Steady Rest

JimDawson

Global Moderator
Staff member
H-M Lifetime Diamond Member
Joined
Feb 8, 2014
Messages
11,138
My lathe did not come with a steady rest and for the first time in over 20 years I actually need one for a project. I have to drill a 1 inch hole about 20 inches deep through a UHMW rod about 3.5 inches dia. Way too much stick out to do it unsupported. When I get to that project I'll post showing how I did it.

I looked on line for a steady rest that might fit my lathe, but what I found were all much too small to handle anything close to 3.5 inches. I can put 6 inch diameter over my cross slide, so you would think that a little bigger hole would be available in a steady rest.

OK, so sit down and design a steady rest that will do what I want. This one will handle a max of 4.5 inches. The design has changed slightly from this drawing. There will be bearings added to the fingers. But I will also make a set of brass fingers with no bearings. The clamp bolt design has also changed to a swing away clamp.

upload_2016-4-19_21-3-57.png

I spent most of the day digging the top part out of a chunk of 4x7.5x1 6061.

I bolted the part down to a MDF spoil board with one 1/2 inch bolt to a T-nut under. Then drilled and tapped for 1/4-20 right into the MDF just to prevent any possible rotation when machining. I started by pocketing the lightning relief, not really to make it lighter, but just to make it look more professional.

1/4 inch, 2 flute, solid carbide router bit. 2400 rpm, 10 IPM, 50/50 mix of kerosene and WD-40 for cutting fluid. I limited the depth of cut to 0.063 because the setup was not the most robust. I would have rather had more bolts in there but no place to put them.

upload_2016-4-19_21-18-16.png

Putting the radius in the bottom of the pockets, just to make it look nice.

upload_2016-4-19_21-20-11.png

Profiling the outside surfaces. This is where it gets a little dicey, I wasn't sure how things were going to react when the piece that is bolted down with the 1/2 inch bolt gets cut loose from the actual part. There is not much holding things down. I went outside until this part of operation completed to get a wall between me and the machine, I didn't want to get hit with flying carbide. :cautious: As it turned out, everything was well behaved, and went exactly as planned.

upload_2016-4-19_21-29-12.png

And the back side of the top is complete. That little flat on the hinge radius was not designed in, I really needed 4.125 wide material but only had 4 inch. No problem, it will work fine, and that part is hidden anyway.:rolleyes:

upload_2016-4-19_21-30-34.png

Now for the other side. First I machined a 0.250 deep pocket into the MDF with the same profile as the part. This allowed a press (OK, hammer;)) fit that captured the part and holds it securely. As you can see, this spoil board has been used for a few other projects. Just about past it's useful life.

upload_2016-4-19_21-33-42.png

Pocketing the front side. The part is held down by one 1/4-20 cap screw threaded into the MDF, it really can't go anywhere, and I probably didn't need the cap screw, but a little extra insurance doesn't hurt.

upload_2016-4-19_21-38-53.png

And the (almost) finished part. I have to do the clearance and slot for the clamp bolt, but that will be after I get the rest of the parts done and put the vice back on.

upload_2016-4-19_21-42-6.png


Somewhere in that 8x10x1 chunk of aluminum is the bottom, I'll dig around in there tomorrow and see if I can find it.;)

upload_2016-4-19_21-43-48.png
 
If I had CNC on my mill I'd cheat a lot. I can't see a tool changer on a MP25, though.
 
Yesterday I got the top half completed, so today is find the bottom half in that block of aluminum

upload_2016-4-20_19-59-52.png

So here it is all bolted down on a sort of fresh spoil board. The bottom is in there, just need to find it.:)
upload_2016-4-20_20-2-10.png

The pocketing is complete on one side. I started with the pockets and will do the other operations while it's bolted down solid. Then do the cut off last.
upload_2016-4-20_20-4-35.png

The finishing cut on the outside profile. Note, I didn't cut out around the hex head bolt, I'm going to use that hold down in the next operations. But the outside is on size.
upload_2016-4-20_20-6-39.png


Corner rounding the outside with a 1/16 radius corner rounding end mill. Note the clearance pocket around the hex head bolt. This allowed clearance for the corner rounder. A stack of spoil boards in the lower left of the picture. It's my preference to bolt parts to the table when possible rather than use a vice. That's why they invented T-nuts and T-slots.;)

upload_2016-4-20_20-9-38.png

And ready to flip over and do the other side. The 1/4-20 button head screws are threaded into the MDF spoil board.

