# PM 1236 tool post issues



## Blackhawk (Nov 22, 2014)

Having a problem with the quick change tool post I got from mat, I did a video because its easier for me to explain, any help would be greatly appriciated 



http://youtu.be/AzaDzwhG3Bg


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## bvd1940 (Nov 22, 2014)

First are you running fast enough for carbide?????
I use HSS for all but the hardest threading, you might also check if your tool bit holder is square, that might be what is out of whack?
HSS for slow cutting, Carbide fast heavy cuts.
Is that QC holder piston or wedge? Wedge is more repeatable and solid.)
Also are you feeding with compound or cross feed?
Use your compound and set at 29.5 degrees OK?
It also helps to hand or power hone the bits.


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## tmarks11 (Nov 22, 2014)

The tool slanting down slightly on the side to the chuck is not going to significantly impact the cut quality.

As BVD above said, the spindle speed when threading is critical. You want nice threads, use HSS and run the spindle as fast as you can control.   Threads cut at 70 rpm are going to look terrible even if you get everything perfect and are using HSS.

HSS will work better at slow speeds than carbide, as carbide relies on speed and pressure to make the cut, and does not work well when cutting very small DOC.  How much were you taking off on a pass when you were cutting the threads?  Carbide does not like only taking off 0.005" at a pass, and will tend to skip across the surface, giving an irregular cut.

The close up of the tool you used looks like you are using a CNMG insert?  You can't cut threads with that.  You need a tool with a 60 degree point (CNMG diamond has an 80 degree point).  A threading tool has a fairly sharp tip, the CNMG you are using has a fairly large radius on the tip (looked like a 1/32", like on a CNMG 332)  

You said that you believed your setup was correct.  Based upon what I have seen so far, I bet you have some other issues with your setup you haven't shown.  Was your compound set at 29.5 degrees from the 90 degree point (depending on how your compound protector scale is labelled)?  Did you feed with the compound while threading?  How much of a cut did you feed each pass?  What was your feed rate?  What was your spindle speed?

By the way, I suspect the damage you showed on your carbide is because you were grinding rather than cutting. Small cuts are death to carbide, as you really need a good chip to remove the heat from the part.  If you barely kiss the workpiece, you will end up eroding the tip of your carbide.

At the end you showed a 60 degree HSS you ground, which looks like it should work (although I couldn't see how much relief you ground into the tool based upon the video).  Were your earlier threads with the carbide?  

Here is great video on grinding a HSS threading tool (this guy was my instructor at one point):

https://www.youtube.com/watch?v=jnmFUBpmEF0&spfreload=10

He also has two previous videos on grinding a LH and RH tool bits.


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## darkzero (Nov 23, 2014)

The first indexable tool you showed is using a CCMT 32.5 style insert, I use the same tool quite often with CCGT inserts. Not sure if you actually did try using that for threading but it's only good for facing & turning since it's an 80° diamond shape insert, not good for 60° thread forms.

If you are threading soft aluminum or finer threads on steel, instead  of the modified flank method (feeding with compound set at 29-29.5°), try threading with just feeding the cross  slide straight in. The modified flank method is the better way to thread  (arguably) since it's less wear on the cutter, less tool pressure,  etc., but if you're not threading a coarse thread you can get away with  feeding straight in with the cross slide on a lathe this size. Align the tool bit tip with the work using a fishtail & give it a try.

You mentioned jagged/sharp threads. If you were using the modified flank method to cut threads, that's usually a good indication of the compound angle set incorrectly. This is a common mistake with Asian lathe owners new to threading. The compound must be set 29-29.5° off the cross slide or 61-60.5° off the spindle axis.

Many (but not all) Asian import lathes do not come with a full protractor for the compound slide like older American lathes do. Most of them indicate 0° when parallel to the spindle (like the PM1236 does, I have the same lathe). So if you set 29° on the scale you are at the wrong angle for threading. You will need a protractor to set the correct angle for threading as the scale on the compound slide is useless for that.



This is what 29.5° looks like using the scale, incorrect for external threading.








This is what 29.5° looks like for threading.







As you can see the scale is useless for that on the PM1236.







I use a preset slide bevel to set the compound for threading.


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## qualitymachinetools (Nov 23, 2014)

You guys seem to have it covered.

