Author Topic: MT2 die holder....attempt  (Read 891 times)

Offline smthrll

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MT2 die holder....attempt
« on: January 23, 2017, 06:17:26 PM »
Here's my attempt at turning a #2 Morse Taper.  My plan was to make a tailstock die holder as some of the rest of you have done.  The taper portion turned out pretty well - after some trial.  I took a 7.3" piece of 1018, and offset the tailstock .183".  I have to admit to being shocked when it turned out correctly, fits the sleeve nicely.  I turned it between centers, then I flipped it end for end to turn the shaft portion (so I could feed with carriage moving to the left).  That's where I had some problems:
-I re-aligned the tailstock before turning the shaft, and the finished shaft portion isn't straight (the .5" portion).  I'd liken it to a bent pool cue.  Could this be due to taking too heavy cuts?  I was cutting .040" experimenting w depth of cut etc,  and looking back, wonder if that would push things out of alignment?
-is it ok to flip things end for end on centers and expect alignment? 
-finish isn't great - I've had success finishing 1018 at higher RPM's (like a .003" at 1500rpm), but with my light lathe and the lathe dogs, things started to shake at 700.  I haven't tried proper cutting oil though as some posts have suggested.
-using 4 way tool post - I couldn't cut the full length of the shaft.  The carriage runs into the tailstock or headstock, so I have to move the bit from the right position to the left position on the 4-way to finish up. I must be missing some easy solution here...

Getting ready for attempt # 2.  Thanks for suggestions.

Rollie

Offline mexican jon

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Re: MT2 die holder....attempt
« Reply #1 on: January 23, 2017, 07:19:08 PM »
You should be able to flip the work when turning between centres  :thumbup: The big question would be how did you realign the tail stock after turning the taper  :scratch: :scratch:
People say you only live once ! I say thank F@*K can't afford to do it twice.

Offline smthrll

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Re: MT2 die holder....attempt
« Reply #2 on: January 23, 2017, 07:38:24 PM »
I used the dial indicator and pushed the tailstock back the other way the same .183".    Maybe that's cheating.  I was slacking and should've used a test bar to verify exact alignment.

Offline mexican jon

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Re: MT2 die holder....attempt
« Reply #3 on: January 23, 2017, 07:56:08 PM »
 :lol: I think you may already know where it went wrong  :clap: I always (I learnt the hard way  :( ) use a test bar to align the tailstock  :thumbup: I've never seen or heard of another way that guarantees parallel turning when using centers, I'll wait to be corrected  :loco:
People say you only live once ! I say thank F@*K can't afford to do it twice.

Offline sparky961

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Re: MT2 die holder....attempt
« Reply #4 on: January 23, 2017, 08:28:20 PM »
I used the dial indicator and pushed the tailstock back the other way the same .183".    Maybe that's cheating.  I was slacking and should've used a test bar to verify exact alignment.

It may be cheating a bit, but I'd think you'd get it pretty close that way.  For your attempt #2 I'd definitely make sure you know that the headstock and tailstock are in alignment when you need them to be.  If you have a compound with enough travel, you may be able to set that to turn your taper instead of setting over the tailstock.  There's less work getting things back to normal when you're done.

A cut that's 0.040" off the radius is pretty aggressive for a small, light machine - especially when the part is between centers rather than gripped tightly in a chuck or collet.  And even more so with the small diameter to length ratio you have with this setup.  It's great that you're experimenting and building your confidence, but you've likely bumped into a machine/setup limitation here.  Save those aggressive cuts for when the workpiece is very well supported and you're cutting close to the support.  There are lots of definitions for this, but one that might work is that you have full engagement the length of the jaws of your 3-jaw chuck, and you're cutting no more than 1.5x the diameter away from the jaws.  I'm totally making up a "rule of thumb" there, but that's pretty much my criteria for pushing the 25HP motor on "my" CNC lathe at work to start whining.

Regarding the vibration, see if you can offset the weight of the dog with something mounted to the faceplate.  That, or see about a smaller dog that isn't subject to as much centrifugal force.  You already figured out part of the trick to 1018 and nice finishes.  Once you get things balanced and can get your RPMs back up where they need to be, try taking a bit heavier cut on the finishing pass instead of a few thousandths.  You'll probably be quite happy with the results.

