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S&S_ShovelHead
12-13-2010, 03:25 PM
Im trying to thread for the first time on my Grizzly G0602 10x22 lathe. I set the compound rest to 59.5 degrees, set the tool post perpindicular to the bar, Im moving the compound with the cross slide handwheel until it just touches the bar, set it to 0. Back it up, move the carriage so the cutter is to the right of the bar, set the cross slide back to 0, move the compound rest in about .003", wait for the thread dial to come to a number (5) and engage the half nut, wait for the cutter to get to my thread relief, disengage the half nut, move the carriage so the cutter is to the right of the bar and wait for 5 to come around and start again (advancing the compound rest handwheel another .003"). The problem is that the cutter isn't cutting in the grooves made by the previous pass, so Im getting a series of peaks. Im probally forgetting something simple.

loose nut
12-13-2010, 03:36 PM
I don't know if you are doing this wrong or have just put it wrong in this post but you are suppose to put the top slide at 29 deg not 59.5 deg.

form_change
12-13-2010, 03:36 PM
If the threads are not coinciding it suggests that the gear train driving the lead screw is out. Even if you have a gearbox that you can select from there are sometimes gears that need to be shuffled, so I'd suggest checking your manual and making sure you have the right gears in place. Related to this is if you are cutting a metric thread with imperial gearing or the other way around.
What size (diameter and tpi/ pitch) are you trying to cut?

Michael

lynnl
12-13-2010, 03:45 PM
The first thing I'd suggest is to check and make sure the threading dial gear is maintaining good, complete engagement with the leadscrew, i.e. that it's not skipping a tooth sometime in the process between starting the first cut and subsequent ones.
That happened to me the first couple of threads I tried on my lathe. I didn't have the thread dial fully pivoted down against the leadscrew.

You are starting with the cross slide set at 'zero', backing out the cross slide at the end of each cut, and then returning to zero for each subsequent cut, right?

The Artful Bodger
12-13-2010, 03:48 PM
I don't know if you are doing this wrong or have just put it wrong in this post but you are suppose to put the top slide at 29 deg not 59.5 deg.

Depends on how your compound is graduated, 59.5 degrees is 90 degrees minus 30.5. I think it should be set. in this case, to 60.5 degrees.


But that is not the major issue here, as I see it.

I think Michael is right and that this is a problem re-synchronising the feed screw to the spindle.

S&S, for the thread indictor to work (that is the device on the carriage with the numbers on it) you need the feed screw pitch to have a relationship to the pitch you ar cutting and the thread indicator must have a pinion to suit. Apparently, with imperial threads on an imperial lathe this is not a problem but when cutting metric threads it is much more complicated and when cutting metric threads on an imperial lathe it is impossible. Common practice when cutting metric threads seems to be to stop the spindle and reverse the lathe between cuts leaving the half nuts engaged the whole time.

John

flathead4
12-13-2010, 03:58 PM
move the carriage so the cutter is to the right of the bar and wait for 5 to come around

This might be a stupid question... but you are turning your lathe off after you disengage the half-nuts, right? If you are doing this with the machine running, I could see how you could get off. I'm always carefull about using the thread dial and make sure I take the slack out of the drive train when re-engaging the half-nuts.

Tom

S&S_ShovelHead
12-13-2010, 04:07 PM
I thought the 29 or 59 degree setting is based on how the manufacturor referances the angle. I was going off this video (same lathe) http://www.youtube.com/watch?v=Qmc4yRJEeAE

Tring to cut 1/2" 20 tpi threads.

The thread dial is making good contact, I've got my eye on it the whole time pretty much.

Just saw the problem, a change gear wasn't in the right place, thanks for the help.

mike os
12-13-2010, 04:34 PM
Are you using the right number for the thread?

ie odd, even, or fractional tpi

oldtiffie
12-13-2010, 04:59 PM
OK.

Here is the lathe in question:
http://www.grizzly.com/products/10-x-22-Bench-Top-Metal-Lathe/G0602

I am going to presume that the lead-screw is 8tpi (lead = 1/8" = 0.125").

I am also presuming that your threading dial is marked off from 1, 2, 3 and 4 with a line between each number ie at the "half-points" and that the threading dial gear (that mashes with your lead-screw) has 32 teeth.

