's cheaper, and more versatile. It does a good job of keeping the tap clean. I've been using the same taps on every job since last October. Here's a description of it from Fastenal.. "Applications: Anchorlube is the solution for difficult metalworking operations including along side welds on carbon steel. It's many uses include: drilling; tapping; sawing; spot facing; counter-boring; milling; fly-cutting; seat forming; engraving; broaching; drawing; piercing; punching; hole extruding"

[DanStokes]

Hey Tardis - Thanks for that tip. Next time I'm at Fastenall I'll pick up a jug.

Tom - I've snapped a few so I know where you're coming from! Really annoying.

Nic - My issue isn't light (though that's a great suggestion). I do use a bright light close to the welding area and focused on the area to be welded but I'm missing "pixels" (don't know how else to describe it) as a result of extreme lasering to save my vision. I have no complaints as I'd be blind w/o the treatments I had but it does mean that I have missing places as I look at anything requiring fine focus. I think I'll try the soapstone thing and see how it works out - it might not help but it might.

And THANKS ALL for you thoughtful suggestions. I love this place!

Dan

[sdwarf36]

I worked in an auto machine shop that had probably too many hands into the tap selection. Guys with the attitude that if it ain't broken, its still good. Thy would chase exhaust holes after heated -rusty holes-then you grab the tap trying to do a new hole. My rule of thumb was-if the high spots of the cutting edges are shiney and have anywidth, its dead.

[Loren]

It's good to have some-sort of magnifying device strong enough so you can actually get a good look at the tap, and think of things at kinda a microscopic level. If the leading, cutting edge is rounded-off at all it's just pushing on the material, jamming it toward the outside and not cutting it away. Common sense, really, but you have to be able to see it. Something else a tap needs is a little "relief" ground into it, i.e. that portion of the tap behind the cutting edge on each flute is not concentric but is angled back towards a smaller diameter...for a tool to be able to scrape away at metal and peel chips off it cannot be "flat" to the material behind the cutting edge or as soon as there is any dulling at all it will never get a good bite but will just ride along over the top, creating scoring and friction and finally breaking in the hole instead of cutting threads. You can sharpen taps if they're not too thrashed, just mimicking the cut that you see on a good new one, and be sure to include that back relief.

When I say the hardware store ones are no good right out of the package, what I mean is what I buy at the local Tru-Value if it's an "emergency" and I need something right now, will likely have a rounded (sometimes severely) edge where there is supposed to be a good sharp cutting edge, and no back relief or even sometimes be cut the wrong direction which results in a tool that...well...couldn't cut wood. I have also bought drill bits that were cut backwards, diving into a piece of metal and getting nothing but heat and smoke with a brand-new tool. This stuff was not made by a factory that didn't know what it was doing, rather it's just plain 'ol sloppy work or it came out of some reject bin where the Tru-Value buyer, who is in these cases an idiot, thought he was getting a deal. Taking any of this back to the store will get you blank stares and pushback ("how could anything be wrong with it, it's brand-new" and the inevitable remark about how you have to use cutting fluid, you big silly), and winds up being not worth the trouble, instead get out the magnifiers and inspect it when you get it home and try to correct whatever mess they handed you before ever attempting to use it. (Unfortunately packaging prevents you from close inspection at the store.) I have over the years purchased perhaps a dozen (not many!) taps of various sizes there...one of those was a metric one in an odd size I never thought I would be able to get and was an excellent well-made tool and I couldn't have been happier...all the rest were the crap I'm talking about, I don't know how they can do it.

BTW here's some applicable info (pdf), look at page two, second panel, the "eccentric relief" one. That is what a general-use tap for around the shop should look like. http://www.amtektool.com/NATool-Tap-EnginData3.pdf

[ImpalaSam]

Remember, if the tap is a "hand" tap it needs to be turned 1/2 turn forward then about 1 turn backward to break up the chips.
If you try to just run it in without backing up, the chips just pack up and it will be nearly impossible to turn. If it is a spiral
point or "gun" tap it can be run through without backing up as the chips will be pushed out in front of the tap. FYI these
should be used carefully when tapping blind holes. Another FYI, I have seen kerosene used when working with aluminum,
worked pretty well.

[dieselhead]

Dan,
If there a FASTENAL store in your area they have all kinds of neat stuff including taps and drill bits ranging from cheap to very expensive. I used one of their better quality drill bits (not highest quality) to drill 144 holes in .080 steel and it's still sharp enough to drill more. I only live about a mile from my local store and drove by it hundreds of times before a friend told me about it and what they sold. He found bolts for his boat that even the dealer didn't have.. If they don't have what you need they can usually get it by the next day. If you live in Wilmington there is a store at 3022 North Kerr Ave.

Victor

[DanStokes]

Thanks Victor! Actually, I bug them from time to time but I generally find I need a tap or some such in the middle of a project and run to the local Ace hardware (it's close) and buy whatever they have not knowing that some of this stuff is junk. I have a full set of MAC (Hansen) taps and dies, metric and English, but they were bought in 1983 or so some some have broken or dulled and been replaced with stuff from the hardware. I'll swing by Fastenal and score replacements for my cheapo stuff - worth it now that I know it make a difference. Live and learn!

Dan