There will be deflection that varies depending on your DOC, so to make sure you hit your target diameter, try the following:

Target Diameter: 0.875"
DOC on finish pass: 0.010"

Let's say you start with 1" stock.  You rough it with whatever works until you're at 0.915" (Target + two more passes).  Adjust to take 0.020 off the diameter (remember, this is the same as 0.010 DOC) and take the cut at the same settings you plan on using for the finish cut.  Although you'd think it would measure 0.895 now, it probably wont.  It should be close though.  Figure out how much you have left and take one more cut with the same settings and adjusted DOC.  At this point you should be pretty darn dead on your target diameter, and a nicer finish than you're getting now.

I apologize if you're beyond this point and it sounds a little basic.  But as simple as this all sounds, it takes some practice to be able to hit a final dimension without sneaking up on it.  I know lots of experienced people who still don't get it.  With some materials it works, but with others (like your 1018), the finish goes to hell if you take light cuts.

Unless you're in a garage with decent ventilation, don't bother with cutting oil.  It won't help much with the finish, if at all.  It will just make a lot of smoke.  If you're going to use anything, use water soluble coolant in a little squirt bottle to keep everything well cooled.  Don't wait for something to heat up before you squirt it, keep it cool.

Regarding not being able to cut the full length, that's kinda the nature of the beast with between-centers turning.  If you didn't have the tailstock quill well-extended, try extending that out enough to get some room but still give good support.

There are so many more things I could go into, but it's probably best if I just let you go figure the rest out for yourself.  You'll get it if you stick with it. :)

Offline ieezitin

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Re: MT2 die holder....attempt
« Reply #5 on: January 23, 2017, 09:06:31 PM »
I agree with everything said with the advice given... i have this to add.. you were surprised when you moved over the tailstock the given amount to give you the desired taper.. that's the power of trigonometry and a the biggest asset to understand  in machining, a humble hobbyist bench top lathe can with reputability remove .0001 (not a typo) with the compound using trig.. as already discovered sliding over the tailstock using math will create accurate tapers.

The process is the same it all boils down to solving a right angle and applying the decimal point and reading as far to the right as needed to get the precision required..im encouraged your experimenting its the best learning practice.. best of luck..

Anthony.
If you cant fix it, get another hobby.

Offline smthrll

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Re: MT2 die holder....attempt
« Reply #6 on: January 23, 2017, 09:20:34 PM »
Thanks for the great tips guys.  I'm totally stoked to try this again.  I've read so many posts and watched so many videos - lots of conflicting advice and some of it is pretty tough to decide what is exactly applicable.   It's nice just to ask a direct question to a real person. 

I like the idea of  "sneaking up" with a heavier cut as well, rather than my .003".  I'll have another go at it this weekend.

Rollie

Offline sparky961

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Re: MT2 die holder....attempt
« Reply #7 on: January 23, 2017, 10:25:35 PM »
I like the idea of  "sneaking up" with a heavier cut as well, rather than my .003".  I'll have another go at it this weekend.

You have the notion of "sneaking up" a bit reversed.

Sneaking up more accurately describes what you were probably doing the first time around.  As in, you take heavy roughing cuts until you're as close as you're comfortable with, then you take a lot of very light cuts trying to end up at the final dimension without going too far over what you want.  You probably only take 0.003" or so because you figure if you go over it won't be by that much and the part will still be ok.  Right so far?  Yup, been there.

The method I'm describing would be called (pretty sure anyway) a "trial cut".  You're essentially taking one extra pass before your finishing pass that duplicates the cutting conditions of the finish pass, except it leaves very close to the same amount of material on the part for one more final pass.  It gives you one chance to make adjustments based on a measurement after the trial cut.  As long as your final cut is removing close to the same amount of material, you should be able to directly dial in the difference and end up with the right size.

I think you probably got most of that the first time around, but if you're telling anyone else what you're doing you'll want to differentiate between "sneaking up" and a "trial cut".  Sometimes you can't avoid the former, and sometimes the latter is the only way that gives acceptable results.

Offline Biggles

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Re: MT2 die holder....attempt
« Reply #8 on: January 24, 2017, 01:01:03 AM »
I agree to all that has been said already except that I would keep the heat down if you’re going for an accurate job. In addition let the work cool down before you take your last few runs.  :coffee:

Online Pete.

