Caution: Drill bits

[garethashenden]

I'm on a few UK model train forums and I'm always amazed at how a lot of the guys building those etched metal "flat pack" mechanisms get away with opening up holes for things like crankpins and axle bearings using tapered hand reamers.

Jeff

It really depends on what you’re trying to do. If you’re trying to create a hole, you need a drill. But if you’re trying to enlarge a hole, or even more commonly, remove the etch cusp from a hole, then a tapered broach is the right tool. At least with the volume of holes we deal with. As has already been commented on, drills have a tendency to catch and twist in thin material. A delicate etch can be rendered useless by use of a drill if one isn’t careful.

[JeffB]

It really depends on what you’re trying to do. If you’re trying to create a hole, you need a drill. But if you’re trying to enlarge a hole, or even more commonly, remove the etch cusp from a hole, then a tapered broach is the right tool. At least with the volume of holes we deal with. As has already been commented on, drills have a tendency to catch and twist in thin material. A delicate etch can be rendered useless by use of a drill if one isn’t careful.

Definitely on the drills creating a hole, that's a given.  Also a given is drills catching in thin sheet metal and destroying the area around the hole, if not the whole part.

The biggest issue I see with tapered reamers is that they create tapered holes.  Of course in thin metal, this is negligible.  I use machine chucking reamers to open up holes, usually on the drill press, but I've also inserted them into a pin vise and used them by hand. 

Jeff

[garethashenden]

I’d use a drill to enlarge a hole if it’s more than about 1mm/0.040” thick. I only really remember one instance of “oops, I made that hole tapered” and the locomotive runs fine, so maybe it’s not a huge issue. Probably not best practice though.

[peteski]

I've looked into Albrect chucks for both my Micro Mark drill press and my Sherline and Taig mills...  Ultimately, the increase in precision over the stock chuck wasn't enough to justify the price of the Albrect chuck.

But the ability to hand-tighten it is a huge benefit and along with the increased precision well worth their price.  You can buy other (more generic) brands of precision hand-tightened chucks which are still quite good but less expensive than Albrecht.  One such brand is ROHM.  I own those too.

[JeffB]

But the ability to hand-tighten it is a huge benefit and along with the increased precision well worth their price.  You can buy other (more generic) brands of precision hand-tightened chucks which are still quite good but less expensive than Albrecht.  One such brand is ROHM.  I own those too.

Hand tightened chucks (no key) are certainly convenient and easy.  Increased precision is always better.  I just couldn't justify buying a chuck that cost a major percentage of the cost of the machine, to replace a chuck that was "good enough".  Will check out ROHM though...  Definitely worth a look.

That said...  Hoping to upgrade my machines to bigger and better (Precision Matthews) in the near future and I'll most likely spring for an Albrect drill chuck for the mill.

Jeff

[Dwight in Toronto]

Thank you to those who took the time to give me the low-down on run-out!