How to chamfer??

[southtexas]

I joined the crowd and bought Smart TabSX and have been reading a lot of old posts from y'all about installation. I think I understand most of it but don't know how to "chamfer". I even looked it up in the dictionary but that was no help...further proof that books are worthless. Thanks for any tips.

 

[Tim Frank]

Re: How to chamfer??

It is roughly equivalent to bevelling, but a bit more specific.
Usually it refers in metalwork to breaking the edge where two surfaces meet (generally meeting at 90 degrees, the chamfer would be at 45 deg). You can do it with a file. a milling cutter, or several other ways.....in soft metals it is not hard to do with sandpaper.

 

[windsors03cobra]

Re: How to chamfer??

 

[Moody Blue]

Re: How to chamfer??

I suspect you are referring to instructions to "chamfer the drilled hole".

This process puts a small angled edge on the perimeter of the hole. The purpose is to minimize (not eliminate) the possibility of cracking the gelcoat when you drive the mounting screws in.

You can achieve the chamfer in a number of ways. Drill the required hole size first. The proper technique is to use a "countersink". They can be purchased at most woodworking or metal working supply shops. Use a SLOW RPM in a hand drill using LIGHT pressure. You want to remove a slight amount of material from around the perimeter of the drilled hole.

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drilled hole chamfered hole

If you a careful (you are warned ) you can use a drill bit several sizes larger to accomplish the same thing. Trouble with using the drill bit is that it tends to chip and grab easily so a higher rpm and light touch is required. If you're not careful, the bit may catch and pull itself into the hole thereby making the hole too big for the screw.

 

[garry454]

Re: How to chamfer??

Save your money on the chamfer bit. If you are only going to chamfer your install holes, simply grab a drill bit maybe 2x the dia of the drilled hole, and follow me here, drill the hole with the drill running in reverse using light pressure.

I know it makes no sense, but it will work, and it works quite well in fiberglass. Makes a nice smooth chamfer, and works slow enough that you don't have to worry about cutting too deep, and it will not chip the gel coat at all.

If you are mounting these on an aluminum hull, then you will need a chamfer bit, but those Vermonts just chatter like crazy.

 

[southtexas]

Re: How to chamfer??

Thank you all for the advise. I am going to mix your suggestions and do this:

drill the hole (counterclockwise) with the recommended bit to depth of screw. Then I am going to use a larger bit, maybe 2x original size, and drill only a small way into the existing hole (counterclockwise) to chamfer it.

Is that correct?

 

[Mark_VTfisherman]

Re: How to chamfer??

.....those Vermonts just chatter like crazy.

That's cuz it gets so cold here

 

[Utahboatnut]

Re: How to chamfer??

I would just get the chamfer bit it is a very nice tool to have around anyway. Anything you mount on your boat will require you to do the same thing, plus it will work on any other hole you drill into something even not related to your boat. It will take the burrs off holes drilled into metal it works well for countersinking into wood, fiberglass, plastic, etc. The key is to use slow speed and light pressure or yes they will chatter. I have even done a number of holes just by turning the bit with my hand. The oversive drill bit will work but if it catches you will have a mess on your hands. Drill your holes with a GOOD sharp bit, chuck the chamfer bit and go real slow drill speed to get the chamfer depth you want and your done. Don't push hard at all those bits can bite if you get too forceful with them. I have used them for 20+ years in the carpentry field I prefer them over the all in one drill/counter sink as they never break like the all in ones ALWAYS do.

 

[southtexas]

Re: How to chamfer??

Excellent info. Thanks to everyone. I'll post some pics once I get them installed.

 

[garry454]

Re: How to chamfer??

texas, yeah you got it right. By using the drill in reverse the drill cannot catch and make a mess of your gel coat because the flutes are made to cut only in the clockwise direction.

It will make a smooth uniform chamfer, no chipping. Doesn't make sense, but it works.

I am a machinist by trade, and I have probably 20 different chamfer mills in my tool box, 1 flute to 8 flutes, 82 deg & 90 deg, but when it comes to chamfering a hole in FG, I still prefer to do the reverse drill method. It just works.

Good luck with whatever you decide, you are going to be amazed at the improvement the Smart Tabs make on your boat!!

 

[Mark_VTfisherman]

Re: How to chamfer??

I would just get the chamfer bit it is a very nice tool to have around anyway. Anything you mount on your boat will require you to do the same thing, plus it will work on any other hole you drill into something even not related to your boat. It will take the burrs off holes drilled into metal it works well for countersinking into wood, fiberglass, plastic, etc.....

Countersinks make a nice cut and are a lot less risky than a drill bit.

I would get the countersink bit too. I always have one or two on hand.