Dowel Pins And Drill Blanks

roadkillbobb

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I have some basic curiosity questions, what are dowel pins and drill blanks used for in the world of machining? thank you in advance for any information..
 
Dowel pins are used to secure two pieces in exact relation to each other, For instance, two flat pieces of steel are aligned, face to face by two dowel pins in reamed holes. Drilled and tapped holes are not accurate enough for this.

Drill blanks are another story, which I've not yet learned, other than being blanks for making drills from. A drill mfgr would buy 13/32 blanks, machine drills from them and harden and grind (sharpen) them.
 
From Wikipedia:

"Dowel pins are often used as precise locating devices in machinery. Steel dowel pins are machined to tight tolerances, as are the corresponding holes, which are typicallyreamed. A dowel pin may have a smaller diameter than its hole so that it freely slips in, or a larger diameter so that it must be pressed into its hole (an interference fit).

When designing mechanical components, mechanical engineers typically use dowel holes as reference points to control positioning variations and attain repeatable assembly quality. If no dowels are used for alignment (e.g., components are mated by bolts only), there can be significant variation, or "play", in component alignment.

Typical drilling and milling operations, as well as manufacturing practices for bolt threads, introduce mechanical play proportional to the size of the fasteners. For example, bolts up to 10 mm (0.394 in) in diameter typically have play on the order of 0.2 mm (0.008 inches).[citation needed] When dowels are used in addition to bolts, however, the tighter dimensional tolerances of dowels and their mating holes—typically 0.01 mm (0.0004 inches)—result in significantly less play, on the order of 0.02 mm (0.0008 inches).[citation needed] Manufacturing costs are inversely proportional to mechanical tolerances and, as a result, engineers must balance the need for mechanical precision against cost as well as other factors such as manufacturability and serviceability.

In automobiles, dowels are used when precise mating alignment is required, such as in differential gear casings, engines, and transmissions.

Bolts in a bolted joint often have an important function as a dowel, resisting shear forces. For this reason, many bolts have a plain unthreaded section to their shank. This gives a closer fit to the hole and also avoids some problems with fretting wear when a screw thread bears against an unthreaded component."

Since dowel pins typically only come in fractional sizes, drill blanks and precision gage pins can be used for other sizes.
 
Thank you for the quick response..I bought a hobby machinists basement shop from family that was selling it after he passed away and it came with boxes of tooling and all kinds of supplies that im still digging and sorting out...lots of dowel pins and drill blanks..also lots of hss made in USA drills.. down the line I would see if anyone wants to trade for other tooling or cutters for a milling machine..
 
I guess I have a related Q. I purchased drill rod from Enco some time ago and haven't yet used it. I was going to use it to make a boring tip to hold in a homemade boring bar. I got the water quenched type. Am I on track or did I miss the boat on this?
 
Should be OK, make the boring tool, all but final sharpening. Heat it glowing red hot, drop it in water and swirl the water until it's cool/cold. Put it on an aluminum pie pan, in the oven, bring it up to 450ºf, hold it for one hour per inch of thickness, (if it's 1/4 inch thick, 15 minutes) and let cool in the oven.
Then do your final sharpening.

A propane torch will not be hot enough, Not sure if the Harbor Freight Benzine (or whatever) torch will do it. I'd use Acetylene/Oxygen, but we don't all have this available.

If you can work it out, suspend the new bit from a magnet over a bucket of water, heat it until the part drops from the magnet. That will be hot enough.

An aside, if you had purchased O1, oil hardening, instead of W1, water hardening, the procedure is the same, but quench it in motor oil or something like that. Ideal Lard oil, but most of us don't have that handy.
 
To be clear, drill rod and drill blanks are NOT the same thing. Drill blanks are made of High Speed Steel (HSS) which is much different than O1 or W1 tool steel. HSS it intended for cutting tools and O1 and W1 are not.

SE18, If you are cutting anything but soft metals, W1 will not last long, even after heat treating as described by Tom. And even with soft metals, I'd say it's marginal - kinda like using carbon steel drills. The heat treatment gets rendered useless at the cutting edge of the tool as it will get hot enough to invalidate it. HSS doesn't have this issue.

I recommend getting a HSS drill blank if you need a round tool bit, otherwise use a lathe tool bit.
 
I use drill blanks as cheap gauge pins. Works fine for me....
 
Somebody said dowel pins only come in fractional sizes but I know they come metric as well and I'm pretty sure you can get almost any size you would need in standard as well
 
Thanks for replies, learning a lot here.

I'm thinking drill rod might also be used for pinning steel parts together?

If that were the case, after drilling thru the parts, I'm thinking widen the outside holes just a bit (sort of a small countersink). Heating the rod and then pounding to form a mushroom at both ends? I'm not sure how hot the drill rod should be though or even if heating is needed since you wouldn't want the rod expanded when it goes into the hole. Or maybe just press it in place? Curious what technique you use and for which projects.

BTW, I unintentionally mushroomed taper pins by using steel to knock try and knock them out. I've since used brass or other soft metals to do that job and haven't had a problem since, other than frequently replacing the soft metal punches as they get torn up.
 
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