upload_2016-4-20_20-14-54.png

I cut a 0.250 deep pocket to locate the part for the second operation. Again a hammer fit.

upload_2016-4-20_20-16-38.png

And bolted into place. The socket head cap screw in front of the part is just to insure the spoil board doesn't pull up in the center. I used a flat head cap screw in the back to make sure I had tool holder clearance when working in that area.

upload_2016-4-20_20-19-43.png

And here are the two halves. Now I need to cut the slots for the hinge and for the clamp screw.

upload_2016-4-20_20-22-18.png


I'll get the base done tomorrow and get the slots cut. Stay tuned! :grin:

EDIT: I forgot to add that it was really exciting running a CNC machine in the middle of a thunder storm, but I wasn't about to shut it down in the middle of the work. Yeah, I'm crazy :confused:
.
.
 
Last edited:
I got a bit more done in the last 3 days, pesky customers keep wanting stuff.

Prepping to put the clamp bolt relief in the bottom side of the clamp. First I milled a pocket to locate the part and keep it from moving around. I could have done this operation in the vice, but I already had the spoil board on the table so I just used it. Only takes a few minutes to cut the pocket.

upload_2016-4-23_19-58-5.png

I located the pocket next to a bolt hole so I could clamp the part down. The part is held securely by the pocket, so only one clamp is needed.

upload_2016-4-23_19-59-50.png

And the bolt relief completed. The slot on the left side was an oops, but it will be gone in the next operation.

upload_2016-4-23_20-5-15.png

The next operation is to radius the clamp to roughly match the tailstock clamp on the left. This is required due to the shape of the lathe bed.

The radius is about 2.8 inches. I concidered a number of different ways to do this. It could be bolted to an angle plate on a face plate on the lathe, bolted to an angle plate on the rotary table, mounted on an arbor on the 4th axis rotary.

upload_2016-4-23_20-15-20.png

Or mounted in the vice and just mill the curve which is what I decided to do. I did 1/2 at a time, just flipped it over and did the other half.

upload_2016-4-23_20-23-38.png

And the finished part
upload_2016-4-23_20-24-33.png

Now to finish the base. I was going to do this operation in the vice but I found I had miss-measured :( the length in the initial design so I needed to take off 0.193 off of each end to keep the holes on center. So I used the pocket fixture technique again so I could work on the V-slot as well as the ends.

The tool bit is a 90° carbide tipped, 3/4 inch dia. router bit. Finish depth is 0.375, @ 0.015 DOC, 2400 RPM, and 10 IPM. I went pretty easy because of the width of the final cuts. In retrospect, I could have taken a bit more but I'm not in that big of a hurry.

upload_2016-4-23_21-0-48.png

And the finished part. The extra hole on the the right edge is the result of the miss-measurement mentioned above. So I moved the hole to the center of the V-slot.

upload_2016-4-23_21-3-49.png

And the assembly kind of in place. Still need to cut the hinge slot, the clamp knob slots and clearance, make the clamp knob, and drill & tap the mounting holes, and make the fingers. And do to the miss-measurement the bottom half needs to be modified at the base. so still quite a bit of work to do.

upload_2016-4-23_21-17-53.png

Stay tuned!
 
I forgot to add these pictures from yesterday.

I needed to modify the hinge end of the top part. I didn't allow enough clearance in the pocket area below the hinge in the lower piece so back to the drawing board (OK, computer) for a bit and figure out how to fix the problem. I'm not about to buy another $40 worth of aluminum to make a new bottom piece.

upload_2016-4-23_21-55-56.png

So I pocketed the spoil board to fit the part and trimmed up the end a bit. Again the pocket locates the part and allows minimal clamping.

upload_2016-4-23_21-56-32.png

And the modified part

upload_2016-4-23_21-58-42.png

Getting set up to cut the top of the base.

First check the bolt length. I use T-nuts without deformed threads in the bottom. This allows the bolt to screw through the T-nut, but you have to be mindful and not allow the bolt to screw through the T-nut and into the bottom of the T-slot. In extreme cases it would be possible to actually break out the T-slot.

upload_2016-4-23_22-9-34.png

Bolted in place. Pocketed the two reliefs that locate the bottom half. Then cut the outside profile. I went easy because it's only held with one bolt. 0.063 DOC with a 1/4 inch solid carbide router bit.

upload_2016-4-23_22-16-59.png

I checked the fit of the pockets before I tore down the setup and found it was a bit undersize. So I re-ran to pocket routine again with a tool offset to account for the undersize.
upload_2016-4-23_22-24-31.png
 
Back
Top