Ugly threads
- Thread starter adamsgt
- Start date
Another thing, there is no reason to advance the tool inward until you have the set up right. When I make my scratch cut I check the resulting marks with the thread gauge just to double check. Then if the pitch is correct I make another pass with the compound set at the same setting as the scratch cut and carefully watch the tool point to make sure it's exactly following the original scratch cut. This is also a good time to practice the 'dance with the hands' that you do at the end of the cut [ the disengaging of the half nuts and the withdrawing of the tool via the cross slide hand wheel ].
A newbie would be wise to do 2 or 3 dry runs like this. Once you are confident that you've got it figured out then start advancing the tool via the compound hand wheel.
A newbie would be wise to do 2 or 3 dry runs like this. Once you are confident that you've got it figured out then start advancing the tool via the compound hand wheel.
J
jdy
Guest
a big thank you 2 bob
Thank You bob 4 taking the time to help & share your wisdom with us. when can a guy get his hands on that cutting oil looks like it works very good. thank's 4 the tip on the Hss insert tool i will be ordering some on monday. also what brand of lathe are you using in your videos look's like like a good quality lathe.
Thank You bob 4 taking the time to help & share your wisdom with us. when can a guy get his hands on that cutting oil looks like it works very good. thank's 4 the tip on the Hss insert tool i will be ordering some on monday. also what brand of lathe are you using in your videos look's like like a good quality lathe.
J
Jdh
Guest
Sorry I mis-interpreted your comment about the gearing. Sounds like you have a decent lathe but one can never have too many toys.
Al's discription is good. It is how you thread if you are using the compound to feed in. That is the textbook way and will give you good threads if done correctly. Doing this I only take around .005 per pass until I get close to the end then take .003" or less and take a few dry passes at the same setting. Using the compound it is not good to take too much of a cut. I also thread at the slowest rpm's I can get. A lot of professional machinists plunge cut the threads using the cross slide. You can take larger cuts and finish the threading operation quicker that way.
Many pro's use carbide inserts to thread with and have good success. HSS tooling is more forgiving and works fine for most steels.
Al's discription is good. It is how you thread if you are using the compound to feed in. That is the textbook way and will give you good threads if done correctly. Doing this I only take around .005 per pass until I get close to the end then take .003" or less and take a few dry passes at the same setting. Using the compound it is not good to take too much of a cut. I also thread at the slowest rpm's I can get. A lot of professional machinists plunge cut the threads using the cross slide. You can take larger cuts and finish the threading operation quicker that way.
Many pro's use carbide inserts to thread with and have good success. HSS tooling is more forgiving and works fine for most steels.
B
Bob Pastor
Guest
Jdh,
You can email me at robpas@btc-bci.com about the high sulfur cutting oil and shipping dates.
Bob
You can email me at robpas@btc-bci.com about the high sulfur cutting oil and shipping dates.
Bob
T
tasy_ted
Guest
hi all
my money is on a metric lead screw.
regards tasy_ted
my money is on a metric lead screw.
regards tasy_ted
adamsgt
Jerry Adams
Al
Thanks for your responses. Haven't had enough coffee yet to get my mind wrapped around all that you said. I went to the school at Trinidad from 1982 -1984 about the same time period as you. When I was in high school I loved geometry and was pretty good at it. Need to re-kindle that enthusiasm. When I finish this response I'm going to print out this thread and take it to my shop and start experimenting with all the suggestions.
One thing about the setup and angles. The first thing I did was set my compound to what I thought was 29 1/2 degrees to the left (CCW). Then I took my fishtail thread gage held it against the workpiece. I then loosened the tool post nut and rotated the tool post to place and align the tip of the bit in the 60 degree notch in the gage. I then tightened the tool post nut and proceeded to set the zeros on the cross slide and compound. Am I doing anything wrong here?
I haven't started any drawings yet but I will when I get to my shop. By the way, my "shop" is a rental 20 X 50 storage unit that has a bathroom and a 100 amp service panel.
Thanks for your responses. Haven't had enough coffee yet to get my mind wrapped around all that you said. I went to the school at Trinidad from 1982 -1984 about the same time period as you. When I was in high school I loved geometry and was pretty good at it. Need to re-kindle that enthusiasm. When I finish this response I'm going to print out this thread and take it to my shop and start experimenting with all the suggestions.
