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PM1340 Solid Tool Post for Dorian BXA QC

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davidpbest

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#1
After some hours of use on the Best & Jacobs Full Custom Edition PM1340, I decided it was time to improve rigidity of the toolpost by implementing a solid tool mount as a substitution for the compound when I don't need the function of the compound for normal turning activity.

In many ways, what I have done is a derivative of what's been done by Jbolt (http://www.hobby-machinist.com/threads/cxa-qctp-on-the-pm-1440gt.57630/#post-479360),

Robin Renzetti

and Stefan Gotteswinter

This implementation is specific to the PM1340 and Dorian BXA Quick change toolpost. I thought I'd document it here in case anyone else is crazy enough to want to attempt this kind of project.

The drawing of the solid tool mounting system I came up with is attached. My implementation is faithful to the drawing.

The first step was to remove the cross slide from the lathe and drill and tap it for mounting the solid tool post mounting system and the registration block. When the solid mount is removed and replaced with the compound, the mounting holes will receive button-head cap screws.

IMG_7694 copy.jpg

For the solid mount, I started with a 28 pound chunk of 1018 I ordered from Speedymetals.com. I squared the block and brought it to final outside dimensions and drilled a center hole which is the basis for all the drawing dimensional references - this hole is concentric with the rotational pivot of the compound and allowed me to re-register the solid block on the mill after it was taken to the lathe for test fitting.

IMG_7693.jpg

Next step - drill the solid mounting block for the mounting bolts, the Dorian toolpost dowel pins, mounting shaft, etc.

IMG_7697.jpg

Then test fitting the Dorian BXA QC toolpost, and checking "wiggle room" in the dowel pin indexing system.

IMG_7701.jpg

IMG_7704.jpg

Good fit. Next step was to finish detailing the solid tool mounting block with chamfers for chip-falls, etc.

IMG_7715.jpg

IMG_7717.jpg

And the most critical step, bringing the final height of the solid tool mount to the exact same height as the compound - this way the individual tool holder height registrations are the same whether using the compound or the solid tool mounting system. The compound height was established on a granite reference plate using a DTI on indicator stand, then the solid mount machined and checked against that as reference. On my PM1340, the top surface of the compound is exactly 2.222-inches above the cross slide. Your mileage may vary - check first.

IMG_7720.jpg

Test mounting of the solid tool mount to the cross slide - checking for fit, registration, etc. I got lucky - everything aligned as hoped.

IMG_7721.jpg

IMG_7732.jpg

After checking the alignment of the Dorian BXA to the spindle centerline and the cross slide movement (video here: https://www.flickr.com/photos/davidpbest/34683487541/in/album-72157684102384825/ ), everything was locked down in preparation for the addition of alignment and registration blocks that would make it easy to remove either the solid tool mount and/or the Dorian BXA QC tool post, and have those same items go back onto the lathe registered and secured to a known position and alignment.

This shows the corner registration block that locks the Dorian toolpost from rotation under load, and registers the toolpost to the same position each time it's secured to the solid mount. The corner block is preloaded against the two 10mm dowel pins that extend from the bottom of the BXA tool post into the solid tool mount. The amount of preload against the two dowel pins is 0.1mm in both X and Z. The inside edges of the corner block are slightly beveled so that the toolpost is forced into registration against the two dowel pins as it's tightened down on the mounting shaft.

After positioning the corner block on the lathe and making sure the Dorian toolpost was properly aligned to the lathe, the solid mounting was taken to the mill, the corner block preload knocked in, then the corner block was drilled and two 4mm dowel pins installed through it and into the solid mount using Loctite.

IMG_7745.jpg

IMG_7734.jpg

IMG_7735.jpg

And finally, an alignment block was added to the cross slide. This ensures the solid mount registers to the same X position each time it's installed, and that it's axial position remains consistent. This registration block is low enough in profile that the compound (when installed) can rotate freely above it.

IMG_7740.jpg

IMG_7742.jpg

Since completing this tonight, I've only had a few minutes to test it out, but some things are already clear. The rigidity is indeed improved. I can now do heavy knurling on stainless steel without the tool post twisting around out of position, and the surface finish on 1018 steel is better. In the next few days, I'll be giving it a full workout - focusing on parting-off difficult materials - and will report back once I have a bit more time in use. Fingers crossed.