If all that is the case and as you are cutting a 1/2-20 tpi thread, you should be able to engage the half-nuts at any numbered or "half" mark on the threading dial.

You should engage the half-nuts and move the lathe say one turn (by hand) and check that the marks on the threading dial line up with the line on the threading dial body (ie casting).

The 30 or 60 degree off-set angle can be a bit confusing. Just set the top-slide to be parallel to the lathe bed and head-stock spindle axis (its normal or default position) and then swing the top/compound slide clock-wise 60 degrees. Your top slide will then be 30 degrees "right" of/from the cross-slide axis.

photomankc
12-13-2010, 05:07 PM
What TPI or Metric pitch are you cutting? I have had a similar issue when cutting 16 TPI but I think I had the B gear in the wrong spot so that I was not really cutting that exact TPI. The B gear has to be at the bottom and the spacer on the top when doing imperial which is the opposite of how it is setup for power feed.

There are some pitches that are easy, any even/odd number on the dial will do, but some have to be done on a specific number. And some I have not found a way to do anything but the same number each time.

I usually try a test bar first now and if I have ANY trouble with staying in sync I revert to leaving the half nut engaged and doing the fwd-stop-rev dance instead. Less to worry about.

I do think you want to go to 60.5* instead of 59.5* since you are measuring the angle from parallel with the Z axis instead of the X axis as most directions are geared for.

photomankc
12-13-2010, 05:08 PM
OK.

Here is the lathe in question:
http://www.grizzly.com/products/10-x-22-Bench-Top-Metal-Lathe/G0602

I am going to presume that the lead-screw is 8tpi (lead = 1/8" = 0.125").


Nope - It's 12 TPI

Carld
12-13-2010, 05:16 PM
From what you described your setting the compound at the wrong angle. Put the compound at the same direction as the crossfeed is and that would be perpendicular to the shaft in the lathe. Now look at the marks on the compound mount to see what it shows. It should be exactly perpendicular to the work. What you want is to move the knob on the compound to the right 30 deg. from perpendicular.

Then you have to set the threading tool perpendicular and on the center line of the part your threading.

Now you have to check the quick change gear box to be sure you have the right settings for the thread your cutting. Then set the rpm to about 100 rpm.

I don't know where your getting the #5 at but I always use the #1 on the threading dial. Most threading dials are laid out with four numbers and maybe a few marks between them. Don't use the marks between them, just use the 1 thru 4 as the chart indicates according to the thread your cutting.

moe1942
12-13-2010, 05:32 PM
I thought the 29 or 59 degree setting is based on how the manufacturor referances the angle. I was going off this video (same lathe) http://www.youtube.com/watch?v=Qmc4yRJEeAE

Tring to cut 1/2" 20 tpi threads.

The thread dial is making good contact, I've got my eye on it the whole time pretty much.

Just saw the problem, a change gear wasn't in the right place, thanks for the help.



On that Griz lathe you have the compound set right.. It actually should read 60.5.. 90-29.5..

Those pesky change gears...

oldtiffie
12-13-2010, 05:35 PM
Originally Posted by oldtiffie
OK.

Here is the lathe in question:
http://www.grizzly.com/products/10-x...al-Lathe/G0602

I am going to presume that the lead-screw is 8tpi (lead = 1/8" = 0.125").


Nope - It's 12 TPI

Thanks.

I will give you the new dial settings later in the day.

dp
12-13-2010, 05:59 PM
The thread dial for that model lathe doesn't work for every pitch - you need to check the manual to be sure your pitch is listed.

whitis
12-13-2010, 06:18 PM
Im trying to thread for the first time on my Grizzly G0602 10x22 lathe. I set the compound rest to 59.5 degrees, set the tool post perpindicular to the bar, Im moving the compound with the cross slide handwheel until it just touches the bar, set it to 0. Back it up, move the carriage so the cutter is to the right of the bar, set the cross slide back to 0, move the compound rest in about .003", wait for the thread dial to come to a number (5) and engage the half nut, wait for the cutter to get to my thread relief, disengage the half nut, move the carriage so the cutter is to the right of the bar and wait for 5 to come around and start again (advancing the compound rest handwheel another .003"). The problem is that the cutter isn't cutting in the grooves made by the previous pass, so Im getting a series of peaks. Im probally forgetting something simple.

