One thing I'll to what Chris said about holding the work in the chuck at one end the other with a center... You can end up with a "thick" spot in the center working with long thin material. Again, it can deflect away from the tool if you're trying to take too much material off per pass. Don't ask me how I know, LOL. Okay, I'll tell, I was doing a piece about a foot long and 3/8" dia and the ends were spot on but the shaft was larger in the center when I measured all along it. I was cutting towards the head, backing the tool out, moving the carriage back to the right and then doing my next pass after advancing the tool in. Everything looked good. I found the issue was from deflection when I backed to carriage across without retracting the tool and it cut in the center of the work. Several spring passes and the rod was the correct diameter the whole way. Just something I recently learned that I wanted to pass along.?
Ryan
On Feb 1, 2022, 12:07 PM -0500, Chris Albertson <albertson.chris@...>, wrote:
Many good suggestions on how to do better works, but none that address taper.
For example the tool.? Good ones cut better but let's say I make a tool bit by putting a drill bit in a vice and breaking it with a hammer and try to turn metalw iththe?jagged end.? It would be a horrible tool but uniformly horrible as it moves left to right
Same applies to a poorly chucked stock.? Lets say I place a square stock on a four jaw chuck and it is so "unstraight" I can see it from across the room.? After turning, it will be perfectly concentric the spin axis
I think there are only a few ways to cause taper
1) the stock deflects when cut, one end is unsupported?and you are taking cuts so deep that the stock deflects or
2) the carriage?is not parallel?to the spindle axis
3) A tailstock is used to short?the stock but the tailstock center is displaced from the spindle axis
Check for #3 with a razor blade. place a dead-center in the tailstock and spindle and move the points together?until?they almost touch.? Place some very thin and hard matter (like an old-style razor blade) between the point and if you can hold it there at 90 degrees.? It needs to be dead-on perfect to do this.
Mving the tailstock off center is the usual wy to?make an intentional taper.? Make sure you are not doing this
Then #2, after adjusting as above, support a rod from both ends and make a cut all the way.? If the work is held between centers there is no way it can have a taper, even if the spindle points away from the bed.
But sometimes?you want to use just?a chuck to hold the part.? You need to measure that the spindle is point down the bad.? ? Place a precision bar in the chuck and adjust out all the runout using a dial indicator.? This takes time.? ? ?Then you can see of the garage runs parallel to the "dialed in" bar.
Yes it is nice to have correct cut tool bits bt really all modern shops use carbide inserts
On Mon, Jan 31, 2022 at 11:53 AM Michael Jablonski <
michaeljab@...> wrote:
You are using carriage handwheel to advance the carriage, and not the
compound to advance the cutter. Your photo almost looks like your compound
is set at an angle, and you are feeding using the compound instead of the
carriage. Another possibility is that you have a lot of slop in your cross
slide and/or compound. Have you tried locking the cross slide and compound
by tightening one of the gibs on them both? Also check the carriage. See if
you can grab the left and right sides, and try to twist, lift, rotate, see
if there is any movement in it that needs to be addressed. And as others
have stated, no back rake on the cutter when cutting brass.
Michael - California, USA
Micro-Mark MicroLux 7x16
LMS 3990 Hi-Torque Mill with power feed
-----Original Message-----
From: [email protected] <[email protected]> On Behalf Of Jack
Lunn via
Sent: Sunday, January 30, 2022 2:33 PM
To: [email protected]
Subject: [7x12MiniLathe] Unwanted taper when turning
Just getting started with a new to me HF 7X10 (extended to 16).? Trying to
practice on brass and the bit ¡°digs¡± in as i move the saddle to the left.
This results in an inward taper.? I¡¯ve tried to adjust the cross slide to
remove any play.? What should i check?
Thank you for any assistance!
Attachments:
image0.jpeg: /g/7x12MiniLathe/attachment/115637/0
--
Chris Albertson
Redondo Beach, California