One thing about the setup and angles. The first thing I did was set my compound to what I thought was 29 1/2 degrees to the left (CCW). Then I took my fishtail thread gage held it against the workpiece. I then loosened the tool post nut and rotated the tool post to place and align the tip of the bit in the 60 degree notch in the gage. I then tightened the tool post nut and proceeded to set the zeros on the cross slide and compound. Am I doing anything wrong here?
I haven't started any drawings yet but I will when I get to my shop. By the way, my "shop" is a rental 20 X 50 storage unit that has a bathroom and a 100 amp service panel.
Gene Beggs
Active member
29.5 vs., straight in
Some say you should feed in with the compound set at a 29.5 degrees when threading while others feed straight in with the cross slide. I've tried it both ways and can see no difference in the final result. Due to my lazy, do-it-the-easy-way nature, I prefer to cut straight in with the cross slide.
Proponents of the 29.5/compound feed method point out that when you feed with the compound you are cutting with only one side of the tool and that's true, but my question is, "What difference does it make?"
Threading at 60 rpm on my little 13-40 Jet lathe with a carbide insert threading tool results in nice threads that anyone would be proud of. I take fairly light cuts beginning with .015 then as the tool cuts deeper, I reduce the cut to .010, then .005 and finally making the final three or four passes with only .001 cuts.
I think it was Yamaha, back in the late sixties, that coined the phrase, "Different strokes for different folks."
Have fun and be safe.
Gene Beggs
Some say you should feed in with the compound set at a 29.5 degrees when threading while others feed straight in with the cross slide. I've tried it both ways and can see no difference in the final result. Due to my lazy, do-it-the-easy-way nature, I prefer to cut straight in with the cross slide.
Proponents of the 29.5/compound feed method point out that when you feed with the compound you are cutting with only one side of the tool and that's true, but my question is, "What difference does it make?"
Threading at 60 rpm on my little 13-40 Jet lathe with a carbide insert threading tool results in nice threads that anyone would be proud of. I take fairly light cuts beginning with .015 then as the tool cuts deeper, I reduce the cut to .010, then .005 and finally making the final three or four passes with only .001 cuts.
I think it was Yamaha, back in the late sixties, that coined the phrase, "Different strokes for different folks."
Have fun and be safe.
Gene Beggs
C
Crow99
Guest
Maybe just a couple more things: From the pic you posted, it looks as though you've got a bunch of "overhang..." The work area is pretty far away from the chuck, and this can cause the work to spring a bit. I think the rule of thumb is 3:1. I.E. for a 1" workpiece it shouldn't be more than 3" out. Closer is better, but don't have a "crash" and run the tool post ot cross slide into the chuck! You might want to try supporting the right side of the piece with the tailstock center.
Next, have you checked the headstock bearings? To do this, set an indicator up on top of your workpiece and "lift" (either by hand or with a piece 2x4 as a lever) and see how much deflection you can get. I bet in your lathe it might be a bunch.. maybe as much as .002" or so. This can really play with your overall surface finish as well as with your threads. The heavier the cut the more it will have effect. And threading places a lot of deflection pressure on the setup... moreso than turning usually. When fully warmed up, this play wants to be maybe .0002 to .0003. With really high quality bearings it can be less of course, but the idea is to minimize it for your machine. So check your manual for how to adjust your headstock bearings. I bet they've never been touched.
Lastly, you want some "side rake" on your (HSS) tool. Looks to me as though it's flat on top and this causes the tool to "hog" rather than cut. With nice tight bearings this might not hurt much, but if your bearings or anything else are loose, it will just aggravate the situation and cause roughness and chatter. The angles will be different from a carbide tool. Remember: Carbide "hogs" and HSS "cuts."
Oh, and Alinwa: What g.s. school and when? I went to Trinidad from '73 to '75 and there was a guy there named "Al" and he was from "WA." and shot on the USAR team....
