Wildguzzi.com
General Category => General Discussion => Topic started by: Canuck750 on December 04, 2022, 07:58:05 PM
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Has anyone have experience welding up the end of a crankshaft? A Benelli single motor I recently picked up has a damaged threaded tip on the shaft end that secures a magneto. Looks like someone tried to get a very seized magneto off the taper and whatever puller was used damaged the shaft. About a 1/2 inch of the shaft is missing.
(https://i.postimg.cc/J04GKr7D/24D56076-6170-4D6C-B229-BD10A6E8BEB2.jpg) (https://postimg.cc/5YT42MCb)
This crank is a spare but I would like to save it if I can
My thoughts are to use a 4 jaw independent Chuck and true it in the lathe, shave off the damage and using MIG weld it back up then turn the tip back to dimension and thread it in the lathe.
It’s not a load bearing part other than it holds the big nut that compresses the magneto onto the shaft.
Thoughts?
To get this magneto off I ended up grinding the brass magneto body off the steel center section so as to get oxy/acet onto the magneto sleeve, red hot, then a big bearing puller. A typical rotor extractor did nothing but damage the crank tip even more.
(https://i.postimg.cc/658QQ18X/57162DE1-1A1B-4EAF-9202-051BCE359A25.jpg) (https://postimg.cc/hfqnys8y)
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With that much damage, I think you would be better off finding find someone who could make a new crank half.
<edit> Is the main shaft pressed into the crank cheek?
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OR . . .
You could have the threaded portion cut off the main shaft, drill and tap the shaft, and fabricate a threaded piece to replace the damaged portion.
Triumph twins retained the alternator rotor with a threaded stud and nut for decades.
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OR . . .
You could have the threaded portion cut off the main shaft, drill and tap the shaft, and fabricate a threaded piece to replace the damaged portion.
Triumph twins retained the alternator rotor with a threaded stud and nut for decades.
Now that’s an idea I hadn’t thought of, interesting.
The shaft and flywheel are one piece.
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Now that’s an idea I hadn’t thought of, interesting.
The shaft and flywheel are one piece.
If you go that route, I'd red loctite the new piece into the crank. If you ever need to remove it, you can heat it with a Mapp gas torch.
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I might be able to help , what is the diameter of the flywheel ? Peter ( in Burnaby, B.C)
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I might be able to help , what is the diameter of the flywheel ? Peter ( in Burnaby, B.C)
A couple of sketches
(https://i.postimg.cc/Y9H0H7Fk/CEC8295E-6D10-4BDC-8E1E-234DDD18B22C.jpg) (https://postimg.cc/FfTNy2Gn)
(https://i.postimg.cc/mrMkJkt8/AC176BA0-6EEB-477B-9C92-75F12C31ABB2.jpg) (https://postimg.cc/R3SvnM1H)
Thanks!
Jim
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I would probably weld up the end and then turn it back to size. My mig has 70 series wire which is not too hard to turn. Holding the large end I would face the small end and put a center hole back in. Then do the job between centers or holding the large end(chuck) and center in the small end. Single point threading the end should not be hard at all with your lathe. As to drilling and adding a piece that would be a second option if you are not confident threading a new end. Too bad you had to destroy the flywheel. I have used my cutting torch head to quickly heat parts like that for removal. You have to be careful and fast but usually I can do it with no damage. I have also had good luck drilling rivets out and then just making new ones in situations where I was trying to save a part. Rivets expand when set but, really with your lathe making new ones any size or shape is pretty easy.
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Would it be a viable option to clean up the damaged portion in the lathe by turning away the affected bits, then turn the recess a bit deeper where the nut and washer beds down and put a bit more thread on the shaft ?
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I'd try what Huzo is suggesting. The tapered shaft part and the woodroof key slot is clean so once the nut is tightened enough, it should all lock in nicely (obviously, they couldn't get it back out). If the tapered shaft were scuffed from stripped woodroof keys over the years, then you'd have to rely on a lot more torque on the nut to lock it all down.
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Drill the end and thread the hole. Works for Moto Guzzi and BMW.
Loctite (RC680) in a quality stud and you have an easy lifetime repair.
