Tap 1/4” steel
- Thread starter Rc_Guy
- Start date
dr_clyde
Well-known member
By hand I assume?
Blind holes or thru?
Just one hole or lots?
I would recommend a tapping block to get started. That will keep the tap straight, which is a much bigger deal on thick stuff. If your tap starts crooked, you'll eventually bind up and not be able to go farther. A tap block will help keep everything square with the world.
Unless you're tapping a blind hole, I highly recommend spiral point HSS taps. Personally I use Butterfield, but any industrial brand will work. These push the chips ahead, unlike a hand tap. This means you don't have to stop, break the chips and clear out the flutes. The downside is they want to start crooked unless held in a machine spindle or with a steady hand/tap guide. If the hole is blind, a spiral flute tap will do the same as a spiral point, just in reverse.
Use dedicated tapping fluid. My favorite is Mike-o-cut, but tapmatic, tap magic or even the Rigid pipe threading oil will work. Don't use engine oil or penetrating oil. WD-40 works on aluminum, but I don't recommend it for steel.
Blind holes or thru?
Just one hole or lots?
I would recommend a tapping block to get started. That will keep the tap straight, which is a much bigger deal on thick stuff. If your tap starts crooked, you'll eventually bind up and not be able to go farther. A tap block will help keep everything square with the world.
Unless you're tapping a blind hole, I highly recommend spiral point HSS taps. Personally I use Butterfield, but any industrial brand will work. These push the chips ahead, unlike a hand tap. This means you don't have to stop, break the chips and clear out the flutes. The downside is they want to start crooked unless held in a machine spindle or with a steady hand/tap guide. If the hole is blind, a spiral flute tap will do the same as a spiral point, just in reverse.
Use dedicated tapping fluid. My favorite is Mike-o-cut, but tapmatic, tap magic or even the Rigid pipe threading oil will work. Don't use engine oil or penetrating oil. WD-40 works on aluminum, but I don't recommend it for steel.
txvwnut
Well-known member
^^^^^^ What he said.
Boogerman
Well-known member
Edit: Dr Clyde covered it pretty well while I was typing!
How many holes, and is it a through hole?
Tapping a hole is pretty easy. First, drill it to the correct diameter. Use a tap chart, and the size of bit for the class of thread you want. That's the reason there's numbered and letter bits, to get the precise size. Then, it's just a matter of starting the tap at 90 degrees to the surface, and threading it in. Use a high quality high speed steel tap. Coat the tap with cutting oil. If you're just doing one hole, and you're not particular about thread class, just eyeball the tap for squareness, or use a square or really anything with a 90 degree angle to check that you're doing it straight.
If you're doing precise work and the workpiece is small, I recommend tapping in the drill press or milling machine. On the drill press, just put the tap in the chuck, put a small amount of down force on the quill, and turn the chuck by hand to thread the tap in. On the mill, I use a spring load tap chuck that allows the tap to self feed into the work.
Another option is a tapping fixture, I have a Phase II, that holds the tap square to the work, and has a crank to turn the tap in.
Many people advocate turn the tap backwards and forwards to break the chips free. You get a better thread if you just thread it in, and if you have a good sharp tap and cutting oil, it's unnecessary. If needed, blow a bit of air down through the flutes in the tap to clear the chips out the bottom of the hole.
One trick for beginners that don't want to invest in tap guides or a tapping fixture is to drill a hole through a 2x4 block with a drill press so it's square. Use that block to hold the tap to start it square. You can make more permanent ones by using steel or aluminum blocks, and for production work, could use hardened steel drill guide inserts.
How many holes, and is it a through hole?
Tapping a hole is pretty easy. First, drill it to the correct diameter. Use a tap chart, and the size of bit for the class of thread you want. That's the reason there's numbered and letter bits, to get the precise size. Then, it's just a matter of starting the tap at 90 degrees to the surface, and threading it in. Use a high quality high speed steel tap. Coat the tap with cutting oil. If you're just doing one hole, and you're not particular about thread class, just eyeball the tap for squareness, or use a square or really anything with a 90 degree angle to check that you're doing it straight.
If you're doing precise work and the workpiece is small, I recommend tapping in the drill press or milling machine. On the drill press, just put the tap in the chuck, put a small amount of down force on the quill, and turn the chuck by hand to thread the tap in. On the mill, I use a spring load tap chuck that allows the tap to self feed into the work.
Another option is a tapping fixture, I have a Phase II, that holds the tap square to the work, and has a crank to turn the tap in.
Many people advocate turn the tap backwards and forwards to break the chips free. You get a better thread if you just thread it in, and if you have a good sharp tap and cutting oil, it's unnecessary. If needed, blow a bit of air down through the flutes in the tap to clear the chips out the bottom of the hole.
