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Shop Built Steady Rest

#1
A steady rest has been on my list of things to build/acquire for years. It recently made it to the top of the list and here is what I came up with:

DSC_9465.jpg DSC_9466.jpg DSC_9468.jpg

It was made to fit an Emco V10P lathe and adjusts from about 1/4" to 3.5"+. That's plenty of range for what I do. The main body is two layers of 1/2" cold rolled plate screwed and welded together and the fingers are 1" hot rolled that have been welded to the main body of the steady rest. The operation of the fingers is kind of interesting. The knurled section you can see is threaded 32 TPI right hand and the extending parts with the brass tips are threaded 20 TPI left hand. The result is that one revolution of the knurled knob advances the knurled knob 1/32" and the tip of the finger by over 1/8". So, it doesn't take a huge number of turns of the knurled knobs to make adjustments and the knobs only have to travel in and out about 1/4 the distance of the tips. Not sure I explained that very well but its like differential threads in reverse.

The welds were cleaned up and then I used bondo to smooth things out prior to painting.
 

Tom Kitta

Active Member
#2
Looks better then many store bought models - how did you make the round parts - i.e. main body round at the top and bottom. For thickness you welded 1/2" steel together but these bars are straight when bought - or did you plasma cut out 1/2" from a plate semi round and welded that together?
 

Johnwa

Active Member
#3
That looks really good!
In Addison to Tom’s questions, how did you manage to get the fingers to line up properly? Did you pre-machine the round parts or did you do that after they were welded?
 
#6
The round parts were band sawed to rough shape then pinned and screwed together. Then I mounted them on a rotary table and milled them round. When I welded on the base and the parts that make up the closure I also added a few tacks between the two plates.

All of the parts of the fingers were machined first and then I welded the outer parts of the fingers to the main body. Originally I was going to braze the outer parts of the fingers to the main body to try to avoid warping them. But all I have is a MAPP torch and I couldn't get it hot enough to braze. So I welded them and they did warp and I had to ream them to size afterwards. Fortunately, the threads in the outer parts of the fingers did not warp (they are pretty far from the welds).
 

PeterT

Ultra Member
Premium Member
#8
That's a good looking part.
Can you elaborate on the base. It has a Vee groove so does that base span the width of the lathe ways? And you secure from underneath with a bolt/plate via the center hole?
 
#9
On my lathe there is a vee and flat for the tail stock separate from the vee and flat for the carriage. I have used the tail stock ways for the steady rest. And yes it just uses a bolt/plate through to the underside of the ways to secure it. It is a bit fiddly to tighten it with a wrench, I should have left a bigger pocket for more clearance, but it works ok. It's not something I will be using all the time so the inconvenience of installing it shouldn't be a big deal.
 

Janger

(John)
Administrator
Premium Member
#11
I concur, nice job. Tell us about the painting. Spray? Brush? How many coats? What kind of paint exactly? Primer? top coat? etc. etc. did you sand the metal first?
 
#12
It's just Rustoleum gloss paint brushed on. There was a lot of filing to round over all of the edges and clean up my ugly welds. Then bondo to smooth out the fillets followed by some light sanding by hand to give the paint something to bite into. For paint I used a sandable primer then the Rustoleum. There are three coats. I had some trouble finding the balance between coats that were too thick (resulting in runs) and too thin (resulting in brush streaks). And it was probably too cool in the garage for the paint to properly level out. Two coats likely would have been sufficient but after two it was still streaky so I added another.
 

PeterT

Ultra Member
Premium Member
#13
Is there anything special about how the locking screws engage the cylindrical posts... like a shoe or wedge part? Or are they just basically like threaded fastener ends that contact the OD?
 

Attachments

#14
There is a slot milled into the fingers that the brass screw engages. There is nothing fancy, threads then turned down to be a good fit in the slot. Here is a picture of the parts. The part in the centre is threaded 3/4" - 32 tpi RH and 1/2" - 20 tpi LH and the top part has 20 tpi LH internal threads.
P_20190510_094641_vHDR_On.jpg
 
#15
The part in the centre is threaded 3/4" - 32 tpi RH and 1/2" - 20 tpi LH
Just curious why those thread pitches. If I understand correctly, each turn advances the finger by about 0.081 in (1/32" + 1/20"). That's quite fine. By eyeballing the picture, it looks like there might be 30 threads on each section. Can the brass rub buttons basically be retracted back to the frame?

Craig
 

Johnwa

Active Member
#17
I found this post on practical machinist. It includes a sectional drawing of the finger assembly for a South Bend. It’s a little different than Brian’s but the concept is the same.

“For what it's worth...

Here's a cross-section I did of the jaw assembly for a 9" telescoping steady:

It's an intriguing design. The inner thread (with the exaggerated root flat)is 3/8-10 LH, while the outer thread is 7/8-14 RH (standard V-thread). Reassembly requires a bit of thought to get full extension and collapsing of the mechanism. Paula”

1BD24B00-EBB2-4C16-A335-CB87207A9E65.jpeg
 
#18
Craig, the advance is about 0.081" per revolution which is about 12 tpi (not 8 tpi as I said before). So, you end up with a pretty wide range of movement of the fingers with a small amount of movement of the knurled part. Yes, the brass tips can be retracted almost entirely into the frame. There are actually more threads than is strictly required for the full range of motion. I didn't do any calculations, I just kind of made them as long as I thought they needed to be.

That South Bend design is very similar. The one I built is based on some pictures I found on Google.