Design Advice!- Warco GH600 Solid Topslide

[Richard Kirkman 1Participant @richardkirkman1]

Good Evening All,

I am the new owner of a 2nd(3rd?) hand Warco GH600. My colchester student was too large and difficult to move, so it was time to downsize.

The lathe came with an unfitted ‘Multifix’ style toolpost and holders. The current topslide is too tall for it to be fitted to, so I am planning on making a solid block to mount it to.

My question is about overhang and Gibs.

The plan is to machine a piece of cast iron into the following shape, with the protrusion being centered in the block.

(Dimensions yet to be finalised; height is likely to change, but I need to measure the lathe (currently away from home))

However, looking at the cross slide, this will place the tool overhang at the weakest part.

So my question is, does this matter?

In my head, the forces should just act through the center and won’t make a difference, but I’d really like a 2nd, 3rd, or 4th opinion.

The design is not finalised, although I have ordered a 60x130x150mm piece of cast iron.

Thanks,

Richard

[bernard towersParticipant @bernardtowers37738]

why have you made the central spigot so small?

[JasonBModerator @jasonb]

The main issue I can see with the central spigot is that your tool will have excessive overhang when set parallel to the lathes axis and may not reach the work when set inline without risk of hitting chuck jaws when you have large work that needs facing in a 4-jaw or are using softjaws.

You may want to think about having the spigot towards the far left corner, similar to this.

like you he has made the spigot the same size as the base of the toolpost, can’t see making it larger would gain anything.

One other thing as I can’t see a DRO on the lathe, say you want to take 0.2mm off the face of a part to bring it to final dimension, Will the carriage handwheel give that accuracy of reading, it’s not a problem to put on a cut that size with the topslide set parallel.

[John HinkleyParticipant @johnhinkley26699]

Richard,
I think that you would get some good ideas and design pointers from watching the videos on this subject by James Clough (Clough42). His lathe is similar to yours, but smaller, I think, but the principles are the same. Search youtube or his channel for “multifix toolpost” and that should bring them up.

John

 

[Clive FosterParticipant @clivefoster55965]

It would seem prudent to place the toolpost close enough to the edge of the slide to permit machining the largest diameter that can be swung over the machine bed. The length of maximum diameter that can be machined will depend on how far in front of the slide the cutting edge actually lies. Personally I’d arrange the toolpost so its base is barely inside the line of the front edge of the cross-slide so the tool and part of the carrier overhang. Structurally speaking the effective stiffness of the tool support is defined bay the diameter of the toolpost base so, as far as the tool is concerned, anything outside that circle does nothing.

I’d not bother with pretty curves. Simple flat topped rectangular block will do fine and provide space to arrange mounts for specialist jobs if needed. Given the minimum of extra work needed I’d provide three tapped mounting holes for the toolpost. One at the front, one in the middle and one at the rear. On (rare) occasions the third set of mountings at the rear of my Dickson tool posts have proven very handy when working on tailstock centre supported components. I consider an extra mount placed so as to use the multifix in that way might also prove useful.

Worth making a boring bar holder to bolt on the carrier block too. QC tool posts severely limit the size and therefore stiffness of boring bar that can be held. Nothing like a hefty bar to make producing a nice finish relatively easy. One for a round bar can be drilled in situ. One for square shank tools can easily be made by screwing and gluing stock sections together.

Clve

[David SeniorParticipant @davidsenior29320]

Having the tool tip within the width of the slide as you have designed it is ideal – ie no overhang. Yes, there may be times when you would want it nearer the chuck, but at those times you just have to rotate the tool by 1 or 2 of the 9 degree steps.

As the dovetails on your lathe are quite wide you could probably offset the central boss a little to advantage.

On my Raglan 5″ the dovetails are closer together so I was able to keep everything central. I made the block as stiff as possible by tapering from top to bottom, but that may be unnecessary.

[Richard Kirkman 1Participant @richardkirkman1]

Thank you for the advice so far.

The main reason I asked this was because of the following two videos I saw during my research.

https://www.youtube.com/watch?v=S7GxY_QVDtk

https://www.youtube.com/watch?v=lbjWQ0G-ZQw

I had initially offset the spigot to the LHS.

The spigot dimensions and clearance etc are not finalised. But I would like to stick to a round feature so I can turn it on the lathe.

