tap and die set?

[Matt Stiegler]

I've neither owned nor used a tap and die set, but to shift the rails of my TS I'd need to tap holes in steel and CI. Since I've made it this far without, I don't think I need to go top-of-the-line here. I'm just looking for something that will do the job for this project and once-or-twice-a-year use in the future.

Is a cheap tap & die set what I want? I see this (http://www.harborfreight.com/cpi/ctaf/displayitem.taf?Itemnumber=39424) cheapo 40 piece alloy steel set from HF, for $20. Slightly more expensive sets are made of alloy coated with titanium, like this (http://www.amazon.com/Neiko-Tools-Titanium-Coated-Hexagon/dp/B0012AQNXA/ref=sr_1_5?ie=UTF8&s=hi&qid=1253289254&sr=8-5)for $36 on amazon. Any better ideas?

[JohnT Fitzgerald]

without knowing what TS or fence you have....

is it possible to just drill holes without tapping? When I mounted a Biesy fence to my old Delta, I had to drill holes into the CI top - but they were located so they could be 'through' holes, and then I just bolted the tube on.

[Matt Stiegler]

It's a Grizzly G0690 cabinet saw. Good thought, but through holes won't work, its up through the angle iron into the bottom of the rail.

[Matt Day]

I have basically that same set from HF, and have done the same operation you're trying to do and they worked great! I have both the metric and SAE sets and they come in handy quite a bit. If you're not putting them to hard use regularly, I say go for the cheap ones.

[Steve Clardy]

Auto parts stores carry each tap and die separately, if you don't need a full set.

[Lee Schierer]

If you've never used a tap, be careful. When tapping, every full turn back up the tap 1/2 turn to clear chips. Use lots of lubricant. Make sure you drill the proper sized pilot hole for the tap, a bit undersized is much worse than a bit oversize. Don't force it. Taps are very brittle and when they break they can be a bear to get out.

[Matt Stiegler]

Thanks for all the suggestions. Sounds like I'll be making my first-ever HF order.

[David DeCristoforo]

Generally, you don't need anything spectacular to tap CI. It's pretty soft as metals go. But buying an entire set of "el cheapo" taps and dies might not be the smartest thing. If you ever need to tap or thread harder metals, you might easily end up with broken or stripped taps and dies. I would just go to your local hardware store and buy the tap you need. If you are going to get a whole set, look for better quality.

[Jay Jeffery]

Generally, you don't need anything spectacular to tap CI. It's pretty soft as metals go. But buying an entire set of "el cheapo" taps and dies might not be the smartest thing. If you ever need to tap or thread harder metals, you might easily end up with broken or stripped taps and dies. I would just go to your local hardware store and buy the tap you need. If you are going to get a whole set, look for better quality.

+1

Get the cutting tool from somewhere you can trust. The last thing you want to do is have the tap break, which cheap cutting tools are prone to doing. You don't necessarily have to use HSS to tap in cast iron, high carbon will probably be okay. The tool you use to turn the tap can be cheap, though.

If you do break a tap in your table saw, post your problem and we'll tell you all the miserable and/or expensive ways to try and get it out.

[Cary Falk]

I would go along with not buing a el-chepo set. Buy the one that you need. I have a medium duty set and still have broken taps. Trying to remove a broken tap from a hole is next to impossible. If it happens you still need to go out and buy another single tap. Depending on the size a tap is about $6. I have moved my fence rails and didn't need a tap. I just measured the spacing of the holes on the table and drilled extra holes in the fence.

[Tom Veatch]

Matt, I'll second David's recommendation to buy a good quality tap of the size you need rather than a full 'el-cheapo' set. Added to that is the recommendation to buy a properly sized tap drill at the same time along with some tap lubricant. Even a full 1/16" to whatever by 16ths won't have the size you need. If its an SAE thread, it'll almost certainly be a number or letter size. The right size drill bit goes a long way toward avoiding broken taps. As far a lubricant is concerned, I've had good luck with the dark cutting oil used when threading iron pipe. I haven't done much CI tapping and will gladly yield to other recommendations.

