Is my lathe level good now? Precision Matthews PM1236T

The reason your lathe dog doesn't reach your drive plate is because you're using an MT5 center instead of a sleeve for an MT3. At least this is what happens on my lathe also.
ALso try flipping that Edge Alignment bar and see if the numbers repeat.
 
TonyBen said:
I'm gearing up to do some chamber cutting and barrel threading. My lathe was set up good enough to do what I've been doing the last 18 months, but I was not confident that it was good enough for precision cutting threads and chambers using the tailstock.

I bought one of those EDGE products alignment bars, a new Bison MT5 dead center and a brand new Starrett 12" level. I don't have any 123 blocks, so I used the flat in front of the carriage to level the bed. I'm solid from end to end. I already had a Skoda MT3 live center for my tailstock and I bought it new, so I know it hasn't been abused.
I seated both centers with a block of wood and a rubber mallet. I also checked both centers and both had nearly no measurable runout. My B&S indicator needle drifted maybe 0.00005" while rotating.

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Headstock to tailstock level...

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I used the EDGE alignment bar and got the tailstock aligned from side to side down to 0.0001" but decided to check the height of the centers as well. Before alignment, I had a bout 0.003" difference between the headstock and tailstock. The tailstock was higher than the headstock. After leveling, the tailstock was now 0.001" higher than the headstock.
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I also used the alignment bar to level the bed from end to end.
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I have a backplate and a dogleg, so I'll do a final cut later but I've never used them before. it wasn't until I tried to get set up to do a test cut that I found out the dogleg was't long enough to reach my backplate. I'll rig up something today to drive the leg.
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I also need to find a way to lock down my cross-slide since the DRO encoder covers up the locking screw.

Tony.
Click to expand...
I have a PM1236 also and the same issue with the DRO Scale on the carriage, I am planning to space the scale out and cut a small hex on a headless bolt so I can get to it with a thin wrench between the 2....
 
David2011 said:
Completely agree. I like to cut the barrel threads to fit into the receiver with just a little drag to assure concentricity. Cut and try, repeat until happy. Not very scientific but it seems to be a reliable method. Theoretically the taper of the threads should make the barrel self aligning but a little extra help doesn’t hurt.
Click to expand...
Aim small miss small...
 
ddickey said:
The reason your lathe dog doesn't reach your drive plate is because you're using an MT5 center instead of a sleeve for an MT3. At least this is what happens on my lathe also.
ALso try flipping that Edge Alignment bar and see if the numbers repeat.
Click to expand...
I never even knew there were sleeves. Thanks for that!
 
Does anyone have a good MT5 to MT3 sleeve suggestion on what brand of to buy? Don't mind paying more for non-chinese stuff.

Tony.
 
Well, it looks like I solved my cross slide lock issue. The bracket that holds the encoder on had a relief cut where the lock screw is. I opened it up and am just barely able to get a ball end hex wrench in there to lock the slide with the encoder fully installed.

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No blockage from the bracket.
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Encoder fully installed. Just enough room to access the set screw!
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The large hunk of steel I have on the lathe is a shot-out test barrel from Bartlein. I measured the OD on both ends and it's accurate within 0.0002" from end to end. I might just throw on a dial indicator and use it as an alignment bar. It's 1.250" thick.

Tony.
 
Okay, so I ditched the plate and the dogleg and used a 4-jaw chuck. I was getting way too much chatter. Now that I have a semi-clean cut I got the ends to within 0.0004" over 15 inches of travel.

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I'm still trying to figure out how to get clean cuts with this, but I think that less than half a thousandth over 15 inches is pretty good.
I doubled the feed speed and increased the RPM to 800 versus 500 and I ended up with a cleaner cut.
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Tony.
 
Last edited:
Tony, I don’t know much about carbide inserts but in the category of the blind hog and an acorn I found something that is almost magic for me. ISCAR offers inserts that have an IC908 coating. I’ve been using them for finish work on my little 11x26 lathe and getting beautiful finishes at moderate speeds. On annealed 4140 about the diameter of a barrel blank the finish is very smooth and shiny at 1200 rpm. What really sets these inserts apart is that they work well at shallow depths of cut and fine feed rates.

I recently did a volunteer job involving making parts from all thread using a DCMT070204 IC908 ISCAR insert and the finishes were great. It’s not what you would find at the hardware store at 1-1/8” x 7 tpi left hand but it’s still in the “go with what’s available” category. That unknown steel finished well at 720 rpm at diameters from 0.910 down to 0.680.
 
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