rebuilding after the crash

Its a gun tap. The "gun" comes from the grind on the tip. It "shoots" the chips forward. It is made for through holes. It is literally the worst tap to use in a blind hole. All the chips get piled up ahead of the tap and binds it worse than a normal hand tap.

 

Roger said just the opposite. The design of the tap is that it removes the chips so it wont bind. Whatever it is the tap worked great. I would use it again. The holes were tapped with the assist of a center in the mill. They were tapped the holes were blown out then the tap ran down again. the sites on taps seem to focus on machines tapping the holes. we did it by hand. that may be why it worked so well.
I like tight group for my 45 reloads.
I'm using strange products for my axle. Jim at chassis service is a dealer. You know were he is located. If you need his number pm me.

 

I’d never argue with someone with far more experience than I have. If it worked, he’s right.

I wonder if that two pass hand tapping operation was why it worked. If the gun tap pushes the chips down in to the hole, then blowing them out would help the tap fully bottom on the second pass, where it may not have on the first. As long as the hole is deeper than the bolt by at least two threads, it seems like bottoming or gun tap should both work ok, but if I understand correctly, the gun tap eliminates the need to constantly back the tap out 1/4 turn to break the chips loose.

Reading that second link, now I’m wondering why not use the thread forming tap instead of the thread cutting tap. That would seem to be stronger still in aluminum. Maybe harder to do in a blind hole? Maybe just overkill?



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I thought some of the same things. As I ran the tap down it cut exceptionally good. As I reversed rotation to break the chip I couldn't feel anything. After I blew out the hole the tap turned about one more turn if that. After I read the tapping info sites it had me thinking about thread forming taps. I have never seen or used them.
The threads on the studs doesn't go to the ends.

 

The thread forming tap is used in a powered operation, not by hand with a tap wrench. It is held tight in a collet and the feed and speed must be controlled, cutting oil is used (a flow of oil, but not enough to flood the operation) and controlling the depth of travel is important to prevent breakage.

 

From the pictures and descriptions, I’m pretty sure Roger and his shop could handle it.



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Thanks go out for sharing all this tapping info. I find it interesting and have learned some new things.

 

I am not here to say one way is right or wrong. I was taught by a long time machinist, that any time a blind hole is tapped using a mill to use a spiral fluted tap. Be generous with the cutting oil, unlock the quill and let the tap draw itself into the hole. The flutes of the tap draw the chip out of the hole and the threading is a single pass operation.

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i should have been more clear on my post. I used the mill with a centering tool in it to help keep the tap straight. I ran the tap by hand as I kept steady downward pressure on the tap with the mill. slow yes but effective. im not good enough to try power tapping holes in my block.

 

Smart man!

Tommy

 

Power tapping is definitely intermediating. I wouldn't have done it with out guidance.

It is really neat to watch it happen though.

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Your comments pretty much sum up the reason for my last post, it can be scary and even more importantly here, the job is on a $$$$ aluminum hemi block. A through hole is one thing but with a blind hole Clint Eastwood comes to mind- “Do ya’ feel lucky...?”

 

this is off topic from Brian's hot rod, but since we're talking power tapping: back when I was a machinist, we did a lot of power tapping.
It could be nerve-wracking. Especially when working on a part that I already had many hours invested in and it was getting close to being done. Spiral flute taps were good for getting the job done when power tapping a blind hole, but if you broke one off they were hard to get out. We had tap extractors that were a tool with strong hardened steel fingers that wood push down into the flutes of a broken off tap and you could use them to twist it out. That worked with straight flute taps, but not spiral! For a broken spiral tap I would pound on it with a punch and hammer and try and shattered into little pieces that I could fish out. worst case scenario we had to send the whole part to a EDM shop and have it burned out.
When power tapping in the mill, I would leave the quill unlocked and let the threading draw the quill and the tap down into the part. The scary part was as it neared the bottom I would flip the electric switch for the motor on the mill into reverse. But it didn't reverse instantly it would come to a stop over a couple of revolutions and then reverse. If you judged it wrong, you could be in trouble. I also power tapped on the lathe. I would have the workpiece in the chuck of the lathe. And then put the tap in the tailstock. I would leave the tailstock unlocked from the weighs, and the tap would just draw the whole tailstock towards the workpiece as it was tapping and then when I reverse direction it would push it away. I always was concerned about breaking a tap during that operation as well.
I usually measured and figured out ahead of time how far the tap would be able to go in and I would mark it so that I would know when to reverse.

 

I power tap frequently. Never gorilla the collet to the tap! I also have a tapping reverser. Rarely use it because it has quite a bit of length, and to be honest, a zeroed hole with the correct hole diameter rarely gives me any problem.

