Topic: drill size for 5mm X 0.8 screw??

[jtb]

The threads for the float bowl screws on a couple of my carb bodies are stripped, and I want to drill the holes and tap them for 5 mm screws.  My calcs come up with 5/32nds for drill size.  Before I drill away, can anyone confirm this, or let me know the right size?  Mike? Terry?

Thanks,
John

[bwaller]

5/32 drill is correct for 5mm as long as there is room.

[Steve F]

To figure the proper drill size for metric screws, subtract the pitch (. from the diameter (5) = 4.2mm which actually comes out at .1654"   tapping a 5/32 hole to M5x.8 would be "snug" but o.k.

[tsflstb]

http://www.engineershandbook.com/Tables/tapdrill.htm

There are a bunch of these on the 'net.  I keep a few print outs in the garage.

[jtb]

Thanks all.  I did the math, and converted to inches and came up with 5/32nds being closest to 4.2 mm.  Since I don't have a set of metric bits (yet) I just wanted a little reassurance before I drilled away.  I believe there is room, If not, I guess I'll have to send them to Big-Jay and let him weld them.

Thanks again.

John

[jtb]

Well, the tap wouldn't start when I used the 5/32nds drill.  Ended up using 11/64ths, 7/32nds for the o\holes in the float bowl (barely fits).  I only did the two holes at the back of the outside carb bodies, used a 5mmx16mm screw and lock washer and it is good.

[upperlake04]

Good work John.  That's one of the to-do jobs on my winter list.