Dull tap/die or poor skill?

[jives]

Hi all;
Pulled out a box of mismatched taps and dies the other day for the first time to use them. Got them from my dad some 30 years ago, and may have belonged to my grandfather. Offhand cannot remember the brands.

Anyway, I wanted to create a threaded rod to replace a missing handle on my Rockwell drill press. Oddish size, 7/16" diameter, 20 tpi. I could buy a single 7" x 7/16 x 20 tpi bolt online (none available locally), or make one myself. All my attempts failed. Watched vid after vid -- seemed simple enough -- but I could not get the die to bite and cut. Tried 3 different dies, one being adjustable. The adjustable one broke.

So. . . is it possible that the dies are simple too dull? Can that be checked and fixed?

 

[bob15]

What is the rod you are trying to tap?

Hardened, tool steel, another bolt?

What is the OD of what you are trying to tap?

Does the tap have lead-in threads or does it say: "start from this side?"

 

[Kenstone1]

When cutting threads with a big die, using a lathe and applying pressure to the die with the tailstock is the way to get the die to "bite and cut".
If you don't have a lathe figure out another way to put pressure on the die, maybe a drill press chuck/quill, arbor press, or something else.
jme,

 

[jayemm]

Did you chamfer the end of the rod so the die can get an initial bite?

 

[RedneckWelder]

Dies are a complete pain in the *** to use freehanded plus with unknown quality you don’t know whether you are using Chinesium or a decent quality one.

 

[engineer2]

If the die is dull, touch up the cutting edges (holes or slots) with a dremel and a small diameter stone.

Your rod should be about .4375 (7/16") diameter
I would grind a slight taper on the end of the rod.
Chuck the other end of the rod in your drill press.
Center the die "start end" in you drill press vise under the rod.
Use the quill to add a little downward pressure.
Add a few drops of oil.
Turn the chuck clockwise by hand until it bites.
Back off to break the chips.
Turn it 1/4 to 1/3 turn or so and back off depending on if it has 3 or 4 cutting edges.
Go CW and CCW until it is threaded the way you want.
Don't go too far without backing it out. You'll feel it get tight.

 

[Rinspeed]

Did you chamfer the end of the rod so the die can get an initial bite?

That was my first thought.

 

[marinusdees]

If you consider the geometry of the die, you can turn it until the chip curls back into itself. Then, you must turn the die "backwards" to break up the chip. Also, in general, dies are meant to be used to rethread or clean up damaged threads. Cutting new threads requires a lot of "back and forth".

 

[ez-duzit]

...in general, dies are meant to be used to rethread or clean up damaged threads...

No. Only re-threading dies.

OP--show close-up photos of the die and accurately identify the bar stock you are trying to thread. Are you using a large enough die handle? Cutting oil?

 

[iajonesy]

Are you absolutely sure you have 7/16" rod ? Taper the end slightly and use plenty of cutting fluid. As stated above, send some pictures of your die.

Mike

 

[toolchaser]

The rod diameter should be about 1% under 7/16" for die threads, it sounds like your trying to thread an oversized piece

 

[woody 73]

All good advice from above. If the die stock ever got rusty that will hurt you in the long run, do you think it was possible that it sat in a humid place for a long time ?

 

[fsae0607]

What's the rod OD? Use a caliper.

 

[Slednut]

I found using cutting oil will help the die to bite.

 

[Jland]

There are actually different types of dies and stocks.. some dies are solid.. stocks for those usually have 2 screws to hold the die. Other have a slot in them and the stock has 3 screws, this type can be "adjusted" to give you more or less clearence.. technique is also hugely important. Tap or die for every half turn I back off at least 1/4 turn.. cutting fluid, while extremely important will also hold onto chips due to surface tension of the fluid. Large material may require backing out a trun or two to blow out built up residue. Carbon steel doesn't work real well on some alloys.. I had a handle strip out on my drill press, I ran a 1/2-18 tap in and used a 12" bolt with a jamb nut...

 

[MushCreek]

Unless you get it started perfectly straight, the threads will be on an angle, and it will get worse until the die won't cut any further. I have a die holder for the tailstock of my lathe that works well. Also, you might be using a rethreading die. Or a dull die, or too hard a material. There are lots of variables. You could just order that bolt, or a piece of threaded rod, but that's not the GJ way. Personally, I would go out and buy a decent lathe if you don't already have one. Ya gotta be practical, man!

 

[dogdog]

Did you chamfer the end of the rod so the die can get an initial bite?

^^^
that and also the holes have the be the proper size to get it tap easier. or the rod have the be the right size for the die to be able to cut the thread.

For example, I have been trying to cut a M18x1.25 thread on a delrin rod forever, so I bought a 19mm delrin rod.. no problem right 1mm over and .5mm in a round. That was not fun chamfered or not.

 

[jives]

OP here. . .
I will caliper the rod to insure that it is 7/16 and I used motor oil, not cutting oil. See below confirming its diameter.

The end was chamfered.

