[SCzEngrgGroup]

I do a lot of tapping in fabricating the products I manufacture in my shop. While I can do it on the mill, in many cases I find it neither convenient nor efficient to do so. A while back I bought one of the ubiquitous $150 hand tapping fixtures. It works great, and is a BIG improvement over using a T-handle. However, when tapping hundreds of holes at a time, it gets very tiresome and tedious.

So, I took a spare stepper motor, and some left-over timing pulleys, wired up a spare axis on the controller for the X2, and converted the fixture to a dedicated power tapper. For now, I've just kludged together a quick and dirty VB macro to prove the basic functionality, but I will shortly build a dedicated microcontroller-based controller to make the whole thing truly stand-alone. Operation will consist of nothing more than selecting the tap size (which will select the correct speed and torque), and the number of threads to tap, then pushing a single button. It will feed and retract as appropriate for the tap size in use.

I still need to add an air cylinder to lift the spindle out of the hole once the operation is complete, or perhaps just a small air spring.

Here is an appallingly bad (sideways) video of one of the very first holes being tapped to 1/4-20:

P1060563 - YouTube

Regards,
Ray L.

[Mad Welder]

This looks interesting

[mrcodewiz]

Sounds pretty cool. I have been debating getting a tapping head but this looks promising.

[wizard]

I do wonder if by the time you are done if it wouldn't have made sense to build a single axis CNC machine? That is a tapping machine with a Z axis and velocity feed back from a servo motor.


This also make me wonder how well something like the Electronic leadscrew controller might work in such an environment. With a bit of modification to the code it would see as though the Electronic leadscrew idea is 80% of what is needed for a tapping machine.

In any event I don't want to detract from the machine you got here. The video looked excellent.

[SCzEngrgGroup]

I do wonder if by the time you are done if it wouldn't have made sense to build a single axis CNC machine? That is a tapping machine with a Z axis and velocity feed back from a servo motor.


This also make me wonder how well something like the Electronic leadscrew controller might work in such an environment. With a bit of modification to the code it would see as though the Electronic leadscrew idea is 80% of what is needed for a tapping machine.

In any event I don't want to detract from the machine you got here. The video looked excellent.

Well, considering that I currently have about 3 hours of my time and zero $ into this (I had the stepper, pulleys, belt, and all necessary materials in my scrap bin), adding a CNC Z axis would've added a great deal of time and cost, and I don't see the benefit. An active Z servo drive is really not required, as the tap feeds itself simply taking advantage of gravity.

Regards,
Ray L.

[doorknob]

It is an interesting approach.

I recently bought a couple of used Tapmatic 30X units at the cost of several hundred $$ (and I don't even have them set up yet). So by comparison, a spare-parts build like you've done looks very attractive.

Are you using hand taps or spiral point taps or something else on the "business end" of your machine?

[john-100]

depending on how many holes your tapping at a time
would it be worth using spiral point taps ?

eg -
http://www.precisiondormer.com/sandvik/2531/internet/USA_English/s005479.nsf/Alldocs/D*2DProduct*2008*2DPDF*2ASharkDIN*2DANSI*PDF/$file/SharkHighPerformanceTaps.pdf

some years ago while repairing some PCB's out of a EMI-MEC sprint automatic capstan lathe ( not my day job )
I noticed the lathes didn't periodically reverse the taps to clear the chips
only reversing to remove the tap at the end
if I remember correctly the taps looked like the E887 taps on page 38

in fact the spindle never stopped during the day, just changed speed and direction as required
(every second counts when your making tens of thousands of parts)

I can see if your tapping a lot of holes
the combination of your tapping machine and taps that can be driven all the way in one go will save a lot of valuable time

John

[SCzEngrgGroup]

It is an interesting approach.

I recently bought a couple of used Tapmatic 30X units at the cost of several hundred $$ (and I don't even have them set up yet). So by comparison, a spare-parts build like you've done looks very attractive.

Are you using hand taps or spiral point taps or something else on the "business end" of your machine?

I never use anything but spiral point taps. I can't imagine why anyone would use plug taps.

Regards,
Ray L.

[SCzEngrgGroup]

depending on how many holes your tapping at a time
would it be worth using spiral point taps ?

eg -
http://www.precisiondormer.com/sandvik/2531/internet/USA_English/s005479.nsf/Alldocs/D*2DProduct*2008*2DPDF*2ASharkDIN*2DANSI*PDF/$file/SharkHighPerformanceTaps.pdf

some years ago while repairing some PCB's out of a EMI-MEC sprint automatic capstan lathe ( not my day job )
I noticed the lathes didn't periodically reverse the taps to clear the chips
only reversing to remove the tap at the end
if I remember correctly the taps looked like the E887 taps on page 38

in fact the spindle never stopped during the day, just changed speed and direction as required
(every second counts when your making tens of thousands of parts)

I can see if your tapping a lot of holes
the combination of your tapping machine and taps that can be driven all the way in one go will save a lot of valuable time

John

I've used spiral point taps exclusively for years. They are FAR superior in every way to plug taps. The cycle in the video was just for testing purposes. That was only the third hole I tapped with this machine, less than a half-hour after I finished building it. When I do the dedicated controller, I will optimize it for much greater speed, and fewer, shorter back-outs.

Spiral points will still occasionally jam up, especially in blind holes. In fact, that's the only way I've ever broken one. So, backing up a bit is still a good idea, especially on deep holes, like the one in the video (1" deep).

Regards,
Ray L.

[ger21]

I'm only gonna say this once...........

ANYONE who mentions wrong forum, or even replies to this post, gets banned. Simple as that.

[BobWarfield]

I think a tapping arm is faster and easier to use when tapping holes, though this sort of thing is much easier to knock together from spare parts.

