# Tapping machine idea



## churchjw (Sep 3, 2013)

I am starting to build (thinking about starting) a pneumatic tapping machine.  I saw one of these at a tool show about a year ago.  Not sure it was this brand but it was similar. http://www.lans.com.tw/10-tapping_machine.html  I have a heavy duty computer monitor arm that is as stable as the tapping machine arm I played with at the show.  Not as much range of motion.  I am thinking of using a reversible impact air screwdriver with a pressure regulator as the driver.  http://www.harborfreight.com/reversible-air-screwdriver-90059.html  It even looks like what they were using in the professional version.   The guy wouldn't say but it felt like an impact wrench when it tapped holes.  I would need to add a tap holder to the end but that looks easy enough.  

So my question to the group does this look doable or am I missing some big problem?  Has anyone on here built something like this and if so what were the problems? 

As I see it I have to have a way to hold the tap, control torque, and keep it square to the work piece.  Anything I am missing.  This would just be for smallish taps ie 6-32 to 1/4-20. 

Jeff


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## Bill C. (Sep 3, 2013)

churchjw said:


> I am starting to build (thinking about starting) a pneumatic tapping machine.  I saw one of these at a tool show about a year ago.  Not sure it was this brand but it was similar. http://www.lans.com.tw/10-tapping_machine.html  I have a heavy duty computer monitor arm that is as stable as the tapping machine arm I played with at the show.  Not as much range of motion.  I am thinking of using a reversible impact air screwdriver with a pressure regulator as the driver.  http://www.harborfreight.com/reversible-air-screwdriver-90059.html  It even looks like what they were using in the professional version.   The guy wouldn't say but it felt like an impact wrench when it tapped holes.  I would need to add a tap holder to the end but that looks easy enough.
> 
> So my question to the group does this look doable or am I missing some big problem?  Has anyone on here built something like this and if so what were the problems?
> 
> ...



Never seen one before but doesn't mean it isn't doable.  Will need a good regulator with a moisture trap and oiler, I didn't see one HF's website.  Make sure you use two fluted taps, they are stronger than four fluted ones.  Nice project.


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## CNC Dude (Sep 3, 2013)

Intriguing concept... 

A question, though. Why does it need to be pneumatic? I have been tinkering with building me some sort of automated tapping machine, but I was thinking about using one of those battery operated drills. It should be easy to reverse direction. I am of course thinking of the electric implications, not the mechanical ones.


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## Bill Gruby (Sep 3, 2013)

Using the drill is a good idea. You already have the torque control challenge partly covered. 

 "Billy G"


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## churchjw (Sep 3, 2013)

I thought about the drill idea.  I have used my hand drill to run some larger taps through thin stock before.  I was thinking that the shorter impact turning of the wench would be better for the tap.  Now I am wondering if the impact from the wrench is linear to the shaft (ie hitting outward like a hammer drill) or rotational. If it is linear to the shaft then it won't work.  The one I tried had a knocking feel for lack of a better word like a impact wrench.  It turned the tap with short turns.  Do you think I would get better torque control with the electric screwdriver vs the pneumatic?  I would be afraid that the electric would have to low a torque and low speed but I guess gearing would fix that.


Jeff


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## CNC Dude (Sep 3, 2013)

Although I am not a mechanical expert, it seems to me most battery based drills will surpass the torque of a pneumatic tool.  These drills already have a planetary gear head, which in my opinion is one of the strongest power transmissions you can get on a confined space (again, not a mechanical expert, so this statement can easily be flawed). If at all, you may need to switch it to the SLOW speed setting to get the torque you need to tap heavy stock, but this is not a high speed application anyway.

Do note that if you want a speed controller for any of these drills, it will need to take on humongous currents (100A are not unheard of on these drills). I am a motor driver designer with a few year's worth of experience. If this is something the community can greatly benefit from, I can easily design a microcontroller based speed controller which should be able to drive the 100A. Won't be tremendously cheap, but shouldn't be too expensive either. I am thinking no more than $30-40 dollars in components. FETs are pricey, when you want to run 100A loads...


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## metalman (Sep 3, 2013)

Three of most important things with a tapping head is adjustable torque limiting, alignment, and lubrication. I have several automatic tapping heads and they can spoil you quick. I always have at least one setup in one of my drill presses. The automatic tapping heads also have a reversing clutch and gearing that allows the tap  to instantaneously reverse when downward pressure is removed. Some units  also increase the reverse speed for faster tapping. They're fast and  almost never break a tap if set up properly.