The test rod I am trying to cut threads on already has one end threaded. This is the end that screws into the drill press handle hub. This end also screws nicely into a 7/16 x 20 tpi bolt. It has no knob on the other end, so I am practicing my threading by attempting to cut threads in the free end. Using a non-adjustable die marked 7/16 20 tpi.

I'll see if I can get some pics tonight.

 

[Jland]

Is it a bolt you cut the head off of? If so did you xheck to see if was marked as a grade 8 or 5?? Either way you may want to heat that end and quench it...

 

[AZ Pete]

Jland, wouldn't it be better to heat it red hot and let it air cool, to soften it?

 

[dogdog]

for steel annealing I wouldn't quench it.. as far as I remember, it was heat it to dull / cherry red then let it air cool... quenching steel makes it hard/brittle. But don't quote me on it. Haven't touch those things for eons.


https://makeitfrommetal.com/beginners-guide-on-how-to-anneal-steel/

 

[Whitworth]

Cutting new threads with a die is a difficult skill to master. Cutting them straight on without the threads going kittywampus is even more difficult.

Just buy a piece of threaded rod.

 

[Downwindtracker 2]

The die could be carbon steel, they get dull easily. If the die is one of the slotted ones open the slot so you are cutting oversized threads, then close it for the second pass. Still it's a pain. Even the type of cutting oil makes a big difference.

 

[Jland]

for steel annealing I wouldn't quench it.. as far as I remember, it was heat it to dull / cherry red then let it air cool... quenching steel makes it hard/brittle. But don't quote me on it. Haven't touch those things for eons.


https://makeitfrommetal.com/beginners-guide-on-how-to-anneal-steel/

Yup..my bad

 

[matt_i]

Cutting new threads with a die is a difficult skill to master. Cutting them straight on without the threads going kittywampus is even more difficult.

Just buy a piece of threaded rod.

This is the best advice yet. I believe your size is probably available at McMaster Carr. Plus you get rolled threads instead of cut threads.

I think if you setup the steel rod in the lathe and used a follow rest to single point a couple of passes to give the die a path of lesser resistance, I think it would come out with acceptable quality but that's a ridiculous amount of work.

All my attempts go wonky after about 2" of threading, even using brand new GTD dies and copious lube. The problem in my case is that the center axis of the die becomes misaligned with the center axis of the rod and once that starts it becomes unrecoverable.

 

[jives]

Just buy a piece of threaded rod.

Yeah, that was the first choice. . . the problem is that I need a 7" long 7/16" diameter rod and 20tpi, threaded on only one end or on both ends. Online the only thing I can find is a grade 5 bolt, 7" x 7/16 x 20tpi. I can cut off the hex head and stick on a knob on one end. Don't really want a hardened bolt.

I thought I'd give a shot at making the DP handle first before ordering a single bolt online. Would even have to order it through Fastenal, though they have since left town.

 

[Whitworth]

McMaster # 94358A455. ????

 

[bob15]

McMaster # 94358A455. ????

That rod is 7/16-20 on one end and 7/16-14 on the other end.

 

[Jland]

While I will admit running threads with a die or tap isn't necessarily "easy".. it is like anything else.. you need to understand whats going on and use good technique. I've never had a beed to dut threads on a rod for much over an inch but geez guys it was pretty straight forward.. I will say for a tap.. to large a handle and you will break that tap but a die.. the puny 8" handle that comes with sets isnt really good for much over 1/4".. that 7/16 rod.. I'd have that die in a 12" stock at least.. my largest is 18" . Leverage is key when cutting thick rod.. if you cant get a half turn then give it a quarter turn, back of and give it another quarter turn.. finesse not speed.

 

[jives]

OP here. . .
Well, I looked at the threaded rod at McMaster-Carr and getting two just seemed excess. Finally ordered from BoltDepot three (got an extra) 6" long grade 5 7/16 x 20 tpi bolts at $1.65 each. No need for grade 5, but I could not find standard steel bolts of the specs I needed anywhere.

As an FYI the dies I tried are Ace, 7/16, 20 NF, which did not seem to fit the existing handle thread, and a brand with a W L over a B in a shield logo. Also labeled was the 20 NL, bu the 7/16 marking looked hand engraved. Funny, but this one fit perfectly.

The 7/16 diameter with a 20 tpi is the right size, as I did manage to find a short bolt with these specs at the local Ace.

 

[RoninB4]

Just an FYI, most newer taps/dies made within the last 10 years or so are absolute ****. That goes double if purchased from a hardware store. Old taps/dies are almost always too dull to cut new threads, they're fine for cleaning gunk from existing threads but not for cutting new threads. Most of the better quality makers of cutting tools (Greenfield, Putnam, CTD, etc.) are gone. The better quality taps/dies (OSG, Guhring) are sold through industrial suppliers. If it's at a big box hardware store it's usually not worth the money spent. The sets of taps/dies are even worse and should not be purchased for anything but cleaning gunk from existing threads.