Author Topic: Tapping help  (Read 4733 times)

Offline Robert Hornby

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Tapping help
« on: November 15, 2017, 12:43:50 AM »
Wherever possible I like to tap holes using the mill drill so that the tap is true with the drilled hole. On my smaller taps (8BA and similar) I made a special holder for the tap and it works well. However with taps in the order of 1/4" and upwards I use a standard tap wrench. The problem is that not enough (usually none) of the tap end protrudes through the holder to be able to support it from the drill chuck. I thought of grinding the square end down further to allow the wrench to go lower down. Any other suggestions out there?
Robert
Age and treachery will always overcome youth and skill

Offline Dave Otto

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Re: Tapping help
« Reply #1 on: November 15, 2017, 12:57:40 AM »
Hi Robert

For most of larger taps that have a center hole I use one of these spring loaded tap guides.
https://littlemachineshop.com/products/product_view.php?ProductID=1963&category=-561984047
It also has a small cup on the reversible center that can be used for the small taps that have the cone instead of the center.
A decent quality tee handle tap wrench will also have a center in the end that can be used with the spring loaded guide.

Dave
 

Offline Robert Hornby

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Re: Tapping help
« Reply #2 on: November 15, 2017, 01:13:19 AM »
Thanks Dave, but a lot of my larger taps don't have either a counter sink or are pointed at the end, ie they are just cut off square at the end.
Robert
Age and treachery will always overcome youth and skill

Offline AOG

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Re: Tapping help
« Reply #3 on: November 15, 2017, 02:04:16 AM »
I will second the recommendation to use a t style tap wrench and a spring guide.

https://goo.gl/images/tTK4bG

They work well for me.

Tony

Offline Jasonb

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Re: Tapping help
« Reply #4 on: November 15, 2017, 07:16:45 AM »
Make a female ctr for the ones without a hole or just hold loosly in the drill chuck to guide them.

I find tightening the tap wrench onto the plan shank gives enough grip to start the tap then if needed move it up to the square end and use without support

Offline Chipswitheverything

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Re: Tapping help
« Reply #5 on: November 15, 2017, 08:34:33 AM »
I tend to use Jason's method of just guiding by the drill chuck jaws.
Depending on the mill and the job, there may not be a lot of headroom to get a drill chuck, spring centre and the Tee wrench and tap length over the hole to be tapped.
 If, when clamping the tap by the shank, the tap wrench is held in the vice ( soft jaws !) and the wrench is done up with a well fitting tommy bar, it can be tightened pretty securely ( rather than holding the tap shank while tightening.) 
  If a more secure grip is wanted, you could use one of the smaller Myford type carriers on the tap shank, or make up an "old fashioned" type of wrench as in the photo, which can be tightened well if two socket screws are employed. 
Dave

Online Jo

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Re: Tapping help
« Reply #6 on: November 15, 2017, 09:05:41 AM »
Hi Robert  :)

From your description you are interested in what we in model making would consider very large diameter tapping, i.e. 6mm + sizes. And you are right these big taps need a strong tap holder clamped around the square bit to be able to use enough force to cut the threads. The one at the top I needed to use recently on my No 5A for the little tap at the bottom but this was still difficult to square up and I had to start them by thread cutting on the lathe  ::)

Silly question: Are you starting with a taper tap? If you are then it should pull itself square very quickly from any slight misalignment you may cause. If you are threading short blind holes you might have to start with a second due to depth and that will not self alight so yes a bit of support wouldn't hurt  :thinking: If there isn't a centre already in the tap shank is it soft enough to add one?

The other option is to put a tool holding chuck like an ER32 in the drill quill and hold the shank of the tap with that. A standard drill chuck is unlikely to have sufficient clamping capability for the really big diameter threads.

