List # 301 = Standard
List # 302 = 1/64 Oversized
List # 303 = 1/32 Oversized

Part number = List and Cap Screw Size
example Series 302 Spiral Flute #4
Part Number = 302-4

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Straight Flute American Standard Dowel Pin Reamer
List # 470 High Speed Steel
List # 1470 M42 Cobalt

Right Hand Spiral American Standard Dowel Pin Reamer
List # 475 High Speed Steel
List # 1475 M42 Cobalt

Left Hand Spiral American Standard Dowel Pin Reamer
List # 475L High Speed Steel

Straight Flute Production Length Dowel Pin Reamer
List # 370 High Speed Steel

Right Hand Spiral Production Length Dowel Pin Reamer
List # 375 High Speed Steel

Few people know the difference between Dowel Pin Reamers and Standard Chucking Reamers. Whereas Standard Chucking Reamers are produced with little back taper and a plus diameter tolerance, Dowel Pin Reamers are produced with increased back taper and a minus diameter tolerance.
(This specification is as suggested by Danly Machine - Chicago, Illinois.)

Yankee Dowel Pin Reamers are produced to Danly's recommended specification with the added feature of precision ground flutes.

To gain maximum results in dowel pin installations, the following is recommended.

1. Drill holes 1/64 under dowel pin size either in cast iron or steel when below 1/2 diameter. For holes 1/2 and over in size, the drill hole may be 1/32 under the dowel pin size.
2. Ream holes in cast iron .0005 undersize. For example, for 1/4 dowel, use a .2495 reamer to obtain a press fit. For tool steel which is to be hardened, use a standard size reamer. The shrinkage in hardening will take care of a press fit. Scale should be removed by polishing or lapping.

How to Dowel Very High Grade Tools or Dies.

1. Drill holes in tool 1/64 undersize when below 1/2 diameter. For holes 1/2 and over, drill 1/32 under dowel size.
2. Ream holes .0020 undersize.
3. Ream holes .0005 undersize. (Note: Tolerance of reamer is + .0000 - .0002 with .0050 back taper per 1-1/2 length. Grind for end cutting with no relief on periphery.
4. Harden tool steel and lap holes to fit reamer.
5. Align and secure tool steel in place on its mounting block or base. Use lapped holes as a jig and follow same drill and reamer sequence as above in Steps 1, 2, and 3.

Part number = Series and Diameter Size
example Series 1475 Right Hand Spiral Cobalt Dowel Pin Reamer .1875
Part Number = 1475-.1875

Diameter Tolerances
All sizes +.0000 / -.0002

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