Taps

[Muley]

No, not the kind on shoes or the kind played, mostly by the military, at funerals and such.  This is the thread-cutting, thread-chasing, variety.  No, not like this thread.  Well, those of you who can answer my question will know what I mean and those who don't can just read and learn like yours truly.

In a previous thread, yes the kind we post on WG, I whined about breaking a tap off in a bolt hole.  It's out, but try as I might to use it again (cheap ass emoticon appropriate here), it just won't work.  So I ordered three since they came as a set, and, I might mention, they are US made .  One is called a taper tap, one is a plug tap, and one is a bottoming tap.  I have searched the web and only confused myself further.  Can someone explain the use and/or difference betwixt these expensive little tools?

My application is to clean out, chase, and/or restore threads in my luggage rack and frame.  The subject holes are metric 8x1.25 sized.  Oh yes, can I use most any type lube with a tap?

[Triple Jim]

Taper taps have a long lead-in, and are easy to start.  Plug taps are kind of a "normal" tap, with about 4 or 5 threads of lead-in.  Bottoming taps have a very short lead-in and are used to thread to near the bottom of a blind hole after using a plug tap.  They'll all work for cleaning up threads.  For general use, I normally buy gun taps, which are medium lead-in and are usually two-flute taps that have a "spiral point", or beveled cutting edges that drive chips forward and out of the way as the tap cuts.  You can put one in a drill press and cut threads in a new hole without having to back up periodically to clear chips.  Buying the 3-tap sets is usually unnecessary.

[Muzz]

My application is to clean out, chase, and/or restore threads in my luggage rack and frame.  The subject holes are metric 8x1.25 sized.  Oh yes, can I use most any type lube with a tap?

It is best to use a cutting oil. Made specifically for drilling and tapping. You will end up with a better job and your drills and taps will last way longer.

Your 8 x 1.25 is your std. Iso metric pitch.  Goes 6 x 1.0, 8 x 1.25, 10 x 1.75, 12 x 2.0 etc.   However, that is one coarse pitch by the time you get up there so you have the "metric fine" range such as 8 x 1.0, 10 x 1.0 or 1.25 etc.

Seeing you already have the hole I would buy the plug or middle range one if you only wanted to buy one. Being the Iso std. it should be cheaper than any of the metric fine range.

[Hymes Inc.]

If you're just chasing threads cheap taps and any lube should do just fine. The threads are already there just need cleaned up. Keeping the tap running straight is way more important of an issue. Cutting new threads is a whole different story. Little nugget of info, bottom taps are designed to pull the chip out of the hole you're tapping instead of shoving it through like your standard tap.

[John A]

turn the tap backward every 1/4 turn or if it gets tight. this will clear the chips as they will break off and go into the space the flutes create. you should develop a feel for when it gets tight which is the chips binding.

[Demar]

The reason there are 3 styles is to cover the different steps in tapping. Taper taps are used to start a thread in a hole. they have a lead-in and don't get to full thread size until a fair distance from the tip of the tap. You can see the differences by looking at the taps. It's harder to keep a plug tap or bottoming tap straight when starting a new thread in a new hole; that's why there are taper taps. Nobody has mentioned blind holes. You have to be careful when tapping blind holes. If you run a taper tap in a blind hole you very well may bottom out the tip before you reach full thread and you will snap the tap off if you keep trying. Thru holes- no problem. Blind hole - start with a taper and change to a plug or bottoming tap to finish.

[pehayes]

Tell us more about the hole you are trying to thread.  Also, tell us more about how you are trying to use the remnants of a broken tap?  I would throw the bits as far as I could.

Was this hole previously threaded and you are just trying to clean it up?  Why are you doing this task?
Does the hole  pass all the way through?  Or come to a blind stop?
Is the hole facing laterally? Up?  Down?
Do you have some way to ensure that the tap remains precisely aligned to the hole as you begin cutting?

