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Lancefitzgiben
03-22-2013, 10:55 PM
Hey guys, I've got a smaller Grizzly bed mill that I've been rebuilding back to a manual machine from the previous owner's cnc conversion. I am keeping one of his mods.. which is a much larger Leeson motor which sits right on top of the headstock.

This means that the whole headstock assembly with motor comes in at about 100 pounds, so I need to counter balance it. Does anyone have suggestions as to how to go about that? I'm also not sure as to how much weight I should counter it with, but I'm thinking 80 to 90 pounds. I've got a 200 pound block of steel that I need to cut down and hang in place once the details are sorted.

I appreciate any insight or suggestions as to how I should accomplish this. Thanks all, I appreciate it.

- Tim

wtrueman
03-23-2013, 12:13 AM
I had the same problem with Lantaine lathes, back mounted motors. I anchored (cemented) steel plates where the feet touched, about one foot square, welded chains to the plates, and then bolted the chains and tensioning devices to the legs. The units were then moveable if necessary. However this was May, 1970 and as of yesterday, March 21, 2013, never moved. Go figure! Wayne.

kf2qd
03-23-2013, 12:18 AM
You are going to need some thing close to the total weight of the head. Just remember that you are also going to have to move that mass every time you lower the head.

Jaakko Fagerlund
03-23-2013, 02:55 AM
80-90 pounds sound about right, keeps the head still a little heavier than the counterweight but is considerably lighter to operate (basically just 10-20 pounds).

Tony Ennis
03-23-2013, 08:29 AM
I need to add a counterweight to my drill press table. It isn't heavy, as such, but it's just clamped onto a round post. If it falls, it will fall like a guillotine.

Stepside
03-23-2013, 09:01 AM
Tony

You don't need a counterweight. Make a safety clamp that bolts around the column and is bolted close to the table position. Make it so you can move it without much hassle, probably just loosen the bolts and lower it to the new spot and tighten. If going up move and clamp the table and then move the clamp. I have put the safety clamp on every floor model drill press I have had in the classroom. This is after seeing what happens when the table gets loose. If it does not maim you it will break where the table connects to the column and then you need parts.

Pete

As to the counterweight on the mill, don't over do it or you might have "head creep" while milling.

Gary Paine
03-23-2013, 12:16 PM
Hey guys, I've got a smaller Grizzly bed mill
- Tim

I'm not sure what you mean by a bed mill, Tim. Are you talking something like the G0720R bench top milling machine?
Are you thinking of hanging a weight off the back side of the column and using pulleys to the top of the column with cables on the headstock? If that's the case, I wouldn't think your counterbalance weight would want to be much more than the extra weight of the larger motor. Taking all the weight off might make the head shake a bit in use.

Lancefitzgiben
03-23-2013, 01:01 PM
Thanks very much for the responses guys. By bed mill, I mean that the headstock moves up and down to form the coarse Z axis, as opposed to the knee mill setup in which the table itself articulates to form the coarse Z axis.

I think the weight of the counter balance will be somewhat crucial, but perhaps not as crucial as I think, depending on the effectiveness of the Z axis lock. Like has been stated, I don't want to lighten the headstock to the point of getting kickback or lift during drilling or plunge cutting.

Is cables over the top and down the back the best method? The model I have is the G0463 I believe.

Black_Moons
03-23-2013, 01:31 PM
I say leave the weight as is, you don't move the headstock that much and 100lbs is likey required to drill larger holes. You really don't want the head to lift, ever, or it will suddenly lurch down once it breaks through.

Extra weight shouldn't hurt the leadscrew/ways that much if you keep them well lubed

Gary Paine
03-23-2013, 01:35 PM
Is cables over the top and down the back the best method? The model I have is the G0463 I believe.

That's the way I'd approach it, similar to putting sash weights on a window.

velocette
03-23-2013, 07:37 PM
""Is cables over the top and down the back the best method? The model I have is the G0463 I believe."

The answer is YES. The counter weight needs to be equal to or preferably heavier than the total weight of the mill head. If it is lighter then ANY backlash makes it very hard to control the depth of the cut.

When both the mill head and counterweight is the same the the effort to move it requires very little effort to move it.

Suggestion Make provision to add extra weight to the counter weight to BALANCE say the weight of a heavy boring head.

Took time out to do a bit of research on Grizzly G0463 it appears to be very similar to a "Seig X3" so a counter balance with the weight at the back of the column would seem to be OK.

Guides to stop the weight swinging in the breeze are essential. Also Ball Bearings in the pulleys will give a smoother action.

Eric

Lancefitzgiben
03-23-2013, 10:26 PM
Eric thanks a lot man. I think my biggest challenge at this point is cutting down my 200lb block of steel and figuring a way to hang it.. also taking into consideration that I need to be able to take the head all the way up without the counter weight coming to rest on the bench.

Tony Ennis
03-23-2013, 10:55 PM
Lance, look up the wikipedia article on pulleys. These may help you trade weight for space.

Rich Carlstedt
03-23-2013, 11:31 PM
What about a gas strut.
Less room
We had nitrogen cylinders on our boring mills
Rich

Lancefitzgiben
03-24-2013, 02:19 AM
A gas strut is a definite possibility as I think the machine had one before anyway. I've got to look into that and see if I could get one powerful enough that would fit

mike4
03-24-2013, 05:48 AM
Search for pictures of the older horizontal boring machines , many of these had two chains attached to a counterweight which allowed a smoothe movement with no surprises when doung heavy cuts..
Michael

Thomas Staubo
03-24-2013, 01:47 PM
One example is shown in the 11th post here:
http://www.chaski.org/homemachinist/viewtopic.php?t=83378

And if you download this file here (1Mb), you can see another:
http://www.mediafire.com/view/?8cphtyypcbyd1dg
(not my file, I just saved it from a Yahoo group)

.

Spin Doctor
03-24-2013, 07:08 PM
Instead of pulleys with I am assuming rope of some sort (Wire?) think about two lengths of bicycle chain with sprockets on two common axles. Industrial equipment often does this (heavier roller chain of course). There is a video on YouTube of a similar set-up http://www.youtube.com/watch?v=ijRL68ZXFRE&list=UUeTlJQ3P5rS9IbzKArj7gUg&index=11

Lancefitzgiben
03-25-2013, 12:05 PM
THANK YOU Thomas! Those images help quite a bit. In the second link it says he is using 100 lbs of counter weight, but it doesn't look like he's got any extra appreciable weight riding on the headstock. At this point I think I'll still be shooting for a counterweight in the 80 lb range. I may have to hang it underneath my bench though, as he has done - albeit with some retainers to keep it from moving laterally too much.

Lancefitzgiben
03-25-2013, 12:21 PM
Spin Doctor, thanks so much. I did run across a similar setup on youtube while searching there. Chain is a definite possibility as I've even got quite a bit of extra bicycle stuff sitting around. Pulleys and cable would be easier however, so unless there's a practical reason to seek out chain I will likely go with pulleys and cable.