Re: Drill bits for Grab Irons

Pete C

  Do you have any pictures of your setup.  Your details are great but a few pictures would help make it a bit clearer, at least for me.  😉

On Aug 29, 2019, at 1:06 PM, Mark Lewis <narrowrails12@...> wrote:


Thanks for the tip and detailed info.

Mark Lewis
narrow gauge modeling in N.C.

On Thu, Aug 29, 2019, 12:38 PM Joseph Melhorn <toyman@...> wrote:

I realize I’m chiming in late (as usual) but another source is Drillman1 on eBay:


I’ve purchased a lot of carbide drill bits, end mills and other various cutters from him over the years. I think his prices are reasonable for the products he offers. Service is excellent.

Many moons ago I shared on one of the lists a low speed alternative to using a Dremel tool to hand drill holes for grab irons using twist drills. It consisted of using a General Tools Miniature powered screwdriver (Lowes Item # 78618 - on sale now for $9.99 thru 11/01/2019), some hex wrench stock (4,0mm hex wrench) and a micro drill chuck with collet set and a couple of grub screws. Since I built mine, I’ve noticed that the brass micro chuck sets now range in size from 0,5mm to 3,0mm - .0196” to .118” (eBay# 192671709836). When I acquired mine they went from 0,0mm to 3,0mm. There is a universal 0,3mm to 3,5mm (.0118” to .1378”) adjustable micro chuck (eBay# 191949240231) that could be used, too. There is still a way to get to zero closing. It requires another mini mandrel with a 0 to 1,2mm (0 to .0472”) capacity (eBay# 200866133453). This mandrel has a 3/32” (2,381mm (.0937”)) shank. You would need to trim ~1” (25,4mm) off the shank to fit in the micro chuck collet. An added bonus of using the adjustable micro chuck instead of the chuck w/collet set is that it opens wide enough to accommodate the 1/8” (3,175mm) carbide PC Board drill bits.

Here’s the procedure: Use an abrasive cutoff disc and cut a piece of the hex wrench about 1-1 1/4" long. Measure across the "points" on the 4.0mm hex wrench. I measured a screwdriver bit from my Micro Screwdriver and it measures ~.175" Take the set screw out of the chuck and drill out the hole to ~.175". Closest is a #17 at .173 or a #16 at .177". If you have a lathe or access to a lathe it's pretty simple. It can be done on a drill press if you have a vise that you can clamp the chuck into. Once the hole is drilled if you used the #17 drill bit, line up a flat on the piece of hex wrench that you cut off and dressed, with the hole for the set screw and press the cut piece in until it is about 1/8"past the set screw hole. Run the set screw in and you're done. I've made several of these for myself and friends, under $20.00 for the whole thing. Yeah, I know it’s brass and will eventually wear out, but I'm betting you'll drill several tens of thousands of grab iron holes before that happens. They're so cheap that you should buy several and you can get at least three pieces out of the 4.0mm hex wrench. Make three or four of them and keep your most used bits chucked up and its quick to change bit sizes for that project you're working on. I made six up for my workbench.

Joe Melhorn

Sahuarita, AZ


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