My version of a "sensitive" hand tapper for lathe

KeithB

Resident Half Fast Machinist
Never really had a good way to tap small holes on the manual lathe. A while back there was a thread posted by one of the members about making a hand tapper for a lathe. I followed that thread with interest, it was a nice project. We have picked up some business from a local company that needs small parts, mostly made from A2 tool steel or 4140. Most of the parts are lathe work and many require tapping small metric threads, i.e. M6 x 1 and M3 x .5. Many of the holes are blind. I was inspired by the hand tapper thread and decided I needed to make one for my own use.

I had made a tool years ago to thread rods using a die. It didn't work very well so I salvaged the #3 Morse taper shank and a 2" long section of the 1" diameter main shaft. I made an 8" long tube with a 1" bore out of a scrap piece of 1-3/4" aluminum round stock and clamped it to the Morse taper shank. We have several collet type toolholders with 1" shanks that could be used to hold a tap so all that was needed was a knurled friction collar to clamp to the toolholder. This was easily made from a 2-3/4" dia piece of scrap 1018 steel. After turning it down enough to get to clean steel I cut it to the closest calculated diameter for a clean knurl and got exactly that. (I used the spreadsheet I posted previously to do the calculations.)

I needed to use a Morse taper sleeve to step up the #3 shank to a #4 to fit my lathe's tailstock, but I keep a variety of adapters on hand so no worries there mate.

The tool works great. The video shows me tapping an M6 x 1 thread into a piece of A2; it's a through hole, but blind hole tapping is just as easy. I use spiral flute taps so it is no problem tapping all the way to the bottom of the hole, there is no chip buildup.

One of the reasons I asked for a machining section here was to share ideas and get inspiration and that is the case here. A previous thread has inspired me to make a useful tool, thanks!

Old tool for threading rods, only the Morse taper shank and part of main shaft were reused.
oldtool.jpg

My hand tapper. The friction collar is clamped to the collet toolholder but is free to spin and slide in and out in the aluminum tube.
tappingtool.jpg

Here is a video of the tapper in action.
 

smokeywolf

Well-Known Member
Very nicely done Keith. Always enjoy being included in what's happening 'the perfessor's shop'. You're always doing something of interest. The gang of toolholders on the cross slide of your NC lathe is still my favorite though.
 

KeithB

Resident Half Fast Machinist
These are the same toolholders that I use on the CNC lathe for drilling and tapping, now I can use them for another application. I also think this might be useful when drilling very small diameter holes where the tailstock handwheel may not be sensitive enough to prevent breaking a drill.
 

fiver

Well-Known Member
I see the threads, but that doesn't look like a normal 'tap' it looks like it would just goober up the hole.
is there something there I'm not seeing?
 

KeithB

Resident Half Fast Machinist
It's a spiral flute tap. They cut perfect threads, their virtue is that the chips are ejected out of the top of the hole (see the video) instead of being pushed to the bottom of the hole like a spiral point tap or being trapped in the flutes like a hand tap. Not recommended for use in unguided applications, as when hand tapping with a tap wrench. But guided straight they do a wonderful job.
 

fiver

Well-Known Member
okay that helps.

you gotta remember I have 0,,, like no experience, with any of these tools.
so I'm sure some of my questions sound like something a fresh off the turnip truck newbie would ask.
aaand that's cause, well,,, I would be fresh off that truck.
almost all of your tooling I understand what they do, it just takes me a bit to actually SEE how they do it.
 

KeithB

Resident Half Fast Machinist
Different tools have different characteristics. Straight flute hand taps are great for re-threading buggered up holes and threading by hand. But the chips get balled up in the flutes which is why you have to constantly reverse direction to break off the chips. Spiral point taps are great for through holes, the cutting edge at the end is angled so the chip goes forward ahead of the tap. For through holes they are great, no need to reverse direction to break off the chip so power tapping is practical. But in blind holes they pack the chips down into the bottom of the hole. Spiral flute taps have flutes that are helical not straight, the cutting edge is inclined backwards at the proper angle to make the chip come out the top of the hole. Its all I ever use for power or guided tapping any more, but they are not real good for cleaning up existing threads or making threads with unguided manual methods.

