Tapping on a Bridgeport

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plongson

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How are you guys holding a tap on your mills? Yesterday I was (attempting) to tap some 1/2"-13 and the tap would just spin before it got too far. Mild steel, 27/64 drill, 3 flute tap, Lot's for Tap-Magic...I first held it in a drill chuck with no luck, tightened it until I was nearly bending the chuck key, then mounted it in a collet again with no luck.
I finally just started the tap in the work, removed it and finished with a big tap handle.

SO again I ask...what is a better way to hold a tap in the mill? Different tap (2 flute), larger tap drill? Maybe the tap is a bit dull??

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If it was spinning in a collet I suspect that the tap may be dull.
I can power tap on my mill/drill using an ER32 collet chuck without issue. I don't tap over 3/8" though so maybe 1/2" would spin in my collets.
 
I hold taps in a Bilz type clutching tap holder. They're not expensive to buy by the bucketful in auction lots. Feed the quill down manually, then stop and reverse out when the clutch slips. Takes some of the risk out of power tapping. I don't think I'd want to drive a tap directly, it's just going to roach the tool and the holder without some sort of clutch.

The other one is a TapMatic. Similar idea, but automatic in operation. Probably preferable for most of us, since the Bilz clutches need some setup and calibration. The TapMatic is more expensive, but it is a more forgiving tool to use for a quick thread in the mill.
 
Spiral flute taps make life so much easier for power tapping.

It's quite acceptable to power tap to start then pick back up later by hand too. As long as you get a few threads going on the mill it'll follow true.
 
plongson said:
How are you guys holding a tap on your mills? Yesterday I was (attempting) to tap some 1/2"-13 and the tap would just spin before it got too far. Mild steel, 27/64 drill, 3 flute tap, Lot's for Tap-Magic...I first held it in a drill chuck with no luck, tightened it until I was nearly bending the chuck key, then mounted it in a collet again with no luck.
I finally just started the tap in the work, removed it and finished with a big tap handle.

SO again I ask...what is a better way to hold a tap in the mill? Different tap (2 flute), larger tap drill? Maybe the tap is a bit dull??
Click to expand...

Prolly the tap is dull. Could be the drill chuck isn't perfect. Could be a lot of things...

What do you have for collets? Mild steel holds great in collets and chucks. Here's a very simple holder. You wanna be sure where you're headed though, clutching is not really an option here...

 
1) Don't use those taps...use spiral flute taps.
2) Don't tap in the Bridgeport, use a tapping head like Tapmatic.
3) If you want to tap in a Bridgeport, go ahead...but this is how I break taps. Or screw up collets and chucks by spinning taps in them.
4) Use a tap guide in the quill and tap manually. This keeps the threads square.

Yep, I know all you guys disagree...fine. It's your part. But I've not broken a tap with these guidelines for a decade or more.
 
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