Buying the set will give you the convenience of (probably) having the right size and pitch the next time you need to tap a hole, but the inconvenience of trying to get a broken tap out of the hole will far more than counteract that convenience - and you'll have to make a trip to replace the broken tap anyway.

It appears that you have little or no experience tapping holes. I'll almost guarantee that gaining that experience is going to cost some broken taps - especially in the smaller sizes. Someone mentioned backing the tap out a quarter turn or so every full turn. I'm more comfortable doing it more frequently than that. My comfort zone seems to be about a half turn in, a quarter turn out. But let the tap tell you when to back out. When the tap gets "stiff" and starts to deflect, stop and back up to clear the chips. Be gentle, taps are hard and brittle, it takes very little muscle to break a small tap.

[Matt Stiegler]

Well, that's all pretty persuasive. And, after looking at it some more, I don't think I need to tap any holes in CI, only in steel. (The rail and the bottom of the tube.) I gather that tapping in steel is more demanding.

[george wilson]

I also advise against using HF taps. While I have seen posts that tell of HF power tools doing o.k.,and while I have a few of their items,I'd NEVER buy tools from China that have to rely upon keeping decent edges to cut something.

You can find yourself in big trouble if a tap snaps off in a hole. Tapping is not the easiest operation,especially if you haven't ever used taps. Go to an auto store and buy the HSS tap you need. AND,be sure you have the correct drill size. like said above,a slightly too small drill will make major trouble.

Tapped holes are supposed to produce only a 75% thread,NOT 100%. there are charts that show you what size drill to use with a given tap.

I only turn a tap 1/4 of a turn,then reverse it to break the chip. With cast iron,since the chips break up pretty small anyway,you can get by with more,but I urge you to err on the conservative side of how far you twist before reversing.

Last note: Cast iron is cut dry. Don't forget,you are tapping CHINESE cast iron,and might run into glass hard spots,or lord knows what. On the machinist's forums,I've heard stories of running into all kinds of trash,like unmelted ball bearings,etc.. Be careful of running into sand pockets,hard spots,or other foreign materials. Quality control over there isn't what it should be yet.

P.S.: I now see you are tapping steel. Lubricate the tap with cutting oil. And,be careful of foreign stuff. If you look carefully at taps,you can actually see them bend when you are twisting them,especially the smaller ones. And,they don't like to bend much at all. HSS,and carbon steels are both brittle,if they are hard enough to tap steel. I have found Chinese taps of HSS to be more brittle than American ones for some reason. Their milling cutters are more brittle,too. Vermont taps are all carbon steel as far as I know. They are the usual sold in hardware stores. Try to get an American tap of HSS.

[Cliff Rohrabacher]

Is a cheap tap & die set what I want? I see this (http://www.harborfreight.com/cpi/ctaf/displayitem.taf?Itemnumber=39424) cheapo 40 piece alloy steel set from HF, for $20. Slightly more expensive sets are made of alloy coated with titanium, like this (http://www.amazon.com/Neiko-Tools-Titanium-Coated-Hexagon/dp/B0012AQNXA/ref=sr_1_5?ie=UTF8&s=hi&qid=1253289254&sr=8-5)for $36 on amazon. Any better ideas?

No, No, and no.
Go to a "real" industrial supply and get TRW, OSG, or Greenlee.

Those items you listed and all such of that ilk that are made for the consumer were not actually intended to ever actually be used.
They will leave you crying in your beer with snapped off taps in blind holes and no way to extract 'em.

[Ed Hazel]

You could just use some self tapping bolts.

