Steady rest

Last update: 7 September 2016

I need a steady rest for my lathe in order to machine circlip grooves into the ends of aluminium tubes (for rocket motor casings). I decided to make my own as the lathe did not come with one, and the stock one looked weak and did not have the diameter I needed (~65mm).

I started a new topic in the prazi-machining Yahoo Group, and uploaded some pics.

Design

After deciding to make a steady rest, I spent some time reviewing designs online. I searched for “lathe steady rest” in Google images, then clicked on interesting looking stuff. I settled on this design as I thought having screw-adjustable fingers would be very helpful during set-up – and this proved to be the case.

I fiddled endlessly with different designs for the base in SolidWorks. The final design was influenced by the availability of materials and my abilities with the lathe and mill. The finger design also meant I could make two sets of fingers – one with roller tips (with Delrin boots, for use with aluminium), and one with phosphor bronze tips (for use with steel).

Having used the steady on various projects, I’d call the design a success. However I had to trim the bottom of the removable way-clamp piece considerably to clear the lathe deck and leadscrew – if I were to make it again, I would use two M6 screws instead of the single M8 in the design below. This would allow the removable piece to be made smaller.

I did destroy a couple of the bearings during my early attempts to set it up on the lathe. This was no problem as they are easily replaced, but the steady does take some time and care to set up (I guess this is so for all steadies?).

MD65-SD300 steady rest design v4

Version 5 of the design, including way bar. The fingers need finishing with the adjusting screws. Mrs Naut: “You’ve been staring at that THING for days – what is it?!”

MD65-SD300 steady rest design v4 - on lathe

Here is v5 on the lathe – looks sturdy and well-proportioned (just like Mrs Naut).

I also did something I have been wanting to try for some time: made an assembly animation in SolidWorks. It’s a bit clunky but overall I’ve very happy with the results. In the final design I used two M5 long capscrews and not four short ones as in the video – I tapped the holes in the removable piece.

Way bar clamp

The D-bar design of the lathe, combined with the close proximity of the leadscrew, made this section a bit of a challenge. However, the finished clamp works very well and could be adapted to many other uses.

First I cut the two main blocks and machined them to size:

  • 30 x 92 x 19 mm for the top horizontal part (2mm oversize on the longest dimension), and
  • 30 x 53 x 30 for the lower part which will be bored to accept the way bar.

The height of the bottom block is a critical dimension, as it dictates the fit of the top section onto the flat top of the way bar.

For the top section, I used a slitting saw to cut out most of the material to be removed – this saved a great deal of time.

Blocks machined

Top block - cutSlitting saw was used to remove most of the material – I finished it off with a hacksaw.

I completed machining on the top section by using a T-slot milling cutter to create the undercuts. I didn’t drill the cross-holes for the M5 bolts – instead I waited until the bottom section was ready and drilled them together.

Next I drilled, counterboredand tapped all of the holes in the bottom block. In hindsight this was a mistake, as the holes made for an interrupted cut during the boring operation, which in turn created ridges in the bore. These ridges caused me some problems when test fitting the bottom clamp to the way bar, and would have made for a less stable/secure finished item. Eventually I removed most of the ridges by using very fine cuts with a honed HSS boring bit, however I had to set the part up again the the four-jaw which took some time…

Bottom block - setupBore centre spotted and the piece in the four-jaw.

Bottom block - indicatingI took my time setting up the bottom block – using wobbler bar and a couple of DTI gauges.

Bottom block - boredBoring nearly finished. You can see the ridges created by the interrupt cut, in turn caused by the holes I had pre-drilled. If I were to make it again I would drill the holes after boring.

After boring the 40mm hole for the way bar, I split the block into two with a slitting saw. I then clamped each of the two side to the mill table, and used an endmill to mill out the steps that fit into the undercut on the top section.

Captain Cockup paid a visit, and I accidentally milled too much off one of the sides… Much cursing followed. In the end I milled off the mess I had made, and brazed a new section on, and then machined this to the correct dimensions. This fix worked really well. You can see the brazing in the pic below on the left hand side.

I then clamped the top and bottom sections together, and used the existing holes on the bottom section as a guide to drill the two 5mm holes across the top section.

During test fitting I found that the top section was too tall, and ended up milling 0.1mm off the face that sits on the flat of the D-bar way. Other than this the test fitting went well, the top surface was about 0.03mm out left to right (in the pic below), and bang on front to back (along the length of the way bar).

None of these dimensions are critical for a steady, as the fingers can easily adjust away and mis-alignment. However I wanted to see how accurate I had made the piece, as it could be used for other applications.

Lastly I drilled and countersunk the two holes for the bolts that secure the ring to the way clamp.

Steady baseTest fitted.

Main ring

The main ring is made from a 5″ x 25mm piece of 6082-T6. Bought off eBay seller alum-droitwich (very good service, arrived quickly, cut straight with unmarked outer circumference).

MD65-SD300 steady rest design v4 - ally disc

The giant disc of aluminium – the height of a two-story Lego house (5 inches).

Getting this giant chunk of metal onto the lathe required some careful thought. In the end I drilled and reamed a central hole as a reference feature, and then drilled and tapped three holes to M5. I could then bolt the piece to the lathe faceplate from the back using M5 bolts. Once it was on the faceplate, I faced the piece and also sized the outer diameter.

Once this initial sizing was done, I drilled the three holes out to 6mm and bolted the piece to my rotary table. Once it was on the table I could mill, drill, tap etc all of the features into the ring.

Ring - rawTest fit on the rotary table after initial sizing on the lathe. You can see the central reference hole and also the three mounting holes which were initially tapped to M5 for bolting to the lathe face-plate, and then drilled out to 6mm for bolting to the rotary table.

Before milling the slots for the fingers, I carefully sized the blanks for the fingers and milled the slots for a close sliding fit.

Ring - millingDrilling and milling the ring features.

After milling, the ring went back onto the lathe faceplate and the central holes was bored out. I bolted the part to the faceplate using the three holes reamed for the posts than clamp the fingers. Lastly I bolted the ring to the bottom clamp section using two M8 countersunk bolts.

Fingers

Fingers

Using the steady

Use - setup   Use - machining wideUse - machining closeSteady - circlip

3 thoughts on “Steady rest

    1. bazmonaut Post author

      Hi John – if you need to ask “how much” then you can’t afford one 😉

      But seriously, I have not yet made one for myself yet, so any orders will have to wait I’m afraid. I have shared the plans/designs in the hope that someone else will go before me and make all the mistakes that I am likely to make, saving me time and money. Win win.

      Bazmonaut

      Reply

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