Sorry for the long post. Hope this is useful to someone here. If anyone wants the drawing, the PDF is attached.



 

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ddickey

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#2
Thanks for posting. I plan on doing this also.
 

jbolt

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#3
Looks great Dave. You will love the improvement. I like the registration bar you did on the cross slide. :encourage:

FYI I spayed the block and cross slide with Fluid Film corrosion inhibitor. I use the flood coolant from time to time and it works well on my CNC mill which uses flood coolant 90% of the time.
 
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T Bredehoft

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#5
Excellent write-up, you've answered all the unasked questions as to why, and done a bang up job of designing and producing a valuable addition to your lathe. Had I a real lathe, I'd duplicate it.
 

rherrell

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#6
Damn, ANOTHER mod, I'm NEVER gonna finish my lathe if I keep visiting this forum!:D:D:D Great job!!!
 

woodchucker

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#7
Nice work. I don't use indexible cutters, so I need to move my tool post to take cuts as the HSS is straight blanks, not offset like a indexable. So this isn't an option for me right now. I do like the work you did. Also like all those nice festool boxes over by the stairs......
 

darkzero

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#8
Nice work. I don't use indexible cutters, so I need to move my tool post to take cuts as the HSS is straight blanks, not offset like a indexable. So this isn't an option for me right now. I do like the work you did. Also like all those nice festool boxes over by the stairs......
I do use indexables but quite often I adjust the postion of my TP as well. The one David made looks nice though, he could simply remove the dowel pins & the fence to reposition the TP if needed. I'm curious about these as lots of people seem to be making them lately. However I use my compound slide quite often so I don't think I will be making one anytime soon.
 

ddickey

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#10
You can still do this without the dowel pins. Removing the compound should still increase rigidity. Not sure how significantly though but I suspect a lot.
 

ddickey

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#11
Would there be any reason to not mill a T-slot on the top of the block?
Then you could use the existing holes for the dowel pins.
 

wrmiller

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#12
I do use indexables but quite often I adjust the postion of my TP as well. The one David made looks nice though, he could simply remove the dowel pins & the fence to reposition the TP if needed. I'm curious about these as lots of people seem to be making them lately. However I use my compound slide quite often so I don't think I will be making one anytime soon.
I too use indexables, and I find myself adjusting the tool post fairly often to the point I am going to replace the top nut with a lever soon to make it easier to do so. And I also use my compound often enough that removing it would not be an option for me. I guess I don't have any reason to do something like this yet, but it is an interesting idea, and David's is a nice example.

However, if I do ever need to start taking large cuts on larger work pieces, maybe I can use that as justification with the Significant Other to get a larger lathe? :D
 

davidpbest

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#13
Update: Since installing this on my PM1340 two months ago, I have yet to remove it and reinstall the compound. Of course, I haven't machined any tapers in that time, but I have enjoyed the additional rigidity.
 

ddickey

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#14
I just finished mine last night. I used the t-slot which already had the holes drilled for the dowel pins.
There is a reason I did this that I'm too embarrassed to say.
 
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wrmiller

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#15
Update: Since installing this on my PM1340 two months ago, I have yet to remove it and reinstall the compound. Of course, I haven't machined any tapers in that time, but I have enjoyed the additional rigidity.
I don't seem to be having any rigidity issues and get good surface finishes on barrels, comps, and whatnot, but then I'm not pushing my lathe very hard. But I do seem to be cutting angled surfaces/bevels quite frequently so the compound gets a fair amount of use.
 

jbolt

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#16
I didn't build my solid tool post riser as a permanent replacement for the compound and switch back and forth when I need to do short tapers. For small tapers I have been grinding tools for that purpose to use with the solid riser. The solid riser is an over all improvement when it comes to finishes but really shines when removing large amounts of material quickly, and for parting & knurling. If what you are doing now is working I would not bother with a solid riser. I built mine to get a little bit more performance out of the size of machine I have. If I had the room and means I would get a second larger lathe for larger work.
 

ddickey

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#18
Well, let's just say because you're excited to use your new spiral fluted tap doesn't mean you don't have to check for correct tpi. Idiot. :bang head:
 

jbolt

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#19
Well, let's just say because you're excited to use your new spiral fluted tap doesn't mean you don't have to check for correct tpi. Idiot. :bang head:
Ha ha. We've all been there!