Next, have you checked the headstock bearings? To do this, set an indicator up on top of your workpiece and "lift" (either by hand or with a piece 2x4 as a lever) and see how much deflection you can get. I bet in your lathe it might be a bunch.. maybe as much as .002" or so. This can really play with your overall surface finish as well as with your threads. The heavier the cut the more it will have effect. And threading places a lot of deflection pressure on the setup... moreso than turning usually. When fully warmed up, this play wants to be maybe .0002 to .0003. With really high quality bearings it can be less of course, but the idea is to minimize it for your machine. So check your manual for how to adjust your headstock bearings. I bet they've never been touched.
Lastly, you want some "side rake" on your (HSS) tool. Looks to me as though it's flat on top and this causes the tool to "hog" rather than cut. With nice tight bearings this might not hurt much, but if your bearings or anything else are loose, it will just aggravate the situation and cause roughness and chatter. The angles will be different from a carbide tool. Remember: Carbide "hogs" and HSS "cuts."
Oh, and Alinwa: What g.s. school and when? I went to Trinidad from '73 to '75 and there was a guy there named "Al" and he was from "WA." and shot on the USAR team....
C
Cheechako
Guest
Al
Can you go over that one more time? Great post.!
If more wannabe gunsmiths would stay with HS bits, and grind their own, they will learn about angles, rake, clearance, and all the other black magic that makes them work. Then they can advance to the inserts and all the other modern gizmos.
JMHO
Ray
Can you go over that one more time?
Great post.!If more wannabe gunsmiths would stay with HS bits, and grind their own, they will learn about angles, rake, clearance, and all the other black magic that makes them work. Then they can advance to the inserts and all the other modern gizmos.
JMHO
Ray
N
NesikaChad
Guest
Free machining alloy carbon steel: Anywhere from 40-100 SFM when using HSS tooling. For carbide you can bump it up to 150-400. Stainless is pretty close to the same.
On a 1.0625 diameter cylinder this works out to a minimum rpm of 160 and a max of 320 with HSS tooling. Carbide is 320-1600 rpm.
80 rpm on this diameter is only 22 SF. The tool isn't really cutting, it's plowing.
Good luck.
C
On a 1.0625 diameter cylinder this works out to a minimum rpm of 160 and a max of 320 with HSS tooling. Carbide is 320-1600 rpm.
80 rpm on this diameter is only 22 SF. The tool isn't really cutting, it's plowing.
Good luck.
C
adamsgt
Jerry Adams
So far So bad
Went to my shop after printing out the thread to see what I could do. The cross slide does indicate the diameter. I checked the compound angle with a protractor and it was on 29 1/2 degrees. I put the Carmex threading tool on and proceeded to cut. Again, it started out OK and then deteriorated. I did about 10 passes without advancing the compound and got chips on every pass. I was very careful on returning the cross slide to zero on the index. When it got too ugly I changed bits and cut off the mess.
I decided to try colchesters recommendation with the same threading tool. Did some practice passes to make sure I understood how to do this without disengaging the half nuts.This looked better but I noticed that on some passes where I advanced the compound .005 I got no chips at all. I kept at it until I had advanced about 90 thousandths on the compound with little thread depth. There was enough thread depth to measure using a thread gage. I got 16 tpi for about 2/3 of the gage and then it started to move out. Another pass and it looked like something was taking off the top of the thread. At this point I had enough and called it a day. Beginning to think there may be an issue with the cross slide. I was careful to return to zero from the same direction and not overshoot. Trying not to feel too frustrated. It can be too easy to say the hell with it.
Went to my shop after printing out the thread to see what I could do. The cross slide does indicate the diameter. I checked the compound angle with a protractor and it was on 29 1/2 degrees. I put the Carmex threading tool on and proceeded to cut. Again, it started out OK and then deteriorated. I did about 10 passes without advancing the compound and got chips on every pass. I was very careful on returning the cross slide to zero on the index. When it got too ugly I changed bits and cut off the mess.
