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brian Rupnow
12-08-2014, 02:39 PM
I want to make a tapered reamer, of a specific taper angle to machine a tapered inlet on model carburetors I make from aluminum. It will be held in the lathe tailstock chuck, while the carburetor body is gripped in the 4 jaw headstock chuck. So--I need a 16 degree included angle taper, which is less than .195" diameter at the small (leading) end, and greater than .315" diameter at the large (trailing) end.--I have some 1/2" diameter water hardening drill rod. I can turn the correct taper on my lathe. I can make the leading end .188" diameter, and the major diameter will be whatever a clean-up pass yields on the 1/2" diameter drill rod. I can cut 4 "flutes" using an end mill. The thing I'm not sure about is how to machine a back clearance behind the cutting edge of the flutes. I know that it can be filed by hand, because I have built a very similar 45 degree tool for cutting model valve seat faces. It's just that my hand filing is far from being consistent or accurate. Is there any kind of machine set-up that will let me put some back clearance on the cutting edge of the flutes that is more accurate and consistent than hand filing?--Keeping in mind that I have a manual lathe, a small vertical mill, and a rotary table.---Brian
http://i307.photobucket.com/albums/nn294/BrianRupnow/BrianRupnow020/TAPEREDREAMER_zpsf27b1ec0.jpg (http://s307.photobucket.com/user/BrianRupnow/media/BrianRupnow020/TAPEREDREAMER_zpsf27b1ec0.jpg.html)

bob_s
12-08-2014, 02:48 PM
I want to make a tapered reamer, of a specific taper angle to machine a tapered inlet on model carburetors I make from aluminum. It will be held in the lathe tailstock chuck, while the carburetor body is gripped in the 4 jaw headstock chuck. So--I need a 16 degree included angle taper, which is less than .195" diameter at the small (leading) end, and greater than .315" diameter at the large (trailing) end.--I have some 1/2" diameter water hardening drill rod. I can turn the correct taper on my lathe. I can make the leading end .188" diameter, and the major diameter will be whatever a clean-up pass yields on the 1/2" diameter drill rod. I can cut 4 "flutes" using an end mill. The thing I'm not sure about is how to machine a back clearance behind the cutting edge of the flutes. I know that it can be filed by hand, because I have built a very similar 45 degree tool for cutting model valve seat faces. It's just that my hand filing is far from being consistent or accurate. Is there any kind of machine set-up that will let me put some back clearance on the cutting edge of the flutes that is more accurate and consistent than hand filing?---Brian

I would think that a device like Evan's hand shaper would be ideal for doing this.

http://bbs.homeshopmachinist.net/threads/15661-Small-project-completed-today/page6?highlight=Shaper

Yondering
12-08-2014, 03:10 PM
A D-reamer would be simpler. Instead of cutting the four flutes, just mill off slightly more than half of the diameter, and harden it.

Richard P Wilson
12-08-2014, 03:36 PM
Make it, harden and temper it, then back off free hand on the grinder all except about 1/16" width at the cutting edge. Fresh grinding on the temper colour will easily show where you are. This will do all you need.

philbur
12-08-2014, 06:49 PM
This is a very, very useful tool for making one off cutting tools in carbon steel, relief and clearance angles are a piece of cake, even on tapered cutters with multiple flutes like yours. Sketch the cross section you want for the cutter, check the angles and off-sets and then you're away to the races.

https://www.grizzly.com/products/Dividing-Head-Type-BS-0/G1053

Phil:)

PStechPaul
12-08-2014, 07:16 PM
I was thinking about a similar problem for a simple tap, and I think it can be done by using a four jaw independent chuck and clamping the tool off-center. You would have to use a toolpost grinder, but as you rotate the chuck, starting with the part at the farthest distance from the grinder, the edge of the tool will move closer as you do. You would have to re-grip the part at 90 degree increments for four flutes, and if you needed better consistency you could make a simple square holder for the reamer. Use hex stock for three (or six) flutes.

The same idea might work on a rotary table tilted at the taper angle. I might need to make a drawing or actually try it, but I think it would work.

brian Rupnow
12-08-2014, 07:21 PM
Philbur--I have dividing plates for use with my rotary table. My rotary table can be bolted to the mill table so that the attached chuck is horizontal or vertical. Paul--I don't have a toolpost grinder.

