While I do love my little lathe, the design could do with improvement in a couple of areas… in particular the topslide (compound slide) which often fouls the tailstock, does not help with rigidity (even when locked), and adjusting it is a pain due to the four mounting screws and limited rotation.
The toolpost described below will hold tools of up to 1/2 inch, and is very rigid. The toolholders themselves can be easily adapted to many specialised tasks, such as a dedicated boring or parting toolholders.
The complete plans are here.
Also my lathe came with a nice little low QCTP, which I considered re-purposing however it features two holes for mounting, which would make it difficult to make a mount that allows it to rotate.
However the problem with most of these options is that they are unsuited to the design of the MD65/SD300, which has a very small distance between the top of the cross-slide and the spindle axis (65mm). For most commercially available toolposts this presents a challenge: either they are just too tall or mounting them onto the cross-slide would be difficult (or both).
Lastly, a QCPT would not help with one of the key design requirements: rigidity.
Norman Patent Toolpost
Enter the Norman Patent Toolpost… not my design of course (probably Norman’s), but it seemed to tick all the boxes for rigidity, ease of mounting to the cross-slide, and the added bonus of being cheap.
There are loads of examples online, my favourites being this beautifully made example (how does he keep his workshop so clean?), and also this one from Morgan Demers’ blog (his site also includes an excellent and fascinating buildlog for a Gingery lathe, including loads of videos).
In my implementation of the design on the MD65/SD300, I wanted to preserve what little swing this little lathe has over the cross-slide. Also I wanted to use the existing four mounting holes in the cross-slide.
Construction method – workholding faceplate
There are many possible approaches to this, however I chose this slightly long-winded way because I felt it would produce the most accurate and tidy result. Also I struggle to produce a tidy and accurate hole with the mill boring head…
This make not make sense just now, but hopefully it will after you have finished reading the rest of this guide.
Boring of the hole in the baseplate, and also finishing of the brazed-together postblock and post, is done in the lathe. This has several time-saving and accuracy advantages over other methods, such as using the mill and a rotary table.
I had some spare 125mm aluminium round (leftover from the fixed steady), and used this as a workholding fixture for the toolpost. First I drilled and tapped three M6 holes so that I could attach the workholding faceplate to the lathe faceplate. I then faced the aluminium in the lathe, and also turned the outside diameter.
I used my CAD drawings of the baseplate to find the measurements for the counterbored holes in the rear of the workholding faceplate that will secure the baseplate . The dimensions are in the plans, however here is what it should look like.
A view of the rear of the workholding faceplate (the side that mates to the lathe faceplate), showing the M5 counterbored holes for holding the baseplate, and the three M6 tapped holes for bolting to the lathe faceplate.
As I say this will make more sense as you read the guide, but here is a brief description of each of the coloured holes:
- Blue = Position A
- Used to finish the post and baseplate after brazing
- These fixing points hold the baseplate right way up (i.e. with the post facing out)
- Green = Position B
- Used to bore the hole in the baseplate (for the post), including the step
- These fixing points hold the baseplate upside down (i.e. with the bottom of the baseplate facing out)
- Orange = Position C
- Used to turn the shapely curves at each end of the baseplate – these are required to ensure the baseplate clears the ways when boring the hole
I am a big fan of the workholding faceplate concept, and have used it for many other projects. Here is a pic of the current state of my workholding faceplate – lots of holes but still plenty of life left in it.
Top and bottom view. The one on the left includes three counterbored holes to attach to my rotary table. This side has seen some action as you can see from the mill marks – no problem I’ll just give this face a skim in the lathe.
The base plate is made using a slab of 60 x 105 x 12.7mm bright mild steel. Cut to size, and make sure you have a decent edge on two sides to act as a datum. Mark the two datum sides for reference (punch mark or engineers’ blue).
Now drill and tap the four mounting holes to M5. Also centre drill the location of the post (you will use this to set the block up in the lathe for boring the hole for the post).
Take care when centre drilling the location of the post! The diagram below shows the dimensions – the position of the post appears to be on the wrong side of the baseplate… however this is correct, as we will be boring the hole (and the step) from the bottom of the baseplate.
