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slamadeleine
03-07-2017, 07:33 PM
Hello, I'd like to say thank you to everyone on this forum. I've been lurking for almost two years now and I've learned a lot.

I acquired a used round column Mill/Drill (King Industrial, RF31 rebadged, made in Taiwan) about a year ago. I know they're not the best but it was already stretching my budget.

I've been learning how to use it slowly.

One thing that bugs me is the requirement of using 2+ hands to tighten the draw bar. I need to hold the collet, the tool at the right depth (no end-mill holders yet) screw the drawbar and hold the spindle. And as most humans I only have 2 hands... So I ended up chipping a few end-mills by dropping them and denting a collet too.. I would rather not have to hold a second wrench if I can so I'm looking to make something that would hold into place and release easy.

I've looked at a lot of options and locking the pulley with a brake or locking the spindle just above the collet seem to be the only 2 workable options.

I am not an engineer or an experienced machinist but would one way be preferable to the other?

Here's the bottom of the spindle example: https://www.youtube.com/watch?v=jVmymjf2LZU

And the pulley brake: http://www.mycncuk.com/attachment.php?attachmentid=826&d=1251658412

Thanks for shedding your lights!

1-800miner
03-07-2017, 11:10 PM
Some where I saw a modification that you may use.
He drilled a couple of hole into the bottom rim of the pulley and fastened a barrel bolt ( door hardware) to the mill so it would slide up into the hole and lock the spindle.

RichR
03-07-2017, 11:18 PM
One thing that bugs me is the requirement of using 2+ hands to tighten the draw bar. I need to hold the collet, the tool at the right depth (no end-mill holders yet) screw the drawbar and hold the spindle. And as most humans I only have 2 hands... So I ended up chipping a few end-mills by dropping them and denting a collet too.. I would rather not have to hold a second wrench if I can so I'm looking to make something that would hold into place and release easy.

I install the collet into the spindle then thread the drawbar by hand most of the way in. Insert the tool at the desired height and finger tighten
the drawbar. That's enough to keep the tool from dropping out. Hold the spindle pulley with one hand and use a wrench in the other to snug
up the drawbar. I choke up on the wrench so I don't over tighten the drawbar.

livesteam
03-07-2017, 11:42 PM
I bought a 1943 Bridgeport M Head mill many year ago which has no spindle brake as later models.
Fortunately it came with the spindle collet ejector device. Use requires 2 wrenches and you have
the same scenario as OP slamadeleine experiences.
Eventually a possible solution occurred to me in the form of a threaded bushing installed in the bottom
surface of the head housing. A short threaded shaft with a leather pad on top and lever on the bottom
rises up to drag on the lower surface of the spindle pulley locking it well enough to hold it as the drawbar it tightened.
Been in use for many years without a problem.
RichD, Canton, Ga

macona
03-08-2017, 01:02 AM
Yeah, tighten the drawbar finger tight with the end mill in place, I have never had one fall out after that. When removing just keep a shop towel under the spindle when changing if you are worried about dropping it.

Paul Alciatore
03-08-2017, 03:29 AM
I have used a round column mill and did much what Rich describes here. The only things I would add are after dropping the first end mill, I would have found a scrap of wood to keep handy. Place it under the spindle while putting an end mill in or taking it out. I never had that problem and could usually hold a rag around the end mill while loosening the drawbar.

The second thing is the round column mill that I used had a large nut at the top end of the spindle. I got a wrench to fit it and used it while tightening the drawbar. For loosening it I would usually strike the wrench on the drawbar sharply with the pawn of my hand. That depended on inertia in the spindle and motor and would usually loosen the grip of the collet and then the pulleys and motor provided enough resistance for further loosening it to remove the tool.

My present mill is a gear head and I just put in the lowest speed setting to loosen and tighten the drawbar.




I install the collet into the spindle then thread the drawbar by hand most of the way in. Insert the tool at the desired height and finger tighten
the drawbar. That's enough to keep the tool from dropping out. Hold the spindle pulley with one hand and use a wrench in the other to snug
up the drawbar. I choke up on the wrench so I don't over tighten the drawbar.

slamadeleine
03-08-2017, 09:57 AM
Some where I saw a modification that you may use.
He drilled a couple of hole into the bottom rim of the pulley and fastened a barrel bolt ( door hardware) to the mill so it would slide up into the hole and lock the spindle.
I would be afraid of imbalancing (sp?) the pulley, is it a valid concern, I don't know...

I just tried hand tightening the collet enough to hold an endmill and I don't have enough hand torque. No matter how hard I try, the end mill don't grab before I need the wrench. Is there an easy way to polish the inside of the spindle (without a lathe)? I read last night about greasing the outside of the collet and I think this might improve my chances.


I choke up on the wrench so I don't over tighten the drawbar. I tried to find a torque spec, how tight should the drawbar be tightened? I've had a few end mills pull out while side milling. I'm looking to get end-mill holders but am not there yet.