90% of threading problem questions that I get are because the compound is set on the wrong 29.5 degrees, just like Will shows here. 

 Thanks for helping him out here guys! Lot of good suggestions here!

I think Will is better than I am at threading, he sent me a piece once that he machined, and the finish and detail on it was absolutely top notch!


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## tino_ale (Nov 24, 2014)

Good reminder!

I plan on setting the exact 29.5° setting using the DRO angle set function, then mark the compound for easy later re-alignment.


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## fixit (Nov 24, 2014)

I think the tool holder is cut wrong. My tools do not rock in the holder, but I don't use 5/8 inch tools. I normally use 3/8 tools.

fixit


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## Blackhawk (Nov 29, 2014)

Thanks for all the replies.
i reset the angle to 29, touched up my 60d cutter and got a much nicer thread but only with the .012 shim taking up the slop in the holder when I take it out there is to much negative rake on the front of the tool to cut a nice thread. Am I stuck with this?

fixit, I think you are right the holder is cut wrong

darkzero, I set the angle the way you mentioned and sped up to 300 rpm and just drove straight in as you suggested, worked good with the shim but not without. And yes I used hss that I ground on a grinder.

and to whoever said I probably chipped my insert taking a light cut you are correct lol, that's exactly what happened,

happy thanksgiving, hope you all have a great weekend, I'll be back in the garage working on my gun barrel

lanham


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## tmarks11 (Nov 29, 2014)

Blackhawk said:


> ... there is to much negative rake on the front of the tool to cut a nice thread. Am I stuck with this?



well the good news is that the cheap Chinese tool holders only cost $17.50.

http://www.shars.com/products/view/1509/Turning_and_Facing_Holder_1_Type_201

The bad news is they are only worth $16....

But as you have discovered, the cheap QCTP isn't all that great.  Put a new Dorian or Aloris QCTP set on your shopping list, and buy them next time they are on sale.  You will be happy you did.

Full disclosure: while I have used Aloris on machines in the past, I am suffering with a cheap knockoff now.  It is on the shopping list, but other more critical things keep rising to the top....

I like this set because you don't end up paying for a bunch of strange tool holders you will never use, unlike some of the way more expensive sets:

http://www.use-enco.com/CGI/INSRIT?PARTPG=INLMKD&PMPXNO=30822329&PMAKA=404-2304

wait for an Enco 20% off coupon, and it is almost affordable....

EDIT: I just remembered I had bought a shars BXA #1 tool holder to see if it was acceptable, but I hadn't used it yet.  So i just went out to the garage and put a DTI and mic on it to see if it was good.
Mic results: slot is consistant within 0.0009" of top and bottom surface along the length of the slot.  Width of holder is within 0.0004" of the ground back face of the dovetail slot. Seems decent, especially given it is 1/3-1/4 the price of an Aloris holder.

The DTI results really just showed me that my cheap Grizzly piston type QCTP is really...well...cheap.

With the shars holder mounted, I ran it along the Z axis, and the slot is dead flat, no slope at all. So far so god.  

Than I ran it in and out on the Y axis.  0.010" in 3" of travel.  Hmmm. That means that my tool height changes as you turn a piece. Not critical, but disturbing.  That 0.010" variation is due to the dovetail being cut slightly crooked on the Grizzly tool post.  All my tool holders gave me that same measurement.

Guess that Aloris moving up the list....


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## chips&more (Nov 29, 2014)

Blackhawk said:


> fixit, I think you are right the holder is cut wrong




The tool holder could have a slot cut in it that is not square. But first check to see if the sharp corner of the tool bit is hanging up on a not sharp corner in the tool holder. And anyway, it does not amount to any problem at all, just make sure the tool bit is set-screwed down tight, that is all that matters…Good Luck, Dave.


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## qualitymachinetools (Nov 29, 2014)

Hey Blackhawk,

 If the holder is crooked, I can swap it out, that is not a problem at all.

 But the problem you are having is not caused by the holder, there is no way. Especially not with a regular turning insert, or a HSS Ground threading too.

 POSSIBLY on a parting or grooving tool, but thats about it. 

 Can you post a pic of the threads and what it is doing? 

 The Aloris posts are great, yet. But don't spend the money on the Aloris just to fix that, that will not do anything, that post that came with it will work fine.

 If you can sent a close up picture of the tool, the threads, or even a video of the process that we can watch, we can help you out a bit more to get you going.