I decided to try colchesters recommendation with the same threading tool. Did some practice passes to make sure I understood how to do this without disengaging the half nuts.This looked better but I noticed that on some passes where I advanced the compound .005 I got no chips at all. I kept at it until I had advanced about 90 thousandths on the compound with little thread depth. There was enough thread depth to measure using a thread gage. I got 16 tpi for about 2/3 of the gage and then it started to move out. Another pass and it looked like something was taking off the top of the thread. At this point I had enough and called it a day. Beginning to think there may be an issue with the cross slide. I was careful to return to zero from the same direction and not overshoot. Trying not to feel too frustrated. It can be too easy to say the hell with it.
D
Don
Guest
Check your compound lash adjustment screw, sounds like it might not be tight and/or missing, not allowing your compound to reposition itself repeatably when transversing in and out.
Also, you have not mentioned anything about "thread infeed pass rate", a very important concept and requirement for proper thread cutting, do you have and understand the proper "thread infeed pass rate" charts and settings?.........Don
Also, you have not mentioned anything about "thread infeed pass rate", a very important concept and requirement for proper thread cutting, do you have and understand the proper "thread infeed pass rate" charts and settings?.........Don
R
Ron of Va
Guest
Adamsgt
When I tried using the cross slide going straight in, I first started with the compound still set to 29.5º. I found that the compound would drift and really screwed everything up. Make sure the compound is parallel to the work, it is less likely to drift that way. Zero the compound dial, and then keep an eye on it to make sure it doesn’t drift. Then advance the cross slide to cut the threads.
When I tried using the cross slide going straight in, I first started with the compound still set to 29.5º. I found that the compound would drift and really screwed everything up. Make sure the compound is parallel to the work, it is less likely to drift that way. Zero the compound dial, and then keep an eye on it to make sure it doesn’t drift. Then advance the cross slide to cut the threads.
D
Don
Guest
see page 5 and 27 of the following link, probably explains it better than I ever could, unfortunately the chart is in mm. infeed for 60 degree threads, dont know why, anyway was the first explanation/chart I came across..............Don
http://www2.coromant.sandvik.com/coromant/pdf/metalworking_products_061/tech_c.pdf
http://www2.coromant.sandvik.com/coromant/pdf/metalworking_products_061/tech_c.pdf
Man, so close!!! But nope, not me.
I was a Charter Member Of Pine Technical Institute In Pine City MN. So far I've only ever run acros't one other person in the world who's heard of this course but AFAIK it's still going and with the same teacher.
I was '81-'82
al
T
TRA
Guest
You are not removing the backlash from your feed screws. Your tool height is probably not at the proper height.
And your chuck is probably suspect, if the work is not stable it will climb over the tool.
AND, if your lathe is really loose the carriage handle can cause your carriage to try to advance or pull into the work.
STOP worrying about the 29.5 degree setting, it's not that important. It is the standard that is accepted as a general rule, but it does not matter where your compound is set to cut threads as Gene has stated. All the angle does is aid in reducing tool pressure in a less than ideal setup with old school tooling.
If you are using 29.5 deg, you only advance the compound between cuts. Using different angles requires differing strategies.
adamsgt
Jerry Adams
To all who've responded
Thanks for your efforts and suggestions. Right now I'm fairly frustrated and discouraged. Not enough to quit, but it shouldn't be this hard. Need to fall back and regroup. No point of chewing up metal and tooling to no purpose. What's that definition of insanity, doing the same thing over and over and expecting different results. Think I need to do more examination of the lathe. I have a 12" metal scale I used to check the leadscrew. I set the start at the back of a thread and each subsequent inch mark was at the back of a thread. The other side of the scale is metric and it did not line up with the threads, so I think the leadscrew is english. I think I'll have to figure out a way to check the repeatability of the cross slide movement. Same thing with the compound. Oh well.
Thanks for your efforts and suggestions. Right now I'm fairly frustrated and discouraged. Not enough to quit, but it shouldn't be this hard. Need to fall back and regroup. No point of chewing up metal and tooling to no purpose. What's that definition of insanity, doing the same thing over and over and expecting different results. Think I need to do more examination of the lathe. I have a 12" metal scale I used to check the leadscrew. I set the start at the back of a thread and each subsequent inch mark was at the back of a thread. The other side of the scale is metric and it did not line up with the threads, so I think the leadscrew is english. I think I'll have to figure out a way to check the repeatability of the cross slide movement. Same thing with the compound. Oh well.