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jack3140
12-30-2011, 08:34 PM
i have a hard time centering the keyway properly when cutting it on my lathe i always seem to end up with a slight angle .. what is the best way to center the cutter to make the keyway accurate .. ? i could use a little help thanks jack

Toolguy
12-30-2011, 08:41 PM
What does your setup look like?

sasquatch
12-30-2011, 09:01 PM
Are you using a milling attachment?

firbikrhd1
12-30-2011, 11:43 PM
Perhaps I misunderstand. Are you talking about cutting an external key way on a shaft or an internal key way?

fciron
12-31-2011, 08:46 AM
For external keyways on a shaft I built the fixture shown in this video. It also works well for drilling cross holes through round stock. I like the way it uses the lathe itself to align everything.

http://www.youtube.com/watch?feature=player_detailpage&v=eVgZol6Mfvo

vpt
12-31-2011, 10:15 AM
What I do to center the shaft and with the lathe turning I bring the shaft up to the cutter just so it barely rubs the shaft and makes a mark. That mark is the high point of the shaft and should be centered. Then move the shaft so the mark is perfectly centered under the cutter and go to town.

http://img207.imageshack.us/img207/3216/brakecoolers032.jpg

http://img705.imageshack.us/img705/901/newscrew043.jpg

http://img405.imageshack.us/img405/3391/newscrew037.jpg

mf205i
12-31-2011, 02:25 PM
http://www.youtube.com/watch?v=vVUK-h-0iWQ&list=UUKLIIdKEpjAnn8E76KP7sQg&index=3&feature=plcp
Mike

Jaakko Fagerlund
12-31-2011, 05:55 PM
http://www.youtube.com/watch?v=vVUK-h-0iWQ&list=UUKLIIdKEpjAnn8E76KP7sQg&index=3&feature=plcp
Mike
Confusing to follow when the axis names (XYZ) are mixed and not as they should be. Otherwise very informative and nice :)

jack3140
12-31-2011, 09:37 PM
sorry about that i am talking about an inside keyway as in a pulley and such i always seem to be slightly angled as to the center because i am not dead center with the cutter hope that makes sense . thanks

jack3140
12-31-2011, 09:38 PM
What I do to center the shaft and with the lathe turning I bring the shaft up to the cutter just so it barely rubs the shaft and makes a mark. That mark is the high point of the shaft and should be centered. Then move the shaft so the mark is perfectly centered under the cutter and go to town.

http://img207.imageshack.us/img207/3216/brakecoolers032.jpg

http://img705.imageshack.us/img705/901/newscrew043.jpg

http://img405.imageshack.us/img405/3391/newscrew037.jpg
thanks for the tip that will help me for sure jack

jack3140
12-31-2011, 09:42 PM
What does your setup look like?
i put the pulley in the chuck and the cutter on a boring bar , then i gradually make the cut using the carriage feed . in a few thou increments , works ok except for the alignment . as i said jack

RussZHC
12-31-2011, 10:25 PM
Noob answer so it may not be the best or even work at all.

If the tool bit has a "square" edge and the very first cut is not on center, will not one edge/corner of the tool cut and the other will not...I am explaining this poorly but the bore is round and if the cutting edge does not make even contact on the interior at the "apex" (misnomer as there is no real "apex") only one corner of the bit will actually be cutting (you would have to barely make contact...)...adjust up or down as needed to center

the only other way I can think of is to have a center on center in a tool post holder and "scratch" the mid-line of the pulley or gear and then center the tool bit on that mark

indicate edges of bore and center accordingly?

Edit: depending on how accurately you can measure, and its similar to the first method I posted, you could use the shank end of a drill bit somewhat smaller than the bore, put it in a tool holder and advance the cross feed...at some point the edge of that shank will contact the edge of the bore, you then note the relative point of the cross feed dial (or reading on DRO), if you think it is not centered, raise or lower the tool holder and contact the edge again, make note of the dial or DRO reading and compare the two numbers, you will now know if you moved further up or down from the center...the true center will be the maximum reading you can get (for a given bore) [not sure if my thinking is correct but all you are doing is finding an internal center so any centering method should work]

vpt
01-01-2012, 10:19 AM
Ahh, internal keyways. I still use a hacksaw or sawzal for those. lol

I would love to get a broach for doing them!

Jack I would suggest a broach unless you really want to use the lathe for this.

http://mdmetric.com/dumont/cat1.jpg

H380
01-01-2012, 10:39 AM
Confusing to follow when the axis names (XYZ) are mixed and not as they should be. Otherwise very informative and nice :)

(XYZ) is correct for a mill. X left-right, Y front-back, Z up-down.

For a lathe (XZ). X feed of tool into and away from the centerline of the lathe. Z is feed parallel to the centerline of the lathe.

firbikrhd1
01-01-2012, 11:46 AM
sorry about that i am talking about an inside keyway as in a pulley and such i always seem to be slightly angled as to the center because i am not dead center with the cutter hope that makes sense . thanks


I don't know if it will help, but I posted this a while back.

http://bbs.homeshopmachinist.net/showthread.php?t=50607&highlight=internal+keyway

Jaakko Fagerlund
01-01-2012, 05:46 PM
(XYZ) is correct for a mill. X left-right, Y front-back, Z up-down.

For a lathe (XZ). X feed of tool into and away from the centerline of the lathe. Z is feed parallel to the centerline of the lathe.
I know, but in the video the Z was shown to be on the milling attachment (up-down) and not where it is supposed to be (axial to spindle), just like in your description too.