If it ever gets messed up just torch out the stud and install a new one.
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Drill the end and thread the hole. Works for Moto Guzzi and BMW.
Loctite (RC680) in a quality stud and you have an easy lifetime repair.
If it ever gets messed up just torch out the stud and install a new one.
I think this is the safer route for me, I trust my ability to weld up the shaft tip but my thread turning skills on a lathe are crap. I can drill a straight hole with the lathe, just have to be very careful to not snap a tap cutting threads. I need to decide upon a stud diameter, I think the threads are M12 on the tip, could probably get away with an M8 or M10 stud.
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I'd try what Huzo is suggesting. The tapered shaft part and the woodroof key slot is clean so once the nut is tightened enough, it should all lock in nicely (obviously, they couldn't get it back out). If the tapered shaft were scuffed from stripped woodroof keys over the years, then you'd have to rely on a lot more torque on the nut to lock it all down.
I’ve had good success with old BSA’s and such on the clutch shaft, by lapping them with valve grinding paste then talcum powder.
All my Beezers had well fitted clutch bodies and all the kids had chaffed arses…..! (We ran out of powder…) :embarrassed: :rolleyes:
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Drill the end and thread the hole. Works for Moto Guzzi and BMW.
Loctite (RC680) in a quality stud and you have an easy lifetime repair.
If it ever gets messed up just torch out the stud and install a new one.
I reckon that’s what I’d do. Seems the best way to save the whole damn thing.
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I think this is the safer route for me, I trust my ability to weld up the shaft tip but my thread turning skills on a lathe are crap. I can drill a straight hole with the lathe, just have to be very careful to not snap a tap cutting threads. I need to decide upon a stud diameter, I think the threads are M12 on the tip, could probably get away with an M8 or M10 stud.
It’s possible your lathe has a metric pitch leadscrew.
If it has then the TPI will almost certainly not be obtainable if attempting to cut the thread.
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Now that you have picked a repair option let's explore the stud size. Metric 8.8 bolt torque for m8 x 1.75 18.8 ftlbs, M10 x1.5 37.2 ftlbs, M12 x 1.75 64.9 ftlbs. Looks like you should be aiming for the M12 if you go this route.
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Agreed, I'd match what is there already, but drilled as you plan (which I think is a great idea). Also, make note of the thread direction and match that.
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OR . . .
You could have the threaded portion cut off the main shaft, drill and tap the shaft, and fabricate a threaded piece to replace the damaged portion.
Triumph twins retained the alternator rotor with a threaded stud and nut for decades.
I would go this route! ^^^^
Hard to tell from the picture, but it looks like the crank end is tapered. The taper hold the flywheel in place, the keyway controls timing and the threaded portion just keeps a bit of compression on the flywheel to keep it from vibrating loose.
Male thread on crank end, or female thread inside crank end. Not a dimes worth of difference either way.
Just be mindful that your final torquing values should always consider thread stress area. Smaller thread, lower torque.
If you decide to go the other route of rebuilding crank end with weld metal, and re-machining the thread, it would be a very easy fix for almost any machine shop I have ever encountered.
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I think this is the safer route for me, I trust my ability to weld up the shaft tip but my thread turning skills on a lathe are crap. I can drill a straight hole with the lathe, just have to be very careful to not snap a tap cutting threads. I need to decide upon a stud diameter, I think the threads are M12 on the tip, could probably get away with an M8 or M10 stud.
If in doubt, load the tap into the tailstock, and just turn the chuck by hand or with a strap wrench.
Just for giggles, check Mcmaster.com for shoulder bolts. You might get lucky and based on the thread size you pick, end of with a should diameter that matches the flywheel inside diameter.
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If that is a flywheel on the crank I'm pretty sure the key is used for timing purposes, not flywheel retention. Flywheels are often located with keys but retained by being bolted firmly on a locking taper. They are fit dry on the taper so they lock. The BMW R60/2 locks its flywheel on to the tapered crank with a single bolt through the center of the flywheel. This bolt is tightened to 175 ft/lb. It is also keyed to put the timing marks in the correct place. If the flywheel is not tightened fully it shears the key then damages the taper.
