Trick to starting threads straight

use a drill?

1) throw out the hex re-threading die and buy a high quality die from MSC. The re-threading dies really are pretty poor quality as a rule. 2) don't use a socket and ratchet to drive the die. Use a real die stock with two handles. 3) reduce the diameter of the first bit of the shaft down nearly to the root diameter of the thread.

Jim

Jim's reply begs the question: Are all hex-shaped dies intended for rethreading only? I have some that appear to do very nice threading, even in steel. Or am I such a poor machinist I can't appreciate the difference.? And thanks, Harold, for setting us straight on the reason for not *using* lapping compound on cast iron. Bob Swinney

Part of the trick is to begin the threading straight--pay lots of attention at that point--then the rest will follow with ease. I taper the diameter of the end of the to-be-threaded shaft by hammering it. I've only done mild steel--never aluminium--so I assume this would work for other metals too. I like to make the length of the taper match the thickness of the die.

Then, if the shaft is short enough, I will clamp it vertically in my vice. Next, I put the die/diestock on top and begin to turn, carefully bit by bit. In the beginning I have to push down as I turn in order to get the tool to start the cut; I have to push down until the tool pulls onto the shaft on its own. It's the pushing down that makes it hard to get the thread started straight.

So, I crouch down to check for level; then stand up and pushdown/turn-to-cut; then crouch to check, then stand turn etc.... At the very beginning, the diestock is very hard to keep level but as I ease into the first few turns correcting all the time I am able to get the diestock level--i.e., cutting straight onto the shaft. So, Bob's your uncle!

David

WRT hex dies: Any I've used have been miserable mothers to originate threads. Chances are, you're merely deforming the aluminum into a threaded condition, sort-of. Get some good name-brand split button dies(round, not hex) and a suitable diestock, life will be much better for it, you'll be cutting, not deforming. There are diestocks that have an adjustable finger set for starting your threading properly, looks like a three-bladed camera iris, these work well except for threading up to a shoulder. The local hardware store carries them in the General brand.

Don't cheap out on diestocks, either.

A nominal 3/8" rod will likely be oversized to run 3/8" threads on anyway. You can reduce the diameter, before threading, in a lathe or make two passes with the round die, one with the adjusting screw all the way in so it cuts oversized and then make another pass with it farther out, so you get the proper sizing. One reason for getting split dies.

Stan

Taper the end of the stock so that it sort of matches the taper in the die. There are several types of dies just like with taps. You want to use the ones that have the long taper into the threading section. Using one with a short taper will make things a lot harder to get the die on straight. Another is to put the die on a flat surface, holding it firmly and put the stock into the die, holding it vertically against the die and turn the stock.

-- Why isn't there an Ozone Hole at the NORTH Pole?

difference.?

Dies, in general, do not generate great threads. I'm of the opinion that you could very likely buy the hex variety that will cut threads in keeping with split dies, but you lose the ability to choose pitch diameter. When using a conventional die, especially in coarse pitches, it's a nice feature to be able to open the die for a roughing pass, then close it down for a finish pass, which generally provides for a better thread. Personally, I avoid dies like the plague, but they're better than not being able to create threads.

Welcome!

Harold

Really helpfull - not. Read the OP. Not even any help if he using a tap

----------------------------------------------------------------------------------------------------- snipped-for-privacy@boltblue.com John Lloyd - Cymru/Wales

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OOUUCH!!!!!

My rod's not all that long, but gripping it in a drill press is far down my list of possible fixes.......

Threading rod is just plain tough, and I'm not sure there's any real good manual method. A die, by nature of it's design will naturally cut more on one side than the other, thus running crooked threads. Never seen joy like the first time I did it by first roughing them in single point on the lathe, then finishing the job by hand. One of those things that made you mad over all the grief you had caused yourself from years of doing it the hard way............

Tom

I used to use drill bushings upside down when I had access to them.

4) Practice, practice, practice.

Steve

How about this...

1. insert tap into cordless reversible drill (the tool not drill bit)
2. apply recommended thread cutting lube
3. hold drill perpendicular to surface of piece being tapped
4. use drill in appropriate direction to cut threads
5. reverse drill direction when desired tap depth reached
6. clean our tapped hole
7. use your hole

Funny that I find using a drill easier and more helpful for getting quick, good threads cut. Starting the tap by hand can be tricky at times, especially if you have weak wrists.

Cheers,

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>

Chuckle!

The OP was discussing the use of a *die*, not a tap. Your information is quite useful, but is hardly an answer for the original question.

Harold

Ideally -- you cut the threads on a lathe, which assures that they are straight and the right pitch.

An alternative, if you insist on using a die, is to turn about the thickness of the die worth of the end of the rod down so the die will just barely slip over it, which will help you to get started straight. (No bets as to whether it will *stay* straight for any great distance -- especially if you are working with one of the softer alloys of aluminum.

Hmm ... this suggests that you were not even using a proper die designed for cutting new threads, but rather a rethreading die designed to clean up bunged-up threads. *Real* dies are round on the OD, so a socket and ratchet (note -- spelled without the 'w') and socket would not work. And *good* ones are HSS, not carbon steel. Yours are almost certainly carbon steel.

The standard die will need a "die stock" (a wrench designed to accept the round die and hold it by pointed screws run into recesses in the edge of the die). Good dies will also offer provisions for adjusting the tightness of the thread.

Don't buy dies (or taps) from Home Depot or the like. They are almost certain to be the hex rethreading dies. Go to a serious tool vendor. I don't know what may be in your locale, but I buy a lot of things from MSC.

Note that there is a line of dies called "Little Giant" which has separate chasers (the cutting part) held into the die body with a plate which screws down onto the chasers. The chasers are adjusted with small setscrews. And the plate has a hole the right size for the stock being threaded, so it is a help at getting the die started straight.

Above are my opinions.

Good Luck, DoN.

Well ... aside from the fact that he said that he was using a die, not a tap, there is one other caveat which needs to be considered when using your technique (which can work nicely under the right circumstances).

That caveat is that you need a tap designed to be used under powered tapping -- either a "gun tap" (spiral point to chase the chips ahead of the tap) or a spiral flute tap which pulls the chips back out of the hole as you go.

Normal taps would clog up and break without frequent reversing to break the chips free. (Something which applies to his die as well, even though it appears to be a hex rethreading die, not one for cutting new threads from scratch.)

Enjoy, DoN.

A 'hex die' is not necessarily a 're-threading' die. I have some hex dies which are not designed for re-threading and produce very accurate (within the limitations of dies) threads. The only method (HSM that is) that produces truly accurate threads is 'single pointing' on a lathe with an accurate (read unworn/quality) lead screw. Your mileage may vary (G).

Regards. Ken.

Take a chunk of stock, you could use hardwood, about 1" thick and, oh,

2" square. Drill a 3/8 hole through the center. Use a drill press to get it perpendicular. Slide the block over the end of the rod and clamp your diestock to it (after you've bought the diestock that others have told you about). The block will hold the die perpendicular and slide down the rod as it's threaded.

Bob

BTW - why is a hole "tapped" with a "tap", but a rod is "threaded" with a "die"? Why isn't the rod "died" with a "die"? (In case it's not obvious, these are rhetorical questions.)

Use split dies or various diam's - Start with a shallow cut and then merge in.

When I cut threads on the lathe, I often chase them with a die to the final form.

Mart> snipped-for-privacy@hotmail.com wrote: