Best choice of material

Good afternoon all,

I am toying with the idea of removing the taper slide on my lathe and replacing it with a solid block to mount the tool post too.

There are a couple of reason for this, partly to improve rigidity (particularly as I don't think I will often use the taper attachment), but mainly to aid in the replacement of the 4 way toolpost for a QCTP.

I was thinking of using mild steel for this, but it occurred to me that maybe I could get away with using aluminium, or maybe I should be using something tougher like stainless.

What are peoples opinons on this?

Thanks,

B

I use my top slide (your taper slide) because on facing or edge cuts on thin work by locking the saddle just out of range of the jaws and with max cut with the top slide hard on the stop. Then I can take a cut to within 1 thou of the jaws without watching a DRO and without crashing anything.

Plus unlike yours my lathe does not have a graduated hand apron wheel.

A good point is raised by Dave there, the ability to accurately put on a cut towards the headstock. What is the accuracy (in terms of resolution) of the carriage handwheel?

For a toolpost Mild steel would be acceptable, but cast iron would probably be better from a vibration damping ability.

Regards,

Martin

I used mild steel when I made a toolpost for my WM250 see ** HERE ** for details.

John

Thanks for the replies gents.

Martin, going by the DRO the carriage handwheel moes in 0.02mm increments.

John, thanks for the link, that's extremely helpful.

Retaining the Top Slide allows trimming up dead centres, or turning chamfers.. Can be use as means of putting on TINY cuts, and the way, advised by many, to screwcut.

Handy, for turning to a specific length, a particular taper.

(bought a drill chuck at a show. Good quality but not a Jacobs taper. Found it was a Jarno taper. Carefully offset Top Slide, and jammy devil, got the 2*15' taper right first time..

Personally, I would not dispense with it.

But your shop, your choice.

Howard

I think it depends on the lathe. I refurbished a 920 lathe for a disabled friend. The design is poor and there is a lot of potential tool movement because of an inadequate base. Even doing one of the standard mods to overcome this, still doesn't give a really firm tool. I took off the topslide and made a "Gibralter" tool mount. That made a huge difference. You can still remove this and reinstate the topslide for the odd time it is needed,

Maybe your lathe is sturdier than the 920, but even so your idea is to be recommended. I very rarely have need to use the topslide anyway.

Andrew,

I happened to get hold of a NOS 4 way toolpost which is bigger than the standard size for the lathe (Smart & Brown model A), and I decided to use it mounted on the cross slide at the same height as the other ones for the lathe. Because it is bigger, 25mm boring bars can be fitted and their increased rigidity plus the rigidity of leaving out the top slide would be an advantage. To partially make up for the loss of being able to make fine adjustments on the top slide, it helps to have an adjustable saddle stop and a box of slip gauges. The block of cast iron which the toolpost sits on helps somewhat with damping, but mild steel would work ok too. That boring bar in the picture is a 16mm with carbide shank which could enter a 20mm hole and bore 96mm deep.

Edited By old mart on 10/06/2021 20:08:25

Thanks for the replies gents.

To clarify, I'm not getting rid of the top slide, it will be kept and stored when not in use. The main reason for my plan is to allow easier fitment of the QCTP. The Warco WM180 has a raised boss on the top of the cross slide which would either have to be removed, or the QCTP bored out to accommodate it.

Not iishing to modify either part this seemed like the best option, with the added bonus of improving rigidity.

The top slide can always be reinstated with the 4 way tool post as and when needed, its only two bolts. .

Edited By Robert Bowen-Cattry on 11/06/2021 09:11:36

Top slides are useful for most jobs and should always be ready for refitting. The lathe in the pictures has a choice of two different top slides, one is brand new even though it is 70 years old. Having the option makes for greater versatility. I also have a rear toolpost which bolts directly to the cross slide for when a particular parting off would be a challenge. That might be another mod you could consider.

Edited By old mart on 11/06/2021 19:07:20

I made a solid block to replace my topslide on a new Warco 290V & really didn't get on with it so I completely re-machined the existing top slide, with a slightly thicker gib strip which was doweled in position. The lathe will now handle any cut I can safely take with no problem.

Tony

I replaced the weedy clamp that holds the topslide to the cross slide on my WM250. It's made of 15mm thick steel plate and is attached with four bolts. It's a lot more stable - the flex in the original was really visible - and capable of taking much bigger cuts.

I did machine off the boss for the toolpost when I fitted the QCTP

I've never understood this idea that top slides lack rigidity. There will be a screw to lock it against the gib strip. Take it out and replace it with a handle.

If you have room, make and fit a Rear Toolpost. It will make parting off, with the tool inverted, so much easier.

I had enough room, so made a Four Way, to match the front post. It carries Front, and Back chamfering tools, as well as the parting tool. (HSS given to me when I bought my first lathe, back in the late 70s, and still not worn out! )

Admittedly, my lathe is larger than most, 1.5 hp VFD, 6" centre height, with 3" square toolposts, but have never taken more than 0.15" cuts. Not seen any problems with rigidity. But depends upon the design of the particular machine.

Howard

Stefan Gotteswinter replaced the top slide on his lathe with a solid block. He made a video of it.

Thanks for all the advice guys, the project is now complete and I have my QCTP fitted.

The box that the QCTP came in is also perfect for storing the original tool post and slide when not in use (with a little modification to the foam) so that is now safely stored until needed.