Guzzi is famous for using pre-threaded bosses and welding them to the frame.  Unfortunately, the welding leaves lots of slag in the final few threads of the boss.  If the bolt it long enough, it binds on this slag and won't tighten properly.  Famous issue when installing luggage (Hepco or Givi) on the 98 EV.  Gently run a properly sized drill ( 6.8mm or H) in there to clean out the majority of slag and then follow with a tap to clean the threads.

Make sure you reach in with some form of needle air gun to blow out the debris or it may bind the bottom of your bolt.

I get most of my taps and dies from:  http://www.victornet.com/  This is a case where 'cheap' can cost you a lot more in grief.  Cheap ones are not sharp and may snap off.


Patrick Hayes
Fremont CA

[Triple Jim]

Nobody has mentioned blind holes.

That's not quite true. 

[Demar]

That's not quite true.

You're technically correct. I was referring to the perils of tapping blind holes. 

[Muley]

Tell us more about the hole you are trying to thread.  Also, tell us more about how you are trying to use the remnants of a broken tap?  I would throw the bits as far as I could.

Was this hole previously threaded and you are just trying to clean it up?  Why are you doing this task?
Does the hole  pass all the way through?  Or come to a blind stop?
Is the hole facing laterally? Up?  Down?
Do you have some way to ensure that the tap remains precisely aligned to the hole as you begin cutting?

Guzzi is famous for using pre-threaded bosses and welding them to the frame.  Unfortunately, the welding leaves lots of slag in the final few threads of the boss.  If the bolt it long enough, it binds on this slag and won't tighten properly.  Famous issue when installing luggage (Hepco or Givi) on the 98 EV. Gently run a properly sized drill ( 6.8mm or H) in there to clean out the majority of slag and then follow with a tap to clean the threads.

Make sure you reach in with some form of needle air gun to blow out the debris or it may bind the bottom of your bolt.

I get most of my taps and dies from:  http://www.victornet.com/  This is a case where 'cheap' can cost you a lot more in grief.  Cheap ones are not sharp and may snap off.


Patrick Hayes
Fremont CA

Exactly!  The pre-threaded boss does have slag left, and that's the one that broke my first tap.  I was merely trying to clean up the threads before installing brand new, stainless hardware.  This was done after I broke one of the '98 EV HB luggage bracket mounting bolts (3 per side).

I'll run a drill bit in there as suggested and hope the new threads(or "chased" threads) work with my new bolts. 

BTW, my source for the hardware and the tap set is belmetric.com  They have nearly every type of fastener that goes on my EV, and it's very reasonably priced, especially if compared to what Guzzi would charge if ordered through a dealer.

Oh, the why I'm trying to use the broken tap is threefold.  One, I'm cheap, two I live in the boonies with no place to buy another metric tap, and three I want to mount my luggage and ride.

[Demar]

Put a little antisieze lube on the bolts before you install them.

[Sasquatch Jim]

 If you break off a tap in something steel, it can be difficult to extract.  I have had success with battery acid or muratic acid.  Just eyedropper some acid into the hole with the tap and wait about ten minutes.  the acid will eat faster on the high carbon steel of the tap than it will on most of the base metal steels.  Rinse with water and blow compressed air in.  Eyedrop in some cutting oil and fit the tap extracting tool.  The broken tap may now be easier to unscrew because the tap is now about a thousandth of an inch or so smaller and will bind less. If you break off a tap in aluminum, do not use acid, use heat to expand the base metal.

[tris]

Especially if it's a blind hole once you get the tap started hold the tap wrench with your fingers.
That way when the tap bottoms out there's less chance of snapping it as your fingers slip off
You do need to develop a "touch" which is difficult if you don't do it often - I'm the same with welding

[Don G]

If you are chasing threads it is best to use the proper thread chasing nuts and taps, regular taps and dies a designed to remove metal, where as the chasers reform the thread to the correct form. You can use 80-90 Hypoid oil for thread cutting to good effect.  DonG

[Rusnak_322]

I ordered a 10mm x 1.0 tap Monday morning using Amazon Prime and it was at my house when I got home from work Tuesday. $6.85 delivered. I will probably use it one time as I have never seen another both with those threads.

