Friday, April 21, 2017

Tapered Reamers

I found two old tapered reamers at a garage sale recently.  Thinking that they could come in handy someday, I grabbed them (along with a few other things).  I never got on the staked furniture train, so I don't know if I'll ever need to taper any holes, but you never know.
The two tapered reamers
The smaller of the two (top in above photo) has "No. 242" stamped onto one side of the back end, with a logo that appears to bear the letters G, T, D.
Smaller reamer markings
The opposite side has the following markings:
Made in USA, EX V5
The cutting edges of this reamer are about 2 1/4" long and form a (approximately) 30° taper.  It's maximum diameter is about 1 3/8"

The larger of the two reamers has the following markings:
1/4 to 1 1/4  ATCO
Made In USA
Not sure if this was original or stamped by an owner
This reamer creates a taper with an angle of about 33° and its maximum diameter is about 1 1/2". There are 10 flutes on each reamer and they are in a spiral pattern.
Ten spiraling flutes
Bottom view
I tested them out on a piece of scrap pine.
Marking a center and drawing a 1" diameter circle
Then boring a 1/2" diameter hole
Then turning the bit in the hole with a brace
A closer view
Well, this got nowhere fast.  It just wasn't cutting.  So I looked on the internet to try to find out how one might sharpen this type of reamer.  I found absolutely nothing (say it again!).  Almost all the information on tapered reamers was for a completely different type of tool (see, for example, this article by Peter Galbert).  If anybody happens to know anything about this type of reamer, please leave a comment.

So I decided to sharpen it freehand.  At first I tried a small file, but found out quickly that wasn't going to work.   Fortunately I have a diamond paddle and this helped a lot.
One flute showing cutting edge and trailing edge
Here's the rub - since the flutes are slightly spiraled, you have to change the angle of sharpening as you go from large end to small end.  In addition, each flute needs to be sharpened so that the leading edge of the cutting flute is higher than the trailing edge.  If the trailing edge was higher (or the same height), the cutting edge would never have a chance to do its job.

I basically just winged it here, realizing the importance of the leading edge and trying to file appropriately.
One of ten flutes sharpened - now for the other nine
All done.  I kept at it until I could feel a sharp-ish leading edge
When I tried it out, it cut so much better than before.  It didn't necessarily cut fast, but not too slowly either.  And it doesn't make shavings, but rather some fine dust.
Stopped to clean out the dust every 10-20 turns
Notice the pencil line of the 1" diameter circle in the above picture.  I used this as a guide to know when I was close to size and how close I was to centered.  When I was closer, I adjusted the angle of the brace to properly center the taper.
Cut just to the layout line
Close-up of the tapered hole shows fairly clean sides -
a little rougher at 2 o'clock and 10 o'clock to the grain direction
While I'm happy about how this came out, I may spend a little more time on sharpening the leading edges.  I'm about to order some more diamond paddles and they should help a lot.

Now I just need to figure out how to make tapered tenons without a lathe!  That'll be the next post.