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joahmon
08-07-2005, 04:21 PM
I need some suggestions on machining a 45* face on the inside of a .438" hole. The author of the plans suggests "Use a small boring bar to machine the 45* angle...", which is no help to a newbie like me.

Is this a place for a form tool? How do I even measure the angle?

http://i14.photobucket.com/albums/a325/joahmon/plan_A.jpg

Here is another view of the part.

http://i14.photobucket.com/albums/a325/joahmon/plan_B.jpg

Mcgyver
08-07-2005, 04:24 PM
not the place for a forming tool, just use the boring but set the compound slide over to 45 degrees and cut the internal taper by feeding the compound

SGW
08-07-2005, 05:56 PM
One can get 90 degree included angle countersinks...which might be the simplest. Check for availablility at www.mscdirect.com (http://www.mscdirect.com) or similar.

CCWKen
08-07-2005, 06:22 PM
You might have a problem geting a 3/8" countersink to bore accurately. You need a piloted reamer or cutter. I think I'd just make one and use the valve stem bore as a guide. You'll want the valve face perpendicular and centered to stem bore any way.

toolsrul
08-07-2005, 09:51 PM
Either buy a boring bar that has an SCMT21.51 insert sitting on a 45 or grind a boring bar with a 45 & plunge or form the angle in your part. I don't know how you turn your toolpost to form that angle in that small of a bore? C'sink will chatter unless you run real slow. Good luck.

JCHannum
08-07-2005, 10:22 PM
Looks like a Phil Duclos engine. Which one are you building?

McGyver has the answer. Use a small boring bar and fine feed with the compound.

You will lap the valve in, and since the body is aluminum, it will seat with little problems.

When you get to the valves, I make then in two pieces. Use drill rod for the stem and turn and bore a valve head with the 45* face. Drill and silver solder together. Finish with very light cuts. It is simpler than trying to turn from one piece of steel.

Mcgyver
08-07-2005, 10:33 PM
"don't know how you turn your toolpost to form that angle in that small of a bore?"

i'd mock up a picture if i was at home, its very simple, set the compound at 45, align the boring tool, obviously a small one, with the lathe axis. move the carriage towards the headstock until the bar is at the bottom of the bore and crank in the compound.

a small boring bar is very easy to make from drill rod and will work well, or if you want to save that for another day, buy one, for example http://www1.mscdirect.com/CGI/NNSRIT?PMPXNO=1779467&PMT4NO=602267

[This message has been edited by Mcgyver (edited 08-07-2005).]

Sprocket
08-07-2005, 11:16 PM
Yup, exhaust valve assembly for the "Whatzit"
(Could be for others too, but I just made one for the Whatzit) McGyver had it right. Set the compound at 45 and feed the compound to make the valve seat. It does take a small boring bar so you don't hit the far side.JC- I think it's steel, but it doesn't matter, it gets lapped with the valve

RAD1
08-08-2005, 12:50 AM
Use a small two flute endmill put it in your tool holder with one of the flutes in the same position you would have a boring bar positioned to cut. angle the tool post slightly so that only the outside corner cutting edge of the end mill is touching the work piece and the length of the end mill shaft and flutes don't touch the part. set your compound to the desired angle and have fun making chips. I frequently use this set up. It works great.

joahmon
08-08-2005, 08:50 AM
Thanks to all.

JC, Sprocket,
Yes, its a "Duclos"; the odds & ends hit & miss. I started it about 1.5 yrs ago (took an 8 mo. hiatus) as a "learning project". I hope I can finish it before I get bored ;-)

McGiver,
Duh, the "hardest" thing become so clear once someone explains them to you. Thanks.
I have made small boring tools by forging HSS bits using mapp gas and grinding. Probably wouldn't work for production, but for occasional use, they do the job.

JCHannum
08-08-2005, 11:19 AM
<font face="Verdana, Arial" size="2">Originally posted by Sprocket:
JC- I think it's steel, but it doesn't matter, it gets lapped with the valve</font>

It is steel, it has been a while since I worked on this one. My engine is the gearless, it has been about eight years since I worked on it.

Phil Duclos used this construction on several engines, and other makers use a variation.

Paul Alciatore
08-08-2005, 03:00 PM
<font face="Verdana, Arial" size="2">Originally posted by CCWKen:
You might have a problem geting a 3/8" countersink to bore accurately. You need a piloted reamer or cutter. I think I'd just make one and use the valve stem bore as a guide. You'll want the valve face perpendicular and centered to stem bore any way.

</font>

Yes, most countersinks will give you trouble and likely produce a "wash board" finish. However, I would bet dollars to doughnuts that one of the "O" flute countersinks would do a bang up job. They come in a piloted version and 90 degree angle. You could drill/bore the hole below to the pilot size first and do the 45* seat with the countersink and then drill/bore it to the final size. Use some grease on the pilot and cutting oil on the cutting edge. You may have to grind a larger countersink down a bit to fit the upper hole.

Or, as suggested, a boring bar on the lathe. The angle could be set to 45# by adjusting the compound with a DI or TI mounted on it and run against a square (45# sied of it) held against a faceplate or against a test bar held between centers. I doubt that split minute accuracy is needed. Considering how short the face is, +/- 10 or 20 seconds (1/6 to 1/3 of a degree) should be OK. If the parts need to mate better, lap them together.

Paul A.