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kong
04-19-2005, 10:17 AM
Next question - I tap a lot of small holes - M2 in aluminium to be precise. These are blind holes, and I currently use quality spiral taps with excellent results.
Whilst hunting aroundebay, I found this tapping head - http://cgi.ebay.co.uk/ws/eBayISAPI.dll?ViewItem&category=92083&item=7509569959&rd=1
and was wondering if all tapping heads are the same? This one seems to be imperial, but will it do metric stuff too? I have no idea how they work, perhaps there is a setting to revolve a certain amount as it is fed into the workpiece, if so, it will not do metric.
Can someone explain how they work please! Thanks, Jason.

Splint
04-19-2005, 12:02 PM
Hi Kong,
I once aquired a tapping head and a friend of mine who owns an engineering business told me I would never use it, he was right.
Tapping heads work by putting the drive from the spindle through a gearset to reduce the speed for tapping. When the hole has been tapped the opperator pushes up on the spindle lever on the drill which makes the tapping head change into high speed reverse and backs the tap out of the hole. Some tapping heads have and adjustable clutch to regulate how much torque is applied to the tap, the one you're looking at appears not to have this feature (guarenteed to break small taps off when they bottom out in the hole).
Yes it will do metric 1.3 to 6.5mm, it has a chuck so it looks like any tap metric or imperial as long as the shank is within these limits. Personally I wouldn't bother unless you're in a production environment tapping hundreds of holes a day, even then a pnumatic tapping tool may be a better option. Depending on your application a cordless drill might be worth investigating to use for tapping.
Cheers
Splint

lerman
04-19-2005, 12:04 PM
I can't tell you about that specific tapping head, but the general principle behind these thing is that when there is pressure on the tap, it rotates clockwise. When there is tension on the tap, it rotates counter clockwise.

So, in general, tapping heads don't depend on the pitch of the tap. Some of them also have a clutch which you can set to help avoid breaking the tap.

I'm told that for blind holes in aluminum, roll form taps work quite well. They have the advantage that since they don't generate chips, there is no chip clearing problem.

I have a pair of Tapmatic tapping heads (I'm told that is a good brand) that I bought on the web. I haven't used them yet.

Ken

DareBee
04-19-2005, 12:13 PM
All the tapping heads I am familiar with work as already described.
I spent quite a few years in tooling shops and during those years I/we had no use for a tapping head.
The places I have worked since then; a tapping head has been a great asset. I find with machine building or fabricating most everything has a 3/8-16 tapped hole. Machine feet, mounting plates, scab plates, guard rail brackets, etc. Most of these items have holes that are layed out by hand or transfered from other parts and have no need to be fixtured in a mill.
I have the tapping head in a dedicated drill press beside my other drill presses, it saves COUNTLESS hours in labour every year.

JFettig
04-19-2005, 01:17 PM
A tapping head would be very nice. I do wish I had one for my drill press to do some tapping. we use these quite often at work when we have a ton of holes to tap.

These things do save a lot of time. If you have a bridgeport, you can tap with those and a regular chuck by running about 60-80rpm and reversing the spindle with the switch. It works quite nicely.

Jon

psychomill
04-19-2005, 02:28 PM
Used to use tapping heads (Tapmatics mostly) a lot in small job shops. Had a couple drill presses with them. Always ran into some problems with a clutch type due to hole sizes changing, lubricity of the tap, etc. The depth would vary. I preferred the gear type and just set a stop for depth. Hits the depth within reason. Never broke a tap in a blind hole because it bottomed out. For 10-20 bucks, it might be worth getting one, especially for small holes. Beyond that, forget it, unless you do alot of threads on a bridgeport.


These things do save a lot of time. If you have a bridgeport, you can tap with those and a regular chuck by running about 60-80rpm and reversing the spindle with the switch. It works quite nicely.

Most people would have a real hard time trying to power tap a M2 thread. Be like doing a 2-56 power tap. A lot people have a hard time doing that with anything smaller than a 1/4-20 without ripping half of the threads.

:cheers:

kong
04-19-2005, 04:49 PM
Thanks guys, I will see what it goes for. I will probably get one, it takes a long time to tap M2 holes, since I am scared of breaking taps!