59.5 degrees is, as others have mentioned, incorrect, but that may not be your biggest problem.

I assume you mean 59.5 degrees from the axis of spindle rotation, as opposed to from the cross slide axis. In the first case, your thread form will be slightly wrong because you are cuttting away slightly too much of the right thread flank. In the second case, you are cutting away way too much of the right thread flank and it is even possible that your problem with threads not aligning could be due to the longitudinal offset produced by the cross slide travel. Set your compound at slightly less than 30 degrees from the cross slide axis; do not exceed 30 degrees or you will produce bad threads. Measured from the spindle axis, this is slightly more than 60 degrees but in no case less than 60 degrees.

If the misalignment of successive thread passes does not go away when you correct the compound angle (which will likley only be the case if you were way off, i.e. 31 degrees off) then you need to look at the feed. Using the same number on the threading dial is conservative and should work in most cases. However, there are situations in which it will not work:

You are threading metric on an inch lathe, or vise versa, without using a special thread dial designed for this purpose or you are using a thread dial meant for cutting the other thread standard.
You are cutting an odd thread size, such as one which is a ratio of pi to produce a hob
You are using the wrong thread gear on your thread dial, if it has multiples.
You have broken a shear pin or key or are missing a key on your change gears or quick change gear box and it is slipping
You have set the change gears incorrectly and are cutting a thread which is not a standard thread which the lathe was designed to handle. Typically, this will be an oddball ratio. For example, 13.090909 TPI is the result of getting a 44 and 48 tooth gear combination backwards when trying to cut 11TPI. In that case, not only do you end up with the wrong thread pitch but the spindle and carriage will not be aligned properly each time the threading dial lines up.


Also, note that the successive passes are not supposed to be perfectly aligned when you are using modified flank infeed. They should be misaligned by about half of your infeed amount on each pass. I.e. about 1.5 mils in this case. But subsequent passes should, if made to the proper depth, erase the grooves left by the previous pass. Make sure you return the cross slide to the same depth after moving the carriage to the right and advance the compound further each time. Since your angle was wrong, though, the grove left by the previous pass will not be completely erased.

The normal threadform used today is 60 degrees full width or 30 degrees half width. You can cut that thread form with the compound at any angle from -30 to +30 degrees from the cross slide axis. 0 degrees, or radial infeed, is the simplest but you can have issues with the chip not getting out of the way. +/- 30 degrees, or flank infeed, advances the cutter to either the right or left flank. This can produce a little too much rubbing vs cutting on that flank and will result in an incorrect thread profile if your angle is slightly off (greater than 30 degrees). Thus, one usually uses modified flank infeed, usually with an angle of 29 or 29.5 degrees though some use 28 or 27. If you use 29.5 degrees, then your angle must be set to an accuracy of better than 1/2 degree and if you use 29 degrees it must be set to an accuracy of better than 1 degree or there is a 50/50 chance the actual angle will exceed 30 degrees, which is not acceptable. Some use alternate flank infeed which is like modified flank infeed but alternates cutting the left and right flanks for more even tool wear; this is harder to do on manual machines.

On page 35 of this document, you will find a diagram of the cuts taken using the subsequent passes in radial, flank, modified flank, and alternate flank infeed:
http://www.secotools.com/CorpWeb/north_america/STEP_training/STEP_1_web/STEP_1_Threading_web.pdf

rohart
12-13-2010, 06:24 PM
If your problem was as you stated, that you had a change gear in the wrong place, then you skipped what I think is a very important stage.

When you set up your gears, take a very thin - less than a thou - pass, just a scratch pass that you can barely see. Firstly, this gives you a much better zero than just banging the compund up to the work, and secondly it allows you to stick a ruler or some calipers against the scratch to check you really are cutting with the right pitch or TPI.

If you had done this, you would have realised you weren't on 20 TPI in the first place, and alarm bells would have rung.

I've just got hold of a lathe with a gearbox and an indicator - I've been doing seat of the pants stuff up till now. I hope to start enjoying the luxury of an indicator real soon now !