RichR
12-08-2014, 09:11 PM
Hi Brian
After you cut the flutes, place a spacer under one end of the rotary table to match the angle of the taper. Blacken the surface behind the cutting edge
with a Sharpie to enhance visibility and use the end mill to cut your clearance. Maybe touch up the edge with a diamond hone when done.

boslab
12-08-2014, 09:17 PM
How about cutting the flutes with a dovetail cutter, 1st cut, the back of the land with the spindle inclined, cutting the back with the angled side of the cutter, then bring the cutter to horizontal for the bottom if you will, each flute would require 2 cuts to nail
Mark

philbur
12-09-2014, 03:56 AM
Philbur--I have dividing plates for use with my rotary table. My rotary table can be bolted to the mill table so that the attached chuck is horizontal or vertical.

The BS dividing head can be set at an angle so you can produce those tapered cutters with ease. Its also much lighter for handling and, because of the threaded/taper spindle, you can easily switch between 3 and 4 jaw chucks and MT collets or MT tooling for work holding. It's much more versatile than a rotary table for small light work like model engines. The only down side vs a rotary table that I know of is that it is not as rigid when taking heavy cuts.

Phil

brian Rupnow
12-09-2014, 11:55 AM
Yowzahhh--Found exactly what I need for the job!! Thank you to P.S.TechPaul--Damned things aren't cheap though. $65.00 Canadian plus tax. Will have to treat this one as a Christmas gift to myself from myself!!!
http://www.conicalendmills.com/wp-content/uploads/2012/12/g11.jpg
http://www.conicalendmills.com/cutting-tools/special-application-end-mills/tapered-end-mill-hss/8-degree-tapered-end-mill-hss/
http://i307.photobucket.com/albums/nn294/BrianRupnow/BrianRupnow020/g11_zps67993bcf.jpg (http://s307.photobucket.com/user/BrianRupnow/media/BrianRupnow020/g11_zps67993bcf.jpg.html)

brian Rupnow
12-09-2014, 01:00 PM
Gail from New Mexico has just warned me to be careful with this type of cutter, because they can grab quite aggressively and "screw themselves into the hole being tapered". I will make sure I try this new tapered mill on some junk stock before using it on a semi-finished carburetor body. There seems to be about .018" linear "slop" in my tailstock chuck (I just tested it with a dial indicator and magnetic based stand.). My Solidworks program tells me that this makes a total of .005" difference in the diameter, which shouldn't be a huge concern on a carburetor air horn, as nothing has to mate with it. I will certainly keep this in mind.----Brian

alanganes
12-09-2014, 05:39 PM
Brian,

If you are going to experiment, why not try the "D" bit reamer that was mentioned above? Guys make chamber reamers for firearms of that style that work just fine, which is a somewhat critical application. I'd think a guy of your considerable skill could whip one up and make that work with little trouble.

Unless you simply want to make or use this style, in which case I do understand, carry on...

adatesman
12-09-2014, 06:39 PM
Not only do they want to grab and screw themselves in, they really like to jump around and cut non-circular holes if the setup isn't rigid. Using one in a drill press was not the brightest idea I ever had.

brian Rupnow
12-09-2014, 06:56 PM
Alanganes--I can not argue with what you are saying. Probably a D bit would work just fine, and I may still make one. I've had a fair amount of "drop in" engineering design work this past month, so figured I would treat myself to the tapered milling cutter, without having to encroach on "pension money".---And true, I have never seen nor used a tapered milling cutter before, so part of the reason for buying is plain old curiosity.---Brian

Toolguy
12-09-2014, 07:01 PM
edit.

mars-red
12-10-2014, 12:00 PM
For what it's worth, I've had great luck making my own tapered reamers with 2 cutting edges. You can easily machine the relief that way (I just file mine though, it's easy if you blue up the edge first) . Here is a small one I made a while back:

http://tapatalk.imageshack.com/v2/14/12/10/e6160e2de9ee37f6764df38e879f9a3a.jpg
http://tapatalk.imageshack.com/v2/14/12/10/5d11ce653275b8f8cd97549b654a3045.jpg
http://tapatalk.imageshack.com/v2/14/12/10/c234c5512dc0b338ec16db4280e9361b.jpg

achtanelion
12-10-2014, 01:19 PM
Every time I see that penny, I know there's awesome attached.

wern
12-10-2014, 02:36 PM
I agree D bit.

Werner