|Hugh Gilhespie||28/10/2011 18:26:28|
|130 forum posts|
Hi, I've just scored a Tapmatic 70X tapping head for my mill from fleabay. I have downloaded the instructions from the Tapmatic web site but they are a bit skimpy.
Does anyone have any experience with using these units? I have a fair number of M12 x 1 holes to tap in EN1A. Some through holes and some blind. Will I need to use spiral taps or will standard second or plug taps be OK?
All help gratefully received.
|398 forum posts|
Sprial fluted machine taps for blind holes, sprial point machine taps for through holes. Its been a while since I used a tapmatic head, but as I remember the tourque settings are adjusted by the ring on the top of the body, depth and auto reverse are engaged by the spindle stop as a normal tapping head. If you can get hold of some tapmatic Gold tapping fluid it makes the tapping twice as easy.
|Andrew Johnston||28/10/2011 19:27:11|
5828 forum posts
Sort of; I've used it's baby brother, the Tapmatic 30X, and a larger, but similar, unit from Edelmatic to tap thousands of holes from M2 to M12 in brass, aluminium, EN1A and EN3.
You might get away with using a second tap for the through holes, but I doubt you will be able to use a plug tap for the blind holes. Just to be clear, each hole is tapped in one operation; there is no guarantee that the tap will pick up the thread correctly if you try a second time on the same hole.
In essence Mick is correct, spiral flute taps for blind holes and spiral point taps for through holes. However, if you want to minimise expense it is fine to tap through holes with a spiral flute tap, but not vice versa.
Again, as Mick says, the torque limit is adjusted by rotating the ring at the top of the unit, against an arbitrary scale. One hint, the ring is normally locked by a non-obvious set screw. If it is stiff, find the screw, don't force the ring.
I don't want to teach you to suck eggs; let us know if you need further details.
|Hugh Gilhespie||28/10/2011 20:35:01|
|130 forum posts|
Hi Mick and Andrew,
Many thanks for the info. As far as teaching me to suck eggs, you won't go far wrong if you work on the assumption that I have never see an egg before, may have read about them in books but wouldn't recognise one if it jumped up and bit me - do eggs bite?
So, yes please to any other info on tapmatic and the like. If possible, a dummy's guide to tapmatic tapping would be incredibly helpful. Like how do you set the torque limit, do you use the self feed on the mill or just use the quill feed handle, etc, etc?
I will bite the proverbial and buy a spiral flute tap, presumably in EN1A I don't need any high performance coatings, just good old HSS?
Sorry to be a nuisance but as I have absolutely no background in machining, a lot - an awful lot - of what most would consider the Janet and John level of engineering skills just aren't there so the more basic the better.
Ta everso, Hugh
|461 forum posts|
OK Hugh, let's try a dummy's guide.
I own a Tapmatic 30 TC/DC, which differs from yours that it is smaller and has a threaded ring above the collet, which allows to limit the 'pullout' of the spindle. As yours don't have this, one problem less.So I would propose that you prepare some scrap pieces (8 - 10 mm thickness) of the material you want to thread. Arrange a stop in your milling vise and drill them with the drill you want to use for tapping. Let's assume 5 mm for a M6, and a through hole. After preparing these mount the Tapmatic with the tap in it. A machine tap with spiral point it has to be. Lower the tap (stationary) to the surface of your test piece (which is in exactly the same position in your vise as when you drilled it). Clamp the spindle, and set your depth stop to a dimension after solving the following equation: The T.70 spindle pulls out 9 mm , my workpiece is x mm thick, and to cut a full thread the tap has to come out of the other end y mm, and it does not hit something hard beneath the hole (e.g. the vise). Unclamp the spindle and bring the head up.
Ok, your depth stop is set now. Ah the torque...well start with the lowest, and when the threading stops prematurely then adjust it for more grip.
Set the mill to say 2/3 of the max speed given on the Tapmatic head. You arranged also a stable stop bar for the arm, didn't you?
Now I hope I have not forgotten too much. Switch on, put some good cutting oil on the tap and maybe also into the hole, and lower the tap quite fast with the quill handle into the hole (1.2 sec. for a thread like I said above). When you reach the spindle stop, the tap stops also (to be exact, after the 9 mm 'pullout'). Move up with the handle (even faster, as the left turn is geared up), and voila...thread done.