When removing just keep a shop towel under the spindle That is one of those little thing that never occurred to me. Thanks.


A short threaded shaft with a leather pad on top and lever on the bottom rises up to drag on the lower surface of the spindle pulley locking it well enough to hold it as the drawbar it tightened. Been in use for many years without a problem. I will definitely look that over see if it's possible.

Thanks for all the input so far!
Sebastien

RichR
03-08-2017, 11:21 AM
I just tried hand tightening the collet enough to hold an endmill and I don't have enough hand torque. No matter how hard I try, the end mill don't grab before I need the wrench. Is there an easy way to polish the inside of the spindle (without a lathe)? I read last night about greasing the outside of the collet and I think this might improve my chances.
Something sounds wrong. When you place a 1/2" shank in a 1/2" collet it should be a pretty close fit and require very little tightening to hold up
under gravity, finger tight. If the threads on your drawbar or collets are damaged or dirty, you can't finger tighten. If you're mixing metric and
imperial shanks and collets, don't do that.

paul463
03-08-2017, 12:49 PM
I would be afraid of imbalancing (sp?) the pulley, is it a valid concern, I don't know...

I just tried hand tightening the collet enough to hold an endmill and I don't have enough hand torque. No matter how hard I try, the end mill don't grab before I need the wrench. Is there an easy way to polish the inside of the spindle (without a lathe)? I read last night about greasing the outside of the collet and I think this might improve my chances.

I tried to find a torque spec, how tight should the drawbar be tightened? I've had a few end mills pull out while side milling. I'm looking to get end-mill holders but am not there yet.

That is one of those little thing that never occurred to me. Thanks.

I will definitely look that over see if it's possible.

Thanks for all the input so far!
Sebastien

As far as balancing goes, you could drill the pulley rim in 3 equally spaced spots like on a Millrite mill pulley.

Arcane
03-08-2017, 02:30 PM
There's quite a bit of information in this PDF.

https://www.tormach.com/uploads/163/ED10067_ToolHolding_Whitepaper_1010A-pdf.html

Jim Stewart
03-08-2017, 05:20 PM
I use a butterfly wrench with the appropriate socket (which I leave on the wrench all the time) - assuming, of course, that you have a compressor. No need to hold the shaft at all.

http://www.homedepot.com/p/Husky-3-8-in-Butterfly-Impact-Wrench-H4410/205841304
http://www.harborfreight.com/3-8-eighth-inch-drive-75-ft-lbs-torque-compact-air-impact-wrench-93100.html

I suspect the HF unit at $20 is plenty hefty enough for this kind of light duty...

-js

slamadeleine
03-12-2017, 05:55 PM
Hi guys, thanks again for all the help.

I will try to just butt a toggle clamp against the bottom of the pulley first (with leather or rubber at the end) see if that does not give me enough brake to torque to 30ft/lb. If not, I'll think about small divots.

I read the Tormach guide and saved it preciously.

I just went ahead and ordered a butterfly wrench to help speed up the process.

I did find something that might explain all my troubles. First I had ground one alignment pin a couple weeks ago but never figured that there were two... (facepalm slap) So I went back and ground the second one. Now collets go in much easier, that set screw was protruding too much. Now, no need to torque with the wrench to get the collet high enough to bite the tool.

While I was in there I found out why the collets would sometimes come out roughed up.

If you look at the picture

http://www.toolsoft.ca/ext/spindle-01.jpg

You can see that the previous owner had carved the bottom part of the spindle. I took some sand paper and deburred that scar. Should help with the collet. I used 180 grit sand paper, should I polish it more than that?

Should I think about replacing the spindle for that scar or should it be fine?

Thanks again!

mattthemuppet
03-13-2017, 11:18 AM
As long as it doesn't protrude into the bore it should be fine.

BCRider
03-13-2017, 04:54 PM
I install the collet into the spindle then thread the drawbar by hand most of the way in. Insert the tool at the desired height and finger tighten
the drawbar. That's enough to keep the tool from dropping out. Hold the spindle pulley with one hand and use a wrench in the other to snug
up the drawbar. I choke up on the wrench so I don't over tighten the drawbar.

That's what I do as well. And if finger pressure isn't enough for the heavier cutters then a light bump with the wrench on the drawbar is enough to pinch it.

The locking device is not a bad ideal though since the pulley is pretty dirty with rubber dust. Just be sure it's not still engaged when you hit the power. I think I'd want one that still needs me to finger tighten and wrench bump to hold initially then the lock is used to tighten but the lock falls or springs clear as soon as it is released just to protect against the easily distracted idiot that runs my own machine.......

Keep in mind that a spindle lock will encourage you to tighten the drawbar quite strongly. And that isn't a good option either. You don't want to need to have to hit the slightly loosened drawbar a big one to snap the collet or arbor loose. That's hard on the spindle bearings.