[RayB]

A good cutting oil for tapping is Tap Magic.

[Chuck in Indiana]

A good cutting oil for tapping is Tap Magic.

I like Tap Magic, too. They make a couple of versions, one for aluminum and one for steel. Don't interchange them. :)

Muley, I've probably tapped more holes than anyone on this forum. Literally thousands, maybe 10s of thousands. Buying the set of three was overkill for what you are wanting to do. A simple hand plug tap would do it.
If you want to try to save the broken tap.. (Guzzi content) :) Get a pan of water, grind the end flat. Don't let it turn color.. that's what the water is for.. then grind an angle on the end, rotating it with your hand for a taper to start it. You can make a bottom tap out of a plug tap using the same method.

[normzone]

If you break off a tap in something steel, it can be difficult to extract.  I have had success with battery acid or muratic acid.  Just eyedropper some acid into the hole with the tap and wait about ten minutes.  the acid will eat faster on the high carbon steel of the tap than it will on most of the base metal steels.  Rinse with water and blow compressed air in.  Eyedrop in some cutting oil and fit the tap extracting tool.  The broken tap may now be easier to unscrew because the tap is now about a thousandth of an inch or so smaller and will bind less. If you break off a tap in aluminum, do not use acid, use heat to expand the base metal.

Damn, that's a new one for me. Wear eye protection is all I can add when you get the compressed air near the acid.

As I lack formal training, you guys have summed up all I learned about taps and then more in one page - just another reason to thank you guys for sharing, and [Luap] for hosting.

[Muley]

Thanks to all of you!   This place is a one stop shopping center for useful information (most of the time ) , and I will refer to this thread, no pun intended, when fixing mine this weekend.

[tris]

One more thing I've just remembered.
If you have a through hole and sufficient space at the back you can screw a taper tap all the way through and you'll get a full size thread in one go 

[Sasquatch Jim]

  If you have a through hole, after you get the broken part out you can run a tap through from the other side thereby reducing risk of cross threading as you clean out new threads.

[tris]

If we keep this up Jim, Muleys' head will explode 

I wonder how many more tapping facts and tips the reprobates on the forum can drag up from their collective ancient training and experience

[Tom H]

Thanks for the info on taps. I knew what bottom taps were for, but never knew about taper taps. I've always used what was in the multi piece set I bought. Might just have to get a few select sizes of taper taps.

Thanks again!
Tom

[Muzz]

I detect a Sunbeam there Les.

[Triple Jim]

Thanks for the info on taps. I knew what bottom taps were for, but never knew about taper taps. I've always used what was in the multi piece set I bought. Might just have to get a few select sizes of taper taps.

Personal opinion based on experience, with disagreement expected: I've never needed one in 50 years of threading for personal projects and professionally.  Gun taps are best for general purpose use and usually don't require reversing periodically to clear chips.  Because they have fewer, wider flutes than plug taps, the flutes tend to advance at the correct pitch right away, so they start easier and cleaner.  With the correct tap hole size and good lubricant, you can put a gun tap in a drill press and run it through a piece of 1/2" thick steel, making good, clean threads.  An old gun tap with the end shortened on a grinder works fine when a bottom tap is needed.  Some suppliers call gun taps "spiral point taps".

Spiral flute (not spiral point) taps are great when you don't want chips crammed in the bottom of a blind hole.  "Spiral flute" is a misnomer, since they're really helical flute taps.  A machinist friend of mine likes forming taps on softer metals like aluminum and mild steel because they don't make any chips at all. 

[Les P]

I detect a Sunbeam there Les.

Yes a 1949 S7 Deluxe Muzz, I have a 1954 S7 Deluxe also.
The 54 has probably not been started for 40 years or more so will probably need a bit more than chased threads, full mechanical refurbishment but retain its cosmetics.
Something for next year.

[Muzz]

Nice patina Les. Keep up the good work.

A nice running Sunbeam purrs like a kitten.