Drill stock, readers and drillbit tolerances

SemoBill

SemoBill

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I acquired a fixture plate for my Taig mill. On this particular version every hole is blind and threaded 10-32. I was planning on drilling out some of the holes to 3/16 and make up some dowel pins from 3/16 drillrod stock. I have discovered that a piece of 3/16 drillrod stock will not fit into a 3/16 reamed hole. I did not know that. I guess I can grind a D bit from the same drillrod stock. That should work. I sure don't want to buy a box of 100 3/16 dowel pins when I only need 6 or 8. Any other thoughts?
 
If you cover one of the flutes of the reamer with .-002 brass shim stock it will cut oversize. Might make you drill rod fit.

Greg
 
What is the diameter of the drill rod? If you are only off by a fraction of a thousandth, you can polish the rod with emery cloth or sand paper to fit. In my experience, drill rod has come slightly undersized.
Come to think of it, I have a box of 3/16+.0002" x 1" alloy dowel pins. I'm sure that I could spare a half dozen. I did have to polish mine to get a tight slip fit with my .1875" reamer though.
 
Do not trust TGP material (drill rod) to be on size, if you are reaming holes for dowel pins why did you not just buy them? They may be purchased oversized and undersized to fit your particular needs.
3/16" x 1" hardened steel dowels are $10.70 for 50 pieces at MCM, and their pricing is high.

Also do not trust a reamer unless you have measured it with a micrometer yourself, regardless of the size etched on the shank, this is especially true of used tools and those of questionable origin.
 
Last edited:
SemoBill said:
I acquired a fixture plate for my Taig mill. On this particular version every hole is blind and threaded 10-32. I was planning on drilling out some of the holes to 3/16 and make up some dowel pins from 3/16 drillrod stock. I have discovered that a piece of 3/16 drillrod stock will not fit into a 3/16 reamed hole. I did not know that. I guess I can grind a D bit from the same drillrod stock. That should work. I sure don't want to buy a box of 100 3/16 dowel pins when I only need 6 or 8. Any other thoughts?
Click to expand...

My dumb mistake, guys. Thanks to all who offered suggestions and encouragement. After struggling with this a while, I took a break to post my problem to the forum. When I went back to the project, I realized I had not beveled the hole I had drilled and reamed (After all, it was just a simple test piece!!!). When I chamfered the hole, my homemade dowel pin slipped in easily. It was probably a little burr or debris I couldn't see.
Sometimes, the solution will come if you just take a break, walk away or eat some lunch. I felt pretty foolish for a bit.
Bill
 
I think I would buy finished dowel pins 100 cost about 15 dollars and they are to size and hardened. And put the rest in your tool box they will come in handy down the road.
Jimsehr
 
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