Hi Joe,

I had thought about building Harold's grinding rest but decided to do something else. The 5.2mm hole is for a screw that passes thru both holes and would be difficult to drill from both sides and have them perfectly aligned. Therefore it would be best to drill from one side only. A 5mm hole should not wander too much if it is sharp and ground correcltly. Us a new drill if you cannot grind your own. Use cutting fluid when drilling.

The only problem with drilling deep holes is swarf removel. Withdraw drill often to clear chips and you should not drill deeper than the length of the flutes on the side of the drill. If the flutes block you could break the drill.

I would mill the cut-out that the hole passes thru first. This will allow the swarf to escape from the drill flutes as you drill the second part of the hole. You will probably get away with a standard length drill instead of buying a long series drill.

Note: A 5mm drill will normally produce a hole slightly bigger than 5mm with enough clearance for a 5mm bolt. You may not need to buy a special 5.2mm drill.

Another option is to drill thru with a slightly smaller drill and finish with a reamer. (reamers bought on ebay are not that expensive and I have not had any problem with them).

Paul

Edited By Paul Lousick on 19/06/2018 05:00:44

Hi Joe,

I peck-drilled mine through with a long cheap 5mm drill and then expanded it to 5.2 from each end. That way I didn't need to buy a long 5.2mm drill. The key is spotting drilling first and frequent swarf removal as Paul and David have said.

It is only a clearance hole for the 5mm leadscrew and so if you make a mistake you could always drill it over-size, fit plugs at each end and drill two 5.2 holes through the plugs in the right places to result in a straight bore at the ends. No one will ever know then and it'll work just fine.

HTH

Jon