GRIZ MOD G9729 SET UP QUESTION

This forum is dedicated to those hobbyists with the 3-in-1 metalworking machines. Mill-Drill-Lathes. Tips, techniques, modification and use of these machines is topical.

Moderator: Harold_V

goodfellow
Posts: 33
Joined: Thu Aug 17, 2006 11:07 am

Re: GRIZ MOD G9729 SET UP QUESTION

Post by goodfellow » Sat Sep 06, 2008 8:15 am

engineer_loves_machines wrote:So I've had this machine 8 months now and still learning what it can and can't do.
Is it possible to change the feed direction for the lathe? Right now the power feed table moves in the direction of the lathe spindle. Can I make it feed in the tail stock direction and still run the lathe spindle forward? Ifso, how?
-- just need to add a simple intermediate gear. Not my idea -- it was posted by a fellow Griz owner. I have been using this setup for reversing the lead screw on my 44142 (same machine as the Griz)
Attachments
4a6f.jpg
31de.jpg
96fa.jpg
a220.jpg

HiramAbiff
Posts: 16
Joined: Fri Dec 12, 2008 12:30 am
Location: Pine, CO

Re: GRIZ MOD G9729 SET UP QUESTION

Post by HiramAbiff » Mon Dec 15, 2008 3:06 am

As I have made clear in the recent past, I am new and grunge to learn as fast as my aging brain will allow.
That Saud, it seems to me that this notion of placing an intermediary gear in the works, in a section of the machine which clearly does not mind having an extra gear placed there, is really a pretty darn smart and KISS idea as long as the gear you use does not mess up your feed rate math to the point of making junk.
This is one I am interested in heiring more about Edith on or offline, should anybody want to "talk shop."

The KISS ideas are the best ones & regards to the creator.

Hiram Abiff in Pine, CO
303-532-1114

Harold_V
Posts: 17138
Joined: Fri Dec 20, 2002 11:02 pm
Location: Onalaska, WA USA

Re: GRIZ MOD G9729 SET UP QUESTION

Post by Harold_V » Mon Dec 15, 2008 4:39 am

HiramAbiff wrote: it seems to me that this notion of placing an intermediary gear in the works, in a section of the machine which clearly does not mind having an extra gear placed there, is really a pretty darn smart and KISS idea as long as the gear you use does not mess up your feed rate math to the point of making junk.
You're right! It is pretty clever, and there is no need to worry about it messing up the feed rate. As the gear acts as nothing more than an idler, to reverse the direction of the lead screw, there is no change in ratio. Motion from one gear is transferred to the other gear a tooth at a time, so they are, for all practical purposes, in lock step.

Harold

HiramAbiff
Posts: 16
Joined: Fri Dec 12, 2008 12:30 am
Location: Pine, CO

Gear Ratio?

Post by HiramAbiff » Mon Dec 15, 2008 1:14 pm

Again,
I am slowly coming up to speed on something takes a lifetime to learn.
Can I assume that your previous note assumes a gear (and I am not sure which one this would be in my collection of Griz. gears, but assume it will be obvious if/when the time comes) with a 1:1 ratio with the other two gears in which it will be interacting? If not, you gotta stat doing some math--or so I assume.
Corrections?
Thanks,
H.A. 32º

Harold_V
Posts: 17138
Joined: Fri Dec 20, 2002 11:02 pm
Location: Onalaska, WA USA

Re: Gear Ratio?

Post by Harold_V » Mon Dec 15, 2008 3:38 pm

HiramAbiff wrote:Can I assume that your previous note assumes a gear (and I am not sure which one this would be in my collection of Griz. gears, but assume it will be obvious if/when the time comes) with a 1:1 ratio with the other two gears in which it will be interacting? If not, you gotta stat doing some math--or so I assume.
I understand your concern.

The idler does not enter into the equation. Any size gear will serve. Regardless of the number of teeth on the idler, the speed of the driven gear won't change, it will be the same as if it was directly coupled to the first gear. Were you to take power off the shaft of the added gear instead of off the teeth, that would not be true because the idler is likely to be driven faster/slower than the third gear. Said another way, if you were to mount the third gear on the same shaft, keyed to the idler, it would then be driven too fast/slow, so feed speed would be altered.

Harold

HiramAbiff
Posts: 16
Joined: Fri Dec 12, 2008 12:30 am
Location: Pine, CO

Gear Ratio

Post by HiramAbiff » Mon Dec 15, 2008 4:40 pm

I am sorry. I feel quite think.
Maybe I am not visualizing this correctly. Maybe I just need to shut up and do it as an experiment to see what actually happens.
All of that said, In envision in a "standard setup" a driving gear which offers power. It has a gear at a given ratio. You then mate it with a gear which receives the power. It also has a given ratio. The two gears operating together create a speed / torque change which is demonstrated in how fast the lead screw turns, etc.
It seems to me that when you place a gear in the center or middle of the works I just outlined, you change that gearing ratio, yet again, along with spinning the lead screw in the opposite direction.
From the standpoint (viewpoint/perspective) of the final gear--the one which turns the lead screw, the idler gear is supplying all of the power which it gets from gear(s) further up the "chain." If you change the size/# of teeth on the idler gear, how can you NOT affect the overall desired speed/outcome?
I know some of you old-timers out there are currently laughing at me the way I laugh at a game show contestant who can not guess the answer to an obvious answer. It's OK though, I can take it. The dumb question is the one not asked or understood when answered :-).
Thanks in advance for your help and patience.
Hiram