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## Blackhawk (Dec 1, 2014)

Mat,

ill post a video in a few days, gonna be 72 here in fredericksburg today so ill be out soaking in the sun

lanham


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## Blackhawk (Dec 3, 2014)

[video=youtube_share;eFLn_0QVw6Q]http://youtu.be/eFLn_0QVw6Q[/video]


It's cold again so I'm back at it, positive results, thanks so much for everyone that helped.



lanham


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## darkzero (Dec 4, 2014)

Good to see you were able to get good threads, congrats.

If the shims are working out for you then that's all that matters. One thing that came to mind watching your video. Tool blanks generally have sharp corners (very little radius). All my indexable tools have a moderate radii on the shanks. I'm wondering if the slots on your holders aren't machined with a perfect 90° and may have a small radius in the corner of the slot? If so that could be the cause of your rocking/gap issue. Probably not the case but just a thought.

Some guys will mount tool blanks slightly pulled outwards for various reasons. You can always turn your tool post to square up the 60° point to the work. I still have the same holders you have, I'll check the slots on them tomorrow to see if I get the same results.

It's better to use the tool holder without the v-groove for flat shank tools. The holder with the groove is for holding round shanks, mostly used for boring bars.


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## Radarguy (Dec 6, 2014)

If you truly want to square the bottom of the holder slot it would be easy enough to get an end mill of the appropriate size (like 1/2") and chuck (collet if you have them) into the lathe and cut a new bottom.

Russ


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## Buggy Chief (Nov 29, 2016)

Great write up!!  So being new, what is the angle of the tool post on compound carriage?



darkzero said:


> The first indexable tool you showed is using a CCMT 32.5 style insert, I use the same tool quite often with CCGT inserts. Not sure if you actually did try using that for threading but it's only good for facing & turning since it's an 80° diamond shape insert, not good for 60° thread forms.
> 
> If you are threading soft aluminum or finer threads on steel, instead  of the modified flank method (feeding with compound set at 29-29.5°), try threading with just feeding the cross  slide straight in. The modified flank method is the better way to thread  (arguably) since it's less wear on the cutter, less tool pressure,  etc., but if you're not threading a coarse thread you can get away with  feeding straight in with the cross slide on a lathe this size. Align the tool bit tip with the work using a fishtail & give it a try.
> 
> ...


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## tmarks11 (Nov 29, 2016)

For cutting threads, you want the compound to be 29.5 degrees off aligned perpendicular to the workpiece.  Which on most lathes is at 60.5 degrees on the protractor (as read from the front of the cross slide, or 29.5 degrees as read from the side of the cross slide... where there is generally no mark inscribed).

You want the tool post and tool bit to be lined up exactly perpendicular to the workpiece. You can achieve that with a small machinist square, or use a DTI fixed to the headstock and run the cross slide in and out with the DTI running on the tool bit edge.  Adjust it until you get (almost) no DTI deflection (a few thousands isn't going to matter).

EDITED: Tom points out that 59.5 + 29.5 leave me a degree short of perpendicular.


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## Buggy Chief (Nov 29, 2016)

thx


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## Muskt (Nov 29, 2016)

BC,
Below is a link to my site where I describe the way I set up the compound for threading.  Granted it was on a 9x20; however, the techniques are the same.
I hope it is of some value to you.

http://www.akpilot.net/Threading Setup/Compound Setup For Threading.html

Jerry in Delaware


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## Buggy Chief (Nov 29, 2016)

Excellent write up Jerry for a beginner like me.  I feel like I have enough to get started.  Excellent forum!!


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## tmarks11 (Nov 29, 2016)

Buggy Chief said:


> Excellent write up Jerry for a beginner like me.  I feel like I have enough to get started.  Excellent forum!!


Just one note: since you have a thread dial and if you are cutting imperial threads, then you don't have to leave the half nuts engaged (as Jerry did because he has no thread dial).


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## higgite (Nov 29, 2016)

tmarks11 said:


> For cutting threads, you want the compound to be 29.5 degrees off aligned perpendicular to the workpiece.  Which on most lathes is at 59.5 degrees on the protractor (as read from the front of the cross slide, or 29.5 degrees as read from the side of the cross slide... where there is generally no mark inscribed).