If your crank is similarly configured. I would suggest you make the stud out of a 12.9 bolt using the threaded portion as a stud (cutting off the rest) Drill and tap the crank the diameter and pitch of the existing stub. Make the working threaded hole depth 2 times the diameter of the existing stud. That way it won't strip out. Then torque to original specs, if available. Otherwise use a good reference chart for the materials used.
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If in doubt, load the tap into the tailstock, and just turn the chuck by hand or with a strap wrench.
Just for giggles, check Mcmaster.com for shoulder bolts. You might get lucky and based on the thread size you pick, end of with a should diameter that matches the flywheel inside diameter.
I see where you going with the shoulder bolt, do you know if anyone makes a stud that is 12mm on one side and 10mm on the other?
Based on the measurements I took off a good 200 cc crank, the threaded end of the crank shaft that takes the rotor nut only projects 13mm (1/2") and is 12mm diameter. I am a little reluctant to use a 12 mm stud into the end of the crank, not much meat there at the end of the taper. I think a 10mm could be drilled and threaded into the crank shaft. Alternately I could just machine up a 10 mm deep nut for the rotor securing fastener. Pretty sure the thread pitch is 1.25 fine (maybe 1.5 - will check tomorrow), will probably need to order a stud, should I use a carbon steel stud or a stainless steel stud?
This is the deep nut used on the rotor, off another engine I have
(https://i.postimg.cc/ZKrRzHMj/C1-F664-FF-871-F-4-C68-AA07-6-F0-EB87-FD1-AA.jpg) (https://postimg.cc/F7HmjymJ)
I usually tap threads on parts I can chuck in the lathe and use a spring die holder tool in the tail stock to keep the tap straight and under light pressure, turning the chuck by hand while holding the tap wrench stationary, rocking the chuck back and forth to clear chips. I can chuck up the crank flywheel in my 4 jaw, center it and if I am real picky set up a steady near the tip before drilling and tapping.
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If that is a flywheel on the crank I'm pretty sure the key is used for timing purposes, not flywheel retention. Flywheels are often located with keys but retained by being bolted firmly on a locking taper. They are fit dry on the taper so they lock. The BMW R60/2 locks its flywheel on to the tapered crank with a single bolt through the center of the flywheel. This bolt is tightened to 175 ft/lb. It is also keyed to put the timing marks in the correct place. If the flywheel is not tightened fully it shears the key then damages the taper.
If your crank is similarly configured. I would suggest you make the stud out of a 12.9 bolt using the threaded portion as a stud (cutting off the rest) Drill and tap the crank the diameter and pitch of the existing stub. Make the working threaded hole depth 2 times the diameter of the existing stud. That way it won't strip out. Then torque to original specs, if available. Otherwise use a good reference chart for the materials used.
Yes, the woodruff key is set the rotor to the timing, the points cam is on a sleeve over the steel spindle riveted to the brass flywheel. The sleeve rotates slightly to form the advance mechanism, a single weight pivoting on a fixed pin and spring retained, causes the sleeve to rotate with rpm.
(https://i.postimg.cc/Zq1ny92Z/00531-F01-15-E2-4979-AD48-21602-BE665-F5.jpg) (https://postimg.cc/94YC6fcN)
Good tip on the stud, I can get a high strength bolt to make the stud
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Not a lot of meat at the smallest of the taper but it is supported by the 12 mm stud inside and compression from the flywheel outside. Alloy steel stud only. Either cut it out of a 12.9 bolt or socket head cap screw if you can't find the equivalent stud material. Stainless is much weaker. There's a reason they put a 12 mm thread there.
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Not a lot of meat at the smallest of the taper but it is supported by the 12 mm stud inside and compression from the flywheel outside. Alloy steel stud only. Either cut it out of a 12.9 bolt or socket head cap screw if you can't find the equivalent stud material. Stainless is much weaker. There's a reason they put a 12 mm thread there.
OK thanks, I will look for high strength M12 bolt to use.
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McMaster Carr has 10.9 12mm threaded studs 150,000 PSI Yield.