Willy
12-13-2010, 06:56 PM
Having assisted several people with this same lathe on this forum and others with the same problem I can say that so far every one to a man has made the same mistake.

As shipped the lathe comes with the change gears in the power feed position shown below.

http://i76.photobucket.com/albums/j31/250willy/3e4f62a4.jpg

When converting the gear setup for inch threading most do not realize that there is a spacer on the bottom shaft inside of where the 104 gear normally resides.
This spacer must be removed when the 104 gear is removed, the "b" gear is then installed and the spacer is then installed on the outside of the "b" gear as shown below.

http://i76.photobucket.com/albums/j31/250willy/730cfd3b.jpg

The metric change gear position has the "b" gear in the same position as where the 104 gear normally resides for power feed.

http://i76.photobucket.com/albums/j31/250willy/c4e474a2.jpg

However since S&S Shovelhead has already found the problem this may all be a moot point.
Whatever he's in the shop and I'm not, still have time for a couple of hours before super.:)

photomankc
12-13-2010, 07:03 PM
That was exactly the mistake I made when it would obliterate my threads even waiting for the same number to come around. Looked close enough based on measurement but that little mistake made it impossible to use the chase dial and I'm sure resulted in a TPI that was actually some kinda close but not quite right number.

oldtiffie
12-13-2010, 08:01 PM
Originally Posted by oldtiffie
OK.

Here is the lathe in question:
http://www.grizzly.com/products/10-x...al-Lathe/G0602

I am going to presume that the lead-screw is 8tpi (lead = 1/8" = 0.125").


Originally Posted by photomankc
Nope - It's 12 TPI


Thanks.

I will give you the new dial settings later in the day.

OK.

For a 12tpi (lead = 1/12 - 0.083333) lead-screw, the thread chaser gear (which meshes with the lead-screw) will have 12 x 4 = 48 teeth.

It is possible that it will have 12 x 3 = 36 teeth (let me know).

The threading/chaser dial, as before, will be divided in eight parts. Four (at the quarter points) will be marked: 1,2,3 and 4. The other marks are lines between the numbers.

For a 20tpi thread and a 12tpi lead-screw you will be able to engage your half-nuts (aka "drop-in") at every number (but not the "lines") on your threading dial.

Tinkerer
12-13-2010, 09:13 PM
(advancing the compound rest handwheel another .003"). The problem is that the cutter isn't cutting in the grooves made by the previous pass, so Im getting a series of peaks. Im probally forgetting something simple.
This is the trouble. You should advance the cross slide not the compound while threading. If you move the compound you will not pick up the same spot. So try setting the cross slide dial to 0 and go from there to advance the cutter in and you'll pick up the same grove/thread start but cut .003 deeper not to the left... ;)

Paul Alciatore
12-13-2010, 10:06 PM
I would suggest that you ignore the post quoted below. The most common method of threading is to cut mainly on the left side of the tool, with only a very slight shaving on the right side. This is why the compound is set to 29.5 (or 60.5) degrees. The cross slide is used to as you described, to move the tool rapidly out of the cut when the end of the thread is reached and to return it to the zero position for the next cut.

THE COMPOUND IS USED TO FEED THE CUTTER DEEPER INTO THE WORK FOR EACH SUCCESSIVE CUT. This does move the tool a bit to the left of where the last cut was made, but it also assures that the left side of the tool is doing most of the cutting and the right side is only shaving a few tenths off. Because the angle is less than half of the included angle of the thread (30 degrees for a 60 degree thread) the movement to the left is not enough to cause a new groove to be cut if the lathe is set up properly for the thread you are cutting.

There are other techniques and you can read about them, but they are not really necessary unless you are experiencing problems.



This is the trouble. You should advance the cross slide not the compound while threading. If you move the compound you will not pick up the same spot. So try setting the cross slide dial to 0 and go from there to advance the cutter in and you'll pick up the same grove/thread start but cut .003 deeper not to the left... ;)

photomankc
12-13-2010, 10:08 PM
This is the trouble. You should advance the cross slide not the compound while threading. If you move the compound you will not pick up the same spot. So try setting the cross slide dial to 0 and go from there to advance the cutter in and you'll pick up the same grove/thread start but cut .003 deeper not to the left... ;)

When you mess up the gears as the OP indicates he did you'll have the point land way off the previous groove. Not just a few thous over but a visually obvious amount that starts destroying the previous thread. The fist time it happened to me I didn't notice it right away but it became obvious after a couple passes when I wasn't getting threads but a mess of ragged nubs.

photomankc
12-13-2010, 10:10 PM
OK.

