Power Tapping on a PM25?

i have a large Jet drill press with a built in tapping head, variable speed, instant reverse, I do 1/2” - 1” aluminum and 1/4” - 3/4” steel all the time.


here is a 12” x 24” x 1/2” aluminum, 253 holes, 127 of them tapped to1/2”-13 and 126 of the tapped to 3/8”-16.B7366172-A8F2-4454-BB9F-3879372B26D4.jpeg
 
you'll be fine, though I wouldn't use a keyless chuck as it may loosen when you're reversing the motor to back the tap out. Stick it in a collet and you'll be fine. Countersink the holes by a thread depth at least and use some good tapping fluid (tapmatic, anchorlube etc). Looks like you have a ton of space underneath the plate so stopping the motor in time won't be a big deal. Also, buy a decent 2 flute spiral point tap. You'll get those done in no time.

I've power tapped a lot, only time I ever broke a tap (a roll form too :( ) was when I failed to notice the edge of a rivet overlapping the hole, so the tap bottomed out and pulled the work up out of the vise. Still bummed about that and it was a couple of years ago!
 
The only drill chuck I have is a keyless. I ordered some 2 flute spiral point taps from MSC, but the box was partially opened and didn't contain the taps. :( I'm trying to get a response from them to address this.

The straight tap I have now measures 0.253", so I can use a 1/4" collet? Yes, I have a 1-2-3 block underneath which gives me plenty of room.
 
I did a 7x24" plate for my G0704 with 3/8-16 tapped holes and .251 reamed holes on offset 1" grids (138 holes each!). If you can lift the plate and leave room underneath, a good sharp sprial point will do the best job. If not, use a spiral flute tap to pull the chips out of the top. My experience is that spiral flute taps don't extract chips in aluminum as well as they do in steel and they are weaker (hence the recommendation for spiral point). Make sure the tap is clean after each hole and is well lubricated.

I was fortunate enough to use a large knee mill with a tapping head to do mine, but you should be perfectly fine if you go slow.

I'd recommend to consider drilling and reaming some .251 holes on the plate. You can drop 1/4" dowel pins in to quickly align your vise or other setups. Just make sure your pallet is indicated true before you drill them! My vise comes in at less than 2 tenths across the 4" jaw without any indicating necessary just by dropping two dowels on the table.
 
macardoso said:
I'd recommend to consider drilling and reaming some .251 holes on the plate. You can drop 1/4" dowel pins in to quickly align your vise or other setups. Just make sure your pallet is indicated true before you drill them! My vise comes in at less than 2 tenths across the 4" jaw without any indicating necessary just by dropping two dowels on the table.
Click to expand...

Thanks for the tip although I'm not sure I plan on leaving the plate on the mill table all the time. I'm not sure I want to lose the 3/4" vertical space. But, it doesn't hurt to add them. I don't have any reamers. I'll have to look into it. Thanks!
 
I found a solution! I just watched Abom79's video on youtube demonstrating the Flexarm GHM-60 Power Tapper and I want one! :)

Too bad it's almost $20,000!
 
$20G, a mere bag of shells, if you/we came into the machining scene expecting to save money, boy we all made a mistake............
 
Here's an indexing table I made with 1/4"-20 threaded holes, along with toe clamps I made. The larger holes are for centering and mounting on my rotary table, and the recesses on the bottom are for mounting in my vise. Best of my recollection, there are 122 threaded holes, and I power tapped all of them with a two-flute spiral tap. Totally uneventful. Just take your time and determine the coordinates carefully.

Regards

IMG_0274.jpg

IMG_0275.jpg

IMG_0276.jpg
 
P.S.: The indexing table in my above post is 1" thick.
 
You must log in or register to reply here.
Back
Top