Maybe there is a way to combine the two?

The most difficult part in building a tapping arm is the tapping head itself. Coming up with one that runs at the right speed, reverses easily, has a good form factor, and has a torque limiting clutch to cut down on breaking small taps is expensive and time consuming. No reason you couldn't put a stepper like this one uses on a parallelogram linkage.

Cheers,

BW

[SCzEngrgGroup]

I think a tapping arm is faster and easier to use when tapping holes, though this sort of thing is much easier to knock together from spare parts.

Maybe there is a way to combine the two?

The most difficult part in building a tapping arm is the tapping head itself. Coming up with one that runs at the right speed, reverses easily, has a good form factor, and has a torque limiting clutch to cut down on breaking small taps is expensive and time consuming. No reason you couldn't put a stepper like this one uses on a parallelogram linkage.

Cheers,

BW

Bob,

I did consider a tapping arm. But, the problem I had with it was coming up with something to drive the tap that had enough torque, and a suitable means of limiting the torque. Drill/Drivers don't have enough torque, impact wrenches beat the he11 out of the poor tap, and the taps tend to come loose and fall out regularly. Then there was the problem of how to hold the tap. A drill chuck just doesn't cut it. And, the arm needs to be quite beefy to deal with the torque needed to tap larger holes (I need to go to at least 1/2" in steel). So, it turned into a big fabrication process, and a lot of cost, I just didn't have the time and money for. This cost me $150 for the fixture, which I've used now for a couple of months manually, so it was productive right away. The power conversion was just a few hours and a few $ worth of scrap. 98% of the things I need to tap fit nicely on the "table", but it will still easily handle the large production milling fixtures (up to ~12" x 36") I often have to build. Once completed, with the dedicated microprocessor controller, it will also take up less space than a tapping arm. In use, I see little difference between this and a tapping arm in terms of either speed or convenience.

Regards,
Ray L.

[Mad Welder]

I wasn't aware of spiral point taps (but ha that's nothing new) I have managed to break many rather large plug taps after binding in blind holes...........again thanks to all for sharing

[john-100]

Hi Mad Welder

your not on your own

If I'd not been asked to have a look at the EMI-MEC lathe
I would not have seen the spiral point taps either
or the Coventry die heads used for cutting external threads come to think about it - not having to reverse the die head off saves time

Workshop Article - Coventry Die Heads


I understand the trick when tapping blind holes is drilling deep enough to give the extra space needed for any chips trapped in front of the tap


has any one else thought a compact version of the tapping machine will make useful live tool tapping cross drilled parts on a lathe or is it just me ??


John

[gd.marsh]

I'm a little surprised no one has mentioned 'Spiral Flute' taps. They are the ticket for blind holes .. They require much less torque than straight flute taps & they lift the chip out in one continuous curl like a drill bit.

They ARE NOT GOOD in smaller sizes when hand tapping. Because of their design they are not as strong. In machine tapping where you get absolute perpendicular motion & constant torque they are the cat's meow!

I use them in all sizes (especially when blind hole tapping) because I also have a dedicated power tapping machine. But I've also used them with great success in sizes of 1/4" & above by hand.

[john-100]

"spiral flute tap" thats a better description of the tap I referred to in post 7
in the Dormer info

John

[SCzEngrgGroup]

"spiral flute tap" thats a better description of the tap I referred to in post 7
in the Dormer info

John

Spiral Point and Spiral Flute are completely different animals. Spiral Flute taps are purely for machine tapping, while Spiral Point taps can be used for hand or machine tapping. As Gary points out, Spiral Flute taps are easily broken by any bending force. I like to be able to machine or hand tap as needed, without having to keep a supply of all the different sizes I need in both styles, hence my preference for Spiral Point taps. Their only significant down-side is when used in blind holes where there is not enough depth to collect all the chips while allowing the threads to reach the desired depth. For me, this has been a minor issue so far.

Regards,
Ray L.

[john-100]

Hi Ray

yes , not being a metalworker I don't always get the names or terms correct
I must try harder


have you considered thread forming taps if they are suitable for your application ? no chips could be a bonus !
eg http://www.directindustry.com/prod/d...61-387059.html

I have been amazed to see how fast an external 20mm thread can be rolled

John

[wizard]

Well, considering that I currently have about 3 hours of my time and zero $ into this (I had the stepper, pulleys, belt, and all necessary materials in my scrap bin), adding a CNC Z axis would've added a great deal of time and cost, and I don't see the benefit. An active Z servo drive is really not required, as the tap feeds itself simply taking advantage of gravity.

Regards,
Ray L.

I was thinking more about approaching and clearing the part. I imagine though that a simple air cylinder or even a lever would do nicely for that.

One question though, how far up in tap size can you go with that motor before torque becomes a problem? I know this depends upon material but for others thinking about the same thing an idea of max tap size would be nice to have.

[SCzEngrgGroup]

Hi Ray

yes , not being a metalworker I don't always get the names or terms correct
I must try harder


have you considered thread forming taps if they are suitable for your application ? no chips could be a bonus !
eg Roll form tap - Dormer Tools

I have been amazed to see how fast an external 20mm thread can be rolled

John

John,

Yes, I have looked at thread forming taps, and plan to explore that at some point. It's been on my ToDo list for a while, with a lot of other things. Maybe after I finish the ATC.

The one difficulty is determining the correct hole size seems tricky, and manufacturers specs are all over the place. You have to drill the hole larger than for a cutting tap, because the material from the thread roots gets pushed up to the tips. Too small a hole, and you WILL break the tap (which is how my one and only experiment so far ended.

Regards,
Ray L.