For a 12tpi (lead = 1/12 - 0.083333) lead-screw, the thread chaser gear (which meshes with the lead-screw) will have 12 x 4 = 48 teeth.

It is possible that it will have 12 x 3 = 36 teeth (let me know).

The threading/chaser dial, as before, will be divided in eight parts. Four (at the quarter points) will be marked: 1,2,3 and 4. The other marks are lines between the numbers.

For a 20tpi thread and a 12tpi lead-screw you will be able to engage your half-nuts (aka "drop-in") at every number (but not the "lines") on your threading dial.

The thread dial on the G0602 has 12 divisions with 1,3,5,7,9,11 marked and the rest are just marker lines. I'm not certain on the number of teeth.

Bob Pastor
12-13-2010, 11:49 PM
I also use a Grizzly lathe. I'm using the larger lathe with the variable speed control. After you figure out your gears and everything seems to be in order, please take the time to watch the five part threading videos. I produced them especially for the novice.

http://www.youtube.com/watch?v=LKGkkGFsF50

I hope these help you. I know how frustrating I was when I first started.

Bob

Tinkerer
12-13-2010, 11:56 PM
Paul your correct... had just came in from the cold and jump in thinking of threading job I was just doing, which was a square thread. Should of thawed out had some hot chocolate then posted so yes disregard my post. :o


I would suggest that you ignore the post quoted below. The most common method of threading is to cut mainly on the left side of the tool, with only a very slight shaving on the right side. This is why the compound is set to 29.5 (or 60.5) degrees. The cross slide is used to as you described, to move the tool rapidly out of the cut when the end of the thread is reached and to return it to the zero position for the next cut.

THE COMPOUND IS USED TO FEED THE CUTTER DEEPER INTO THE WORK FOR EACH SUCCESSIVE CUT. This does move the tool a bit to the left of where the last cut was made, but it also assures that the left side of the tool is doing most of the cutting and the right side is only shaving a few tenths off. Because the angle is less than half of the included angle of the thread (30 degrees for a 60 degree thread) the movement to the left is not enough to cause a new groove to be cut if the lathe is set up properly for the thread you are cutting.

There are other techniques and you can read about them, but they are not really necessary unless you are experiencing problems.

oldtiffie
12-14-2010, 12:10 AM
Originally Posted by oldtiffie
OK.

For a 12tpi (lead = 1/12 - 0.083333) lead-screw, the thread chaser gear (which meshes with the lead-screw) will have 12 x 4 = 48 teeth.

It is possible that it will have 12 x 3 = 36 teeth (let me know).

The threading/chaser dial, as before, will be divided in eight parts. Four (at the quarter points) will be marked: 1,2,3 and 4. The other marks are lines between the numbers.

For a 20tpi thread and a 12tpi lead-screw you will be able to engage your half-nuts (aka "drop-in") at every number (but not the "lines") on your threading dial.

The thread dial on the G0602 has 12 divisions with 1,3,5,7,9,11 marked and the rest are just marker lines. I'm not certain on the number of teeth.

photomankc.

Can you post pics of your quick-change gear-box, threading dial and number of teeth on the threading dial gear please.

Willy
12-14-2010, 12:26 AM
photomankc.

Can you post pics of your quick-change gear-box, threading dial and number of teeth on the threading dial gear please.

Tiffie, the illustrations I posted in my earlier post were taken from the owners manual for the lathe in question.
All the info you asked for is there except for the number teeth on the threading dial.

Here's the link to the pdf.

http://cdn4.grizzly.com/manuals/g0602_m.pdf

oldtiffie
12-14-2010, 01:06 AM
Thanks Willy.

I had already down-loaded that pdf manual file.
http://cdn4.grizzly.com/manuals/g0602_m.pdf

The answers are at page 33.