They also have alloy steel socket cap screws 12 mm 170,000 PSI Yield.
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I see where you going with the shoulder bolt, do you know if anyone makes a stud that is 12mm on one side and 10mm on the other?
Based on the measurements I took off a good 200 cc crank, the threaded end of the crank shaft that takes the rotor nut only projects 13mm (1/2") and is 12mm diameter. I am a little reluctant to use a 12 mm stud into the end of the crank, not much meat there at the end of the taper. I think a 10mm could be drilled and threaded into the crank shaft. Alternately I could just machine up a 10 mm deep nut for the rotor securing fastener. Pretty sure the thread pitch is 1.25 fine (maybe 1.5 - will check tomorrow), will probably need to order a stud, should I use a carbon steel stud or a stainless steel stud?
This is the deep nut used on the rotor, off another engine I have
(https://i.postimg.cc/ZKrRzHMj/C1-F664-FF-871-F-4-C68-AA07-6-F0-EB87-FD1-AA.jpg) (https://postimg.cc/F7HmjymJ)
I usually tap threads on parts I can chuck in the lathe and use a spring die holder tool in the tail stock to keep the tap straight and under light pressure, turning the chuck by hand while holding the tap wrench stationary, rocking the chuck back and forth to clear chips. I can chuck up the crank flywheel in my 4 jaw, center it and if I am real picky set up a steady near the tip before drilling and tapping.
I'm sure there are lots of double sized studs out there to buy off the shelf, but off the top of my head, I can't think of a vendor. Any local machine shop could probably fab one for you.
I would stay away from stainless in this application and use a good high quality steel stud or bolt. Grade 8 in the US, I forget the DIN equivalent. IIRC, L10 is even stronger than grade 8. Carbon steel shoulder bolts are usually very high strength. McMaster-Carr will have all the specs you need.
I'd bet good money, that a high strength bolt will be much stronger than the steel in the crankshaft. Occasionaly I might lose a bet, but not often.
My thought process was to use the shoulder bolt instead of a double threaded stud. I was thinking you might be able to match the shoulder diameter to the diameter of the thru hole in the flywheel.
If you think about, the primary use of the nut on the end of the crank is to press the flywheel on to the crankshaft taper. Once that is done, it only serves to keep the flywheel from vibrating loose on the taper.
Some of the engineering reference materials will state that the first 3 threads that get stretched carry 90% of the bolt tensile load. I would be reluctant to put a lot of confidence in that with my own equipment. One thread diameter of thread depth is usually plenty, two is kind of a "rule of thumb" upper limit, and when you are designing, a thread depth of 3 diameters often gets overly expensive to machine.
So if you use a bolt instead of a stud, I would shoot for 1-2 thread diameter of bolt engagement in the crankshaft.
Of course, make sure you torque is not attained by bottoming the bolt in the blind hole.
So far, it looks like you are thinking this thru properly and getting plenty of good advise from the posters on this thread. Should work out fine.
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I confess to being interested in this thread and out of my depth but I've had a though. Could you not buy an M12 stud and cut an M10 thread in one end, or is there not enough metal?
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I am missing something here. I thought I saw pictures of your lathe in a previous post and it looked nice. You all know lathes are great at making round parts and round parts with threads right?. Why are we not thinking of making parts exactly as we want instead of buying one that is pretty close. I think a little more time to learn how to use a lathe is in order. I have been making parts for quite a while and these are some of the most basic parts one might make with a lathe. I have seen your work on more than a few bikes and see no reason lathe work should not be an easy step forward.
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https://youtu.be/AuS6HDHc7XE
Wasn't mentioned in the South Bend book.
(Ignore the audio)
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I am missing something here. I thought I saw pictures of your lathe in a previous post and it looked nice. You all know lathes are great at making round parts and round parts with threads right?. Why are we not thinking of making parts exactly as we want instead of buying one that is pretty close. I think a little more time to learn how to use a lathe is in order. I have been making parts for quite a while and these are some of the most basic parts one might make with a lathe. I have seen your work on more than a few bikes and see no reason lathe work should not be an easy step forward.
