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.

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[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]

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]

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]

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]

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]

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.

[BillTodd]

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 secret here, is to raid your brother's ball-joint collection, rather than buy them yourself

I had considered cylindrical bearings but I decided my engineering skills required a level of 'flexibility' in the design

[BillTodd]

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?

My mill is NuTool MD500-30 which is yet another Ru Fong replica probably very similar to your Warco.

I've fitted it out with roller nuts (long thread) with the idea of cnc at some stage.

In the pipeline, is a lever action quick-clamp for the head and a spindle lock/brake.

[irving2008]

My mill is NuTool MD500-30 which is yet another Ru Fong replica probably very similar to your Warco.

I've fitted it out with roller nuts (long thread) with the idea of cnc at some stage.

In the pipeline, is a lever action quick-clamp for the head and a spindle lock/brake.

Yes that looks virtually identical (27" x 8" table, 8" throat), but mine dates from 1994...

[sharpshooter90]

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.

With floor mounted drill presses available for 150.00, using the mill for those operations is not really practical. The whole concept of the jointed assembly is clever, but I think small block has the most practical solution- either the front mounted bar, or the rack gear held in place. My opinion is that for most people operating these bench mills, they could center the head over the table, plumb the rack gear and bolt it solidly to the column every 3-4 inches with flathead screws between the teeth. Then just shim the clearance between the gear and the casting. The whole thing could be done for near zero cost and very little time.

[Kipper]

With floor mounted drill presses available for 150.00, using the mill for those operations is not really practical. The whole concept of the jointed assembly is clever, but I think small block has the most practical solution- either the front mounted bar, or the rack gear held in place. My opinion is that for most people operating these bench mills, they could center the head over the table, plumb the rack gear and bolt it solidly to the column every 3-4 inches with flathead screws between the teeth. Then just shim the clearance between the gear and the casting. The whole thing could be done for near zero cost and very little time.

Nah, nowhere near as much fun

Bill it reminds me of the suspension on some aeroplanes (If you hear of one going missing from the L&B airport don't mention my name )

[BillTodd]

With floor mounted drill presses available for 150.00, using the mill for those operations is not really practical. The whole concept of the jointed assembly is clever, but I think small block has the most practical solution- either the front mounted bar, or the rack gear held in place. My opinion is that for most people operating these bench mills, they could center the head over the table, plumb the rack gear and bolt it solidly to the column every 3-4 inches with flathead screws between the teeth. Then just shim the clearance between the gear and the casting. The whole thing could be done for near zero cost and very little time.

I have to say, I wish now I hadn't sold my old Delta pillar drill but, I needed the space for the mill/drill. (I really ought to sell my Ducati 851 to make a bit more room in the shed...)

As Kipper says, half the reason for doing the modification is the fun of designing and building the thing. Part of that fun, is coming up with a new way of doing it; I saw the rail idea on this forum, it's a great idea, but I like to be different and quirky, it's part of my nature

[Kipper]

I had a little dig around and found some SKF cast pillowblocks today....and some 50x20 rectangular tube....Also some spare HR1530 linear bearings and 650mm long rails.......I may be a defector

[BillTodd]

I've had to abandon plans to use the screw jack as it's too long to fit So, after a quick re-think, I knocked up the wish bones. I just have the to make clamp and find a way of mounting the upper wishbone it to the head.