 

With 50+ years in machine shops myself, I'm finding this discussion of tapping interesting also.
Hemi Joel, if it took 2 revs for your mill to reverse it must have been on single phase??
My Bridgeport is on 3 phase as I was lucky enough to find a shop where 3 phase was available merely by having at least one 3 phase motored machine of at least 7.5 hp to justify it
When I flip that switch, reverse is instantaneous

 

I had a conversation with hemi joel about weight savings. He knows how to make things light. His 67 hemi four speed gtx that runs in the fast racing series goes in the tens on bias ply 14 inch poly glass gt tires. Its lightened to the max yet appears like a concourse restored car. He told me he runs a zero gravity battery that weighs only 7.5 lbs. His coupe had no problems on drag week running it. The battery is a lithium ion 750 cranking amp. He mounts it on the inner frame rail close to the starter. The added benefit is removing all the heavy cables for additional savings. So without hesitation I'm into a battery relocation project. With just the pieces I have removed I'm over 50 lbs. I will easily hit my goal of removing 100 lbs. Now I need to look for the next hundred. That's going to be tough. Remaking the gas tank out of aluminum will save about 15 lbs for a start on that goal.

 

I'm curious how you'll do the cutoff switch, and meet the letter of the rules. Mostly because I want to do the same thing, but haven't figured it out

 

The shut off switch will be moved up near the battery. A chromoly hollow rod will go from the trunk to the switch. I will have to get creative. I may have to use a bell crank somewhere to make it work. I might also have to put a few drilled brackets on the frame to act as supports for the rod. The switch will still function from the rear of the car following the rules. The rule says the cars power has to have a way of being shut off at the rear of the car. It doesn't say were the switch has to be mounted.

Another thing about this battery idea is the fact that if they start on fire conventional fire suppressants wont work. I plan on putting a t fitting into my halon system for a nozzle to be pointed at the battery. My fire lines already go down the inner frame rail right were I plan to put the battery. This will be easy to do for extra safety. My son works on some of the new electric cars at chrysler. He says halon and its replacements will extinguish a battery fire.

 

That's what I thought, then I read the rules again...it says the switch "must be installed on the rearmost part of each vehicle". I could not figure out an easy way around that...I put mine behind the tire, but a couple feet forward of the rear panel of the body.

The rule:

8:4 MASTER CUTOFF
Mandatory when battery is relocated, or as outlined in Class Requirements. An electrical power cutoff switch (one only) must be installed on the rearmost part of each vehicle and be easily accessible from outside the car body. This cutoff switch must be connected to the positive side of the electrical system and must stop all electrical functions including magneto ignition. The off position must be clearly indicated with the word “OFF.” If switch is “push/pull” type, “push” must be the action for shutting off the electrical system, “pull” to turn it on. Any rods or cables used to activate the switch must be minimum 1/8-inch diameter. Plastic or keyed switches prohibited. Switches and/or controls must be located behind rear wheels on rear-engine dragsters.

 

Looks like I'm going to have to get more creative than I thought.

 

Have you seen this battery cable? It feels like a piece of rope its super super lite. I have it on the Skairlane works great. I also run a lithium battery its 6.4 pounds. Been running it 3 years with no issues. My car is 15:1 compression wings it rite over. I put it to the test also I very rarely prime it to start it.

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Thanks. I will be looking into that. I will also see if they are at the upcoming pri show.

 

Brian, it looks like you will need either a two pole cut off switch, or a separate cutoff switch hooked up to the same linkage to ground the magneto

 

“Switch must be installed on the rearmost part” sounds clear, but then “rods or cables used to activate the switch” seems to allow for the switch itself to be mounted elsewhere, as long as the switch handle is accessible and there is an 1/8” rod or cable.

Is there someone who can clarify this rule?



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I will be calling nhra and jim at the chassis shop.
I have never ever had a tech inspector even look at my kill switch.

 

The tech inspector at the track you're trying to race at, is who gets to interpret the rule. Do you play it safe, or come up with a good line for him?

 

Only the control for the switch needs to be at the rear of the car. So they know where to go to shut it off. Nobody cares where the actual electrical component is located. Many cars use a rod or a morse cable to operate the switch.

 

well that's good to know.

English is difficult.

 

Examples like this abound in the rules. You'd think they could be more concise.

 

Here is how I do mine. The lithium battery is on the inside of the frame rail by the transmission. The cutoff switch is under the driver side floor, so I can operate it from inside the cockpit if need be. The 5\16 x 16 ga 304 stainless tube weighs 1 pound and operates it fine. There is only a couple feet of cable total. This set up spins the 13.5 to 1 Hemi over like the plugs were out of it.