I am trying to clean out some blind holes and really need bottoming taps to do the job right. I checked several places and it looks like bottoming taps are special and fairly expensive. I was wondering why I couldn't take regular taps and carefully grind the tapered ends down to make them like a bottoming taps. If I don't get the taps really hot when grinding them down, thus loosing hardness, it would seem like an easy and inexpensive way to get closer to the bottom of blind holes, like in the engine block. Thanks in advance for any advise.
Bottoming taps
- Thread starter wrndln
- Start date
I have done that very thing for bottoming taps. Like you say, be careful not to let the tap get too hot. Have a container of water handy to keep the tap cool as you are grinding it and you should be okay. It works fine for just a few holes. That would not work very long for production jobs, but in my case, I have more time than money. Don/WI
d.j. moordigian
Well-known member
Rusty... We do it all the , go for it , trust me. Having problems with the computer,
have had to restart 5 time in the last hour, mite be a few days. Dudley
have had to restart 5 time in the last hour, mite be a few days. Dudley
Special Coupe Frank
Well-known member
Just keep an eye for bluing at the end being ground; try to avoid that. Keep a big can of water at hand for dunking, and take your time.
When you get the end of the tap shortened to where you want it, chamfer the ends slightly, for easier starting, and make your last couple of cooling dunks into some clean oil.
In the old days, taps used to come in three legnths: starting, "finishing", and "bottoming"...
When you get the end of the tap shortened to where you want it, chamfer the ends slightly, for easier starting, and make your last couple of cooling dunks into some clean oil.
In the old days, taps used to come in three legnths: starting, "finishing", and "bottoming"...
Brentwood Bob
Well-known member
blow out the hole real good as you go. I like to use a penetrant/orwd40 as I cut. Used to do a lot of cast iron roof drains with broken bolts. got into trouble with no air on the roof to blow out the holes. tried a hand held magnet on a small diameter shaft. That worked for me to remove the chips. Used quarter turns to keep from powling the threads with chips.
Special Coupe Frank
Well-known member
Good point, Bob !
When I was doing my heli-coils a few weeks ago, I did not have air, so I used one of my magnetic bit-holder screw-drivers to clean-out the chips... a "stick magnet" would have been better, but you "use what you've got", eh ?
Frank
When I was doing my heli-coils a few weeks ago, I did not have air, so I used one of my magnetic bit-holder screw-drivers to clean-out the chips... a "stick magnet" would have been better, but you "use what you've got", eh ?
Frank
Rich in Tucson
Senior Member
For cleaning purposes, I prefer to make my own out of a well-fitting grade 5 or 8 bolt. Grind it flat or even make the end concave and cut four grooves or flutes along the the bolt.
Unless your bottoming tap is well worn, you risk cutting sound metal from the threads with a tap (and they were and are available in different sizes) and since most of the threaded holes I mess with are used and ~80 years old, I prefer not to risk boogering them up any further with a tap.
Unless your bottoming tap is well worn, you risk cutting sound metal from the threads with a tap (and they were and are available in different sizes) and since most of the threaded holes I mess with are used and ~80 years old, I prefer not to risk boogering them up any further with a tap.
Jerry Parr WI
Well-known member
Quick check shows regular and bottoming taps at the same price at McMaster Carr. I'm close so I get next day delivery.
http://www.mcmaster.com/#
http://www.mcmaster.com/#
just plain bill
Senior Member
Just Google cutting tools or taps for a of source reasonably priced cutting tools. There are companies such Enco or Rutland supply that have reasonably priced tools. Some companies sell taps that are made for cleaning up threads.
Chris in CT
Senior Member
hi wrndln, Yea, you can do that, but bottoming taps are available at the same price as plug taps. The difference between a plug tap and a bottoming tap is that the plug tap has a 5 to 7 thread lead (taper to size). A bottoming tap has only a 2 thread lead (you must leave this on your re-ground tap), so grind off the excess, but leave a 2 thread lead. Start your tap carefully in the hole you are trying to re-thread, or you will cross-thread it and make a mess. Do NOT use a lubricant in cast iron; DO use a thread cutting oil in steel and other metals. Good Luck!
Kurt in NJ
Well-known member
http://www.tooldiscounter.com/ItemDisplay.cfm?lookup=KAS971
there are taps, & dies for cutting threads, and there are thread restoring tools that do not cut the metal, they reform existing threads and clean them.
i have bought many tools from http://www.tooldiscounter.com/default.cfm?nav=inc/specials.cfm they have most of the best brands, very little of the cheap import stuff, some of the best prices on quality tools, it may take a while , do not expect your order the next day, brouse their vendor list and you will find tools that you thought you would never find.
there are taps, & dies for cutting threads, and there are thread restoring tools that do not cut the metal, they reform existing threads and clean them.
i have bought many tools from http://www.tooldiscounter.com/default.cfm?nav=inc/specials.cfm they have most of the best brands, very little of the cheap import stuff, some of the best prices on quality tools, it may take a while , do not expect your order the next day, brouse their vendor list and you will find tools that you thought you would never find.
Terry NJ
Well-known member
In the shops and toolrooms, this is done all the time. Nother secret! If you need .005 out of a nominal size hole hole, make a reamer from an old tap, one that has the same shank dia. as the threaded body. Taps generally run .005 over nominal size. By carefully hand grinding a "Diamond point" drill, one can remove .0025 on a side for a looser fit. Old, broken taps are seldom discarded, just put in a box for old, broken taps until they can render secondary service.
Terry
Terry
Larry Brumfield
BANNED
The best advice in my opinion is post #9, Rich in Tucson, above!
I would avoid taps unless the part you're working on does not require much thread strength, like maybe some kind of lightweight cover or bracket or something. In other words, just enough strength is needed to hold it on.
With a tap you may weaken the threads in the hole significantly if there are any slight distortions in those old threads from use.
Also, the tap you use more than likely will have slightly different specs from the tap that threaded the hole originally even though it is of the same diameter and threads to the inch. In addition, even if the tap is well worn or you make a reamer from an old tap, the specs may be different or come out different than original and you may still remove metal.
Moreover, I've never really cared for the so called thread restoring tools either.
Now if the threads in the hole are so screwed up that a tap is the only thing that will go through; you didn't have much to start with and may not have much when you're done. Time for an insert or a heli-coil .... or another part.
Just my opinion.
Larry B.
I would avoid taps unless the part you're working on does not require much thread strength, like maybe some kind of lightweight cover or bracket or something. In other words, just enough strength is needed to hold it on.
With a tap you may weaken the threads in the hole significantly if there are any slight distortions in those old threads from use.
Also, the tap you use more than likely will have slightly different specs from the tap that threaded the hole originally even though it is of the same diameter and threads to the inch. In addition, even if the tap is well worn or you make a reamer from an old tap, the specs may be different or come out different than original and you may still remove metal.
Moreover, I've never really cared for the so called thread restoring tools either.
Now if the threads in the hole are so screwed up that a tap is the only thing that will go through; you didn't have much to start with and may not have much when you're done. Time for an insert or a heli-coil .... or another part.
Just my opinion.
Larry B.
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George Miller
Well-known member
I agree with Larry. Best to keep taps out of there. Most people think a tap is just a tap. But there are differn't class threads. Which one do you have.