PM 1236 Headstock alignment

Actually the RDM is also for adjusting - unfortunately it is a trial and error process. Without photos or the manual, it's hard to give you any better advice. Please forgive me for repeating that the chances of the bar being perfectly straight are limited. I bought two from McMaster (12" and 18" lengths) and both are great diameter wise and both were out over the length.

Mark's advice to contact @darkzero and @Ray C is still one of your best bets for help since no other PM1236 owners have picked up on the thread thus far. I believe Will and Ray get a "notice of mention" since I used the "@" in front of their user names and perhaps will pick up here. But a p.m. from you would be more certain.

First things first... Matt and I are friends and I still think the world of him, his business and the equipment he sells but, be apprised, I do not represent his company nor, do I provide warranty work for his fielded equipment. I'm purely a customer and matter of fact, need to give him a call to order another big heavy box. Anyhow, due to the difficulties in working commercially in the "hobbyist" arena, I no longer conduct business transactions in that area. After 3-4 years away from this web site, I'm back only to show shop and fabrication techniques purely to help keep the trades alive -and do it in a friendly forum.

Alignment:

In general, this style of lathe has (as I recall) 4 main bolts that keep the headstock on. I'm pointing at two of them and the other two are back by motor. I cannot take pictures because of the way the shop is currently laid out. Those bolts back by the motor had a a couple push-pull screws associated with them and that is how the head is moved precisely. All 4 bolts have to be loosened to utilize the push-pull bolts.

If a lathe has been assembled properly at the factory, it should survive shipping and only need leg/bench adjustment to make it cut straight. However, rough shipping can bump things out of whack. If it's been disassembled, alignment goes out the window. I'm not sure what bolts the OP believes are missing but, it sounds like he's talking about the alignment pin holes for the lower gearbox. Without pictures, it's hard to say.

Even after 4 years, Matt has supported many customers with issues that cropped-up down the road -and for a variety of reasons. Strongly advise that Matt be consulted. As far as I know, that lathe is still the same pattern as they have always been and he knows every nut, bolt and screw in them.
IMG_20180112_135232.jpg
Regards

Ray
 
I sent an email to Matt, now awaiting a reply. Thank you to everyone that has responded so far!
 
I find pictures get things resolved much quicker. Get a browser plug in for the picture mark ups, the screen grab plug ins have drawing and text ability usually.
 
You are right, pictures are the best. He did send one, and I knew what they were right away. Those screws would have had to be removed to take the headstock off when it was taken apart.
Its just something you can pick up at a hardware store for about a buck, just a pair of 8mmx1.25 socket head cap screws. He sent me a pic, they are the adjustment screws that are above the motor, that are talked about on the top of page 30 in the manual.
http://www.precisionmatthews.com/wp-content/uploads/2017/02/PM-1236-v4-1-2017-indd.pdf
It will be a whole new machine with those back in and it adjusted right, you can adjust that in as close as you want now, I would shoot for about .0005 over 6" or even better, the closer you have it the better, but it may take some time to get it that close!

Hey Ray, great to see you on here!
 
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I picked up the recommended bolts from the hardware store but ended up having issues getting them started in the holes. Since the back of the lathe is fairly close to the wall it was difficult to align the head so I could get the bolts started. I dropped one of the new bolts and it fell into the cabinet, when I got in the cabinet I found 2 bolts still in a sealed plastic wrapping that were the same size as the ones I had just bought except they were slightly longer. I was able to get these started in the holes much more easily!
After a couple of hours of tinkering I got the head aligned better than it was before but still not as close as I would like. Since I needed the lathe to do some work on a project that a slight taper isn't an issue, I tightened everything down and put the lathe back to work. I'll re-visit the alignment process later, hopefully it will go much more easily next time.
Thank you to everyone that offered advise and suggestions to help get me up and running again!
 
I received my PM-1236 in the spring of 2017. I've been impressed by how straight it cuts. Absolute confidence that when I turn the cross feed to take a cut that's what it does & without taper.
A few weeks ago that changed. I started getting .002 taper over a couple inches. (I'm sure I know what caused it) Yesterday, I put a piece of 2" diameter material (cast) in the lathe. Sticking out about 2 3/4" Took a clean up cut to get rid of the "crust" then took a .015 doc & check with a mic & had .003 taper.
Out came the cast, I put a piece of 1 1/4" tool steel in & started to adjust the headstock. I got it adjusted to no taper over about 5". I put the cast back in & was disappointed when I still had 3-4 thousands taper! I spent the afternoon adjusting, taking .010 doc's, adjusting, more cuts more adjusting until I had less than a few tenths difference. I made sure everything was tight, covers replaced & buttoned up. Took a deep breath & took another cut......perfect:)
I sure hope this was the correct procedure. I don't want to go through it again. I'm getting too old for all the kneeling/squatting/deep knee bends associated with getting it squared away.
 
Just to be clear the two collar test cut method does eliminate any issues with chuck, whereas the OPs method clearly does not. As I've recently learned even 4 jaw chucks dialed in at the chuck will almost always be out a little a few inches down the bed. RDM can be used but is not as fool proof as the two collar method, and to me is more work. Both are impacted by bed wear and twist.

A method that can be used to get very close more quickly and isn't impacted by bed twist or wear is to take a facing cut on a large diameter (like a face plate). A lathe with the headstock misaligned will cut concave or convex on a facing cut in addition to the taper in the turning cut. By taking a facing cut and running an indicator along the back side of the cut you can find whether you are cutting concave or convex (running an indicator on the front side should read zero as it follows the tool path). Then you can adjust the headstock so that the error is split across the front and back. This will get you very close with one test cut. You can chase it from there as precise as you want.

Fixed headstock lathes HS/bed to cross slide perpendicularity is typically specified to well under 0.001" in the swing on a facing cut and only on the concave side. This is closer to zero than most of us can hope to achieve and on these imports with "adjustable" headstocks getting as close as possible as you can/desire to this is the first step in my mind. Once this is done, the lathe can be "leveled" and finally adjusted to cut without taper using RDM or two collar method and fine adjusting the twist.
 
Bob,
If you need some help I can call you in the morning and tell you what to do. When you moved it down to the basement the head wasn't put back on right or got bumped. Private message me your phone number and I can give you a call. Rich
 
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