How to hold a very small drill bit in a pin vise

Model Railroader General Discussion (Model Railroader)
1

Trying to drill out holes for grab irons with a # 81 bit but i can’t get my pin vise to hold the bit

it’s just too small

Ideas ?

2

Terry,

I mentioned this to forum member in a similar thread a month or so before. Do yourself a favor and buy a Starrett 162A pin vise. It will hold #61-#80 wire drill bits and run you about $15-$20 but it’s WELL worth the money. It will tighten around and hold the wire-size drill bits VERY well. (Easy to loosen, too.)

You should be able to pick one up at a production tool store in the Houston area somewhere or order it online, as with the link above. A good tool is worth it’s weight in gold.

Terry, do you really need a #81 wire-size drill bit for those grab irons? A #78-#80 will allow you to add some CA to the hole(s).

Tom

3

Terry,

I agree with Tom that you need a different pin vise (the Starrett 162A is an excellent choice) but in an pinch you can wrap the end of bit with a layer or two of tape. Note that this is not recommended for long term use.

Joe

4

Size 80 is a PITA as it is, what are you doing that you need size 81?
Even the old school Micromark small drill bit gauge goes down only to #80 (hmm, I see General makes those now - was that always the case for Micromark?)

5

Trying to drill out holes for grab irons on a caboose

6

Different pin vises have different size colletts, some will not hold the smallest drills, some will not open enough for large ones. If you are just enlarging a hole, try a reamer, if you are drilling the holes, as suggested, make them a little big, grab irons and the like are small and break easily. If the hole is just a little big, they go in much easier. Experience speaks from adding grab irons to P2K kits.

Good luck,

Richard

7

Unless you are working in N scale and have some special fine cross section grab irons, I have to say that I’m highly doubtful that you are using a number 81 drill bit. I would go further to say that probably most of us on the forum don’t even have a bit that small.

Anyhow, I looked up the diameter of the #81 bit and it is 0.0130 inch. A number 80 is shown to be 0.0135 inch. A number 79 is 0.01449 inch, and a number 78 is 0.01600 inch. So the difference between the 78 and the 81 is 3 thousandths (0.003) of an inch. If it were I, I’d use one of the larger sizes and save myself the aggravation of multiple broken drill bits.

Just my opinion, of course.

8

Terry. …

I have slipped wire insulation around the tiny drills before inserting in the pin vise. It has to be very small gauge wire insulation. It’s less expensive than buying a new pin vise if you are on a tight budget.

9

Of course buying a better pin vise is the answer, but there is always one brilliant answer amongst the range of replies to questions like this one.

and Garry has it! Well done, what a clever idea.

10

I’m working in HO gage and following the instructions on a Warthers HO scale caboose

I have a whole set of bits in a small metal box that go that far down in size and i may go with a larger bit after tring one of the grab irons to see how it fits but even the bits in the 70s are small

11

This sounds like a good idea now that you mention it i wonder if i coluld use some shrink tubing

12

Terry,

Because heat shrink is rubbery, it might flex with the drill bit and be more apt to break the bit. Wire-sized drill bits that small don’t take much to break.

Tom

13

LOL LOL on my third bit Tom so yes they do break easy

14

Buy the Starrett 162A, Terry. You’ll be happier for doing it. [:D]

Tom

15

Looks like something was cut off in your reply. What did you mean by “even the bits in the 70s are small”? And exactly which kit are you building? I just find it hard to believe that Walthers would recommend a bit as small as an 81, but I don’t have the directions in front of me.

For what its worth, here’s a link to someone who had an issue with a walthers caboose because it was advertised as read to run and he found that he needed to install some small parts. He quotes the Walther instructions as saying a #80 is needed: http://www.mcor-nmra.org/Publications/Articles/A%20Not%20So%20Ready%20to%20Run%20Model.pdf

Regardless of what the instructions say, you will probably end up using what works best for you. As a suggestion, drill some sample hole in a scrap piece of plastic and try the grabs in them. Use whichever size seems to work best.

One other thing to look out for is if there are any burrs on the ends of the grabs. I don’t know how they make them these days, but sometimes you’ll find a burr on the end of the grab that makes it difficult to insert the grab in the hole even if the hole is otherwise the proper diameter.

16

Actually the instructions do call for a # 80 bit but i’m using a # 81 because i broke the #80 bit

as i said even the bits#in the 70s are small and the pin vise won’t hold them either

but the wire insulation i

17

Ah, I get it now. You’re saying that the pin vice won’t hold the small diameter bits. I’m wondering what pin vice you have. Many of the available items have interchangeable collets contained in the same handle. It’s possible that you were given the wrong collet to use with the small size bits.

On the other hand, you may just have a poorly designed tool. Those that suggested the Starret pin vice are correct. Save up for one if you can. It will save you a lot of aggravation in the future.