Still-Learning
Posts: 11
Joined: Tue Sep 02, 2008 9:33 am
Location: SC

Re: Gear Ratio

Post by Still-Learning » Mon Dec 15, 2008 6:57 pm

HiramAbiff wrote:I am sorry. I feel quite think.
Maybe I am not visualizing this correctly. Maybe I just need to shut up and do it as an experiment to see what actually happens.
All of that said, In envision in a "standard setup" a driving gear which offers power. It has a gear at a given ratio. You then mate it with a gear which receives the power. It also has a given ratio. The two gears operating together create a speed / torque change which is demonstrated in how fast the lead screw turns, etc.
It seems to me that when you place a gear in the center or middle of the works I just outlined, you change that gearing ratio, yet again, along with spinning the lead screw in the opposite direction.
From the standpoint (viewpoint/perspective) of the final gear--the one which turns the lead screw, the idler gear is supplying all of the power which it gets from gear(s) further up the "chain." If you change the size/# of teeth on the idler gear, how can you NOT affect the overall desired speed/outcome?
I know some of you old-timers out there are currently laughing at me the way I laugh at a game show contestant who can not guess the answer to an obvious answer. It's OK though, I can take it. The dumb question is the one not asked or understood when answered :-).
Thanks in advance for your help and patience.
Hiram
Hiram,
If you have read all the previous posts on this subject you no doubt had to get a good chuckle over my claims of turning a left hand thread when it was obvious that I had not. It's amazing how the brain works. I had to setup and turn a thread to convince myself that I was wrong.
Right then I modified my machine to reverse the lead screw and then was able to produce a left hand thread. This modification took less than an hour and is one of the easiest mods to do.
First I turned the dummy shaft to match the ID of the change gears then center drilled it.
I only drilled the depth to the length of the of the gear and then parted off the shaft.
The remaining shaft was then drilled and tapped for a 10-32 and parted off about 3/8" long.
A screw throught the shaft and tightened in the threaded piece joined them back to one piece and then milled at the part line on both sides with a 1/4" end mill.
Next remove the spider and mill the slot with a 1/4" mill.
The shaft and nut will engage in this slot and the slot will keep then both from rotating.
Also, the nut is captive and stays between the spider and the gear cover when not in use.
You will have to determine the details of the slot and shaft for your machine.

Good Luck,
SL
Attachments
Idler gear1.jpg
Idler gear2.jpg
Idler gear3.jpg

Harold_V
Posts: 17138
Joined: Fri Dec 20, 2002 11:02 pm
Location: Onalaska, WA USA

Re: Gear Ratio

Post by Harold_V » Mon Dec 15, 2008 11:19 pm

HiramAbiff wrote:It seems to me that when you place a gear in the center or middle of the works I just outlined, you change that gearing ratio, yet again, along with spinning the lead screw in the opposite direction.
Nope.

Stop looking at this as if you are transferring rotation to the middle shaft, which you are not. Look at it from the perspective of tooth to tooth.

Assuming your driving gear is a 20 tooth, and the idler is a 40 tooth, driving an 80 tooth, as long as the gears move tooth by tooth, the same ratio is established. Remember, you have to discount the center gear, because it does nothing more than transfer power from the driving gear to the driven gear, which it does a tooth at a time.

Lets look at it like this. The driving gear makes four revolutions for one of the driven gear.

You now introduce the idler, which has 40 teeth. Driven by the 20 tooth gear, it will revolve twice for every four revolutions of the driver. In turn, being half the teeth of the driven gear, it will revolve twice for every revolution of the driven gear. Same ratio as if they are directly coupled.

If the idler was some off-size gear (33 tooth, for example), same results, just different rotation ratios. Driver to driven remains unchanged.

Make a setup and observe. It will be clear as mother's milk.

Harold

HiramAbiff
Posts: 16
Joined: Fri Dec 12, 2008 12:30 am
Location: Pine, CO

Gear Ratio?

Post by HiramAbiff » Tue Dec 16, 2008 1:48 am

Harold,
First, I appreciate the time you are spending with me. I will make a mock setup and I am sure it will be clear.
What is not clear to me is that your explanation should be the same with or without the passive gear. There is a big gap between what you are telling me--and I DO understand your explanation--and what I THINK I have always known about gear ratios.
An example; just look at any bicycle--a larger gear driving a smaller gear. Change to a larger gear (lets just assume a rear wheel gear change) in the rear and speeds/ratios, etc. change, assuming the same amount of power (torque and revolutions) offered from the bike rider. Ok, so no passive gear in my example. In the end, I am trying to reconcile your example with the task at hand and what is clearly a gap in my understanding of the issues at hand. My frustration with myself starting to simmer :-) please fill in the gap??? Maybe its just brain freeze on my part from dealing with the sub zero temps. here in Pine, CO.......
Thanks & Regards,
Hiram

HiramAbiff
Posts: 16
Joined: Fri Dec 12, 2008 12:30 am
Location: Pine, CO

Gear Ratio?

