Unimat SL modification to improve control of milling depth

[Barkersoldbean]

I am a hobby user of a unimat sl and struggled to control the depth of cut when milling - due to the crude and coarse action of the splined handle that moves the milling head up and down.

I’ve seen some rather elaborate add on devices to better control the milling depth; but these seemed to junk what is a good basic mechanism for moving the milling head up and down - it’s just too coarse.

I decided to try and retain the existing mechanism but just add a method of finer control - via a 1:30 worm drive.

Essentially, the existing splined shaft is rotated indirectly via a worm drive assembly bolted to the milling head using the existing M6 bolt holes.

It was all made on the unimat sl, works really well and cost around £10 to make - you just need to source the worm drive gears from eBay.

If anyone’s interested in exact drawings and a work plan - I can try and pull it together.

[DIYSwede]

Nice! Thanks for sharing.
So how much/ little travel per turn of the worm did you achieve?
Then just add a graduated scale to the worm and it'll be entirely repeatable!
Personally, I'm into this idea as a "poor man's dividing head" for the lathe's headstock for toolpost milling.

[Barkersoldbean]

Nice! Thanks for sharing.
So how much/ little travel per turn of the worm did you achieve?
Then just add a graduated scale to the worm and it'll be entirely repeatable!
Personally, I'm into this idea as a "poor man's dividing head" for the lathe's headstock for toolpost milling.

Thanks for the reply - I've checked the travel with a dial gauge (which is how i monitor travel across all axis rather than rely on the graduated scale).

Quite serendipitously - for each complete turn of the thumb wheel it moves the carriage by 1 mm - making operation using the thumb wheel (it's a unimat one with markings) without a dial gauge really simple.

The worm drive can be purchased via the following eBay link.

https://www.ebay.co.uk/itm/1-30-Redu.../362593141972?
ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2057872.m2749.l2649

All you need is then a small block of aluminium that you mount everything into and a few bits of 3mm, 4mm and 10mm rod to make the various studs, bushes and axles.

The hardest bit was machining the aluminium block for the worm drive and the main drive gear - I took the easy route and used a pillar drill first to remove as much as I could before finishing it off via the milling head - even then it was very small cuts and a lot of shaking about!

[DIYSwede]

Thanks, I guess you were lucky for the 1 mm/ turn ratio?
I've scrounged a complete, tight and rugged 30:1 brass gear/ steel worm tilt drive from an old Strand TV studio light we scrapped at work,
so now "I'll just" have to find a hopefully clever, non-destructive and reversible way of attaching this to the lathe's headstock,
and conceive and (ahem -) manufacture a few index plates...
All these projects to do...

OTOH: "Idle minds are the Devil's workshop, and ditto hand His tools!"

ATB

[Paul Alciatore]

Instead of a worm drive, I added a mount for a DI to show the actual distance traveled. It has a handwheel for setting it to zero.



I found that with a delicate touch, I could easily set it to a thousandth. A piece of tubing slipped over the Unimat lever would allow finer adjustments. It is a joy to be able to work to actual numbers in the Z axis.

[DIYer]

Thanks Barkersoldbean! We've added your Unimat Depth Control Modification to our Machining category,
as well as to your builder page: Barkersoldbean's Homemade Tools. Your receipt:

Unimat Depth Control Modification by Barkersoldbean

tags: milling