Need To Make Multiple 1 & 17/64 Hole

[Cactus Farmer]

I might have bought the same 5C rack you did. I opened the holes on my drill press with a 1" sanding drum. I turned a piece of scrap to just over the 5C diameter, set it on the rack, scribed a line around the round, sanded to the line.

If its Only .008 inch to open up the holes the abrasive paper sound like it would be easiest and cheepest. Also will leave them nice and smooth (probably).

Stuart

This is what I did, too. Easy and fast. 0.008 is child's play with a drum or flapper wheel. <10 min and I was done.

 

[w9jbc]

I'd upload a photo of it but I am not certain how to do that yet.

 

[rick9345]

sanding roll, die grinder

 

[scrdmgl]

Hi,
I bought a couple of cheap 5C collet racks. The holes are a bit undersized. The biggest reduced shank twist drill I have is 1 & 1/4. I need to open the holes up to 1& 17/64. I have to do this for 70 holes. I considered buying a chunk of O-1 and making a D style reamer but the material cost will be as much as the drill bit. Any suggestions besides buying that size twist drill?
Thanks,
Chris

Hi Chris: The racks being sheet metal makes using a twist drill dangerous when enlarging a hole because it will sink, grub and destroy the rack. Use a drum sander with a close size in your drill press (they sell them in sets very cheap and they are useful for many jobs). Replacement sleeves for the sanders are also sold separate.

Jorge

 

[Tonym47]

Hi,
I bought a couple of cheap 5C collet racks. The holes are a bit undersized. The biggest reduced shank twist drill I have is 1 & 1/4. I need to open the holes up to 1& 17/64. I have to do this for 70 holes. I considered buying a chunk of O-1 and making a D style reamer but the material cost will be as much as the drill bit. Any suggestions besides buying that size twist drill?
Thanks,
Chris

If you know a plumber borrow his pipe reamer.

 

[Highsider]

Hi,
I bought a couple of cheap 5C collet racks. The holes are a bit undersized. The biggest reduced shank twist drill I have is 1 & 1/4. I need to open the holes up to 1& 17/64. I have to do this for 70 holes. I considered buying a chunk of O-1 and making a D style reamer but the material cost will be as much as the drill bit. Any suggestions besides buying that size twist drill?
Thanks,
Chris

You could try making a Piloted boring bar from shop scrap. Turn a running fit pilot to fit the existing holes on the bottom end . Just above that, cross drill for the cutting tool and D&T for a recessed set screw to hold it. Turn a drive section on top to fit your chuck or other driver. For size adjustment, start w/a trial adjustment that you know will be a bit small and cut and try 'til it's working for you.

 

[stevemetsch]

Decide what Dia hole you want to end up with. Take a plate of something , probably hardwood if your sheet metal is aluminum or 24 gauge steel. Bore a hole in it the size you want and clamp it on your drill press centered under the chuck.
Turn a tapered plug just the size you want the hole =/- 1/32" and mount it in your drill press (or other press). It will self center the rack hole and leave a nice finished hole with a rolled edge. No rotation is required.

 

[gi_984]

Hi, thanks for everyone's feedback. The racks were $5 each and the seller told me they were undersized. So I knew what I was getting. My original plan was to fabricate my own 5C collet racks but when I found these I said "Why Not?". I hear the warnings about using a twist drill in sheet metal. I've seen some impressive distance out of pieces of thin material thrown by the twist drills from lazy students in the machine class I take at the community college. They still try to do it even though they have been warned multiple times. Never done it myself. I actually saw a video on You Tube by MrPete222 or Tom's Techniques (don't remember which) where they demonstrate knocking down the rake on a twist drill to safely drill thru plexiglass and sheet metal. So I was considering getting a junk twist drill for that express purpose after altering.

 

[gi_984]

I'll probably go with the D style reamer since I haven't made one yet and this would a simple project for it. In other words I could screw up the reamer pretty good and it would still be plenty sufficient to make the required holes