If any questions remain, just ask
Edit: depth stop = x + y - 9, if my 'rithmetic is still working.
Edited By Versaboss on 28/10/2011 22:15:52
|Andrew Johnston||29/10/2011 20:13:59|
5828 forum posts
Hugh, you're not being nuisance at all; we all have to start somewhere. I might earn my living from engineering, but I'm definitely not a professional machinist.
Sound advice from Versaboss to try a few test holes first in a piece of scrap; and he has also captured the essence of using the device.
First, a note on tapping drill sizes. Generally I aim for a thread depth of 60-65%; so for M6 I'd use a tapping drill of 5.3mm. In general the shear strength of a material exceeds the tensile strength. In simple terms the bolt will break before the thread in the hole strips.
Now some notes from my experiences of using Tapmatic style tapping heads. The first thing you need for the Tapmatic is a stop bar; on the Bridgeport I either use a round bar in the hole in the convenient lug at the bottom of the quill housing on the right, or a convenient lump of metal bolted to the table. The stop bar counteracts the torque from the Tapmatic, it does not need to be attached to the stop arm at the bottom of the Tapmatic.
I set my depth in a similar way to Versaboss; through holes are less critical than blind holes. The important point is that you want the clutch in the Tapmatic to dis-engage before the tap gets to the bottom of the hole. You do not want to rely on the torque limit on the Tapmatic kicking in because the tap has hit the bottom of the hole.
Torque setting on the Tapmatic is a case of trial and error; think about the size of the tap relative to the range of the Tapmatic and the material to be tapped. Start low and try it out in a piece of scrap; if it slips up the torque a bit.
I tend to use speeds about half those recommended by Tapmatic; for M12 in EN1A I'd be running at about 250rpm.
The hole is tapped by using the quill feed handle, just like a pillar drill. The feed is fairly quick. The important point is that when the clutch has dis-engaged at the bottom of the hole you need to reverse the Tapmatic by moving the quill feed handle upwards sharply; don't dilly-dally or in time you'll wear out the clutches in the Tapmatic!
On low carbon steel I don't tend to bother with cutting fluid, may be a little WD40.
You certainly don't need fancy coatings on the tap for EN1A, HSS will be fine. It's more a question of what you can buy, as a lot of machine taps will come with a coating anyway.
Here's a picture of the Edelmatic unit tapping blind M10 threads on my Bridgeport. The machine vice and large lump of hot rolled steel was just a convenient stop bar; it doesn't need to be that big!
Anything I've forgotten, just ask.
|Hugh Gilhespie||31/10/2011 09:28:47|
|130 forum posts|
Many thanks Andrew and Hansrudolf, I am very encouraged and looking forward to trying out my new toy. I have ordered an M12 x 1 spiral flute tap and, after a little revision of basic geometry, an 11.3 mm pilot drill - I was pleased when I checked my calculations for percentage of radial thread engagement with Machinery's Handbook and found that it agreed! The 11.3 mm will give me about 65% which is more than enough, even if the drill is a bit oversize.
Andrew, from your photo, I assume that the Tapmatic unit will try and rotate in the same direction as the quill(clockwise from above), hence the position of the stop bar to prevent this. Does the unit spin around when you reverse direction to remove the tap? Or put it another way, do I need to take cover when I move the quill up smartly to start it coming out?
Hansrudolf, I will definitely prepare a good supply of scrap pieces and practice until I have a feel for tapping this way.
I will have a go later this week when my tap and drill arrive and report back!
Thank you again gentlemen.
|461 forum posts|
Hugh, I'm glad that I could give some tips. As a matter of fact, I never use larger drills as the metric 'standard', diameter - pitch. You should have no troubles with 11.3 mm
Don't be afraid when you see the tap running with a lot of runout - well I was when I first saw it. That's why I said to tap with the workpiece in the same position as when drilling. But if it is necessary, it is possible to 'pick up' a hole position with the point of the tap, if one is prudent. The Rubberflex collets are quite forgiving.
No, the torque arm stays in the same position, even when the tap runs backward!
And for blind holes - I use to set the depth on the safe side, then check with a thread gauge (or screw, if you have none, and adjust the depth accordingly. Then finishing the too short thread manually. I have to confess that I in some cases thread the workpiece a couple of turns on the tap, then clamp it down in the vise and switch on power! Usually I am lucky with this method, but it's up to you (and I don't know your machine).
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