# Mill-Drill rack and pinion?



## Omnimill (Mar 11, 2010)

If you go to: http://www.axminster.co.uk/Downloads//700093_manual.pdf

and go to page 16: "Rise and fall mechanism (See Fig Eight) 
The rise and fall mechanism is a rack and 
pinion device, which drives the head up and 
down the main tool post. The rack is mounted 
on the main tool post, housed in two bevelled 
cup keepers (one at the top, one at the 
bottom) which allows the rack to pivot around 
the tool post with the milling head"

Now given the main objection to Mill-Drills is lack of head alignment when it's moved up and down, has anyone pinned and bolted the rack to the coloumn to improve things??? It could always be un-bolted if you wanted to rotate the head.

Vic.


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## Jasonb (Mar 11, 2010)

Usually the fit of the rack into the slot in the head casting is quite loose so you would still get quite a bit of play, you would never get it as firm as a dovetailed column.

Lazer pointer on the head and a vertical line on the workshop wall method sounds a better cure to me

Jason


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## mklotz (Mar 11, 2010)

People have done that but, as Jason points out, it's a complete waste of time given the slop in the rack and pinion.

With a bit of judicious planning you can avoid the problem in work of the model engine variety. If it's really a problem with the work you're doing, perhaps it's a signal that you should buy a knee mill.


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## tel (Mar 11, 2010)

Like Marv sez - a bit of pre planning goes a long way towards eliminating the problem. Even so, it's not a big deal to clock the workpiece back in after a shift.


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## Maryak (Mar 11, 2010)

Omnimill  said:
			
		

> Now given the main objection to Mill-Drills is lack of head alignment when it's moved up and down, has anyone pinned and bolted the rack to the coloumn to improve things??? It could always be un-bolted if you wanted to rotate the head.
> Vic.



Yes, I did that used cap headed 1/4" screws and it improves things quite a bit. There is still some flex in the rack and it's nowhere near as accurate as a triangular key. I always, (well nearly always), fit my longest bit first and adjust the column height to suit that before I start a serial operation. With 130 mm of column travel it's a rare event to move the column if you do this 1st.

Best Regards
Bob


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## Twmaster (Mar 11, 2010)

I'm looking at the Rong-Fu style of round column mills. This is an issue with them. The work around is as above by planning your workflow in advance. I wish I had the space and the power to feed a much larger machine like a Bridgie.


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## Omnimill (Mar 11, 2010)

Thanks for your thoughts guys. Have a look at: http://lathes.co.uk/ixion/ The head is fixed to the column and the whole lots moves up and down through the table. This seems to work much better. I can't help thinking that keying the rack to the column could work well, and if it's a poor fit in the housing I know a guy who could make a new (better fitting) rack. I wonder if Axminster tools will lend me one to take apart and have a look-see?! :big:

Vic.


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## Blogwitch (Mar 11, 2010)

Vic,

You must be about the squillionth person to ask the same sort of question, and of all the mods I have seen on these machines over the years, I don't really think anyone has come up with a perfect alignment system for them without fully machining up the head and column.

I did some great work with mine, never gave any trouble and amazed me sometimes at what it could cope with, and it stood me in good stead for many years, but almost every job you did had to be pre planned so that the column was never touched while doing it.

Bogs


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## kcmillin (Mar 11, 2010)

I can't help with the head problem. But I have a mill/drill same as yours and A full set of collets greatly reduce the need to move the head up and down. I use collets for just about every milling and drilling operation.

Also, a set of machine length drill bits would help alot too. It seems the biggest need for head cranking is drill bits.

for what its worth.

kel


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## Davo J (Mar 11, 2010)

Hi,
You could add another post about half the diameter beside it. A bracket off the top of the original post, and off the base to hold it. Then make up a bracket off the head to hold a piece of tube bored to suit the additional post, about 200mm away would be enough to keep the head rotating. A bit of bright bar would work.
Davo


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## Omnimill (Mar 12, 2010)

Davo J  said:
			
		

> Hi,
> You could add another post about half the diameter beside it. A bracket off the top of the original post, and off the base to hold it. Then make up a bracket off the head to hold a piece of tube bored to suit the additional post, about 200mm away would be enough to keep the head rotating. A bit of bright bar would work.
> Davo



This is also something I've thought of Davo! Some of the smaller round column mills have a threaded height adjuster that must have a similar (though not as good) effect. Seen here: http://cgi.ebay.co.uk/Axminster-Mil...ultDomain_3?hash=item2c536b9a67#ht_500wt_1161

Vic.


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## portlandron (Mar 12, 2010)

There was a series of articles in Home Shop Machinist on Mill Drills that covered that subject and other improvements. Will check latter and see if I can find the dates.


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## portlandron (Mar 12, 2010)

The article is in the May/June 1998 issue of The Home Shop Machinist.
The basics are get the rack square to the table. Use flat head socket head screws top and bottom and two roll pins in between on the rack. He states there is clearance between the head and the rack but it is always taken up in the same direction. Claims accurate to .002 in 5".


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## Omnimill (Mar 12, 2010)

Thanks for that, sounds like it's worth doing!

Vic.


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## Lytle78 (Jun 11, 2010)

What about mounting a webcam on the head - offfset from the spindle. Using Centrecam software www.miketreth.mistral.co.uk/centrecam.htm , center a target placed on the mill table. Loosen the head, raise or lower, then either move the head around until the target is line up or (if you think tightning the bolts will shift it - which will probably happen) just tighten the bolts and then x-y the table until the target is lined up again. You have to r-zero your dials of course.

Is there some reason this won't work - my mill is 2000 miles away at the moment so I can't try it out.


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## BillTodd (Jun 11, 2010)

I used a wishbone mechanism to fix mine:
see:

http://www.homemodelenginemachinist.com/index.php?topic=9356.0


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