A drill with a torque limiting chuck held in a cheap drill press stand or parallel arm would the closest low cost option. A drill could be rewired to make reversing automatic too.  I just don't know how good it would be with small taps. Some pneumatic screw drivers have a built in torque limiter, but I'm not sure about the HF model you listed. Better units are as expensive as a real tapping head...


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## DAN_IN_MN (Sep 3, 2013)

Jeff

How many holes are you planning on tapping in a day?  Is this going to be for production or just your hobby shop?

I've power taped 4-40 into steel (backing plate in a control box) with an extension and didn't break a single tap with a cordless drill.  I used it on and off for a week or so.  There were after build changes on a few machines and I either had to remove the backing plate in the box or get a drill and tap in there some way.


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## churchjw (Sep 4, 2013)

I don't tap that much so this is just for hobby.  It was more about making a new tool  I know no one here would do something like that.  Sounds like getting an electric drill is a better option or just buying a tapping head. LOL

Jeff


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## dogbed (Sep 4, 2013)

I have used a cordless drill for tapping numerous times. Mostly in the field and for jobs that were non-critical. I always use a clutch. 

I remember doing about 40 holes of 3/8 16 thread in 3/4" aluminum stock. I broke one 1 tap when I got lazy from the monotony. Basically I was too aggressive and gave it too much throttle, the tap grabbed, and the drill torqued off axis when I caught the drill, snapping the tap. 

IMO totally avoidable.

I think you could hack the drills (electrical) reverse switch and add an button to do your reversing.


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## lrsglory (Sep 9, 2013)

churchjw said:


> I am starting to build (thinking about starting) a pneumatic tapping machine. I saw one of these at a tool show about a year ago. Not sure it was this brand but it was similar. http://www.lans.com.tw/10-tapping_machine.html I have a heavy duty computer monitor arm that is as stable as the tapping machine arm I played with at the show. Not as much range of motion. I am thinking of using a reversible impact air screwdriver with a pressure regulator as the driver. http://www.harborfreight.com/reversible-air-screwdriver-90059.html It even looks like what they were using in the professional version. The guy wouldn't say but it felt like an impact wrench when it tapped holes. I would need to add a tap holder to the end but that looks easy enough.
> 
> So my question to the group does this look doable or am I missing some big problem? Has anyone on here built something like this and if so what were the problems?
> 
> ...



Larry Smith here: Lets skin another cat. I presume your wanting a tapping apparatus for power hand tapping off of your mill. If not lets start with your mill. A decent BP or clone will power tap on the table after the hole is in all day long. 1/2 -13 and have even done 5/8-11. Obviously use the mill while the piece is on the table and already lined up with the hole. put your tap in the collet or even a good true drill chuck. Low speed. Start feeding it in, after the start it feeds itself. hand on the reverse switch. When your there, reverse it and out it comes. No prob bob. be sure to keep the quill lock loose. This applies to taps no 10 and up. For the small stuff, depends on how brave you are, See the pic below. Collet, center, taphandle, tap. Bring the quill down, normal pressure. tap by hand. Keep light pressure on the quill to keep the tap and handle going in straight. Shazaam. When your there, hand back it out. Straight and true. Now for off the machine. See pic. I worked for an outfit for a year building automotive tube assembly machines. The frames were 3/8 thick, 3x3 soft steel. Tons of holes to drill and tap by hand to mount tooling. Might be building 20 machines. Hand tapping gets old. Ordered a butterfly 3/8 impact air tool. Wow. and cheap. Bought two generic tap handles. popped out the t bar, found a 3/8 drive socket to fit each one. welded them on, shazaam tap holder for impact tool. This butterfly worked great, fast reverse and air pressure regulator on the end. You could use a tapping block to keep it straight until your in. Season everything with your specs. tap size,depth, blind or thru. etc. Jusst spewing out some possible answers. Re: taps. Sprial Point tap ie gun taps are for thru holes as they push the spaghetti ahead of the tap. I preferred these even in blind holes. I would stop 3/4 thru in a blind hold and finish off of the machine after I cleaned the hole out. I agree with a previous post that Spiral Flute taps are weaker. They pull the chip out as they are tapping. Common to break a few of these if you use a real dull one. As always lots of oil, slow feed on the machine etc. Get a piece of scrap and try a few on the machine and offl. Before you assault the finished product.