90 - 29.5 = 60.5 
Just saying. 

Tom


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## tmarks11 (Nov 29, 2016)

oops... math in public is hard.


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## Silverbullet (Dec 2, 2016)

I left a comment on your YouTube trying to explain the steps to cutting threads on the lathe. Also I think your tool holders need remilling to get them flat. If it were warmer weather and my back wasn't causing so much pain I'd offer to mill them for you . Shouldn't take much about 15 thousands on the inside bottom. Question when you turn the hold down bolts how much force are you using. You may be bending them.


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## jbolt (Dec 2, 2016)

Just to add a note about Shars. When ever buying from them always check to see if the same item is offered on ebay. If so it is usually (not always) less cost and less for shipping. As an example I just recently bought a BXA#1 tool holder to see how they compare to the CDCO tool holders. They list for $17.50 on the web site and shipping to me was going to be $15 (insane). The same item on ebay was $12 and shipping was $6, a $14.50 difference for the exact same item.


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## tmarks11 (Dec 2, 2016)

only time it seems cheaper to buy off their website is when you are have a discount coupon.  strange way to do business, since eBay fees are so high.


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## Lucky Liverider (Aug 7, 2019)

darkzero said:


> The first indexable tool you showed is using a CCMT 32.5 style insert, I use the same tool quite often with CCGT inserts. Not sure if you actually did try using that for threading but it's only good for facing & turning since it's an 80° diamond shape insert, not good for 60° thread forms.
> 
> If you are threading soft aluminum or finer threads on steel, instead  of the modified flank method (feeding with compound set at 29-29.5°), try threading with just feeding the cross  slide straight in. The modified flank method is the better way to thread  (arguably) since it's less wear on the cutter, less tool pressure,  etc., but if you're not threading a coarse thread you can get away with  feeding straight in with the cross slide on a lathe this size. Align the tool bit tip with the work using a fishtail & give it a try.
> 
> ...


darkzero, how do you like the cold gun? how often does your compressor cycle?


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## Dabbler (Aug 7, 2019)

There's a simple test to see if your QCTP holders/toolpost -end up- having a properly horizontal base for the tool...

Put a test indicator in either the chuck or on the ways and measure the bottom of your tool holder by moving the carriage back and forth (in the Z direction)... It should read less than a thou.  Check all of your holders, and if they are consistent and it is not less than a thou there was a manufacture or mounting problem for your tool post.  If your holders vary (are different from one another) then it could be the holders fault and you might need new ones.  A last test is to check the same holder 4 or 5 times, taking it all the way off, and snugging it in place each time.  If that measurement isn't exactly the same every time then there are serious problems with your tool post - for sure.

Although offshore tool holders and tool posts are more likely to have problems, even a big name top-of-the-line one will have problems the odd time.  Please ensure that your tool post is properly mounted;  there should be .010 to .020 between the top of the nut and the top of your compound slide, or nothing will hold down properly (and nothing will line up, either).

I once helped a guy that thought the two 'hold down' screws that are sometimes provided with the T nut were to hold everything down.... Of course that isn't the case and  the tool holder didn't do its job.  Removed the hold down bolts entirely, milled the top of his T nut and problem solved...


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## darkzero (Aug 8, 2019)

Lucky Liverider said:


> darkzero, how do you like the cold gun? how often does your compressor cycle?



I wouldn't recommend them especially for what they cost (the Exair ones anyway). They use a lot of air & I only run them at 50-60 psi. I got 2 of them for cheap (at different times) years ago. On the lathe I only use it when drilling titanium to help cool things down in addition to spraying on coolant manually. Sometimes I use it when knurling depending on what I'm knurling. Other than that I really don't use it much. They do actually blow pretty cold air though. The one for my lathe is stuck the back of the stand most of the time for storage (magnetic mount).

A few months ago I finally hooked up the other one on my mill. I wanted to hook up an air line to blow chips away & figured I might as well just use the second one rather than sell it.
https://www.hobby-machinist.com/threads/my-misc-quickie-projects.76777/#post-661372

I bought them when I was looking for an alternative to flood coolant or a mister as I didn't want to run flood coolant at home. I wouldn't buy them again that's for sure but they're there & I'll keep using them when needed. I think I may buy a fogbuster some day or stop being a wuss & finally hook up the flood coolant on both my lathe or mill.


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