Cutting a clean hole

birdman · Jan 15, 2007

I need to create a bigger hole in my firewall for my new wiring harness. The hole right now is 1" diameter and needs to be 1 3/8 in. What would be the best method to get a nice clean cut.
I know plasma would be the best but, I don't have access to one.
Thanks

03COBRA · Jan 15, 2007

http://www.lowes.com/lowes/lkn?action=productDetail&productId=178363-28303-30120-K20L&lpage=none

This help?

jdevon · Jan 15, 2007

i used one of those on my firewall. worked well.

broncow72 · Jan 15, 2007

Have any electrician friends? If so ask if they have a hole punch. With he existing hole the holesaw will not work but a hole punch will. This site shows what they are.

birdman · Jan 15, 2007

That was my concern with an existing hole the pilot drill would be ineffective. I may be able to come up with something. On second thought I do have an electrition friend. Thanks

1975stroppebaja · Jan 15, 2007

broncow72 said:
Have any electrician friends? If so ask if they have a hole punch. With he existing hole the holesaw will not work but a hole punch will. This site shows what they are.

I'll second this suggestion. I used an electrician's hole punch to cut the hole in my new qtr panel for my front gas tank. They do a very clean job. Do borrow it though instead of buy because they're quite pricy.

mag409 · Jan 15, 2007

Depending on the difference in hole diameter, you can sometimes use a holesaw inside a holesaw. Cut a piece of 1/4 or 5/16 rod, depending on your holesaw pilot size, and put the 1" holesaw onto the rod and tighten. Slide the assembly into the 1.375" holesaw and tighten the setscrew leaving enough to go into your drill. You want to leave the 1" holesaw slightly longer then the bigger diameter. Slip it through the existing 1" hole and fire it up. with this setup you are using the outside diameter of the 1"holesaw as your pilot. Good Luck.

Naildriver111 · Jan 15, 2007

If you can find a way to align and attach a thin piece of steel over the hole, you could just use a hole saw. I tack welded a plate to the backside of my dash so I could drill a larger hole, but that was before having it painted.

birdman · Jan 15, 2007

Good Idea on the double whole saw I may try that I was also thinking of the other suggestion of tacking some sheet metal up and doing that way also.

bax · Jan 15, 2007

Find the hole saw you are going to use. Drill a hole in a peice of wood, say 3/4'' thick. make sure the peice of wood will fit in the area you want to drill. Line up the wood hole with the hole you want to drill. fasten the wood with screws and washers using some of the other holes close to the hole you want to drill. I am assuming that your truck is apart right now? Room to work I hope. The wood will act as a guide not letting the saw wander and eliminating the need for a center. sounds kind of weird but it works.

bax

bcrump5252 · Jan 15, 2007

I used a plazma but as u stated you dont have one, I think the only way your going to get a clean hole is with a hole saw. unless u dont care then I would use a sawzaw LOL

birdman · Jan 15, 2007

Thanks Bax. I do have plenty of holes to attach the wood and that does sound like it would work. Tonight my mother-in-law is here so I have all night to get this done no rush if you know what I mean. So I will be tinkering until its time for her to go. What a way to spend my day off.

scsm76 · Jan 15, 2007

A step bit would work well. They are harder to find in large sizes but they are available up to 1 3/8".
http://www.lenoxsaw.com/varibit.htm

67u13 · Jan 15, 2007

Harbor freight or Vatozone has a Unibit that would work just fine.

SteveL · Jan 16, 2007

uni-dit or step bit are the better drill to use. The best way is a KO set. Electricians and plumbers carry em. I have one on my work truck. They are a hydrolic puller which makes purfect holes.

BigO · Jan 16, 2007

If you have to buy a new drill bit, I would buy a UniBit (step bit). I love them! They can easily be used to enlarge an existing hole, make a clean cut, and can be used on other projects for drilling a variety of hole sizes.

deltarat · Jan 16, 2007

If you have a die grinder and a carbide bit, you can trace the sze hole you need around the existing hole.Then carefully ease up the the line with the carbide bit. The other suggestions are very good,it is just what you have that you can use without buying any new tools. You know how we hate buying new tools...lol

birdman · Jan 16, 2007

I went to Harbor Freight today and they did not have a big enough unibit and didn't know when to they would get one. I do have smaller unibits and this would be real easy if I had the right size. I will probably try one of the other methods tomorrow when I have time.

bax · Jan 16, 2007

a word of caution about using the Knock out tool. the hole you want is not really much bigger than the hole you have. If the fire wall was heavy guage steel then the knock out would work. However with lighter guage steel the tool may just roll the sheet metal back and not cut all of it clean. Good tool but it's not going to work for what you want to do. Only because the hole is close to the same size. If you had a 1/2'' hole it would work great.

Bax

Bax

scsm76 · Jan 16, 2007

http://cgi.ebay.com/Greenlee-MULTI-...8-36414-ave_W0QQitemZ4387517052QQcmdZViewItem

Cutting a clean hole

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