One trick for beginners that don't want to invest in tap guides or a tapping fixture is to drill a hole through a 2x4 block with a drill press so it's square. Use that block to hold the tap to start it square. You can make more permanent ones by using steel or aluminum blocks, and for production work, could use hardened steel drill guide inserts.
Leon bee
Well-known member
75 years old and can't recall ever seeing a thread tapping block. I'm gonna get me one.
mreisner
Well-known member
Leon bee
Well-known member
Do you clamp that thing on? Or just hold it after hole is started?
C-clamp works.
dr_clyde
Well-known member
Depends on the part.
I usually start the thread, then if I need more clearance, I'll slip off the tap wrench and pull off the block, then keep going. If it is a fairly shallow depth of thread, I just leave the block on.
dnschmidt
Well-known member
If through hole I also recommend a gun tap (spiral point tap). I use a Milwaukee corded drill with a key chuck or the really good all metal Japanese keyless chuck Milwaukee used on their Magnum drills to actually do the tapping. I've placed a bubble level on the back of the drill to get it fairly straight and power tap the hole if I've got more than one hole to drill and tap. I use Anchor Lube or Boelube on the tap but Tap Magic works fine as well.
Wamsutta
Well-known member
I never heard of one of those things until now. There's been many instances where I could've use one.
I've made a few with just drilling a hole in some square tube when I had a bunch if holes to tap, especially at odd angles.
I’ve showed this picture on this site before but maybe it deserves to be repeated in this thread.
Big Gator drill guide (made in USA) clamped to the axle on my pressure washer in order to cross drill a hole for a cotter pin.
No way I could do this as easily or well by hand and eye.
Axle is welded to the frame so a lot of disassembly would be necessary to fixture this in a drill press.
Big Gator drill guide (made in USA) clamped to the axle on my pressure washer in order to cross drill a hole for a cotter pin.
No way I could do this as easily or well by hand and eye.
Axle is welded to the frame so a lot of disassembly would be necessary to fixture this in a drill press.
Wamsutta
Well-known member
I'm assuming you had a drill press to get the hole straight in the square tube.
Wamsutta
Well-known member
That thing is bichin. I gotta have one.
Hand drill is fine too. Easy to drill reasonably straight on a bench vs under something in the dark with arm stretched out.
BillK
Well-known member
I would have been done quicker than it took to type the question. Just make sure you have a sharp tap and use tapping oil if you have it. If not 10w30 will work just as well.
Sometime I cheat and use a drill bit just a tiny bit bigger then what's stamped on the tap for thicker steel. By bigger, I mean just the next tiny increment in size. For example a 1/4-20 hole says to use a #7 bit (ie .2010). For 1/4 thick, I'd choose a 13/64 bit at .2031 which is the next bigger drill bit on the chart.
A broken off tap will ruin your entire day.
This assumes it's just a general shop project and not something super critical.
Skyman
Well-known member
More tools I didn't know existed or that I needed. This forum is hazardous to the wallet.
mreisner
Well-known member
Ain't that the truth!
rdoty
ALLIANCE MEMBER
Don't use cheap taps - the ones you get in sets from the big box stores or Harbor Freight. Pick up two or three 1/4" high speed steel industrial taps. Don't get cobalt or carbide taps - they are brittle and tend to snap unless you are using them in something rigid like a milling machine.
Make sure the tap is sharp. As noted above, make sure the tap is perpendicular to the surface. If using a regular tap wind it backwards periodically to break the chips.
Don't force the tap - that is how you break them. A good tap running straight shouldn't require that much force. If it gets hard to turn, stop, back it out a turn or two, and try again. If it is still hard to turn, back it out and figure out what is going on. A broken tap is like a broken bolt - except it is too hard to drill out...
Based on recommendations here in Garage Journal, Harry Epstein is a great place to get taps.
Make sure the tap is sharp. As noted above, make sure the tap is perpendicular to the surface. If using a regular tap wind it backwards periodically to break the chips.
Don't force the tap - that is how you break them. A good tap running straight shouldn't require that much force. If it gets hard to turn, stop, back it out a turn or two, and try again. If it is still hard to turn, back it out and figure out what is going on. A broken tap is like a broken bolt - except it is too hard to drill out...
Based on recommendations here in Garage Journal, Harry Epstein is a great place to get taps.
RTM
Well-known member
I’d just open the two links of chain drop them thru, and close again. Just need a big enough chain.
Edit: or maybe not, forgot about 1/4” thick, those don’t look that beefy. Chain that would fit would be too beefy, and welded.