Now mount the baseplate onto the workholding faceplate using Position C (orange holes). I used four 1mm shim washers to hold the baseplate off the faceplate – this is not necessary but it does save the workholding faceplate from wear (I used these on all of the baseplate turning operations).
Mount the assembly onto the lathe faceplate. Use an HSS tool to turn the outside radii of the baseplate (carbide tools do not like interrupt cuts). Use 500rpm speed and take it slow… you may wish to shortcut this process by trimming the corners off with an angle grinder (or similar).
When you are done your baseplate should look like this.
Remove the assembly from the lathe, and remove the baseplate from the workholding faceplate. Re-attach the two pieces using Position B (green holes). Make sure that the centre-drilled hole is facing outwards.
Mount the assembly onto the lathe faceplate, and centre the work using a wobbler bar and the centre-drilled hole. Drill and bore the hole and step for the post (see plans).
Boring the hole and step for the post. The edge of the baseplate only just clears the ways – take care when setting up and swing the assembly the check clearance before switching on the lathe. You may also wish to attach counterweights to the spare holes to the right of the picture.
Turning the post
Turning of the post is straightforward. Aim for a loose sliding fit with the bore and step in the baseplate. The target gap will depend on the brazing rod you are using – check the manufacturer’s recommendations.
As described in the plans, turn the post 1mm oversize on the diameter, and 0.5mm oversize on length. Reduce to final size after brazing the post to the baseplate.
Also ensure that you centre-drill the top end of the post – this is essential for the finishing operation.
Due to the sheer mass of metal, this is best done with the help of a fire brick or ceramic wool ‘cave’ – otherwise it’s likely your flux will go off before the work is up to brazing temperature.
I brazed my assembly with the post up (as in the photo below). Liberally position shaped lengths of brazing rod around the perimeter of the post and apply heat.
What a mess! Hey ho, I’ll just turn my troubles away… As you can see the braze went right through the gap and out the other side, indicating that it had penetrated all the way through. Note the centre-drilled hole on the top of the post. In the pic above I had leaped ahead of schedule and turned the boss on the top of the baseplate – you don’t need to do this.
Finishing the post and baseplate
If you have access to a mill you may choose (as I did) to fly cut the bottom surface. Otherwise, tidy the bottom of the assembly by rubbing with sandpaper set on a surface plate (or sheet of glass). Drill a >4mm hole in the centre of the base, to clear the 4mm post in the cross-slide (I did not try for a good fit on the post, I drilled my hole to 4.5mm to clear it).
Mount the assembly into the workholding faceplate using Position A (blue holes). Use a wobbler bar and the centre-drilled hole in the top of the toolpost to centre the work. Turn the post to final size and also turn out the boss around the post. The final thickness of the main part of the baseplate should be 8mm (see plans).
(Unfortunately I don’t have a picture of this final finishing – I hope the above makes sense).
Finally drill out the four mounting holes to 5.5mm, and countersink.
I would also suggest aiming for as smooth a finish on the post as you can manage. This will make for a closer fit with the tool holder and also make it easier to adjust the height. The exact diameter of the post is not important as we will be making holders to fit.
Making the toolholders and other hardware
Machining of the toolholders is straightforward and does not require much explanation.
I mounted the blanks in my 4-jaw chuck and bored a hole close to the measured final dimension of the post. I then test fitted the bore of the tool holder on the post after each pass. When I got to a tight sliding fit I stopped boring, and finished the inside of the bore with sandpaper.
I used a 12mm end mill to mill the large slot in the toolholders. You may choose to make a lever or other fancy arrangement to clamp to the toolholder to the post – I chose a simple M8 capscrew as the allen key for this is the same as those on the tailstock, and is therefore always close to hand.
The only real decision to make with the tool holders is which side to mount the clamping screw. I made one of each, and find that each one is better suited to some operations. For example, if the clamp bolt is mounted on the left (as per the pic below), the capscrew head can get in the way when boring.