# Another solid tool post riser



## spumco (Jul 31, 2019)

Thanks much to the folks here for inspiration - and of course Robin Renzetti (and others) who got me thinking about this.

Not much to say that hasn't been covered before, other than it's really handy to have a trunnion table. Three ops and done.

No interesting design details  - basically a copy of the versions everyone's posted here and on Youtube.  Only difference was that I relieved the bottom about .025" and left 4 'feet' to make post-tensioning easier to lap flat to the cross slide.  Also some extra holes at the rear of the slide for future rear-mount tool post.

Threadmills are your friend for stuff like this.

Yes, it makes a huge difference in all operations I've done so far.  Radial infeed threading works fine, as does cocking tools over for small chamfers or tapers.  I can get away with much heavier cuts with better surface finish, and of course parting under power feed is trivial.

Pro Tip:  Completely remove both gib adjusting screws before drilling the cross slide.  Doh!

-Ralph


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## Nogoingback (Aug 1, 2019)

Great job.


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## Creativechipper (Aug 1, 2019)

Looks fantastic, my poor 10x30" lathe does not like parting operations.
Broke my 1st insert on some copper the other night.
Its amazing how much flex parting can cause on the QCTP as the lathe tries to suck it under my work, even with everything tightened down centered and minimal hang out from spindle.

  Your set up looks solid!!  I like it


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## NortonDommi (Aug 2, 2019)

*Creativechipper,
*Have a look at the thread called Parting trick.


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## alloy (Aug 2, 2019)

I like thr trunion table.  I'm getting a machine with a 4th and a table is on my short list of things to make.


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## spumco (Aug 2, 2019)

Thanks everyone.  Drilling with the carriage went exceptionally well.  Decent Shars chuck on a 3/4" straight shank in the boring bar holder.  No worries about the toolpost rotating!

Note the swanky oxide finish - rust is the enemy in my shop.




This is no longer a dreaded operation but I think a pilot hole would be adviseable for this sort of thing.




Next trick is to set up all my tool offsets in the TouchDRO.  The drill chuck took a few minutes to indicate in, but was very repeatable.

-Ralph


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## spumco (Aug 2, 2019)

alloy said:


> I like thr trunion table.  I'm getting a machine with a 4th and a table is on my short list of things to make.


Thanks; it's unbelieveably useful.  I've got a painfully long thread about the DIY 4th and trunnion table in the CNC section.


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## Indexmill (Aug 4, 2019)

Hi,

Why does one need a tool post riser?


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## Nogoingback (Aug 5, 2019)

Solid tool post mounts replace the compound when it isn't needed, which is often most of the time.
The advantage of having one is that they  provide greater rigidity to the tool.  This allows greater depth of cut,
better surface finish and fewer problems with  operations  such as parting off.

A number of folks on the forum have them, and the general opinion is that they are worthwhile.  They probably provide the greatest benefit to smaller lathes that are inherently less rigid.

I put one on my Logan, and I wouldn't be without it.


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## spumco (Aug 5, 2019)

Indexmill said:


> Why does one need a tool post riser?



The theory is that substituting a solid block in place of the compound will improve the cutting tool rigidity.  Assuming that compound is the most flexible component in the chain between the part and the tool, if one mounts the toolpost on a solid block there is no (or less) possiblity of the tool moving out of position while under cutting forces.

The 'riser' is simply a big lump of metal to get the tool & toopost to the correct height.  In addition to eliminating any clearances in the compountd assembly, the compound mount and T-slot itself can flex.  The toolpost is also usually free to rotate around the hold-down bolt if the cutting forces are high enough.

Robin Renzetti (youtube) did a great job of explaining the theory, as well as demonstrating the advantages to eliminating the compound.  My experience in the short time I've been using it has been very positive.

The downside, of course, is that short tapers require some sort of alternate strategy.  One option is to angle the tool in the tool holder and treat it like a form tool.  The improved rigidity makes using form tools much easier - I can attest to that personally. Or I can re-install the compound if I have something longer to do.

Radial infeed threading works fine for me - I'm not cutting very large, coarse threads - and the thread surface finish is acceptable with sharp tools.

This also means I don't have to re-indicate my tool holders to square/parallel to the Z axis, and once I set my  X off-set for each tool in the DRO switching tools is very repeatable.

-R

Nogoingback beat me to it!


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## spumco (Aug 5, 2019)

Creativechipper said:


> Broke my 1st insert on some copper the other night.


BTW, copper is not self-lubricating like brass or bronze.  It's very ductile - stringy chips and 'grabby'.  I'm not an expert, but the times i've done work on copper a mist setup worked well to keep the part, tool, and chips cold.  Colder = more likely to break chips than birds-nest and jam up.


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## hman (Aug 5, 2019)

I recall from deep in my dim past that the preferred lube for copper is "lard oil."  Back when I was a grad student, I'd occasionally have to drill tiny holes (~#60) in copper, and lard oil, borrowed from our on-site machine shop, definitely helped.


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## Creativechipper (Aug 6, 2019)

I read somewhere that full fat milk is great for copper.

 I will have to check into a better set up for my parting operations. I really dread parting on steel or anything tough.


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