Wishbone stabiliser for round post drill/mill

[BillTodd]

Hi all,

I've been thinking about how solve the problem of raising and lowering the head on my round post mill without losing position.

I've come up with this double wishbone design: The clamp at the bottom fixes the rotational position. The upper wishbone is bolted directly to the bottom of the head (this could be tricky in practise).

ATM the design shows two ball joints on the upper wishbone at the mid-point, in reality I think just one would do and I will probably beef-up the whole upper wishbone design, so I can push on it with an electric screw jack (satellite dish postitioner) to lift the head.

I'd like to run it past you for comments before sawing/drilling commences. In particular I'd like to know what level of slop to expect in the rose joints.

[smallblock]

Bill,
I like the idea- its pretty clever and will probably work. If you buy high quality rod ends you will have no slop. I did a similar thing years ago- I bought an older shoptask 3 in 1 machine with the rotating mill head. As a lathe it was good, but the milling was limited. I decided to remove the head and use it on a home-made mill. I built a bench and bought one of those cross slide tables from Harbor Freight. That gave me a home-made bench mill for under 150.00 investment and I still had the Shoptask lathe. I ran into the same issue with my design that you have- whenever you move the mill head up or down, it rotates out of position. My idea was different than yours- I used some surplus aluminum stock and built a twin column front support- this eliminated the rotation and also stiffened up the mill head by a huge amount.

[BillTodd]

Nice machine is it small or are those stepper motors Huge?

[smallblock]

Bill,
The mill table is 6 X 18- the stepper motors are NEMA 34 size- 250 Oz/In

[cnczoner]

I've thought about the same thing (eliminating rotation), but my plan was to use a linear slide -- the rail would be bolted vertically to the side of the column, then the bearing would be bolted to the head (with some type of L-bracket). The head would have to be notched to clear the rail.

I had a drawing of this, but not on this computer now, so I post it later.

Cheers,
-Neil.

[cnczoner]

Okay, here it is...

[BillTodd]

Originally Posted by cnczoner I've thought about the same thing (eliminating rotation), but my plan was to use a linear slide -- the rail would be bolted vertically to the side of the column, then the bearing would be bolted to the head (with some type of L-bracket). The head would have to be notched to clear the rail. I had a drawing of this, but not on this computer now, so I post it later. Cheers, -Neil.

That would work (I have seen something similar in a thread on this forum).

I am hoping to retain the rotation option. It's handy to be able to drill the ends of long items by clamping to the side of the machine.

[irving2008]

Originally Posted by BillTodd Hi all, I've been thinking about how solve the problem of raising and lowering the head on my round post mill without losing position. I've come up with this double wishbone design: The clamp at the bottom fixes the rotational position. The upper wishbone is bolted directly to the bottom of the head (this could be tricky in practise). ATM the design shows two ball joints on the upper wishbone at the mid-point, in reality I think just one would do and I will probably beef-up the whole upper wishbone design, so I can push on it with an electric screw jack (satellite dish postitioner) to lift the head. I'd like to run it past you for comments before sawing/drilling commences. In particular I'd like to know what level of slop to expect in the rose joints.

Bill, I'd be interested to know how you get on. Ingenious solution to the problem. I've been considering ideas to resolve the issue for my Warco MD30. What mill have you got?

[smallblock]

Originally Posted by BillTodd I am hoping to retain the rotation option. It's handy to be able to drill the ends of long items by clamping to the side of the machine.

Most of the bench mills I have seen have a drill press style rack gear that rotates around the column . A simple solution would be to make a clamp that would lock the rack gear in place at top and bottom, then the only rotational error would be in the slot where the rack passes through the head casting- some sort of shim or gib style adjustment could take that out.

[irving2008]

Originally Posted by smallblock Most of the bench mills I have seen have a drill press style rack gear that rotates around the column . A simple solution would be to make a clamp that would lock the rack gear in place at top and bottom, then the only rotational error would be in the slot where the rack passes through the head casting- some sort of shim or gib style adjustment could take that out.

In theory you are correct, however the rotational play on the rack is very large as its not intended to provide any locating capability whatsoever. On mine you can turn the head 5degrees or more on the rack (but maybe a new one would be better) and i doubt a gib on the rack would work, the rack is quite narrow and flexible if only located top and bottom, I think there'd be a problem getting enough accuracy - to keep the spindle within 0.001" of position at a radius of about 10" requires location to 0.005degrees or 0.00017" on the circumference of the pillar - thats a tall order...

[Kipper]

I like it! is it finished yet? Bill I was searching my emails yesterday and I saw your name on one?

[Torsten]

Originally Posted by BillTodd Hi all, I've been thinking about how solve the problem of raising and lowering the head on my round post mill without losing position. I've come up with this double wishbone design: The clamp at the bottom fixes the rotational position. The upper wishbone is bolted directly to the bottom of the head (this could be tricky in practise). ATM the design shows two ball joints on the upper wishbone at the mid-point, in reality I think just one would do and I will probably beef-up the whole upper wishbone design, so I can push on it with an electric screw jack (satellite dish postitioner) to lift the head. I'd like to run it past you for comments before sawing/drilling commences. In particular I'd like to know what level of slop to expect in the rose joints.

I like the concept. You would retain rotating ability by making the lower collar so it can be clamped and unclamped as needed.
One point so the expensive balljoints could be eliminated by making the upper and lower triangular supports each a stiff structure and using simple radial bearings, 2 each joint totaling 6 bearings.
The bearings could be simple Bronce bushings on a tight fitting shaft.
I would expect this to retain anglinement on the Quill to less then about 0.002" of position.
Good Job.