Tapping Heads Tapmatic A5 and ?

Topics include, Machine Tools & Tooling, Precision Measuring, Materials and their Properties, Electrical discussions related to machine tools, setups, fixtures and jigs and other general discussion related to amateur machining.

Moderators: Harold_V, websterz, GlennW

User avatar
ctwo
Posts: 2779
Joined: Tue Mar 27, 2012 12:37 pm
Location: Silly Cone Valley

Re: Tapping Heads Tapmatic A5 and ?

Post by ctwo » Mon Mar 30, 2020 9:15 am

Found some time to weld up the stripped threads. Wondering where I went wrong.

The 16 tpi nut threads seem OK, but a bit worn. A caliper measurement yielded a minor diameter of ~1.170" max, so the question was what diameter to machine the welds. I decided to machine the major diameter to 1.208", expecting a thread depth of 0.038". This is a thread depth chart:

https://www.mitsubishicarbide.com/appli ... _en-us.pdf


I made a few passes until I started to get a thread form and decided to try the fit. The nut screwed right on and was a tad looser than I wanted, but the thread was not done.

So, I guess I have a 1.219 x 16 tpi thread. A 1-3/16 is too small and 1-1/4 is too large for the nut, so something in-between there...

The threads aren't as smooth as I want either. It will work but debating on welding it up again and trying again.
Attachments
buck-tappinghead-chuck-20200330_064717.jpg
Standards are so important that everyone must have their own...
To measure is to know - Lord Kelvin
Disclaimer: I'm just a guy with a few machines...

spro
Posts: 7899
Joined: Mon Feb 20, 2006 11:04 pm
Location: mid atlantic

Re: Tapping Heads Tapmatic A5 and ?

Post by spro » Tue Mar 31, 2020 1:47 pm

I've been reading your progress and find it very informative. Maybe I can restore the "under bench" project. Mine doesn't even have the collar and the threads are pretty nasty. Thanks for sharing the procedure to remake them. This is a wear point and maybe you could build it up further, so the collar doesn't strip out.

Harold_V
Posts: 18137
Joined: Fri Dec 20, 2002 11:02 pm
Location: Onalaska, WA USA

Re: Tapping Heads Tapmatic A5 and ?

Post by Harold_V » Tue Mar 31, 2020 3:41 pm

Your math isn't correct. Thread depth is on the radius, not the diameter. You should have added an additional .038" to your target diameter.
I strongly suspect that the thread is 1¼"----but I agree that the minor diameter is a bit small if it is. A real puzzle unless the thread is a bastard.

H
Wise people talk because they have something to say. Fools talk because they have to say something.

User avatar
GlennW
Posts: 6851
Joined: Sun Apr 15, 2007 9:23 am
Location: Florida

Re: Tapping Heads Tapmatic A5 and ?

Post by GlennW » Tue Mar 31, 2020 3:53 pm

1 1/4-16 2A has a major dia range of 1.2485"-1.239" and a minor dia range of 1.1808"-1.1622".

Pitch dia 1.2079"-1.2028".
Glenn

Operating machines is perfectly safe......until you forget how dangerous it really is!

User avatar
ctwo
Posts: 2779
Joined: Tue Mar 27, 2012 12:37 pm
Location: Silly Cone Valley

Re: Tapping Heads Tapmatic A5 and ?

Post by ctwo » Tue Mar 31, 2020 9:07 pm

Thanks folks. What a face palm and yet such an excellent learning experience. Aside from the pitted welding, it does look like I'm half way there.
Standards are so important that everyone must have their own...
To measure is to know - Lord Kelvin
Disclaimer: I'm just a guy with a few machines...

User avatar
GlennW
Posts: 6851
Joined: Sun Apr 15, 2007 9:23 am
Location: Florida

Re: Tapping Heads Tapmatic A5 and ?

Post by GlennW » Wed Apr 01, 2020 6:15 am

Thread wires!
Glenn

Operating machines is perfectly safe......until you forget how dangerous it really is!

