Need To Make Multiple 1 & 17/64 Hole

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gi_984

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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
 
gi_984 said:
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
Click to expand...

Are you enlarging holes in sheet metal? If so, a UniBit step drill or facsimile will open the hole to 1-3/8". HF across from Home Depot sell a facsimile set for $19.00.
You could also make a slightly tapered mandrel with a shank to fit your mill or drill press and glue some wet or dry paper to it. It should work to remove the .008" per side.
 
+1 on the step drill. Drilling those holes in sheet metal with a standard twist drill would not be fun. If they are a bit oversize it won't hurt a thing.
 
I do have a nice Hertel step drill set. Alas, it does not go up to the required size. I'll look for alternative brands of step drills.
 
This might be a silly idea but I sure hear you about the cost of large diameter O-1.

70 holes in thin (it's aluminum, right ?) sheet metal may not be too much to ask for a simple high-carbon steel tool. So my suggestion is to buy a piece of inexpensive steel rod with a fairly high carbon content - 1020 or higher alloy, make a "D" drill or tapered reamer and torch-harden it.

Might even make it a tad greater diameter than you actually need to accommodate one or two sharpenings.

Just a thought :)
 
I think the steel would cost more then it would cost to buy some trays.
 
A sheet metal shop could punch the holes out larger. Better yet, have them make a new top plate with the correct size holes. Probably would cost more that a new collet rack, though.

Have you contacted the seller to complain? They might replace them with better ones.
 
I thought of the punch. I think punching out .008" of material would be problematic, not even considering centering issues. A guide could possibly be made to center a punch. Taking it to a sheet metal shop would most likely far exceed the "investment"
Another idea that could work would be to make a die plate with a hole slightly larger than the 1.267" + twice the thickness of the metal = a bit extra for clearance. Turn a tapered plug, slightly smaller than 1.25 on the small end and 1.267 or slightly larger on the large end and about 2" long. Weld or thread a 3/4" shank, not critical diameter, to the large end. You now have a drift that you can drive through the hole with a press or by hammer. The result would be a nice little fillet on the top side to help guide the collets in and no sharp edges to possibly mar the surfaces.

One drawback would be the noise. Not sure where in Madison you live Chris; out here in the country that would not be an issue .

I am sure we have all fell into the trap of buying something on the cheap and spending way more in money and effort to make it right.
 
  • just made a collet rack for my 2J collets out of 3/4 thick wood and the hole saw cut holes so tight it was like a press fit so I used a carbide burr and just ran it around the inside of the holes by hand .And it opened holes up too a nice slip fit. Had about 100 holes to open and done in quick time. jimsehr
 
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