Bernard- I haven’t made anything yet, just a concept. At least 3 weeks before chips can fly.

John- I follow Clough42 and watch his videos regularly, so I have seen how he went about it.

Jason- The lathe did come with a DRO, but not installed. I was hoping to get the toolpost mounted before the DRO. So, it is next on the list, although my work doesn’t often require precision. Would you be able to link the video you took that screenshot from?

[JasonBModerator @jasonb]

You will want to switch on sub titles.

Clive’s suggestion of multiple mounting points is a good one even more so if you are going to fit the DRO scale to the right of the cross slide. When using tailstock support it can be useful to be able to wind the topslide fully to the right to avoid excess tailstock extension so being able to reposition the toolpost may be handy.

Changing the bottom locating ribs to pegs would allow the support to be repositioned 90deg which would allow a turned spigot to be mounted to the left or right.

[DC31kParticipant @dc31k]

Another small thing to consider is versatility. Looking at the proposed design and the circular Raglan one, they are symmetrical. That reduces their versatility as they are the same any way you rotate the main block.

With the one described as “having the spigot towards the far left corner”, potentially that could be bolted to the cross slide in four different orientations. As shown it is ‘forward, inside’. Rotate the block 90 degrees anticlockwise and it would be ‘forward outside’ (handy for larger diameter turning). Rotate so it is ‘backward’ and it gives extra reach towards the tailstock end for turning long stuff.

Thus, my gut feeling is that having the spigot non-central to its base would offer both a ridgid and flexible solution.

[Richard Kirkman 1Participant @richardkirkman1]

Thanks for the link Jason

As far as I know, my plan is to mount the DRO scale to the LHS of the carriage, as that’s how Warco usually does it. I did enquire if they had any specific instructions, but they didn’t; they just sent a few pictures.

To summarise so far:

Moving the spigot to the LHS will give more clearance, maintain rigidity, and allow for reversal if needed. However, it will put more pressure on the left of the cross slide.

Having a central spigot will perhaps be more rigid and spread pressure more evenly but at the cost of clearance and versatility.

I am going to offset the spigot (or mounting point, depending on the final design).

I’ll test some more ideas and see what looks right. Ultimately, it will depend on the measurements I take from the lathe.

Thanks to all, always open to more suggestions/opinions.

[Richard Kirkman 1Participant @richardkirkman1]

[John HinkleyParticipant @johnhinkley26699]

Just a quick thought. If you make the tool post offset and able to be mounted towards the rear of the cross slide, might it be possible to mount a parting tool for rear parting, if that’s your bag?

John

 

[Richard Kirkman 1Participant @richardkirkman1]

John- I’d need to see some examples of what you mean. I suspect a rear parting tool post would be best left for a separate project, if front parting with this new solid compound doesn’t help.

[John HinkleyParticipant @johnhinkley26699]

Richard,

I’ve never had the need or desire to use a rear parting off tool post, but some on this forum insist they’re the dog’s danglies.  It was merely a random thought that made into my other brain cell when browsing the thread.  I’d ignore the suggestion, if I were you, just like 99% of other readers will.

John

 

[Clive FosterParticipant @clivefoster55965]

Jason, thanks for the support over having an alternative position for the toolpost.

But not just for when you need to wiggle around the tailstock barrel though. Having left and right side mounts for the tool carriers on the Dickson made this little job so much easier that I’m convinced that equivalent functionality is highly desirable whatever breed of toolpost you use.

 

That’s a 6 cylinder BMW crankshaft on the P&W B getting the weight watchers treatment to loose 2.5 kg for a classic saloon car racing engine. This sort of thing possibly explains why Jason and I tend to look at machining and set up issues a bit differently.

Using a separate block to replace the topside as you plan without an extra mount point restricts how far back the MultiFix post can position the tool when swung round.

As the top picture shows I was struggling for access even with a top slide to give rather more movement. I’ve learned from bitter experience that it’s best to engineer maximum versatility into the sort of modifications you are considering. I see little value in the cosmetic sweeps you are considering. For me a nice flat top so I can add a fixing hole or three if its the only way out of a tricky situation beats aesthetic appeal.

Clive

[Richard Kirkman 1Participant @richardkirkman1]

I appreciate the practicality, but it’s nice to make something that isn’t just a rectangular block, and it will assist in my plan for machining. I will not be machining any crankshafts in the near or distant future.

 

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