Motorola ST-157 Hole Saw

[ASTROMODAT]

Motorola has long since discontinued their NMO hole saw tool, the ST-157, with no replacement. Does anyone know what the next best thing is? IMHO, the UNIBIT doesn't seem as good of a cutting tool as the old the ST-157, but that may be just my biased opinion, too! YMMV!

The Antennex X-ACT hole cuttter sure looks alot like the old ST-157. I wonder if Antennex are the folks who made the ST-157 for The Big M?

Question: Does anyone know if the X-ACT has outer cutters that scrape the paint off arond the 3/4 inch hole, so as to provide a better contact for the ground plane? I can't tell by the picture, and I have never seen an X-ACT in person.

Thanks, in advance, for any kind help on this!

ASTROMODAT

[Bill_G]

I always used a high quality electricians 3/4in hole saw with adjustable depth mandrel. The scrubbing lip on the Moto hole saw wasn't so much to remove the paint for a good electrical contact, as it was for deburring and flattening the hole for a better water seal. You'll notice the underside of an NMO brass ring has an O ring that you're supposed to grease. The brass doesn't contact sheet metal until the last tug of the wrench, and it's usually into painted territory. The ground occurs on the underside where the teeth of the mount bite into the sheet metal. There is little, if any, primer coat underneath, and the ground connection is theoretically protected from weather if your water seal is good.

The hole saw lip also doubles as a depth stop for the installer with the gorilla touch.

[Batwings21]

We have used these hole saws forever, I think originally they were from motorola, but i've gotten them and blades from tessco for years.

http://www.tessco.com/products/displayP ... ventPage=1

[ASTROMODAT]

The Ripley Tools HSK-19 looks to me like this is the antenna hole saw tool Motorola previously sold (ST-157), or at least as close of a match as I have seen. I'm sure this will be perfect, and the price is good, too (about $27 list).

Thanks for the kind help on this!

ASTROMODAT

[tvsjr]

I've drilled many a hundred antenna mount holes using that Ripley part. They work great.

[giguchan]

I use a Greenlee chassis punch, enough with the drilling already too messy. One small Bit to get the Punch through the roof and the rest is pure magic. One you do this you wont want to use a drill again.

[Batwings21]

I use a Greenlee chassis punch, enough with the drilling already too messy. One small Bit to get the Punch through the roof and the rest is pure magic. One you do this you wont want to use a drill again.

This requires access to both sides of the hole, a luxury not always available. No need to drop the headliner on a car when you can pop one in from the top and fish it out the side.

[giguchan]

Hello,
This is also true.. I just like the nice clean hole it makes... removing the HB, while might be a PITA is normally not that big of a deal-when it can be done easily i guess.
Alot of the vehicles have audio/video devices(attatached to the HB that might make it more diff to utilize a Chassis punch.. I guess then it would be ok to use a hole saw..

[fineshot1]

I either use a standard 3/4 inch hole saw or the Antenex HS34 along with ordering the HS34RB replacement blades
and they both have served me well.

[motorola_otaku]

No need to drop the headliner on a car when you can pop one in from the top and fish it out the side.

But then how are you supposed to split-loom the cable and zip-tie it neatly out of the way? ;p

Sort of on-topic: whenever possible I use 3/8'' NMO mounts like these. While they do pretty much require you to have access to the bottom of the hole, you can pop said hole with any ol' 3/8'' drill bit AND they're sturdier than a 3/4'' mount thanks to the larger underside surface area.

[Bizkitjmd1]

I use the Antenex HS34 and it works great, it even scrapes some of the paint away around the hole for a better ground plane.