Solid Toolpost Mount

Hi folks, I thought I would share this as I hadn’t seen any discussion on the subject.

I bought my Myford Super 7 new about two and a half years ago. I bought it without a tool post and ordered a Multifix clone separately. It was a size A so was a bit big for a Myford with 5/8” tooling so I had to reduce the thickness of some of my tools to achieve centre height. Around that time, I saw a video on YouTube by Robin Renzetti who inspired me to remove the compound slide from my machine. The reason for doing this was initially to gain more stiffness from what is a small machine and the compound slide is a source of deflection that can be avoided if it doesn’t need to be used. Instead of the compound slide, I made a solid tool post mount.

There were a number of benefits to doing this.

The first was that I was able to eliminate a source of deflection in the machine. It is good practice to lock down any axes of a machine that are not being used to make a cut and I only occasionally needed to use the compound slide. Therefore, the convenience of having a compound slide was outweighed by the disadvantages it posed when not in use. The absence of the compound slide has stiffened up my machine and I can part off and work the machine harder without having chatter problems.

Secondly, I fitted a Newall DRO (digital read out) to my lathe and with it came the facility of a tool library. This enables me to assign a tool number to each tool / tool holder and the offsets for each tool can be stored in the tool library. The benefit of this is that for all but the most accurate features, I don’t need to measure length or diameter and I can machine parts based on the coordinates shown on the DRO as long as I have the right tool called up from the library. It is very simple to use and makes jobs on the lathe an absolute pleasure as well as more efficient. Tool libraries are most effective when the compound slide has been replace by a solid tool post mount. This is because any positional error or hysteresis in the angle or linear position of the compound slide can throw all of the tool offsets out of the window. They can only be approximate without accurate resetting which can be time consuming and easily lost again if the dial is inadvertently moved.

I have been using the lathe in this way for quite a while now and I have no plans to put the compound slide back on unless I have some short tapers to machine. Even then, it takes about 5 minutes to revert the machine to standard. Some people say that threading needs the compound slide to advance the cut to reduce the cutting force by ensuring that the cut is taken from one side of the tool only but I have done plenty of threading without the compound slide and it works perfectly satisfactorily.

I have documented how I designed and made the solid tool post mount and the videos can be seen on my YouTube channel, Optical Mechanic.

https://youtu.be/lu5GAovWXQ0

The Gibraltar tool post, designed by TD Walshaw ,did this more years ago than I care to remember. Hemingway do a kit for the Gibraltar ,using a large casting for the main body But easy enough to make out of a lump of steel.

Andrew.

Or aluminium as the great man himself did although one feels this would not be as good.

That looks great Optical.

I did a similar mod for my machine as below. Really very easy to make and it is definitely solid. The rigidity of the toolpost stiffens the whole topslide as well.

Edited By lfoggy on 22/01/2023 17:43:22

It also makes sense to do this if a lathe is converted to CNC or ELS with X axis drive.

Martin C

I only have my compound slide on when its actually needed.

Jim

Similar for my WM250, a very useful mod definitely improves rigidity. Top-slide not used most of the time. No problems screw-cutting.

A good mod easily put together from bar stock Journeyman's Workshop.

John

I’ve also bought a boring bar holder to take a morse taper adapter so that I can mount my drill chuck to the carriage. This makes rapid retraction much easier than winding the tail stock in and out. The other benefit is that by assigning a tool number to the drill chuck in the DRO, I can ensure that I’m bang on centre every time and can more easily drill to a known depth. I can even use the longitudinal feed to drill the hole. As a result, I get excellent surface finishes and it really works a treat!

My version, base carved out of a backplate casting. I concur absolutely about being able to set tool offsets - this is on a CNC converted S7. Not as elegant as yours. I have been meaning to organise a mounting for a drill chuck, excellent.

I bought a NOS four way toolpost cheap on ebay, it was too big for the Smart & Brown model A at the museum, so direct mounting on the cross slide was the solution, not to mention the increased rigidity. It can fit in minutes in place of the compound and is held down by the 4 swivel bolts plus two 6mm SHCS. It is exactly the same height as all the other toolposts, but can hold 25 and 32mm boring bars, wheras the standard ones can only manage up to 20mm. Not pretty like the others, but it does the job. That boring bar shown is a 16mm solid carbide.

Edited By old mart on 22/01/2023 21:35:09