Howto sharpen reamers.

No one has mentioned the difference between chucking reamers and hand reamers.The most obvious difference is:

Chucking reamers have a straight shank. They cut on a 45º at the end of the reamer.

Hand reamers have a square end to fit in a tap driver. They cut on a long angle perhaps 3/4 of an inch long, depending on the diameter.

I expect there are exceptions to this so I'm prepared to be corrected.
 
T Bredehoft said:
No one has mentioned the difference between chucking reamers and hand reamers.The most obvious difference is:

Chucking reamers have a straight shank. They cut on a 45º at the end of the reamer.

Hand reamers have a square end to fit in a tap driver. They cut on a long angle perhaps 3/4 of an inch long, depending on the diameter.

I expect there are exceptions to this so I'm prepared to be corrected.
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One might refer to "chucking" reamers as (machine) reamers, then taper shank reamers also fit the definition; also, shell reamers also fit the machine reamer definition by cutting only on their chamfered end. Generally, machine reamers have no radial relief, that is they are ground cylindrical, then (usually) an angled secondary relief is ground to reduce drag, leaving a narrow cylindrical land, and also there is a small amount of back taper to the cylindrical portion, also to prevent drag and binding.
Machine reamers take out a fairly large cut, depending on size, perhaps 1/64" in small sizes and even over 1/16" in larger sizes; hand reamers on the other hand only remove a few thousandths at maximum, they are strictly ONLY for bringing a undersize (bored) hole to standard size.
 
T Bredehoft said:
Good reply, Ben, broadens my comment by a lot. Thanks
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We could go on ad infinitum regarding reamers! Another type of hand reamer is the adjustable type, starting with the Critchley type with adjustable removable blades, each size has a considerable range of adjustment, but can be fussy to use, and have a tendency to chatter at times. The other common one is the Keystone type (Keystone reamer and tool Co.); these have a narrow range of adjustment, but are wonderful to fit standard size bushings to fit the pins that fit in them; I have one set made to fit automotive wrist pins to either the piston or the rod bushing, and numerous others that are made to fit anything else to a pin that is nominally sized.
A note on shell reamers; I was given a lot of shell reamers that were in the most awful condition, they looked like they had been tumbled in a cement mixer! I made arbors to grind them between centers And ground the whole mess to one size under, including the area that the size was stamped on, I then reground the chamfers and the backoff, left a small margin full size and etched the new size on each; on some, I had to stone some minor burrs on the faces of the flutes, and ended up with a set up to over 2" diameter.
For special jobs in my shop, it was not uncommon to regrind an old reamer to a new size, for odd work or metric sizes.
 
benmychree said:
How does your wooden propeller machine function?
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Pretty good, thank you. Its a can of worms, invented by a real mechanical genius.

The short version is "there is a vertical cutter (7/8" 80 grit sanding roll 3" long which oscillates up and down) spinning at 10,300 rpm, and a carriage which traverses left to right and back, rotating as it goes."

Long version. In addition to the above, there is a template which a roller follows, rotating the carriage, which determines the pitch of the prop, and a profile which another roller follows which determines the profile of the prop. The sanding roll is guided by the profile pattern, the carriage by the template for the pitch. The pitch template is changed for different length props.

The larger props, up to 17" take four or five passes, on each side to get to finish thickness (3/16 at the blade tip) the short ones 6 and 7 inches can be done in two passes each side.

On the carriage there is a 3/32 pin in the middle and clamps on each end to hold the blank in place. Ideally the wood has a density of 4.5 to 8 pounds per cu ft. Softer it won't hold up the sanding roll, when it gets beyond about 11 lbs, it tears up the sanding roll.

When we acquired the machine in 2014 it was about 30 years old, the carriage rode on iron ways. It had worn the supports so that it dropped about .015 on each end. I installed rails and ball guides and eliminated the droop. Its driven by a cable drum.
 
It would be a treat to see a video of it in operation! I was told that Mare Island Navy Yard near here had a machine called a "pitchometer", that sounded very similar; it had a central post to mount the pattern for marine propellers, and at a certain radius, angle knees were set up, and a strip of metal was sprung around the inside of them in a spiral, then a arm that was counterweighted and had bearing on the center post and was equipped with a milling and drilling head, which traversed on the arm and generated the spiral on one side of the prop pattern; then, a large number of holes were drilled through that face at regular intervals, and dowels driven in flush, that were made in specific lengths for their locations to create the "airfoil" shape shape on the bottom side of the pattern; that process of the final shaping was done with hand tools until the surfaces were flush with the dowel lengths.
All this was told to me by a retired patternmaker who worked there; the other consideration for these large marine props was that the pitch changed from that of the pattern due to shrinkage when the metal solidified and had to be predicted and allowed for when the pattern was made.
 
Sorry, I'm not literate enough to supply a video. The navy machine sounds awesome. I had to generate both the profiles and the templates. Subsequent to acquiring the machine the executives decided to change the product just a tiny bit and production (I) had to do it. The props are basically an airfoil, (we supply the blank, the customer sands it to final shape.) The backside of the prop is flat, a straight line (on center) from end to end, the airfoil side is tapered .020 per inch. The back side is where the pitch is measured.

OK, enough sidetrack, back to reamers.
 
Just a point of clarification....my reamers are either square at the end for a hand tool or lots of them are MT1 which fits my 618 very well....length wise about 5 inches of flutings.......

Will try a larger 1/2 in. one first and keep you posted.
 
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