Thread: Are zero clearance fences worthwhile?

Jill,
I found it reduces breakout.

Ian

As you might expect, close support right up to the carbide will reduce the chance of chipout. However I would be a bit cautious about having a melamine face on the sub fences in this scenario, because you need to reshape the end of the subfence every time you change bit profile, height, or fence position to control depth of cut to preserve the zero clearance.
With melamine, I would anticipate accelerating bit wear rates, and I would also be concerned about melamine chips jamming between the subfence and bit while preparing the zero clearance.
Personally I would stick with MDF sub fences, possibly using replacable insert blocks compound mitred between the subfaces for interchangability and replacability.

When you CNC Melamine, it turns into a white powder and is rather bit friendly.
I have never made a Zero fence from melamine though, always been lucky to have lots of perspex offcuts for it.
I make the 2 halves, butt them together and run them against the bit, raising the bit a tiny bit higher than the height of the job I am doing.
The beauty of a zero fence is your job will always be straight up against the fence and no chance of bumping the left side.
If I use another bit which is larger than the cutout in the first fence, I just run that bit through it as well but I always kept the ones I used most.
They lasted a lifetime
Cheers
Wolffie

Thanks everyone for your valued comments. Yes, reduction of tearout / breakout is the main reason, and is very nicely demonstrated in [ame="http://www.youtube.com/watch?v=EJ6u9YH1fBI"]this video[/ame]

The video says it all.

Hi Jill,
Cut the ends of your sliding fence on an angle (45 degrees) use a scrap piece of MDF same thickness as your sacrifical fence cut two sides at 45 degrees and place that in between your sacrificial fence an slide it up to the scrap piece. Saves haveing to replace the sacrificial fernce and you always have the inset for later projects.

Regards
Harold

Thanks for the suggestion, Harold, that's a good idea. Thanks too for posting the pics, but for the life of me I cannot work them out

Harold is suggesting to trim the ends of both sub fences at an angle so you can wedge replaceable inserts with matching angles in place with them. I originally suggested using a compound mitre as that also stops the replacable insert from moving vertically as the compound mitres hold it against the main fence frame and push it down to the router mounting plate. Either way means that you can swap out the insert when you swap bits or adjust the cutting depth, so you rarely replace the actual sub fence panels.

Hi Jill sorry for the quality of the shots. malb has explained it much better than I did, thanks malb
Jill go to this forum and check bobj3..
http://www.routerforums.com/router-b...-question.html

He has many posts on many things but if you check his uploads you will find alot on zero clearence fences

thanks to pal and malb. This week will have a go at cutting the sub fences at 45 degrees, and making inserts. Sounds like the way to go, but might have problems matching the exact thickness of mymelamine subfences ( 16.2mm) - it seems to vary with every piece I get from Bunnies.

Another thing, , if only using sliding fences and not the inserts, is it only necessary to do the zero clearance on the right hand side of the bit, rather than the whole bit?

Hi Jill
you could get a way with only doing the right hand side as that is where the chipout occurs but as a personal preference i would move the left side up to the edge of the bit without actually cutting the board.
Did you have a look at bob's inserts. On some of his he uses tongue and groove, in using that you could overcome the difference in the thickness of the melamine board.

Regards
Harold

Simplest way to get consistant sub fence and insert thickness it to get a piece of board that is oversize, rip it to desired width, cut a pair of sub fences from it, then cut as many inserts as possible from the remainder hen put them away for future use as the need arises. There will be some variation in sheet thickness from manufacturers batch to batch, very little sheet to sheet and virtually none within a sheet.