What's new
What's new

Tapping quite a few holes in a flat bar of hot rolled steel

oceanobob

Plastic
Joined
May 18, 2014
Location
Oceano, CA
Took on a fab job for drilling & tapping 36 (thirty six) 1/2-13 holes in piece of 5/8" thick hot rolled plate: Flat Bar Dims 4" wide by 75" long by 5/8" thick.

Plate is about 55ksi yield - meets A36 as well as Gr50. Cold Roll too much $ as material is only 12' long, drop is too big.

~~~~~~~

Thinking of this method:
Sandblast the plate(s) to remove the mill scale

Machine avail is a vertical knee mill with a DRO. Has the larger table.
Holes are to be three repeating patterns of twelve each per pattern, the pattern O/A dim is about a little less than 20" distance.

Use 27/64" stubby screw machine drill bit to make the hole (following the pilot drill). Was wondering if I should hand (27/64") ream the hole to make sure it is round?

Lightly chamfer the start of the hole; use the tapping head with either a new spiral H3 tap or a new gun (spiral pointed) H3 tap.

Twelve holes thus made: swap the drill to the tap head and go back (DRO) and tap them.

Relocate the plate for the next group of twelve, repeat above.

~~~

They wanted one plate yesterday, but they really want three plates done.
 

memphisjed

Stainless
Joined
Jan 21, 2019
Location
Memphis
Do not need to blast or ream for those holes. Drill in mill or press. Flexarm would be first choice for tapping, second would be cordless drill. The cordless way you will need to add three small flats on your tap for the chuck to grip. Goes fast- gravy job.
If you have 300 holes the same, maybe move to an impact tap on cordless impact at around this number.
 

Ries

Diamond
Joined
Mar 15, 2004
Location
Edison Washington USA
36 isnt a lot.
I use my metabo cordless tapper all the time for runs of much more than that, doing a project now that is 325 holes, in material from 1 1/2" down to 3/8" thick, 3/8-16 threads, they are all coming out plenty straight using the metabo. Trick is its not really a drill- its really slow rpm, and high torque, and has autoreverse when you pull back- means it does much better than a higher rpm drill would.
Comes stock with different chucks made for taps, no grinding required.
602362840, Metabo GB 18 LTX BL Q I CORDLESS TAPPERS | Quality Tools & Accessories
 

memphisjed

Stainless
Joined
Jan 21, 2019
Location
Memphis
Unless the OP has really good spatial coordination, tap in the mill. I've been doing this a very long time, and I still don't trust myself to use a hand drill and tap true to the hole unless it's not at all critical.

Not a bad idea to tram the mill first if there's any question of it being out of square, but it doesn't sound like a super-precision job.

You could use a tapping block. Like most manual technics how you stand and brace tool to you and the part is crucial.
I do agree after re reading the op might not be fluent in tapping - and it is a bit harder to feel the tap and trust your self for level when you are running with a high torque drill.
Bright side is it is good practice, the tap is not going to break easily and will want to follow the hole. If you are slightly out of plumb it will let you know.
 

BT Fabrication

Hot Rolled
Joined
Nov 3, 2019
this is crap all, ive had 9 holes drilled and counter sunk per part by 20 parts.
holes drilling would only take 1 min a hole at most. so 30 min to complete drilling
then 30 min to tap it all. easy.
 

oceanobob

Plastic
Joined
May 18, 2014
Location
Oceano, CA
The drilling and the tapping (using the tapping head) went quite smoothly - me thinks the Drill and Tap DARP was the most straightforward.

The other issue is the strict layout tolerances on the hole placement. Which is not really related to the tapping. Thanks for the assistance!
 

oceanobob

Plastic
Joined
May 18, 2014
Location
Oceano, CA
Having the three types of tooling on hand...a question has arisen.

The mill will place the tool (spiral pointed tap or the other one the spiral tap) directly over the center of the completed 27/64 drilled hole. And this project is strict on the layout thus a vote for the mill vs the drill press.

But in reading the comments, and for other projects, the idea of using the drill press and/or a manual tapping drill sprang into the mindset and it appears the combination drill and tap (Drap?) is perhaps the only choice for the drill press as the drill press ability to put the tap directly over the center of the hole may be more toward happenschance.

Following the steel supplier delivery of the cut to length bar stock, I always ask for the drops thus I have some extra pieces to try out these differing taps. FYI the local steel supplier has a auto bandsaw with feeder and a plasma table and a shear and they like to prep the pieces, and we find it a great timesaver and many times we simply cant compete with their prices. Did some tests using the drill press on the drop.