Jo

P.S. Don't forget cutting lubricant  ;)
« Last Edit: November 15, 2017, 09:17:06 AM by Jo »
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Offline Ramon

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Re: Tapping help
« Reply #7 on: November 15, 2017, 12:01:32 PM »
Hello again Robert,

Were you to look in my motley collection of taps from smallest to fairly big (14-12 BA to 3/8-1/2 BSW) you'd find most of them have a flat ground (by hand) on one side just above the thread. This positions the tap holder and the portion of the shank above is held in the chuck, either very lightly closed jaws to guide the tap or in a brass sleeve held more tightly the bore of which is a nice slide fit on the tap.  This allows tapping with ease, in and out without any side pressures involved. I've been grinding these little flats on for years and though there's been the odd broken tap it's never ever been at the ground area so it does create a stress riser as such.

The flat just needs to be deep and wide enough for the wrench to bear against. I've found its much better to bear the flat against the fixed part of the wrench rather than use it as a flat for the moving part.

I've had a look through my pics but can't find any of this - I'm happy to take a couple should the above not be clear enough.

regards - Ramon
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Offline Ramon

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Re: Tapping help
« Reply #8 on: November 15, 2017, 12:13:05 PM »
Here you are Robert - this is from the Waller build, I think the tap is 12BA but the principle is the same on all taps.

The 'wrench' in this case is the knurled disc which gives much better control on tiny taps but once up to 8BA then normal flat tap wrenches take over



In use - the brass sleeve makes things much easier as the chuck jaws are tightened as opposed to being 'just tight'- 'just loose'.  The only problem with making a sleeve being is that there appears to be no standard on tap shank diameter sizes and some are very odd diameters indeed.


Hope that helps some  - Ramon
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Offline mklotz

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Re: Tapping help
« Reply #9 on: November 15, 2017, 03:32:22 PM »
I too use the mill drill as a tap guide when tapping.  After all, what could be better aligned with the hole you just drilled than the device with which the hole was drilled?

For larger taps (> 6-32) I made a low-profile, piloted tap holder that takes collets.  Each collet has a cut-away section that allows a setscrew to bear on the tap's flat section to keep it from rotating.  Only a few collets are required since many taps have the same diameter shaft.  The holder is shown on the far right in this photo of tap holders I've made...



The article about these holders is here...

http://www.homemadetools.net/forum/tap-holders-26298
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Offline fishy-steve

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Re: Tapping help
« Reply #10 on: November 15, 2017, 10:56:27 PM »

Offline mklotz

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Re: Tapping help
« Reply #11 on: November 15, 2017, 11:10:53 PM »
I use these.
http://www.warco.co.uk/tap-die/302931-spindle-tap-wrench.html
Steve.

I have several of those.  They're fine on the lathe but eat up too much z-axis room on the mill.
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Offline fishy-steve

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Re: Tapping help
« Reply #12 on: November 16, 2017, 11:44:23 AM »
Hi Marv,
I tend to use it straight into a mt2 collet untightened, which greatly decreases the head clearance required. I believe the shank is 1/4" diameter.
It does mean, however, that I have to drill the hole then remove the chuck and replace it with the collet  ;)
All the best.
Steve.

Offline Ramon

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Re: Tapping help
« Reply #13 on: November 16, 2017, 08:01:36 PM »
I don't know if you've looked back in to your question Robert but I was thinking about it today when tapping some holes as described.

So - for your edification I took these - hope they show just what a simple mod to a tap can bring without the need to make or purchase further kit (Not that there's anything wrong  with that Marv, Steve, but why spend time or money when it's not required  :) )

I really can't afford to break a tap in this casting




All successfully done - 5 BA by the way, 10mm deep



Hope that's of further use to you and others

Regards - Ramon
"I ain't here for the long time but I am here for a good time"
(a very apt phrase - thanks to a well meaning MEM friend)

Offline 10KPete

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Re: Tapping help
« Reply #14 on: November 16, 2017, 08:15:44 PM »
OK, gotta know...

Jo and Ramon: Tell me more about that little tap driver. The flat one with the dimple at each end and the little screw thingie to tighten the wrench on the tap...

Where are they purchased?????

Thanks,
Pete
Craftsman, Tinkerer, Curious Person.
Retired, finally!
SB 10K lathe, Benchmaster mill. And stuff.