Post by HiramAbiff » Tue Dec 16, 2008 4:09 am

Harold, et al.

Well, I sat down and did some math. Regardless of my intuition, the math agrees with Harold and I can at least now visualize the example he illustrated. Always better to find a way to make an explanation work for you, rather then fight it if you can.

I will still prove it in a mock setup, but again, the math proves out well.

Thanks VERY much!!

Hiram

HiramAbiff
Posts: 16
Joined: Fri Dec 12, 2008 12:30 am
Location: Pine, CO

Re: Gear Ratio

Post by HiramAbiff » Sat Nov 14, 2009 1:58 am

SL,
I hope you are still out there. It has been a while since I last looked at this and now feel that the time has come to implement (gear ratios are no longer my concern--contrary to some of my posts of a few months back). What I am concerned about now is the ease of use of your idler gear implementation. I would see this as quite valuable if I could easily engage and dis-engage at will, with a lever or some such. In this way, I could engage the cutter when moving in either direction, rather then having to dis-engage and reset for cutting in one direction only. As I view your modification, it seems as if there is no easy way to move the idler gear in and out of play without stopping the machine and introducing/removing the idler gear with needed adjustments. Trying to have my cake and eat it to I suppose. Can you or anybody else who has implemented this (or something like it) advise?
Much thanks,
Hiram

Still-Learning wrote:
HiramAbiff wrote:I am sorry. I feel quite think.
Maybe I am not visualizing this correctly. Maybe I just need to shut up and do it as an experiment to see what actually happens.
All of that said, In envision in a "standard setup" a driving gear which offers power. It has a gear at a given ratio. You then mate it with a gear which receives the power. It also has a given ratio. The two gears operating together create a speed / torque change which is demonstrated in how fast the lead screw turns, etc.
It seems to me that when you place a gear in the center or middle of the works I just outlined, you change that gearing ratio, yet again, along with spinning the lead screw in the opposite direction.
From the standpoint (viewpoint/perspective) of the final gear--the one which turns the lead screw, the idler gear is supplying all of the power which it gets from gear(s) further up the "chain." If you change the size/# of teeth on the idler gear, how can you NOT affect the overall desired speed/outcome?
I know some of you old-timers out there are currently laughing at me the way I laugh at a game show contestant who can not guess the answer to an obvious answer. It's OK though, I can take it. The dumb question is the one not asked or understood when answered :-).
Thanks in advance for your help and patience.
Hiram
Hiram,
If you have read all the previous posts on this subject you no doubt had to get a good chuckle over my claims of turning a left hand thread when it was obvious that I had not. It's amazing how the brain works. I had to setup and turn a thread to convince myself that I was wrong.
Right then I modified my machine to reverse the lead screw and then was able to produce a left hand thread. This modification took less than an hour and is one of the easiest mods to do.
First I turned the dummy shaft to match the ID of the change gears then center drilled it.
I only drilled the depth to the length of the of the gear and then parted off the shaft.
The remaining shaft was then drilled and tapped for a 10-32 and parted off about 3/8" long.
A screw throught the shaft and tightened in the threaded piece joined them back to one piece and then milled at the part line on both sides with a 1/4" end mill.
Next remove the spider and mill the slot with a 1/4" mill.
The shaft and nut will engage in this slot and the slot will keep then both from rotating.
Also, the nut is captive and stays between the spider and the gear cover when not in use.
You will have to determine the details of the slot and shaft for your machine.

Good Luck,
SL

Still-Learning
Posts: 11
Joined: Tue Sep 02, 2008 9:33 am
Location: SC

Post by Still-Learning » Sat Nov 14, 2009 10:44 am

Hiram,
You're correct in that changing the direction of the lead screw is time consuming and requires stopping the lathe. I have a Craftsman 109 lathe that has a lever for forward and reverse, however the machine has to be stopped before the lever is moved. You will need some kind of clutch to disengage the power flow (like in a car w/manual transmission) to eliminate gear clashing and teeth shedding. The best way that I've found to disengage the power flow is the power switch, turn it off.

If needed I may be able to pull out the 109 and get a picture of the reverser gearing or you could do a search for this as there are loads of pictures on the net. I found this one on Lathes.co.uk

The only reason that I can think of for changing lead screw direction in the middle of a cut is to produce a cross pattern knurled result.

Honestly, since I modified my lathe I have only used it once to cut left threads. I have moved on to CNC and in the process of building my second router table using the first to cut out all the parts. The lathe is deligated to cutting and turning the lead screws for my new toys.



Take care,
SL
Attachments
Lathe Gearing.gif

Post Reply