Tapping and threading question

[EVAN WYNES]

Hi all.... I am pretty new to machining and have a tapping and threading question for you all. I am working on a project that requires a 9/16-20 tap and thread. I have neither the tap or die for that. My question is at what point do you guys cut the thread yourself? I have done some thread cutting on my lathe but no internal threading. I’ve looked on line and haven’t seen a tap and die set that contains that size, so I don’t know if there’s a max size where you have to start buying individual taps and dies. Thanks in advance.

 

[chucketn]

Being of modest income, I single point any thread internal or external that I don't have taps or dies for. Exception being extremely small threads, for which I have purchased taps and dies for over the years. I have even made a few taps for oddball threads, such as 1/4-40.

 

[petertha]

I have had to go down that same path. This is a great resource to get your sizing right.

tap hole size (select pilot diameter from drop down or your own unput, calculates % thread fit)
http://theoreticalmachinist.com/TapDrillSizeCalculators

thread calculator (determines OD, depth of thread cut, resultant measurement parameters)
http://theoreticalmachinist.com/Threads_UnifiedImperial.aspx

 

[john_reese]

Evan,
You said tap & die set. Most packaged sets are of questionable quality. If you need taps and dies buy them as you need them. Puchase them from established tooling vendors like Victor, Travers,or eve (God forbid) MSC, or one of many others. Try to buy name brand tools. Irwin quality is questionable.

 

[Asm109]

As said, you buy individual taps and dies to meet your needs. 9/16-20 is an oddball size and I would be astounded if there were a set that included it.
I think I have seen that size on bicycle pedals. So a left hand threaded version should be available as well.

 

[tornitore45]

An internal thread 9/16 is not that difficult. You will ever learn if you never start.
The time to start is when you need it. Like anything there are a few thing you need to learn the hard way. Book learning is a good start, then pay attention and it will work out.
For blind hole put a travel indicator so you know exactly when the tool is in the lading grove. Thread in reverse coming out of the hole.

I do not trust my threading dial or myself so I engage the half nut before starting the motor to be sure to be on the right spot.

 

[Rod Cole]

Internal or external can be fun once you get used to it, and it brings so much satisfaction when the nut goes on or the bolt goes in. My old Monarch 12CK is designed for threading, it has a stop on the crossfeed screw for repeatability. Once you set the half nut, you run the thread, and while backing out the crossfeed, shift into reverse while running, once you've backed past the thread, throw it into forward and turn the crossfeed back to the stop while adjusting the compound. I love this machine~

 

[RM-MN]

If you are into production and need to make threads that fit what someone else made, single point threading can be more difficult as have to make the threads match someone else's threads. If you are doing a one-off for yourself, single point is easier as you can make a thread and then test if it fits. Making an internal thread in a through hole isn't any amount more difficult than external threading which is so easy that even I can do that. Threading to a shoulder or in a blind hole gets more complicated but not overly so.

 

[EVAN WYNES]

Thank you all for your responses......I made a mistake when I said 9/16-20.....the thread I need is actually 9/16-18. I think I may cut the thread myself after looking at the prices for a tap and die. I will definitely practice on scrap before I try on the workpiece, which is a pm research boiler feed pump. That’s going to present another challenge due to its shape, but that’s half the fun.... figuring it out.
Thanks again

 

[Tim1974]

Just make it 9/16 unf (18 tpi) why make it hard ?

 

[john_reese]

Evan,
I will search my assortment of taps tomorrow. If I find a 9/16 -18 I will be happy to lend it to you.

Evan,
I have the tap. Check postage both ways. It might be cheaper to buy new on eBay. PM me if you want me to send the tap. It is a plug tap, not bottoming.

 

[Wizard69]

I'm not sure I can hit anything new here.

In any event as pointed out cheap tap sets are next to useless, junk really. They aren't even worth the money spent on them to get a tap wrench. Case in point just today at work I ran a die over a piece that came out grossly undersized, the cheap die being way off removing way to much material. The place I work at can be extremely cheap, plus it is run by people with no mechanical skills at all. You simply can not trust the low end sets and frankly most of us can't afford the high end sets.

This leaves only one avenue but taps and dies as you need them. The exception here is common sizes that you would likely use regularly. Take good care of them and they will last a lifetime. Make yourself a set of wrenches for the dies and taps. With careful selection of dies you might get by with one die stock.

Single point cutting is still a valuable approach to cutting threads, sometimes it is the best solution. I'd make a point to learn the techniques ( there are actually multiple techniques that you can select from ).

 

[Wizard69]

Thank you all for your responses......I made a mistake when I said 9/16-20.....the thread I need is actually 9/16-18. I think I may cut the thread myself after looking at the prices for a tap and die. I will definitely practice on scrap before I try on the workpiece, which is a pm research boiler feed pump. That’s going to present another challenge due to its shape, but that’s half the fun.... figuring it out.
Thanks again

Yeah the pricing can be a killer and frankly you want to buy decent quality taps and dies. There are lot of threading videos on line but a recent post by
Joe Pieczynski over on YouTube covers a technique he uses when a shoulder is involved. Joe certainly has some interesting videos and they reflect his slant as a manufacture of specialty products.

 

[Roger Pry]

I learned my lesson on purchasing off of ebay, I thought I was being smart but after buying a tap/die set, a complete indexed drill set and 1/2" NPT pressure regulators I found all were out of tolerance pieces. I guess you really don't get something for nothing(or cheap in my cases).

 

[SpringHollow]

I have bought many fantastic quality things on Ebay including taps and dies and pressure regulators. But almost all of my tooling is bought used off of Ebay. I have been happier usually with quality used vs cheap new. Every so often, an Ebay purchase turns out to not be good.

 

[john_reese]

I've had good luck with taps from Shars. YG tools from Amazon are very good.

 

[chrsbrbnk]

try to buy only high speed steel taps and dies maybe carbon steel for some large die if the material is soft like brass or alumin. been pretty happy with greenfield stuff think about how hard its going to be getting a broken tap out when your looking at cheap carbon and use a real thread cutting oil!!! dull drills or cutters can give you work hardened surfaces that mess up your threading

 

[RM-MN]

I have bought many fantastic quality things on Ebay including taps and dies and pressure regulators. But almost all of my tooling is bought used off of Ebay. I have been happier usually with quality used vs cheap new. Every so often, an Ebay purchase turns out to not be good.

This happens, you are dealing with an individual and taking a chance. However, I consider it a fair trade as I have bought so many things that would have cost way more locally if I could even buy them that it has way offset any losses I have taken.