Thread: Accurate countersinking into masonite

This past spring I screwed down Masonite to slats making a roof for the Model T Towncar I posted about earlier. 150 each of #6 x 3/4" steel flathead wood screws, I drilled a pilot hole for each and adjusted the clutch on my battery drill to stop the screws at the surface, they drove their own countersink (of course this created a Crater effect but a quick pass with the mouse sander and 220 paper they were flat and level. I was laminating 3 sheets of 1/8" over a curved and arched roof. Be advised, I was not concerned with loosing the slick surface when sanding as it was to be covered later.

Two suggestions,

Where practical, use a drill press, or even a hand drill mounted in a column adaptor system, with a stop set to limit pentration. Most of the column adaptors I have come accross have a hole about 20mm diameter through the base beneath the bit so you could run down through that.

If you are doing a lot, consider looking for aircraft countersink and cage sets on US ebay. These are used for countersinking thin ali sheet for flush rivetting aircraft skin to the support structure. The cage structure surounds the bit and is a microadjustable depth stop. Units normally run from air drills but will run happily from a battery drill.

Should be able to get them new in OZ, but I wouldn't expect them to be cheap, but s/h in US maybe $US30 for a cage and a set of bits (used but still viable for wood). Probably a slight difference in c/s angle, they normally run 82 deg from memory, but masonite and screw will resolve that.

By far the best option is a plasterers screwdriver...they actulay sink the screw to a set depth.

If you don;t want to buy one....most hire shops will have them available.

cheers

I think these are what you need & they work in an ordinary drill/driver.

http://www.leevalley.com/wood/page.a...80,42240,53317

They should be available here, but you might have to ring around several plaster board places to find them. If no luck here, Lee Valley takes about a week for air & are very reliable.

Originally Posted by bsrlee

I think these are what you need & they work in an ordinary drill/driver.

http://www.leevalley.com/wood/page.a...80,42240,53317

They should be available here, but you might have to ring around several plaster board places to find them. If no luck here, Lee Valley takes about a week for air & are very reliable.

I agree, Most likelyyour best bet, Had I had one I would have used it on my Roof top but being the tight wad stingy arsed frllow I am. I use what I got that will do the job...

Only concern is that it dimples the screw below surface and that may be a problem (or Not) Use it in conjunction with a clutch and you may be able to make it "Just Right"

I have seen them at our local Box stores and DYI supply stotresl, I'm going to pick on up next time I see one and then I can spend a day and a half looking for it when I need it. (refer to the string on the wormhole https://www.woodworkforums.com/showth...light=wormhole)

A Microstop Countersink would be perfect for this application , adustable in .001" incremints.

Festool do an adjustable CS which works really well and it should for the price! There is a cheaper one around, maybe Mcjings?