# Lowering topslide of a mini lathe



## petcnc (Dec 29, 2014)

*Lowering topslide in my 7X12 (Clarke) Lathe*

One of the problems with my 7X12 Lathe was the height of the topslide.
Although the tool holder can easily hold a 12 mm tool, the tool is too high to be of any practical use.





Even a 10 mm tool was high and I had to use only 8mm tools.
The biggest problem I had was while I was trying to use my cut-off tool. I never managed a cut. I just had it stored together with other thicker tools… 
A QCTP does not help either as it can elevate the tool but can’t lower it below topslide.
A careful investigation on how to reduce the height of the tool (H) and to have it aligned to the centre of the lathe could be tackled in lowering either the tool (A), the toolpost base (B) or the compount slide base (C). 




As you can see in the above photo I had chosen the easiest solution: That is to make the 10mm tool thinner.
This gave me a useful tool but nothing more. I could not use thicker tools or my cut-off tool. 

A tempting thought was to lower the toolpost base (B) but a careful examination prevented me to do that as it supports the long bolt that holds the toolpost.

A quick research in the Internet revealed that the solution is to make a new lower topslide to solve the problem once for good. But this is a big job that I was not prepared to tackle.

Instead I made some measurements and calculations and decided that the compount slide base had enough meat to allow me cut a 4mm slice from the bottom.

I took the base off supported on the mill vice, made careful measurements and with the fly-cutter I lowered the base by 4 mm.

Below is the base on the mill vice after several passes with the fly-cutter




In the next photo you can see the old holes for the protractor.




Naturally, as the base gets thinner, the protractor goes higher and new holes, just above the old ones,  needed to support it.




After drilling and tapping job done! 

The base is now 4mm thinner.




Of course some details had to be fixed:

The center hole had to be deepened to exactly 4,25 mm




Also The nuts supporting the base to the cross-slide had to be 4mm shorter...




And the new base fits the cross slide like a glove.




Now 12mm tools are aligned with the lathe centre




Even the cut-off tool is at the right height!




My mini lathe now can make full use of my 12 mm tools and the bigger chucks (5 inch or 125mm)




I'm ready to tackle any precision project now!!!!

Thank you for reading this

Petros


----------



## Zoltan (Mar 6, 2015)

You may want to consider deleting the compound entirely and replacing it with a solid block of steel or iron.


----------



## LEEQ (Mar 6, 2015)

For those less adventurous, LMS sells compound bottoms that have been milled down so that an axa post can fit 7" lathes. I don't recommend the axa size post as oxa is a lot better match in size. If you put the oxa on the milled compound, it should take bigger tooling though. I played with different set ups and settled on oxa with regular compound.  If I need to use 3/4 tooling, I'm on the wrong lathe anyway.  Congrats on your successful mod, happy turning.


----------



## bladehunter (Mar 7, 2015)

Zoltan said:


> You may want to consider deleting the compound entirely and replacing it with a solid block of steel or iron.


 One of the best things to do to increase rigidity. It makes a whole world of difference.


----------



## bpratl (Mar 7, 2015)

bladehunter said:


> One of the best things to do to increase rigidity. It makes a whole world of difference.


 I replaced my upper compound slide with a solid 1.5" high aluminum block and it made a big difference. I only use this lathe for small simple one-shot turnings and never for threading.


----------



## David Kirtley (Mar 7, 2015)

bladehunter said:


> One of the best things to do to increase rigidity. It makes a whole world of difference.


I also went that route. I have the post if I want more rigidity, I made mine fit the same fasteners that hold on the compound.


----------



## Zoltan (Mar 9, 2015)

Sorry for the large picture, but this is my Block O' Steel. It's reversible for small diameter (pictured) or large diameter work.


----------



## petcnc (Mar 12, 2015)

Zoltan said:


> Sorry for the large picture, but this is my Block O' Steel. It's reversible for small diameter (pictured) or large diameter work.



This looks a very interesting approach. Did you notice any improvements in rigidity? Any changes in the way the cutting tool treats the workpiece (i.e. does it give better surface or so)?

Petros


----------



## Zoltan (Mar 13, 2015)

It's definitely more rigid and I'm getting quality of finish as well. 

However, now I'm seeing flex and rotation in my cross slide gibs instead. But I don't think I can do much about it. The problem is the cross slide gib should be in the left side of the carriage instead of the right.


----------

