Auto reverse tapping head

[Chris Richards 3Participant @chrisrichards3]

[Chris Richards 3Participant @chrisrichards3]

hello,

Does anyone have any experience with tapping head attachments?

Basically I use taps between 2mm and 3.5mm in various sizes and tpi's and tap 80 holes by hand currently on each job.

I'd like to know if you need to set the feed rate on your lathe or milling machine to match the tpi of the tap?

Thanks,

Chris

[Bob Brown 1Participant @bobbrown1]

see **LINK** or https://www.youtube.com/watch?v=_CUGz0jXvWQ the machine just runs forward but as you move the head up the tapping head automatically reverses the direction. Torque on the tap can be set so you should not break taps and as a note you need to use machine taps. One problem is they can occupy a lot of the throat on small machines.

Bob

Edited By Bob Brown 1 on 02/02/2015 20:33:01

[Chris Richards 3Participant @chrisrichards3]

Thanks Bob, that video makes it quite clear in operation. So I see the head allows the tap to float and find its own path and bottoms out. The machine tap part and throat space may make it tricky for me to do. The taps I need are not easily bought unless I'm just looking in the wrong places so I need to make them maybe that needs a new thread in itself.

[Bob Brown 1Participant @bobbrown1]

what size taps are you using?

Take a look here http://www.dormerpramet.com/en-gb/products/round-tools/taps-dies

 

Edited By Bob Brown 1 on 02/02/2015 20:56:10

[JohnFParticipant @johnf59703]

Hi Chris, I have used these extensively in industry many years ago, I would suggest caution if purchasing a used one, make sure it works well before handing over the dosh. Also you DO need to use good quality well branded taps and make sure they are sharp, if not disaster will surely follow. Otherwise they work well and speed production.

Regards John

Ah! also stating the obviouse make sure the unit is compatible with the tap size you want to use

Edited By JohnF on 02/02/2015 21:24:05

[Chris Richards 3Participant @chrisrichards3]

The taps are bscy, I'll have a look through that site just in case they have them.

John do you think home made taps are a non starter?

[Anonymous]

Posted by Chris Richards 3 on 02/02/2015 20:11:52:

Does anyone have any experience with tapping head attachments?

Yes. On the manual Bridgeport mill I use a Tapmatic 30X up to 6mm and an Edelmatic onwards up to 12mm. I use spiral point taps for through hole and spiral flute for blind holes. Feedrate is set by the user, ie, how fast you move the quill lever. It doesn't take long to get the hang of the rates needed. Both the tapping heads reverse at a higher speed. The trick is to smartly reverse the movement of the quill lever once the tap stops rotating. Spindles speeds range from 200rpm to 1000rpm depending on tap size and material.

On the CNC mill I use a tension/compression tapping head, reversing is done by reversing the spindle. The feedrate is set in the G-code by the spindle rpm (which needs to be accurately known) and the thread pitch. Spindle speeds are normally a few hundred rpm.

Similarly to the CNC mill I use a non-reversing tapping head on the repetition lathe, since reverse is simply done by throwing a lever (that controls an electrical switch) to reverse the spindle. Feedrate is set by simply manually operating the lever at the correct rate. Tapping is normally done at around 500rpm.

All in all I love tapping units, it's a darn sight quicker to tap the hole than it is to drill it; usually a few seconds.

Andrew

[Clive FosterParticipant @clivefoster55965]

I use Pollard tapping heads, mostly on my Pollard 15 AY drill. Like Andrew I have considerable affection for the beasts as they make tapping a simple process.

The Pollard versions have simple forward and reverse cone clutches controlled directly by feed pressure. As soon as you stop feeding the tap draws forward reducing clutch engagement pressure and rapidly interrupting the drive. Offhand I'd say no more than half a turn from stopping feed to loss of drive. My practice is to lubricate the holes properly before starting to tap and apply only enough feed pressure to drive the tap. Even on the big 15 AY its a quite sensitive process and its easy to feel if the tap needs too much drive power for any reason. If the tap does seem to want too much driving simply lifting the feed lever so it can reverse back clears the thread, just like manual tapping, so a second attempt usually allows the thread to be completed.

Proper machine taps are pretty much never any trouble unless blunt or the material unfriendly. Soft aluminium and phosphor bronze are my least favourites. Ordinary hand taps work well enough in most materials if you keep the speeds down and are careful on feed pressure. Second cuts from good brands have worked fine for me when needs must. Not a place for bargain basement no-names.

You should always set the depth stop so feed stops before the tap bottoms. Big gear driven drills like mine will snap a half inch, or even larger, tap like a carrot if it bottoms out. I suspect than anything under 3/8 is at serious risk in smaller belt drive machines. Remember its a square drive so the tap cant slip like a drill in a chuck. One of my Pollard No 2's came with a normal, decent quality, drill chuck instead of the proper square drive and allignment chuck assembly. Pretty much useless as anything over 5 mm slips at the slightest provocation. No worry to me as I got it in a job lot, for effectively less than nothing as the rest was worth more than I paid, as a spare parts source for the one I was using.

The morse taper needs to be a good fit lest the head be pulled out when you reverse. My spinde was somewhat bruised. The MT3 reamer went in approaching 1/8" before everything was properly cleaned out. It now grips like a bolshie badger with only modest fitting effort.

Clive

Edited By Clive Foster on 03/02/2015 00:09:43

Edited By Clive Foster on 03/02/2015 00:10:26

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