My lathe skills are very basic at best, agreed I need a lot more practice before I could replicate the entire left hand crank piece. Welding an extension on the broken tip and machining it back with threads is doable but I think the threaded stud insert is a good option. I am still learning to make decent nuts and specialty bolts.
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I confess to being interested in this thread and out of my depth but I've had a though. Could you not buy an M12 stud and cut an M10 thread in one end, or is there not enough metal?
The minor diameter of the thread is the major diameter of the thread minus the thread pitch. It is any easy way to figure out what minimum size tap drill is needed for a female thread, or what maximum diameter rod you will have when you remove the threads from a bolt.
for example an M6 thread with a 1 mm pitch requires a 5 mm minimum tap drill. Same with standard US threads, tapping a 1/4-20 thread, requires a .200" tap drill (.25"- .05").
Inceasing the calculated tap drill size by .1-.2 mm or more is pretty common practice. Increase even more on larger threads.
As shown below, turning the threads off a M12 bolt with a 1.5mm pitch will give you a 10.5mm rod.
https://www.boltdepot.com/fastener-information/Measuring/Metric-Thread-Pitch.aspx
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https://international.optimas.com/technical-resources/metric-thread-dimensions/
For a 60° thread 75% depth is pretty much the standard.
https://drillsandcutters.com/metric-tap-and-drill-chart/
Metric tap drill size chart.
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Well after planning on drilling, tapping and fitting a stud I changed course, thought what have I got to loose trying to build up the crank, worst case I just grind off the attempted weld and threading and go with the original plan.
four jaw chuck centered the piece with a dial indicator. Not the easiest piece to secure in the jaws, with the weight on the back of the web three jaws just reach the sides of the flywheel. I trued the face with a dial indicator as well and found the shaft is slightly bent, I can true the tip but the bearing contact surface is then out so I went for the mid length, I don't think I would use this piece given the slight bend (about 15 thousands +/-).
I bet someone went to town with a hammer trying to get the flywheel off after tearing the puller threads out of the rotor.
(https://i.postimg.cc/h48MXth6/15185-D02-4-EAE-4-EE9-B75-B-1-EAC51-FC3044.jpg) (https://postimg.cc/4ndpMZ6Q)
I welded and turned the extension a couple times, weld imperfections kept showing up until I got it as good as I can
(https://i.postimg.cc/VLYgnPC6/A9-B7-AD85-1-B72-4571-B381-9-DE3-CAB9-F2-D8.jpg) (https://postimg.cc/14jD1TMh)
I threaded it with a die, 1st attempt not the best, re-welded it and turned it once again and used a new tap M12 x 1.25. I had turned the stud end to 11.85 mm before placing the die, could not get the die to start at 12.0 mm.
(https://i.postimg.cc/pLSJw91h/4-F619691-51-CD-47-F5-AB48-BD39336050-E6.jpg) (https://postimg.cc/K1nTLYbx)
The threads are pretty tight, it would have been better if the threads were lathe cut but I can't seem to figure out the gear box on my lathe, can't get the lead screw operation to reverse, needs some digging into.....
I built up the threads an extra 10mm from the original good crank I have, setting the rotor over the shaft it seemed it could use more length on the threaded end
(https://i.postimg.cc/SsF7KB4m/FB6855-C0-D71-F-4-A47-94-EF-278-CDC1-CD272.jpg) (https://postimg.cc/DW6bjYmN)
It will work, just not sure I would use the piece but it was worth the effort
(https://i.postimg.cc/g06HmYfM/2452-E516-3577-4420-8-C63-567-BA2-D40-D72.jpg) (https://postimg.cc/2qrZxfjv)
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Very nice work! Jim(?)
Using a die means you did not have to cut a thread relief at the crank end of the thread.
Interesting that you could not get the die started at 12.0mm, but it worked at 11.85mm. 0.006" smaller diameter for us Yanks.
Always fascinates me what a big difference a few thousands of an inch can make in metal work.
I salute you from afar! :thumb:
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Very nice work! Jim(?)
Using a die means you did not have to cut a thread relief at the crank end of the thread.
Interesting that you could not get the die started at 12.0mm, but it worked at 11.85mm. 0.006" smaller diameter for us Yanks.