User avatar
ctwo
Posts: 2779
Joined: Tue Mar 27, 2012 12:37 pm
Location: Silly Cone Valley

Re: Tapping Heads Tapmatic A5 and ?

Post by ctwo » Wed Apr 01, 2020 10:07 am

I don't even think a thread mic could have helped me.
Standards are so important that everyone must have their own...
To measure is to know - Lord Kelvin
Disclaimer: I'm just a guy with a few machines...

Harold_V
Posts: 18137
Joined: Fri Dec 20, 2002 11:02 pm
Location: Onalaska, WA USA

Re: Tapping Heads Tapmatic A5 and ?

Post by Harold_V » Wed Apr 01, 2020 3:30 pm

Harold_V wrote:
Tue Mar 31, 2020 3:41 pm
I strongly suspect that the thread is 1¼"----but I agree that the minor diameter is a bit small if it is. A real puzzle unless the thread is a bastard.
Heh!
For what ever reason, I had 20 pitch stuck in my head. It's obvious that Glenn is correct, that the bore is well within range for 16 pitch.
Thanks, Glenn. I should have referred to the charts.

H
Wise people talk because they have something to say. Fools talk because they have to say something.

User avatar
ctwo
Posts: 2779
Joined: Tue Mar 27, 2012 12:37 pm
Location: Silly Cone Valley

Re: Tapping Heads Tapmatic A5 and ?

Post by ctwo » Sun Apr 05, 2020 10:06 am

GlennW wrote:
Tue Mar 31, 2020 3:53 pm
1 1/4-16 2A has a major dia range of 1.2485"-1.239" and a minor dia range of 1.1808"-1.1622".

Pitch dia 1.2079"-1.2028".
I was reading a bit about thread wires and read a bit about "best size wires," which, if I understand correctly, contact the pitch diameter. What this tells me is that I could have still made my oversight and would still measure the correct thread pitch, even tho the major diameter is lacking.

I'm still going to order some thread wires, and to go along with that I should find some good thread charts and print them out.

Thanks for all the tips. :)
Standards are so important that everyone must have their own...
To measure is to know - Lord Kelvin
Disclaimer: I'm just a guy with a few machines...

Harold_V
Posts: 18137
Joined: Fri Dec 20, 2002 11:02 pm
Location: Onalaska, WA USA

Re: Tapping Heads Tapmatic A5 and ?

Post by Harold_V » Sun Apr 05, 2020 4:26 pm

Correct. If you mistake a major diameter, no method of measuring will correct that.
The problems I find with the (relatively) inexpensive thread wires is that they don't always fit the pitch diameter as is recommended, and they may or may not provide a tolerance for major and minor pitch diameters. That has always confused me, as they tell you to add a given diameter to the thread size, with no regard for tolerance. Is that the top end of the tolerance, or the low end? Is it the middle? One has no way of knowing without doing some extensive math. Could be I'm just plain old stupid, and don't get it, but I'm used to proper thread wires, which provide a constant that is added to the pitch diameter, both upper and lower limits, so there is no confusion.

That said, proper thread wires are not cheap, nor are they a real requirement for the home shop. I used to pay $40 for a single set, and that was at least 37 years ago. I suspect that, today, you'll lay down at least $90 for a set, and they're good for only one thread pitch.

To justify the cost, these wires are sized to five places, and are acceptable for certifying thread gauges, assuming one has access to a super mic. They're worth the money if there is need. I might also add that I own a set of inexpensive wires, and highly recommend them to the home shop types. They are far better than nothing.

I am NOT a fan of thread mics. I can't see even one reason to own them, but that's me. YMMV.

H
Wise people talk because they have something to say. Fools talk because they have to say something.

User avatar
ctwo
Posts: 2779
Joined: Tue Mar 27, 2012 12:37 pm
Location: Silly Cone Valley

Re: Tapping Heads Tapmatic A5 and ?

Post by ctwo » Sun Apr 05, 2020 11:13 pm

Harold, thanks for the discussion. I am a bit confused though on your point about inexpensive thread wires, but then recommend them. I imagine they would work just the same as expensive thread wires, but without the tight tolerance. I was looking at the popular PeeDee wires vs. some of the other less expensive sets (48 wire sets). There is a broad range in price.