Sent from my SM-G955U using Tapatalk
 

9t8z28

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#20
Amazing job and super clean manchine! I am doing this mod right now to my Sieg SC4 8x20 lathe. I purchased 2 blocks of 1.5" x 4" x 4" in 01 tool steel and the other cast iron. I chose to go with the cast iron because I think it will do better to dampen vibrations if any. Right now I am drawing it up on paper and seeing your thread has given me a lot of great ideas. I too saw Stefan's and Robin's videos and after knurlering some 3/4" and seeing the toolpost and compound deflecting I chose to do this mod. I do not think that initially I will use dowel pins and corner block to secure the toolpost because I still want to be able to rotate the tool post if necessary. I do like the way you are using the stop to register your solid post.
Did you have any purpose behind tapering the block the way you did or It was just for cosmetics ?

Thank you
Brandon
 

9t8z28

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#21
I can either use class 40 cast iron or 01 tool steel. What do you recommend ? My block will be very similar in size, height and width to yours.
 

davidpbest

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#22
A
Did you have any purpose behind tapering the block the way you did or It was just for cosmetics ?

Thank you
Brandon
Thanks. I angled the solid tool block to encourage chips to fall away and not collect on various ledges. I can't really speak to your question regarding cast iron or tool steel. I used steel because it was more easily obtainable and less expensive than cast iron (at least from the suppliers I use), and because I try to avoid machining cast iron when I have that option.
 

Buffalo20

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#23
Interesting project, the workmanship is excellent, you had me right up until, the alignment blocks. I'm constantly angling and pivoting the QCTP, to me the blocks, would be a limiting PITA.
 

ddickey

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#24
The solid tool post even without the alignment block and the dowel pins will still increase rigidity.
If I will just be turning or using my knurler I'll put my dowel pins in. If not they come out.
 

davidpbest

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#25
Interesting project, the workmanship is excellent, you had me right up until, the alignment blocks. I'm constantly angling and pivoting the QCTP, to me the blocks, would be a limiting PITA.
To each his/her own I guess. Like Robin Renzetti, who initially posted on YouTube about this, my tool inventory on QC tool holders has grown extensive enough that I no longer have to rotate the tool post for the types of things I do.

IMG_7210.jpg

I also like being able to program the DRO with my tool library, and just call up the tool number of the just-mounted tool and know that it's cutting position relative to the CL of the spindle is already calibrated in the DRO.

But I completely understand the sentiment and need for a rotating tool post if the selection of tools is limited or you need more flexibility. It's hard to know how much rigidity would be sacrificed without the anti-rotation stops since I never tested it in that manner. In an ideal world, I suppose this could be a rotating sold mount with some kind of plunger-indexed stop system operable from above to secure the tool post from rotating - at least in a few positions, one of which is indexed to 90-degrees off spindle CL axis for parting operations (which is one of the main motivations for me tackling this project in the first place).
 

Buffalo20

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#26
David,

I wasn't trying to belittle your project in any way, maybe I'm lucky, but I've never has the QCTP twist, no matter what I've done, including breaking the head off a boring bar. I broke the brass shear pin in the drive, but the QCTP never flinched. Obviously, I'm still learning, by watching and listening to other people practices and opinions, to me, is like going to school.

I have about 75 blocks load with tools, but no DRO as of yet.

To me, the block, you made, to replace the compound is excellent, that alone should increase rigidity greatly. What do you think. the block weights??
 

davidpbest

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#27
To me, the block, you made, to replace the compound is excellent, that alone should increase rigidity greatly. What do you think. the block weights??
Thanks Jack. The solid tool mounting block, without the Dorian QCTP attached to it weighs 15 pounds, give or take a few ounces. I've had the QCTP twist off axis on the compound many times using a scissors-type knurling tool with 12 TPI pitch straight cut (not diamond) carbide knurling wheels when machining 316 stainless steel. Example - 1.25" diameter, couldn't get the knurl buried deep enough to get a clean point between teeth no matter how honked down the tool post was:

IMG_5730a.jpg

With the solid mount I no longer have that problem and can really bury the knurling teeth in stainless. The extra rigidity has really helped parting-off ops too - especially in stainless. But I have yet to break a boring bar - that does not sound like fun. Maybe I should push it harder? FlusteredFlustered
 
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