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## churchjw (Sep 9, 2013)

Thanks for the reply.  My mill is a small bench top with no spindle break so no power tapping.  But I like your description I will try in on one of the BP at work.  I do use a tapping handle on the mill and that works great to get the taps started straight.  I am very interested in the set up you have for the butterfly impact tool.  I used one just like that to make my power drawbar for the mill and it works great.  Why did you choose that over a power drill and how small a tap have you done with it?  Again this is mostly to try building the tool not for any kind of production.  

Jeff



lrsglory said:


> Larry Smith here: Lets skin another cat. I presume your wanting a tapping apparatus for power hand tapping off of your mill. If not lets start with your mill. A decent BP or clone will power tap on the table after the hole is in all day long. 1/2 -13 and have even done 5/8-11. Obviously use the mill while the piece is on the table and already lined up with the hole. put your tap in the collet or even a good true drill chuck. Low speed. Start feeding it in, after the start it feeds itself. hand on the reverse switch. When your there, reverse it and out it comes. No prob bob. be sure to keep the quill lock loose. This applies to taps no 10 and up. For the small stuff, depends on how brave you are, See the pic below. Collet, center, taphandle, tap. Bring the quill down, normal pressure. tap by hand. Keep light pressure on the quill to keep the tap and handle going in straight. Shazaam. When your there, hand back it out. Straight and true. Now for off the machine. See pic. I worked for an outfit for a year building automotive tube assembly machines. The frames were 3/8 thick, 3x3 soft steel. Tons of holes to drill and tap by hand to mount tooling. Might be building 20 machines. Hand tapping gets old. Ordered a butterfly 3/8 impact air tool. Wow. and cheap. Bought two generic tap handles. popped out the t bar, found a 3/8 drive socket to fit each one. welded them on, shazaam tap holder for impact tool. This butterfly worked great, fast reverse and air pressure regulator on the end. You could use a tapping block to keep it straight until your in. Season everything with your specs. tap size,depth, blind or thru. etc. Jusst spewing out some possible answers. Re: taps. Sprial Point tap ie gun taps are for thru holes as they push the spaghetti ahead of the tap. I preferred these even in blind holes. I would stop 3/4 thru in a blind hold and finish off of the machine after I cleaned the hole out. I agree with a previous post that Spiral Flute taps are weaker. They pull the chip out as they are tapping. Common to break a few of these if you use a real dull one. As always lots of oil, slow feed on the machine etc. Get a piece of scrap and try a few on the machine and offl. Before you assault the finished product.


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## awander (Sep 9, 2013)

An battery-operated "drill" with impact could be one of two things:

1) An impact drill(typically will have a chuck), made for drilling holes in concrete and the like. It will provide impacts parallel to the shaft, and would not be a good idea for tapping.

2) An impact driver(typically will not have a chuck), made for driving screws etc, using impacts, which will provide impacts tangential to the shaft. This is what you would want for tapping.


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## lrsglory (Sep 10, 2013)

churchjw said:


> Thanks for the reply. My mill is a small bench top with no spindle break so no power tapping. But I like your description I will try in on one of the BP at work. I do use a tapping handle on the mill and that works great to get the taps started straight. I am very interested in the set up you have for the butterfly impact tool. I used one just like that to make my power drawbar for the mill and it works great. Why did you choose that over a power drill and how small a tap have you done with it? Again this is mostly to try building the tool not for any kind of production.
> 
> Jeff



I recall doing a bunch of 10-32, what a breeze. Never had to do anything smaller. If I did, I would probably figure a better way, since those small taps are easy to break or just try a few to see what happens. This of course was production tapping off the mill. Ya know, git er dun or else find another job. ! The occassional tapping would most likely be done by hand. you know a few. Our shop used air drills off the mill. When you did anything there was always a air hose within arms reach, never an extention cord. A good hand air drill will blow the socks off of any electric drill. man will they blow holes in and it doesn't take a lot of sweat. Re: tapping block. Just take a 1" thick 3 x3 piece of tool steel. Drill and ream some holes to match the tap dia. #6 to 1/2" heat treat and you got your guide for hand tapping. Hope this helps.


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