I've always relied on grinding the tool "properly" and starting from the correct diameter, and doing test fits along the way. And if I did not have a "gauge" to test with, I'd probably rely on a dial indicator on the tool post and shoot for thread depth.

Now, about the tap jaws, the broken jaw is the right-hand thread. It would be good to remake them both. I thought of using some drill rod I have and threading it on the lathe. Why would I do it the easy way?
Standards are so important that everyone must have their own...
To measure is to know - Lord Kelvin
Disclaimer: I'm just a guy with a few machines...

Harold_V
Posts: 18137
Joined: Fri Dec 20, 2002 11:02 pm
Location: Onalaska, WA USA

Re: Tapping Heads Tapmatic A5 and ?

Post by Harold_V » Mon Apr 06, 2020 3:44 am

ctwo wrote:
Sun Apr 05, 2020 11:13 pm
I am a bit confused though on your point about inexpensive thread wires, but then recommend them. I imagine they would work just the same as expensive thread wires, but without the tight tolerance.
Not exactly. The inexpensive thread wires may or may not provide wires that are optimal for a given thread pitch. The wires they use are not high precision, unlike purpose made thread wires, which are the exact size for a given thread pitch, with diameters of each wire held to five places, and certified. While the wires are used in the same fashion, the lesser expensive wires may measure the thread (slightly) above or below the pitch diameter. Assuming one has a properly configured threading tool, that may or may not matter. I recommend them because they allow the home shop to take measurements, which remove doubt about the pitch diameter of a thread. To be clear, measuring a thread by the depth of cut is a miserable way to gauge a thread, and is more likely to be wrong than right. There's several reasons for that if you give it some thought.
I was looking at the popular PeeDee wires vs. some of the other less expensive sets (48 wire sets). There is a broad range in price.
I haven't been in the market for a set for many, many years, but I can remember when $20 would buy a set of PeeDee (which I own).
I've always relied on grinding the tool "properly" and starting from the correct diameter, and doing test fits along the way. And if I did not have a "gauge" to test with, I'd probably rely on a dial indicator on the tool post and shoot for thread depth.
Ok, lets take a look at this from a realistic point of view, keeping in mind that in my world, I was not afforded the luxury of being "close enough". For the home shop guy, maybe it doesn't matter, but I'll explain it from my point of view.

Lets start with the major diameter of the thread. Is it nominal? Do you include any variations of size in your math when you make the decision to use thread depth? The tolerance for the major diameter of pretty much all threads is greater than the tolerance of the pitch diameter, which is critical in threads. When you pick up the major with your tool, how much do you penetrate? A thou? Maybe two? For small threads, you've just used up half your tolerance, and don't even know it.

Thread tool. Is it safe for me to assume that you have an optical comparator, with which you can properly measure the flat (and form) on your threading tool? The tolerance for that flat is so great that a variation quickly overcomes the limited tolerance of the pitch diameter. To be clear, I can not recall even one instance where I relied on depth of cut, in part because there are far too many variables to allow any meaningful determination.

When you use wires, you learn where you are in regards to pitch diameter, and it's all independent of any of the other features. Use wires. You won't regret doing so. If you need a little guidance on how to apply them without much effort, just ask. I suspect that Glenn will provide excellent guidance, and I'll certainly do my best to do so. Mean time, a clean chip pan is a good investment (for recovering dropped wires), and you should understand that the wires should NOT be restrained by any means. They must be free to conform to the helix of the thread pitch, and to be brought parallel by the spindle and anvil of the micrometer in use.
Now, about the tap jaws, the broken jaw is the right-hand thread. It would be good to remake them both. I thought of using some drill rod I have and threading it on the lathe. Why would I do it the easy way?
I'm afraid my old mind is not getting the picture here. Would you please elaborate, so I might better understand your point?

H
Wise people talk because they have something to say. Fools talk because they have to say something.

Post Reply