Notices
Marine Electronics Forum

Transducer Upgrade Needs Bigger Hole

Old 02-06-2012, 05:44 PM
  #1  
Junior Member
Thread Starter
 
Join Date: Oct 2011
Location: Lexington Park, MD
Posts: 2
Default Transducer Upgrade Needs Bigger Hole

I'm moving up from an AIRMAR through-hull with a 33mm shaft from one with a 31mm shaft. My problem would be a 31mm hole in my boat. I need to make the hole bigger without destroying my hull. Trying to over-drill an undersized hole in wood is usually a disaster and I don't expect fiberglass to be much better. Ideas?
MISCHIEF3800 is offline  
Old 02-06-2012, 05:52 PM
  #2  
Senior MemberCaptains Club Member
 
Join Date: Feb 2002
Location: North Charleston, SC USA
Posts: 22,073
Default

One way - get a long hole saw blade that fits your existing hole and a shorter one the diameter of the desired new hole. Put them on the same mandrel. The longer one wiill act as a guide through the existing hole to center the shorter hole.

Going from 31 mm to 33mm may not be possible with this method. A router with a template may be an option. I used this method to enlarge cup holder holes from 3" to 3 1/2" or something like that.

Or, just a rotary rasp in a drill motor and some skillfull handling might do it. There's a lip and caulk on the outside and a washer on the inside, right?
rwidman is offline  
Old 02-06-2012, 06:21 PM
  #3  
Admirals Club Admiral's Club Member
 
Join Date: Jun 2008
Location: Plymouth Ma.
Posts: 8,049
Default

5 min epoxy a scrap of wood on the inside of the hull, use the wood to center the new hole saw. After you start the hole it should guide in fine. Don't put too much epoxy on since you will have to remove the wood.
CMEBoston is offline  
Old 02-06-2012, 06:39 PM
  #4  
Admirals Club Admiral's Club Member
 
Join Date: Jun 2008
Location: Plymouth Ma.
Posts: 8,049
Default

Just use 5 min. Epoxy! And don't scuff or prep, you only need it to steady the centering bit for a short while! Usually I use an oops arbor, but you don't have enough size difference for it.
CMEBoston is offline  
Old 02-06-2012, 10:33 PM
  #5  
Senior MemberCaptains Club Member
 
Join Date: Aug 2002
Location: Surfside Beach, TX, USA
Posts: 2,500
Default

two millimeters? I'd use an abrasive cylinder on a RotoZip or similar to make it a two minute (1/2 beer) job.

In fact, the new transducer I installed last weekend called for a 60 mm (2-3/8") hole. I had a 2" hole saw, and a 2.5". Used the smaller one, and then ground the hole bigger in about 5 minutes with the abrasive bit and the blower running to keep plastic dust off my face.

Good light, good marks, and a light touch are all you need.
savage is offline  
Old 02-07-2012, 05:15 AM
  #6  
Admirals Club Admiral's Club Member
 
Join Date: Nov 2007
Location: Long Island, NY
Posts: 8,450
Default

2mm is what 3/32" (about 2 nickels stacked) - get out the round file - it won't take but five minutes to get it to the right size.
LI32 is offline  
Old 02-07-2012, 09:13 AM
  #7  
Senior MemberCaptains Club MemberPLEDGER
 
Join Date: Oct 2002
Location: mass/Point Judith, RI dockage
Posts: 11,842
Default

A trick that is used is to get two hole saws, one for the smaller size and one for the larger. The smaller one should be taller than the larger one.

Then, nest the two together (will look like a wedding cake with the smaller diameter taller than the wider one). The taller and narrower one will fit inside the existing hole and act as a guide for the larger one.

May not work for you since they are so close in size (may not nest together), but I've seen it work in other cases.
gerg is offline  
Old 02-07-2012, 10:55 AM
  #8  
Senior MemberCaptains Club Member
 
Join Date: Mar 2004
Location: Highlands, NJ
Posts: 2,011
Default

I would go the round file route. Might take a while, but better chance of not screwing up.
Fcal is offline  
Old 02-08-2012, 11:33 AM
  #9  
Senior Member
 
Join Date: May 2010
Location: North Palm Beach, FL
Posts: 1,314
Default

gluing a piece of wood to get the pilot started if the best bet outside of stepping the diameters on the mandrel(Which i dont think you can do with this close of a size)
GatorContender is offline  
Old 02-08-2012, 12:18 PM
  #10  
Senior MemberCaptains Club Member
 
Join Date: Mar 2005
Posts: 375
Default

Get a one inch dowel cut to about 3-inches. Drill a 1/4-inch hole down the center (use a lathe if you own one). Mount the dowel on your assembled hole saw bit. Wrap masking tape around the dowel until you have a snug fit in the existing hole. Then have at it with your drill. Easy-breezy.
dogfather is offline  
Old 02-08-2012, 05:44 PM
  #11  
Admirals Club Admiral's Club Member
 
Join Date: May 2010
Location: Puerto Rico
Posts: 1,126
Default

I just have the same problem.. Just change my Airmar B60 to a B164 that its bigger hole ... After thinking a lot how to do it I go with the abrasive bit and job done!!! works for me!
splinter25 is offline  

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are On
Refbacks are Off


Thread Tools
Search this Thread