Always fascinates me what a big difference a few thousands of an inch can make in metal work.
I salute you from afar! :thumb:
Thanks for the kind words!
Jim
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Playing around with a piece you may not need is a great way to learn by doing. Using a die to cut full threads is never the best way, so overall that is as good as it gets. I like to use the lathe to at least cut most of the new thread and do a final chase with a sharp die if needed. Reversing the die will get you close to a shoulder. As with any thread champhering the lead end is a must. When I single point with no place to end I will use a handle on the lathe spindle to hand feed the last partial turn. Or in this case(short thread) maybe even cut the whole thread by turning the spindle by hand. Did this piece have a center in the large end already? I have always checked pieces like that between centers and then used a rawhide faced heavy mallet to tweak them back before and after machining. It was mentioned you lathe may not have metric capabilities so, if doing a job like this again you may opt for a thread your lathe can make. Then just make a nut fit. Nice work and pictures.
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Thanks for the kind words!
Jim
You are more than welcome Jim.
I appreciate you (and others here) taking the time and effort to document your practices. The internet is a great place to learn from the experiences of others, as well as to marvel at human creativity. You, Charlie, Huzo, Chuck in Indiana and a dozen or so others make Wild Guzzi a valuable, real time tutorial.
I often find myself thinking: "Holy Cow! That is 50 hours of work to perform, and another 50 hours to document and post!!!"
Another great motorcycle tinkering source is "Some Assembly Required" at ADVRider.com.
Decades of experience in machine/tool design, fabrication, development and testing have led me to REALLY appreciate those who can knuckle down and get things done, and disregard those who turn every repair/fabrication into a NASA/Rocket science experiment endless argument about minutiae.
Everyone who likes to tinker should sit thru a dozen Design Review Board meetings with 5 or more white collar types and an equal number of blue collar/machinists/rednecks. Amusing, entertaining, and educational all at the same time.
Do you plan to test your repair by installing the flywheel and torquing the nut?
Keep up the good work!!!
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Congrats on having the balls and using the skills to do it !!
You always do such nice work.
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use to fear threading on a lathe till I worked in shops that had Hardinge lathes. So painless using a hardinge. Been watching this thread,glad to see you dived in . Just make sure your center is spot on for truing your crank assembled.
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use to fear threading on a lathe till I worked in shops that had Hardinge lathes. So painless using a hardinge. Been watching this thread,glad to see you dived in . Just make sure your center is spot on for truing your crank assembled.
...especially the "Toolmaker" version of the Hardinge. It had a hand cam advanced tool post that allowed you to thread up to a shoulder without a relief groove.
You could get similar results with the old South Bend by running in reverse with the toolbit inverted. But it was nowhere as quick or elegant.
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Just a heads up on cutting threads on the lathe. *If* your lathe can run in reverse, you can put the tool in upside down and run the threads toward the tailstock. No pins and needles making sure you stop just in time. :smiley:
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Just a heads up on cutting threads on the lathe. *If* your lathe can run in reverse, you can put the tool in upside down and run the threads toward the tailstock. No pins and needles making sure you stop just in time. :smiley:
That’s something I’ve never considered, it’s brilliant in its simplicity.
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Way to go, Jim- I love it! Glad to see old parts saved, even if it’s only practice. Very cool.
Consider this good practice.. when you come to the studio to carve that granite statue you’ve always wanted to carve, just remember that when you cut stone, you will only get one chance to do it right..
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There is a gal Blondihacks who does lathe machining on tube. She has one covering machining threads in which she covers doing them in reverse to prevent a crash. She is an excellent teacher mainly covering the basics especially for noobies like me. Even experienced operators have good things to say about her. I will try to find the video and post a link.
kk
Edit: Here's the link. https://youtu.be/q7scadYptTI
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There is a gal Blondihacks who does lathe machining on tube. She has one covering machining threads in which she covers doing them in reverse to prevent a crash. She is an excellent teacher mainly covering the basics especially for noobies like me. Even experienced operators have good things to say about her. I will try to find the video and post a link.
kk
Edit: Here's the link. https://youtu.be/q7scadYptTI
Blondihacks is great, I subscribe to her Youtube!