Roughly categorized, mechanics and maintenance people need good hand taps, hobbyists and general machinists need spiral point taps, production machinists need spiral flute taps. Here is some good information on different types of taps:

https://www.natool.com/engineering-data/tap-style-guide
 

fiver

Well-Known Member
that was way helpful.
I only knew of three of the ones shown [the first 2 and the internal pipe]
 

KeithB

Resident Half Fast Machinist
There has been a ton of progress made in machine tools and tooling in the last few years. Even something relatively simple as a tap now comes in all sorts of materials and geometries.

I haven't tried tapping any holes with forming taps. They do not make chips at all, they just displace material to form the thread. Most tap guides now list drill sizes for thread forming taps. The holes are a little larger than the cut thread hole size, roughly the same size as the pitch diameter of the thread. Supposed to work well in ductile material such as aluminum. You can tap all the way to the bottom of a hole and not have small chips to clean up. Important especially when automating the part changing process as little chips can get on setup surfaces and misalign a part.

Fiver, you and probably most of the other members here know much more about guns, reloading, hunting and shooting than I do. I read a lot of your posts just to absorb a little of what you guys know. But I am pretty good at keeping up with what's going on in a machine shop and I like to share what little I know with you guys. Hadn't posted in a while and didn't want to let down my end of the deal. :)
 

Brad

Benevolent Overlord and site owner
Staff member
Keith, I learned a bit when I looked at taps and watched your work. Decided to try a spiral flute tap and WOW, was I ever impressed! Not needing to go in 1/2 turn, back 1/4 turn, repeat made it so much faster. And with the tapping tool I made for the lathe they are the only way to go.
Only have one spiral point tap and screwed up a little on it. I didn't pay attention to H values and got one a few thou larger than desired. Hole isn't that critical so I went with it.

Like anything else the right tool makes it easier. Not always better, but easier. I like easy.
 

KeithB

Resident Half Fast Machinist
I like easy also. My apprentice used to work in a fab shop, lots of beating on things with hammers and such. I told him that if we ever got to the point where we have to solve a problem with a hammer we were going stop right there and figure out an easier way to do things. And we carry that philosophy out with every shop equipment improvement project we undertake. I'm an old man, it's much easier for me to beat on something with my brain and power equipment instead of using my back and a bigger hammer.

My apprentice occasionally runs into some of the guys he used to work with and when he tells them he's making aircraft parts, sits down to work, measures things to a ten thousandth of an inch, and doesn't use anything heavier than a 2 lb deadblow hammer the comments he gets are priceless. His old employer was, um, reluctant to buy decent tools until something was worn out to uselessness. We buy or make what we need to make the job easier and the parts better. I want to foster an attitude of continuous improvement and education, it makes working together so much easier, even in a two person shop. And it makes us VERY productive.
 

fiver

Well-Known Member
every time you post something I learn something new, so I'm really happy to see you post stuff.
I might not have the equipment you have [any actually] but I do fix a lot of stuff and it's really neat to see how things are made.
I have a super nice tap and die set in a box about 3' wide [it goes from machine screws up to about 3/4" bolts] but it's from the 70's and is all hand use stuff.
when I seen that tap I was like...?? how? I guess it's like looking at a CNC cherry for the first time.
 

smokeywolf

Well-Known Member
fiver, even if you've made your living as a machinist, there's always more to learn. One of the reasons machining is fun. I always look forward to Keith's posts.
Have had the itch to do some machining, but have been sidetracked by several issues which required most of my attention.
 

Pistolero

Well-Known Member
Keith said "if we ever got to the point where we have to solve a problem with a hammer we were going stop right there and figure out an easier way to do things."
Heck, YES! I use hammers to drive nails and drift sights around, occasionally to set rivets and peen back a damaged
screw or dovetail.
Too many folks' standard approach is "Get a bigger hammer".

Love to learn about your shop, Keith. Thanks so much for sharing.

Bill