[Floyd Mah]

Try this site. www.mcmaster.com (http://www.mcmaster.com)
They sell high quality taps. Look at this page: http://www.mcmaster.com/#taps/=3ov173
It explains the different types of taps. If you have a thru hole in a plate, a spiral point tap will work really well. I've used these both with and without backing up. Also depending upon the thickness of your workpiece, you might even be able to drive it with a power drill, although I wouldn't do it in a piece that was critical or irreproducible. Besides lubrication, the most important thing to do is to drive the tap in squarely. Torquing the tap off the axial direction is the most likely reason that a tap will break. One way to prevent this is to drill a hole in a wood block vertically that will guide the tap in and start the tap with the block clamped in place over your workpiece. The "H" number specifies how loose the resultant threads will be relative to the intended screw. The usual spec is H3. An H2 tap gives you a tighter fit. The coated taps, titanium nitride, are only slightly more expensive, and seem to cut very smoothly. The number of flutes affect the number of cutting edges but also might mean a tap has less metal (and hence strength). Another consideration, mentioned by someone is how much oversized the initial hole is. The larger the hole, the lower the percentage of thread supporting the screw. Obviously, the more oversized the hole, the easier it is to tap the hole (less metal to remove) but you give up strength in the resulting screw hole. Consult a table of recommended clearance holes for the material you are working with. I guess before people get upset with me mentioning a power drill, I would like to say that it can be done, but only with caution, and after you have some experience, in non-critical work.

Anyway, buy the taps only as you need them because you can be assured that you are likely starting with a fresh tap or one that you know the history of, and most importantly, the quality of, relative to getting a box of taps that may be of questionable quality.

[Josh Brouse]

Well, I have done metal fabrication for years professionally, and it is easy once you get that first time over with (just like everything). i personally use a drill when tapping. but i have been doing it awhile and know the toque that they generally break at. and i know my drills settings well enough. with a little practice you'll be using your drill to speed up the process in no time. but just starting to get the "feel" use the little bar that's made for it.

1. use this chart to get the right drill size http://www.korit.com/tapndrill.htm

2. use a lubricant (as another has stated) I like "drill chill" but anything that qualifies will work

3. starting the threads is the "most" dificult part or the process. try and keep the tap plum as you go in. you can easily tap the hole at a angle. and the head of the bolt will then not sit flat on the head and be prone to breakage (at the head). This is one of the reasons i use a drill easy to plumb. other reason is fast!

4. as you go in you'll feel the tap get "bound up". this is the metal shaving getting to long and hitting and/or clogging the flute of the tap. as stated again you no in reverse to clear/shear that metal.

5. Now your threads are done put a bolt i right, Yes? Well, no. Debur the the mating surface for sure (small shavings may scratch and add material between the parts) and I like to debur both sides of the hole if i can reach them. I use a simple 45 degree chamfer bit. but using a larger drill will do just fine without buying something your not going to need that often.

K my rambling is done. hope it was useful

[george wilson]

How thick is the steel to tap?

[Josh Brouse]

well i figured id post a what to do if you get the tap broken off in the piece.

--------
scenario 1

you break the tap off a work piece that you can get to the back or the tap broke off with room at the top.

fix
easy vise grip pliers and get to twisting (tap are brittle so tighten just enough to grip and twist. more torque will just break the tap again)
------------

scenario 2

you now break it off in the rail and can get to the back side and have broke it off flush or nearly flush and cant get a grip with anything enough to twist it.

fix
well not hard but not easy either.

using a punch. knock the tap through and go up one size in bolt. that will require you to go up in drill & tap and redo the process again with that hole.

or

use Self-Clinching Fasteners generally called a PEM nuts. (PEM is a manufacturer)
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hope this part will not be used. but its there if you need it :)

good luck

[ROY DICK]

Matt,
Which ever you decide get some of this tap magic.
http://www.tapmagic.com/.
Works like cutting butter on drill bits and taps.

Roy

[Jay Jeffery]

Those items you listed and all such of that ilk that are made for the consumer were not actually intended to ever actually be used.
They will leave you crying in your beer with snapped off taps in blind holes and no way to extract 'em.

Those cheap taps are often suitable for cleaning up existing threads. If you have done any extensive automotive repairs on older cars, you will know how important that can be.