It is not at all clear to a new user - or probably to a lot of others as well.

The rotating threading dial on the thread-chasing unit IS marked off at 0 to 12 (0 and 12 are the same and are located - but not marked - between 11 and 1).

I suspect that the threading dial gear has 6 x 4 = 36 teeth.

The "Indicator Table" shows the "Scale" (on the threading dial) as being "1 -12".

What that means but does not say is that you can engage your half nuts at any position between and including 1 to 12 IF and only IF the tpi being cut is either 9 or a multiple or sub-multiple of 12,18 or 24 tpi.

9 1/2, 11 1/2 and 13 1/2 tpi must only be engaged at position 1 and 7

All others must only be engaged at positions 1, 4, 7 or 10.

It IS important that when you choose a threading dial to engage your half-nuts at that you stick to that same number while you are threading a particular part.

I suggest that you stick to your lathe hand-book/manual until you get used to it.

I would work it out and label and do it another way with the same result.

S&S_ShovelHead
12-14-2010, 02:59 AM
Thanks for all the responses.

The problem was the spacer for the b gear. I also used 7 on the thread dial.

Here is the finished result (new bearing/bolt for leg extension station for my gym). Huge improvment over original for both stability (much tighter fit, 0.003") and comfort.

http://forums.corvetteforum.com/picture.php?albumid=9404&pictureid=68747
http://forums.corvetteforum.com/picture.php?albumid=9404&pictureid=68746

dp
12-14-2010, 03:12 AM
The rotating threading dial on the thread-chasing unit IS marked off at 0 to 12 (0 and 12 are the same and are located - but not marked - between 11 and 1).

I suspect that the threading dial gear has 6 x 4 = 36 teeth.

It's a 4" dial. I have the same one.

Willy
12-14-2010, 07:44 AM
Originally posted by, S&S Shovelhead,

Thanks for all the responses.

The problem was the spacer for the b gear. I also used 7 on the thread dial.

Here is the finished result (new bearing/bolt for leg extension station for my gym). Huge improvment over original for both stability (much tighter fit, 0.003") and comfort.




Glad it worked out for you.
Don't feel bad about the mistake, you are obviously not the first to make this error.
The manual is a little ambiguous about the change gear re-positioning procedure. Although the illustrations show the spacer, the manual makes no mention of it's presence. No consideration is given to the first time user in this regard.

By the way, nice "handle".

http://i76.photobucket.com/albums/j31/250willy/e43a1432.jpg

moe1942
12-14-2010, 09:08 AM
If your problem was as you stated, that you had a change gear in the wrong place, then you skipped what I think is a very important stage.

When you set up your gears, take a very thin - less than a thou - pass, just a scratch pass that you can barely see. Firstly, this gives you a much better zero than just banging the compund up to the work, and secondly it allows you to stick a ruler or some calipers against the scratch to check you really are cutting with the right pitch or TPI.

If you had done this, you would have realised you weren't on 20 TPI in the first place, and alarm bells would have rung.

I've just got hold of a lathe with a gearbox and an indicator - I've been doing seat of the pants stuff up till now. I hope to start enjoying the luxury of an indicator real soon now !




Saves a lot of time...

moe1942
12-14-2010, 09:10 AM
I would suggest that you ignore the post quoted below. The most common method of threading is to cut mainly on the left side of the tool, with only a very slight shaving on the right side. This is why the compound is set to 29.5 (or 60.5) degrees. The cross slide is used to as you described, to move the tool rapidly out of the cut when the end of the thread is reached and to return it to the zero position for the next cut.

THE COMPOUND IS USED TO FEED THE CUTTER DEEPER INTO THE WORK FOR EACH SUCCESSIVE CUT. This does move the tool a bit to the left of where the last cut was made, but it also assures that the left side of the tool is doing most of the cutting and the right side is only shaving a few tenths off. Because the angle is less than half of the included angle of the thread (30 degrees for a 60 degree thread) the movement to the left is not enough to cause a new groove to be cut if the lathe is set up properly for the thread you are cutting.

There are other techniques and you can read about them, but they are not really necessary unless you are experiencing problems.



Thank you...Saved me the trouble.