I have not been able to get my carriage drive to reverse and the cross slide power drive never did work since I bought the used lathe years ago. I decided after this die threading exercise its time to get into the lathe and see what's up and fix the thing. I got a bunch of the lathe stripped today and it looks like the gear box is the source of the longitude travel issue, a very ugly gear, hopefully I can find a replacement.
broken teeth, not pretty
(https://i.postimg.cc/4xZcS7wz/080-E2-A57-8333-4-BA2-BE44-28-B8-C0478-F20.jpg) (https://postimg.cc/ykQWJNMd)taking a screen shot (https://postimages.org/app)
My lathe is the same as a Grizzly 10" x 36" gear head lathe (many different name tags on this lathe by various distributors).
I haven't got into the carriage yet to see why the cross slide drive is not engaging.
Always something to fix, I wanted to clean up the lathe anyways so this is as good a time as any.
(https://i.postimg.cc/Df9L1YXp/A5-F1889-F-AFF4-46-EF-94-A5-E549-FFACC0-C6.jpg) (https://postimg.cc/DmcST651)print screen windows (https://postimages.org/app)
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Just a heads up on cutting threads on the lathe. *If* your lathe can run in reverse, you can put the tool in upside down and run the threads toward the tailstock. No pins and needles making sure you stop just in time. :smiley:
Yes you can Chuck as I’m sure you have, but you need a damn solid cross slide to do so, because the force is lifting the slide instead of pushing down on the bed.
But nothing ventured, nothing gained. :popcorn:
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Well after planning on drilling, tapping and fitting a stud I changed course, thought what have I got to loose trying to build up the crank, worst case I just grind off the attempted weld and threading and go with the original plan.
four jaw chuck centered the piece with a dial indicator. Not the easiest piece to secure in the jaws, with the weight on the back of the web three jaws just reach the sides of the flywheel. I trued the face with a dial indicator as well and found the shaft is slightly bent, I can true the tip but the bearing contact surface is then out so I went for the mid length, I don't think I would use this piece given the slight bend (about 15 thousands +/-).
I bet someone went to town with a hammer trying to get the flywheel off after tearing the puller threads out of the rotor.
(https://i.postimg.cc/h48MXth6/15185-D02-4-EAE-4-EE9-B75-B-1-EAC51-FC3044.jpg) (https://postimg.cc/4ndpMZ6Q)
I welded and turned the extension a couple times, weld imperfections kept showing up until I got it as good as I can
(https://i.postimg.cc/VLYgnPC6/A9-B7-AD85-1-B72-4571-B381-9-DE3-CAB9-F2-D8.jpg) (https://postimg.cc/14jD1TMh)
I threaded it with a die, 1st attempt not the best, re-welded it and turned it once again and used a new tap M12 x 1.25. I had turned the stud end to 11.85 mm before placing the die, could not get the die to start at 12.0 mm.
(https://i.postimg.cc/pLSJw91h/4-F619691-51-CD-47-F5-AB48-BD39336050-E6.jpg) (https://postimg.cc/K1nTLYbx)
The threads are pretty tight, it would have been better if the threads were lathe cut but I can't seem to figure out the gear box on my lathe, can't get the lead screw operation to reverse, needs some digging into.....
I built up the threads an extra 10mm from the original good crank I have, setting the rotor over the shaft it seemed it could use more length on the threaded end
(https://i.postimg.cc/SsF7KB4m/FB6855-C0-D71-F-4-A47-94-EF-278-CDC1-CD272.jpg) (https://postimg.cc/DW6bjYmN)
It will work, just not sure I would use the piece but it was worth the effort
(https://i.postimg.cc/g06HmYfM/2452-E516-3577-4420-8-C63-567-BA2-D40-D72.jpg) (https://postimg.cc/2qrZxfjv)
Is the leadscrew on your lathe metric Jim ?
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Yes you can Chuck as I’m sure you have, but you need a damn solid cross slide to do so, because the force is lifting the slide instead of pushing down on the bed.
