# Using the Sieg mini mill to run a tap into steel?



## Kmot (Jan 19, 2011)

I was wondering if it would be possible to let the mini mill do the work of running a 14mm tap into a piece of steel. I want to tap a .500" hole so that I can mount a QCTP stud into the steel.

Has anyone been doing this? I figured maybe by getting it to turn really really slow it might work.

Or is this just a really bad idea?


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## IronHorse (Jan 19, 2011)

I would not have the nerve ;D


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## Kmot (Jan 20, 2011)

lol... I've done dumber things before. ;D

But on second thought, it's a bad idea.


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## imagineering (Jan 20, 2011)

I have an SX3 and have tapped 6mm into Alloy OK. You need to watch the Forward/Reverse though, as the Motor doesn't always change direction when the Button is pushed. I suspect that the Buttons on the Handles are not the best quality for this operation. I wouldn't dare to try a blind hole. ;D 

I do however, use it under power, to start a Tap square to the Hole. Stop the Motor using the STOP Button, (not the Handle One), dechuck the tap, & finish by hand.

Murray


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## Troutsqueezer (Jan 20, 2011)

Considering the Pulse Width Modulation circuitry that allows the motor to run slow on these mills I think you would be pushing your luck by stressing the FET's that turn the motor. The larger amount of torque required to run a fairly large tap thru steel at a slow speed might bring the mill to the brink of those limitations (safe operating area) designed into the semiconductors (drive circuit). Like many things, semiconductors have a recommended duty cycle.


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## kvom (Jan 20, 2011)

I've use a mill to tap through holes using a spiral flute tap. Wouldn't try it in a blind hole.


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## Mainer (Jan 20, 2011)

I wouldn't have the nerve, either. I think I've power-tapped approximately two holes in the 30+ years I've been doing this stuff. The heart-stopping stress of it led me to decide I wasn't in that much of a hurry.

I was certainly over-reacting. Under the proper conditions, people power-tap all the time. But I'd rather do it by hand.


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## Kmot (Jan 20, 2011)

> heart-stopping stress of it



lol... Yep, that would probably be me once I started! ;D


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## rake60 (Jan 21, 2011)

I've power tapped thousands of holes.

The biggest were 1-1/2" 6 pitch on a 8" column Carlton Drill Press.
Lots of nerve racking snapping and cracking going on there!

I don't think it would be that unnerving in a mini mill.

A puff of smoke - the smell of a fried controller board - and a Hi Ho VISA card....  *bang*

Don't try it Kmot.

Spoil the tap handle, Spare the VISA card. 

Rick


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## Kmot (Jan 21, 2011)

Got it! 

Or, as I discovered last night, a simple aftermarket stud could solve the whole issue. oh:

http://www.littlemachineshop.com/products/product_view.php?ProductID=3712&category=

But I think I will go ahead and drill/tap my compound anyway.


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## QSPSB (Jan 21, 2011)

I used my X2 to tap a 15/16-16 manually in 6061 T-6 aluminum and it works quite well... Just mount the tap in a Collete and draw the tap down using your draw bar manually..gradually lower your spindle as your taping... Then gradually raise the spindle as your backing out the tap//

1/2'' would be a breeze... even in steel!!


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## MachineTom (Jan 21, 2011)

I power tap all the time, but use a BP, seeing the mini-mills with no backgear, zip chance for 14mm in steel. Does the motor have an overload? or does something smoke when stalled at low speed.


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## Troutsqueezer (Jan 21, 2011)

Unless Kmot's got the belt drive modification, the unit has an "overload" gear. Stalling the machine is likely to break the plastic overload gear, thereby saving the other components in the drive chain. :big:


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## Kmot (Jan 22, 2011)

I heard ya'll lound and clear. ;D

I just drilled and tapped the new M14 stud to fit over the stock M8 stud. The QCTP is now mounted and there is no longer a need to tap a M14 thread.


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## bazmak (Dec 22, 2012)

Hi the only problem with machine tapping (if you have the power) is breaking the tap The Larger the tap the smaller the problem. Slowest speed,plenty of cutting oil,use the taper tap and only tighten the chuck lightly.Trial and error. You want the tap to slip under hi load as a safety factor.If you chicken out just aim to part tap for sqareness and finish by hand.I would recommend WD 40 as cutting fluid and you really need a machine tap (chipbreaker) Regards BAZMZK


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## gus (Dec 22, 2012)

My workmen has to tapped hundreds of holes per day using hand held Ingersoll-Rand Pneumatic Tapper with auto-reverse.Tapper will reverse out when pulled back.
This is limited to 1/4-----3/8 M.S. plates and thru holes.
Following conditions must be met.
1.Taps are sharp and holes drilled to correct I.D. Tight holes breaks taps. Big holes = shallow threads
2.Tapping oil applied. Normal lube oil no can do.
3.Workmen are given training.
4. Tapping tool is given a few drops of lube oil in the morning and after lunch break.

I have done tapping with Bridgeport Mill but never with shallow blind holes.
There are very good Taiwanese Drill cum Auto Tapping Drill Press and again ---bilnd holes are dangerous.

With hand held Air Tappers,please avoid big taps,you break your wrist.

Oh !!!! One more hint.Use machine taps which will cost min 2----4 times hand taps. Spiral Taps best but cost a bomd. Wear eye goggles. I use machine taps for ease of hand tapping on the drill press using drill chuck turned by hand with job clamped with drill vice..

You could also use the very expensive Auto Tapping Head which fits into the drill chuck. Auto reverse when pulled back. Not good for blind holes.For us-----hobby machinist,this is a want and not a must have.


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## purpleknif (Dec 24, 2012)

Where I work no one likes to tap 3/4"-10 holes cuz "they're so damn small"  We use tapping heads with interchangable collets that have spring clutches in them. Run the tap in till it clicks and back it out. Never seen one small enough for a mini mill tho.


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