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Re: MT2 die holder....attempt
« Reply #9 on: January 24, 2017, 04:38:31 AM »
Next time you are going for a parallel cut make a trial cut then measure eaxh end with a mic. Adjust the tailstock until its cutting true then bring it down to size. Of course now you have hit the taper angle first time with your set-over you're guaranteed never to manage it again :)

Offline smthrll

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Re: MT2 die holder....attempt
« Reply #10 on: January 24, 2017, 08:13:34 AM »
I appreciate all the pointers.  When I set the tailstock over, I took a couple test cuts and then tried the procedure I saw on the college machinist Youtube channel.
-painted the taper with dye
-scribed a line every .5"
-measured the diameter at each line, and found it was uniformly increasing by .025"

If somebody had been watching, I would've struggled to keep the shock off my face and replace it with a look that said "ya, I meant to do that".

I'm starting to gain an appreciation for the possibilities of accuracy.  So, for next time:  Trial cut for finishing, heat, and recentering the headstock.  3 things to nail down!!!    Oh, and extend the quill so I can cut shaft in a complete pass...



Offline smthrll

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Re: MT2 die holder....attempt
« Reply #11 on: February 12, 2017, 11:30:17 PM »
I just wanted to give an update on my project.  It's taken me a bit of time but I managed another MT2 holder.  Pete was correct when he told me that I'd never hit the taper angle first try again - I promptly ruined my second attempt at the holder, thru a process of over and under correcting.  However, the 3rd attempt went reasonably well.   I tried the recommendation of trial cuts, and managed to nail down the final diameter of the taper and the 1/2" shaft portion by taking a final .010" cut, and the finish came out pretty decent.  I watched the heat buildup, and let things cool as I approached my final diameters.  Of course, stupid mistakes prevailed - I was cleaning up the 1" diameter that separates the shaft and taper, that's when I discovered that I cannot multi-task.  I left a plunging tool bit on the other side of my 4/way tool post, which bit into the taper when I wasn't looking.  You'll note the mess where my extra tool bit in.    From now on, only 1 tool bit loaded at a time (and a QCTP on the Christmas list)!!

The knurled cylinder turned out ok as well.  I did some reading and originally thought I had a 21 pitch knurl.  I counted the knurls and found 51 teeth on a .75" wheel.  This works out to 21.656 teeth/Inch circumference  OR .046199"/tooth.  I originally based my calculations on 21, thinking I could just drop the decimals, but found my lines overlapping.  When I took into account the extra 0.656, things seemed to work out right.  If my notes are right, I ended up with 73 lines on 1.072" diameter. 

Drilling:  I drilled out 4" of cylinder to 1/2".  I used several drill bits (every bit in my kit) between 3/8 and 1/2", but the bore is not smooth,  There are still rough marks.  I'm wondering if a reamer is the better option?  Each bit passed through easily enough, and thought I was taking small steps, but the bore is still kind of rough.  It fits nicely on the 1/2" shaft though. 

Still learning lots every time I touch my lathe.  I also learned what to do when the MT2 drill chuck gets stuck in the tailstock, and how to lengthen it with a small bolt tapped into the end, so that it will eject without problems. 

Thanks again for the tips and advice.   Onto making the actual piece that will hold the dies now.

Rollie

Offline ieezitin

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Re: MT2 die holder....attempt
« Reply #12 on: February 13, 2017, 06:39:27 PM »
Rollie

Glad your still into experimenting its the only way to learn.

Drills don't create smooth holes neither do they drill to size also they have a tendency to wonder, Getting a better finish plus a more accurate diameter a reamer will do the job, remember though the reamer has to follow the hole before it, reamers are not perfect.

Dead nuts holes sized and located are bored and layout plays a major factor, but that's not an everyday thing but keep it in mind when your planning out your work.

if its just holes you want and need drills do the work and with correct layout methods and tools will get you within .003.

I use spot drills for centering my work I don't like center drill because the tips break, I use a prick punch to center pop my layout as it eliminates somewhat the drill wondering in fact its a three facet punch. I have a trash set of drills which obviously i use for trash work I have a pristine drill set i use on my more important work, I have full sets from letter number and fractional very handy to have. I use slot end mills a lot for drilling to being held in a collet.

Drilling / boring holes, locating them, getting finishes correct is a vast subject which I would suggest you dive into the Internet, you-tube is a formidable resource as you are aware and when you need down to earth live answers asked them on here.

All the best

Anthony.
If you cant fix it, get another hobby.