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Thread: Thread Chaser or Tap ?
12-20-2011, 03:01 PM #1
Thread Chaser or Tap ?
(Backyard Auto Mechanic)
Ok I've read all the data I've found about why you should use Thread Chasers to clean threads instead of just a tap or die. They say the chaser has duller cutting edges (less angle) and is slightly less diameter than the tap and terms like less aggressive than the tap.
Here is what gets me. If I use a tap (instead of chaser) to clean my threads, it says that it will cut my threads too much causing the bolt to be slightly wobbling around in the hole. If this is the case, then why doesn't the first OEM tap cut the same exact depth and cause the same exact scenario. I don't get this ?? I mean isn't it the same thing as the tap I would be using ?
Appreciate any insight on this .
12-20-2011, 05:39 PM #2
Wow 40 views and not one comment. I would have thought this to be right on point for a machinist forum.
12-20-2011, 05:48 PM #3
Never used a chaser. Always used a tap, die, or triangle file.
12-20-2011, 06:04 PM #4
There are several kinds of tools meant for repairing damaged threads, but I don't recall any of them being called chasers. But that could just be a problem with my leaky old brain.
I have not seen any reason to avoid running a tap into a threaded hole to clean it out. I do it.
12-20-2011, 06:27 PM #5
What the hell is a 'thread chaser'. Is it one of those garbage taps that you get a the hard ware store that have essentially no cutting edge and at best should be used to tap holes in swiss cheese?
12-20-2011, 07:06 PM #6
warm swiss cheese at that.
12-20-2011, 07:34 PM #7
I have never seen a "thread chaser", and have successfully "chased" using taps and dies.
I think if it would have said that, "With a tap, you must be careful to not recut the threads oversized. A threadchaser makes it easier." I'd agree.
12-20-2011, 07:36 PM #8
Fact is thread chasers are not hard to find, they are available at just about every auto parts store and online. They go under the title of "Thread Repair" Thread Chasers" or "Thread Restorer". You can buy them separate or in a kit, such as this one at Amazon
Amazon.com: Kastar 972 40 Piece Fractional and Metric Thread Restorer Kit: Automotive
But if you read the manuals or specs they "ALL" say they are for "cleaning" the threads and not for creating new threads. Many will further state that using a tap for this will cause damage.
I have a tap and die set already. From what you guys just told me, I would surmise that chaser kits are a sales gimmick put out quite awhile back to push cheap made dies.
Any other comments ?
12-20-2011, 07:39 PM #9
12-20-2011, 07:43 PM #10
12-20-2011, 07:45 PM #11
12-20-2011, 07:49 PM #12
Here is one of the better posts on the auto forums. This guy makes a good case and could convince a novice like me. You guys want to comment on this. Also my only reason for asking this is to find out if I really need to spend $60 to buy a thread chaser kit when I already have the taps and dies.
======insert paste post from other auto forum====
A thread cutting tap is designed to cut threads. It will never engage the already cut threads in the same manner every time. You can take a new drilled and tapped hole and run the tap back through it and it will remove more metal. It won’t only remove material from one side; it will remove it from the entire circumference of the hole. It is almost impossible (by hand) to get the tap lined up in the exact same orientation to retap a hole.
In a poor example that I can do like this the first time you cut the threads they will look like this > <, every subsequent time you run a thread cutting tap through the hole will remove the point of the threads and round them off, reducing your thread depth making them look like this ] [. This is from the tap being slightly out of alignment with the original threads and it is cutting the threads in the alignment it is at now. That is the material that is getting removed.
What are you wanting to clean out? If its a non stressed part then using a normal tap wont be a really big deal. I would not use a normal tap for any critical fastener. Something like and intake or accessory bolt holes is no big deal. But definately use a thread chaser for something like main bearing caps or head bolt holes. Just bear in mind that threads cleaned with a normal tap wont be able to take the same torque load due to the reduced thread depth and contact area.....
======End of post, begin my reply
Ok you reply is very good. I'm still not totally sold but since I no expert, you do make a good case. As to why I need to clean the threads out, they are rusted and full of old loctite etc and are for cylinder head, intake manifold and exhaust manifold bolts.
======End of paste from other auto forum.
12-20-2011, 07:58 PM #13
I noticed that you are talking about chasing threads in an old rusty engine block.
I should say that my experience is different than yours.
I will admit that if an engine rebuilder had some priceless vintage block that needed some thread restoring, he'd have a case for "ABSOLUTELY! NO TAPS! - use a thread chaser".
12-20-2011, 08:03 PM #14
I'm still confused, what the hell is a thread chaser?
Is it a form tap?
Honestly if you can't line up a tap into a hole, you're a ham fisted monkey. It lines itself up very nicely.
I don't have rigid tapping and start threaded holes on the machine all the time and never have a problem finish tapping them afterwards. Even with a cordless drill. They gage out just fine, even though I was ham fisting them with a drill and a tap, a cut tap, a real one, that can actually cut, lined up on nothing more than the threads I had already put in.
Sounds like BS to me, if a tap doesn't have to cut, it won't unless you force it to(you'd have to push it to the side while turning it in), then you'll probably break it anyways, and then we'll all laugh at you and make you clean a sump, and then you can figure out how to get the tap out, while we are still laughing at you.
12-20-2011, 08:09 PM #15
If the threads are really cruddy and rusty then you will damage the tap, not the thread. The tap acts as it's own lead screw and once it is in one full revolution it is not going to cut anything that is where it should be. If the thread is deformed and material is in front of the cutting edge it will be removed and it should be. If they are finding threads looser after cleaning the rust and such out the remember that the rust is part iron and yes it will be looser, but not because of the tap, but because metal has been removed by rusting.
I am in the power generation industry. When we disassemble a turbine we clean every thread. We start with a wire brush and if that doesn't do it we run a tap or die. It's the last resort because rust and grit will ruin a 500 dollar tap in one hole. Small holes we tap.
12-20-2011, 08:09 PM #16
12-20-2011, 08:29 PM #17
If I needed to clean up a thread, I'd look for a tap with the same thread. As I mentioned, I've never seen a "thread-chaser".
12-20-2011, 08:39 PM #18
12-20-2011, 08:40 PM #19
Internal ones look like this: Image Detail for - http://www.bikernet.com/news/images/PhotoID38562.jpg
Kind of a cross between a form tap and a dull standard tap..
I have used them, but a dull standard tap used with care, works just as well...
12-20-2011, 08:43 PM #20