But nothing ventured, nothing gained. :popcorn:
Blondihacks added that doing this can be hard on the lathe. She also said that some SAE lathes can do metric threads with the addition of a 39 tooth gear.
kk
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i've got a 127 tooth gear for the carriage drive of the lathe if i want to do inch sized threads , and a 120 tooth gear for metric.
should work the other way round if you have a SAE spindle on your lathe
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The instructions for many lathes include threading details. That would include gear changes for imperial and metric threading if your machine is capable. I never see anything about reversing the carriage for threading, just release the half nut and move it back and watch your thread dial for reengaging. That gear appears to have been damaged by someone trying to engage it under power. Sourcing a new one should be fairly easy once you identify it's specs. Or make one using your lathe and mill. That is what I do when one is not easily sourced.
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The instructions for many lathes include threading details. That would include gear changes for imperial and metric threading if your machine is capable. I never see anything about reversing the carriage for threading, just release the half nut and move it back and watch your thread dial for reengaging. That gear appears to have been damaged by someone trying to engage it under power. Sourcing a new one should be fairly easy once you identify it's specs. Or make one using your lathe and mill. That is what I do when one is not easily sourced.
Thanks Mike,
I got the gear box tore down, four gears needed, lucky Grizzly has them all in stock. I know why the left hand feed position pin would not budge
(https://i.postimg.cc/NGTdvDd2/5-C5-B9-A2-A-1-A40-410-E-866-A-22-E3-AF41-F9-EB.jpg) (https://postimg.cc/F1ryjy5h)
(https://i.postimg.cc/yNdfqzG7/4-D320352-25-C0-4719-AF9-F-3-DE239-F6955-D.jpg) (https://postimg.cc/VJx9M21h)
(https://i.postimg.cc/0yZtHNct/411-A2447-9-E75-4-C4-D-92-C3-7-F05-C06-CF440.jpg) (https://postimg.cc/682L8BsR)
the power cross slide does not work because the gear on the cross slide lead screw is missing!, again in stock at Grizzly. Why would anyone have removed the gear in the first place ??
This lathe comes with change gears that are swapped for the various metric pitches and then the positions of the quick change gear box are set to the corresponding pitch chart. On my old Myford ML7 if I cut a metric thread change gear swaps were required and I had to stop the lathe and reverse it, could not release the 1/2 nuts as the manual said the thread indicator could only be used for imperial threading. With this Chinese lathe I don't know if that applies, supposedly I could just try backing off the lathe and follow the thread indicator dial to re-engage the 1/2 nuts, that would be nice.
My lathe is a Grizzly is a G400 3G - 12" x 36" Model, anyone know if these are built as metric or imperial machines? not hat I would know what the difference is or why it matters.
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Hmmmm…
You can tell a lot about a bloke by his fingernails.
(https://i.ibb.co/TtQznzH/783-DD87-A-7-BA2-4-AD2-B9-C9-309-CE41745-EF.png) (https://ibb.co/TtQznzH)
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I take my hat off to you Jim. If I ever learn half of what you have forgotten I would be a happy man.
Those teeth have had some "abuse". :shocked: Power fed the toolpost into the headstock?
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Hmmmm…
You can tell a lot about a bloke by his fingernails.
(https://i.ibb.co/TtQznzH/783-DD87-A-7-BA2-4-AD2-B9-C9-309-CE41745-EF.png) (https://ibb.co/TtQznzH)
You can tell I can be careless swinging a hammer! My split in half index finger nail has finally grown out, I slipped with a long punch, guess how much that hurt when the punch met the finger. Think dropping to floor.
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You can tell I can be careless swinging a hammer! My split in half index finger nail has finally grown out, I slipped with a long punch, guess how much that hurt when the punch met the finger. Think dropping to floor.
Did I ever tell this forum about the time that I clouted a finger with a heavy hammer? I made it inside, turned on a ceiling fan Flat Out and lay under it on the tiled floor, for a Long Time. Thanks for reminding me Jim :laugh: I'm ok now and can talk openly about it but I do know how those things can weaken a bloke. Sorry to hijack. It was compulsive. Hey, maybe I'm not ok after all :huh: