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Max drill depth for dowel pins

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Verkstad

Mechanical
May 17, 2011
44
Hi

For milling there is design guidelines that you should not mill deeper the 3 times the diameter of the tool.

Are there any similar design guideline when you drill holes for dowel pins? How deep can you go?
 
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If you are looking for maximum limits, I'd say the reamer is your limiting tool. The tool itself is fine but it's difficult to get it mounted perfectly. An angularity error would produce a bell mouthed hole. We go a bit over 2:1 L/D for our 1/4 inch pins. I'd bet a real careful mounting could get you 3:1 or 4:1. A boring operation (instead of reaming) might get you to 6:1 with a carbide boring bar.
 
Thank you for your inputs :), yes Brain it is mostly the maximum limits i am looking for.
 
You only need 1.5D to 2D depth for a viable positioning dowel joint.
 
TheTick said:
You only need 1.5D to 2D depth for a viable positioning dowel joint.

Exactly. And from an inspection point of view, the true position of the reamed hole only matters where it intersects the mating surfaces. Deeper dowel holes are a machining and inspection nightmare.

Excessively deep finished dowel holes are terrible for everyone involved. Where I have thick parts that require dowel pinning, we oversize or undersize the hole deeper than 2 dowel diameters.
 
To clarify this do not for positioning this is only for taking the shear load. The fitted items will be drilled together.
 
The limiting factor is the dowel pin. You can gun-drill forever and floating reamers will follow the hole and make it on-size, but the deeper you go the less-straight the hole will be. Also, the longer the dowel the more installation force is needed for a given interference fit. IOW, a deep hole means you need a more ductile dowel with less interference.

FWIW, the 3xdiameter rule of thumb for end mills is a relic of manual machining with HSS and a bad one at that. Using a light depth of cut you can go significantly deeper.
 
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