The obvious finding was the less steps for the Drap (regardless of machine utilized mill or drillpress) was a time saver. And because my company also does 'field work', it is always good to think how something can be done while on a scaffold or a scissor lift etc etc.

~~~~~~~~~~~~~

Am I to conclude (again: Not for this strict layout project): if using a drill press, probably use the Drap? trying to get the drill press exactly in the center of the existing hole for the tap in one step - without taking out the tap and using a drill rod jig or similar- seems challenging. That hand held drill tool sounds pretty cool too. (FYI we jig two squares set at 90 to help with alignment when eyeball is the tool)...

Are there any tricks on aligning just the tap [not the Drap] in the drill press to the hole? eg allowing a little float when starting the hole....this plate is a bit over 6' long and is pretty heavy and may not be in the mood to float.
 

Garwood

Diamond
Joined
Oct 10, 2009
Location
Oregon
Having the three types of tooling on hand...a question has arisen.

The mill will place the tool (spiral pointed tap or the other one the spiral tap) directly over the center of the completed 27/64 drilled hole. And this project is strict on the layout thus a vote for the mill vs the drill press.

But in reading the comments, and for other projects, the idea of using the drill press and/or a manual tapping drill sprang into the mindset and it appears the combination drill and tap (Drap?) is perhaps the only choice for the drill press as the drill press ability to put the tap directly over the center of the hole may be more toward happenschance.

Following the steel supplier delivery of the cut to length bar stock, I always ask for the drops thus I have some extra pieces to try out these differing taps. FYI the local steel supplier has a auto bandsaw with feeder and a plasma table and a shear and they like to prep the pieces, and we find it a great timesaver and many times we simply cant compete with their prices. Did some tests using the drill press on the drop.

The obvious finding was the less steps for the Drap (regardless of machine utilized mill or drillpress) was a time saver. And because my company also does 'field work', it is always good to think how something can be done while on a scaffold or a scissor lift etc etc.

~~~~~~~~~~~~~

Am I to conclude (again: Not for this strict layout project): if using a drill press, probably use the Drap? trying to get the drill press exactly in the center of the existing hole for the tap in one step - without taking out the tap and using a drill rod jig or similar- seems challenging. That hand held drill tool sounds pretty cool too. (FYI we jig two squares set at 90 to help with alignment when eyeball is the tool)...

Are there any tricks on aligning just the tap [not the Drap] in the drill press to the hole? eg allowing a little float when starting the hole....this plate is a bit over 6' long and is pretty heavy and may not be in the mood to float.



Draps are tricky for tapping in manual machines because you often have to change RPM from drill to tap. If you're drilling at 600 RPM and catch the thread making parts then you gotta stop the spindle pretty quick. Or you're drilling at a compromise speed so you can react fast enough to stop the tap and reverse it.

When you have a heavy part and need to align a tap over the hole you can chuck a tapered rod in the drill chuck and push it into the hole to center it, then clamp and use the tap.

Usually taps center up the part well enough, but you can't move a 50lb part with an 8-32 so there's a time for common sense to be used.

YOUR SKILL determines the precision of the machines you have for the process at hand.

For me, a drill press pretty much just lives with a single flute countersink in it and that's all it ever does. I don't expect locations better than .02" or so using a drill press. Bridgeport is a within 5 thou process in my shop. I don't use a manual mill everyday. I'm a self taught machinist and manual mill is not my strong suit. I don't know all the neat tricks for speed and accuracy nor do I invest much into manual mill tooling because it's not a revenue generator for me. A Bridgeport can be very accurate, but you gotta have the skills to get there with it. When I need a quantifiable level of accuracy I use a quality CNC machine.
 

Nmbmxer

Hot Rolled
Joined
Jun 22, 2008
Location
VA
In a kneemill, I typically swap tools in a drill chuck then move after drill/csk/tap vs using one tool and moving to all the locations, then swapping tools, and cranking around again unless the pattern is really simple. For random dimensions swapping is faster for me. I can set a screw machine drill, csk, and tap on the side of the vise and swap them pretty quickly in my Jacob’s superchuck.

I never use a tapping head unless ALL I am doing is tapping, I like all my tools to be the same length if at all possible.

Sometimes it’s faster to rapid the table off to one end and chamfer all the holes with a cordless drill rather than crank around the pattern with a csk in the spindle. If I’m swapping parts in the vise between operations I’ll also chamfer with the cordless while the parts are on the bench.
 

Walter A

Titanium
Joined
Jul 7, 2007
Location
Hampton, Virginia
Took on a fab job for drilling & tapping 36 (thirty six) 1/2-13 holes in piece of 5/8" thick hot rolled plate: Flat Bar Dims 4" wide by 75" long by 5/8" thick.

Plate is about 55ksi yield - meets A36 as well as Gr50. Cold Roll too much $ as material is only 12' long, drop is too big
No sandblasting or reaming. Stack drill on mill with long enough TS drill to get thru several bars.
Take to drill press and chamfer both sided of bars.
Set up tapping head with tap. We have a drill press with a quick reverse tapping function. If you don't have that use a reversing tap head.
Tap all the holes occasionally checking with gage.
Blow out and you're done.
 








 
Top