Tapping Technique Treatise

Post by **ARCHINSTL** » Sat Jul 22, 2006 1:48 pm

This is a fascinating and very informative link on taps I found on TN. It is from Virtual Machine Shop, which is worth exploring as well, especially for people like me who have had no formal training in machine shop procedures (I know - I operated a bicycle shop for 30 years, but the extent of "machining" 99.9% of shops do is cutting/chasing threads, facing fork crowns and bottom brackets and minor hole tapping/cleanup, with an ordinary tap/die set and some bicycle-specific taps/dies/tools).
An example of just a cursory perusal of the info revealed that there are 3 types of "ordinary" taps: I had thought there was but one - the tapered tap....actually 3: Tapered, plug, and bottoming...would have been helpful in many instances to have known of the other two....

ANYway, here is the link to the taps' info:
http://www.jjjtrain.com/vms/cutting_too ... tap.html#6
Tom M.

shogun · Post by **shogun** » Sat Jul 22, 2006 3:44 pm

very nice, i also have a shop and i operate the machinery but have not had any training, just with the hydraulic stuff and cars

Post by **ARCHINSTL** » Sat Jul 22, 2006 10:42 pm

Do you own a bicycle shop, or were you speaking of your home shop?
Cool if it's a bike shop - MootsMan works part-time in one, and someone in Chicago who very infrequently posts is also a wrench at a store.
Tom M.

jetswim · Post by **jetswim** » Sun Jul 23, 2006 9:58 am

Yeah that's a great website! Did you read the article by Jay Leno? I have immense respect for machinists. One time driving in Mexico with my VW bus I had adjusted one of my valves too tight and right near Chiapas the spark plug shot out of the engine! Turns out the previous owners had stripped a cylinder hole and then put in a heli-coil as a fix. Well it popped out and I needed a machinist to repair as I couldn't find a heli-coil anywhere. It wouldn't have worked anyway because the hole was stripped! I went to one place in the village( drove there on three cylinders ) and they were rebuilding engines all over the compound. There were guys everywhere taking engines apart and rebuilding them. Really cool to watch but they were too busy.
Finally found a machine shop and the guy came out, measured the stripped hole and went back in the shop. He came back out about ten minutes later with a bronze heli-coil he made and tapped a new spark plug hole very carefully with a magnet to catch all the filings from going in the engine. Then he screwed in the heli-coil and $20 bucks later I was on my way again! That lasted two years until I finally rebuilt the engine and replaced my crappy heads.
The machine shop near the town I live by is all but abandoned with some equipment still there. Sad to see.......

Typrus · Post by **Typrus** » Sun Jul 23, 2006 11:00 am

I have about 4 in the smaller of my local towns and maybe 10 in the Fort... The one I am using did a great job on my crank and block. Figure I'll have them do the rest of my machining... I'll likely shell out the $200~ to have them clean up my gasket-match job. I'd like to see it done right. They applauded my job, asked how many I'd done before, and were shocked when I said this was my first. Not quite pro, but good...

Errrrmm.... Heli-Coil?

Post by **ARCHINSTL** » Sun Jul 23, 2006 1:13 pm

jetswim wrote:Yeah that's a great website! Did you read the article by Jay Leno? I have immense respect for machinists.

Yes - it is a great article by Leno. And it is certainly correct!
Tom M.

takza · Post by **takza** » Mon Jul 24, 2006 5:34 am

Got a link for the article by Leno?

takza · Post by **takza** » Mon Jul 24, 2006 5:39 am

jetswim wrote: One time driving in Mexico with my VW bus I had adjusted one of my valves too tight and right near Chiapas the spark plug shot out of the engine!

I had a VW bus in Mexico and was doing fine till I went down behind a dam on a steep gravel road and had it start rocking side to side trying to get out...made it, but it chewed some teeth off the side gears in the diff. It would act weird on corners...with the back end moving side to side as the teeth skipped.

Ended up at a VW place in Mexico City to have the spider gears replaced...had chips all thru the trans...made it back and drove it awhile....maybe 5K miles.

Post by **ARCHINSTL** » Mon Jul 24, 2006 12:41 pm

Leno's article:
Just go to the link posted above, then click on "Library" (at the top), then "Home," and finally "Leno's article."
Tom M.

takza · Post by **takza** » Tue Jul 25, 2006 5:36 am

Interesting....got some air scoops made for that VW van in Mexico...just stopped at a shop in some town...and managed to sign language the guy into understanding what I wanted...and he made them while I waited. Took about 1/2 hour from stopping to driving away with them mounted on the van. $12 US.

kamiphloj · Post by **kamiphloj** » Sat Aug 12, 2006 11:02 am

That is a good article.I will offer a few more tips.
If you go to your Yahoo search up top,type in MSC.That will get you a big industrial supply house.They sell everything.Hardcopy catalogue is about 4 inches thick.Tools,machines,taps,tapping fluids,fasteners.Take plastic,same day ship.Usually get things in 2 days.They sell chrome moly tube,bronze,aluminum,welding supplies.
The spring loaded tapping guide they show is a good doohickey.Greatly reduces tap breakage.pretty cheap,too.There is another style of tapping guide that is a tee-handle tap wrench that slips into a base and holds the tap square to a surface.
I like to start by using a center drill.They are a stubby drill made to put the 60 deg center hole in a part.They don,t walk around.You may prefer a spotter drill to start the hole.Center drills have a tip that can be broken off.
I also chamfer the tap drilled hole with a contersink or just going deep with the center drill.Do this before tapping.It eliminates a raised burr at the tap start.If you do it later,the first thread will be deformed and you will have to retap.
Lubrcation is critical.The material specific fluids offered in the MSC book work great.WD-40 is good in aluminum.The black nasty sulpher oil like plumbers use to thread pipe is easy to find and works good in steel.In polycarbonate,go slow,use water.Breaking the long carbon chains releases a lot of heat.

Every chance I get,I use a 2 flute spiral point tap.They follow themselves thru the hole better.They are less likely to break.On through holes,they are always the choice.They push the chips in front as they go thru.Blind holes that dont need threads to the bottom,they are still good,but youll have a little chip ball to pick out.4 flute taps,go easy,and maybe every turn,sometimes less,you will feel slight resistance from the chip.Gently back the tap up a quarter turn or so,breaking the chip.Go easy,some back and forth may be necessary.A little chip can bind and chip the tap.Back out and clear your chips often

Good luck,kamiphloj