MWF FEED
19th February 2022, 12:00 AM
Vintage engine guy repairing a tractor engine. It has spun a big end bearing, so needs two new bearing caps. These things are roughly 75mm diameter, and we don't have any suitable thick wall tubing around.
Now, a sensible man would go to Edcon and but some, but he had some 100mm diameter slugs of 4140, so the usual drilling, boring, and outside turning occurred.
Shaving away ~3kg of steel to make a 200g ring :o:
IMG_2523.jpg (https://metalworkforums.com/attachment.php?attachmentid=397087&d=1645184093)IMG_2524.jpg (https://metalworkforums.com/attachment.php?attachmentid=397088&d=1645184099)IMG_2533.jpg (https://metalworkforums.com/attachment.php?attachmentid=397089&d=1645184104)
which will then be cut in half (off centre) so there is enough to grind away to make an exact half.
For the second shell, I decide to try and save the middle. So I take the slug, Hercus it round, and machine a line to indicate the ID:
IMG_2534.jpg (https://metalworkforums.com/attachment.php?attachmentid=397090&d=1645184234)IMG_2535.jpg (https://metalworkforums.com/attachment.php?attachmentid=397091&d=1645184238)
On the other side, I face off but leave a little nub in the middle (from setting the tool too low), as a hook for marking a circle:
IMG_2536.jpg (https://metalworkforums.com/attachment.php?attachmentid=397092&d=1645184242)
then mark, centre punch, and drill a bunch of holes 6.99mm apart:
IMG_2537.jpg (https://metalworkforums.com/attachment.php?attachmentid=397093&d=1645184438)IMG_2538.jpg (https://metalworkforums.com/attachment.php?attachmentid=397094&d=1645184442)
My plan is to drill thru, and then hammer/press/grind the centre slug out.
I have a bunch of old 1/8" drills, so try to get most of the way through with them, then enlarge to 1/4".
A few go well, but then one of the little ones breaks. IMG_2539.jpg (https://metalworkforums.com/attachment.php?attachmentid=397095&d=1645184645)
And its getting late, so I go home to deal with that the next day.
Next morning, I ignore the broken one, and drill a few more to 1/4", but the wear rate on my drills is higher than expected. So I look at alternatives.
•Don't have an Annular cutter. Particularly not one at 65mm or 70mm diameter.
•Don't have a Trepanning cutter (like a parting blade, but curved).
•Do have a little high speed spindle. Lets see how that goes on the lathe:
Half an hour. Only 4mm deep: IMG_2540.jpg (https://metalworkforums.com/attachment.php?attachmentid=397096&d=1645185102)
Two hours. About 8mm deep. Another second-hand carbide insert (which had broken face) is destroying itself...
IMG_2541.jpg (https://metalworkforums.com/attachment.php?attachmentid=397097&d=1645185250)
but I'm nearly through the broken drill?
Keep going???
It gets to lunchtime. My groove is about 16mm deep, in a 38mm deep slab of steel. The day is getting hot (about 31° inside), I realise that I didn't have enough sleep, and could have drilled all the way through by now - even if I had to hand-sharpen two drills every three holes!
So, instead of waste the whole day, I admit defeat, throw the chunk of steel in the big lathe, and drill about 30mm deep, then bore the usual cavity out. At least I will keep the 16mm deep disc, right?
WRONG!!!!! I somehow mis-calculate the depth of my bored cavity, and end up saving a whole 11mm thick disc of 55mm diameter steel.
Sigh.
Maybe next time I'll borrow a rotary table, and mill the disc. That's sure to let me save the material from the centre. Right?
Attached Images
https://metalworkforums.com/images/attach/jpg.gif IMG_2541.jpg (https://metalworkforums.com/attachment.php?attachmentid=397097&d=1645185250) (143.5 KB)
https://metalworkforums.com/images/attach/jpg.gif IMG_2540.jpg (https://metalworkforums.com/attachment.php?attachmentid=397096&d=1645185102) (145.1 KB)
https://metalworkforums.com/images/attach/jpg.gif IMG_2539.jpg (https://metalworkforums.com/attachment.php?attachmentid=397095&d=1645184645) (217.3 KB)
https://metalworkforums.com/images/attach/jpg.gif IMG_2538.jpg (https://metalworkforums.com/attachment.php?attachmentid=397094&d=1645184442) (188.4 KB)
https://metalworkforums.com/images/attach/jpg.gif IMG_2537.jpg (https://metalworkforums.com/attachment.php?attachmentid=397093&d=1645184438) (224.5 KB)
https://metalworkforums.com/images/attach/jpg.gif IMG_2524.jpg (https://metalworkforums.com/attachment.php?attachmentid=397088&d=1645184099) (257.3 KB)
https://metalworkforums.com/images/attach/jpg.gif IMG_2533.jpg (https://metalworkforums.com/attachment.php?attachmentid=397089&d=1645184104) (159.5 KB)
https://metalworkforums.com/images/attach/jpg.gif IMG_2534.jpg (https://metalworkforums.com/attachment.php?attachmentid=397090&d=1645184234) (184.0 KB)
https://metalworkforums.com/images/attach/jpg.gif IMG_2535.jpg (https://metalworkforums.com/attachment.php?attachmentid=397091&d=1645184238) (169.9 KB)
https://metalworkforums.com/images/attach/jpg.gif IMG_2536.jpg (https://metalworkforums.com/attachment.php?attachmentid=397092&d=1645184242) (172.4 KB)
https://metalworkforums.com/images/attach/jpg.gif IMG_2523.jpg (https://metalworkforums.com/attachment.php?attachmentid=397087&d=1645184093) (257.9 KB)
Read the full thread at metalworkforums.com... (https://metalworkforums.com/showthread.php?t=207787&goto=newpost)
Now, a sensible man would go to Edcon and but some, but he had some 100mm diameter slugs of 4140, so the usual drilling, boring, and outside turning occurred.
Shaving away ~3kg of steel to make a 200g ring :o:
IMG_2523.jpg (https://metalworkforums.com/attachment.php?attachmentid=397087&d=1645184093)IMG_2524.jpg (https://metalworkforums.com/attachment.php?attachmentid=397088&d=1645184099)IMG_2533.jpg (https://metalworkforums.com/attachment.php?attachmentid=397089&d=1645184104)
which will then be cut in half (off centre) so there is enough to grind away to make an exact half.
For the second shell, I decide to try and save the middle. So I take the slug, Hercus it round, and machine a line to indicate the ID:
IMG_2534.jpg (https://metalworkforums.com/attachment.php?attachmentid=397090&d=1645184234)IMG_2535.jpg (https://metalworkforums.com/attachment.php?attachmentid=397091&d=1645184238)
On the other side, I face off but leave a little nub in the middle (from setting the tool too low), as a hook for marking a circle:
IMG_2536.jpg (https://metalworkforums.com/attachment.php?attachmentid=397092&d=1645184242)
then mark, centre punch, and drill a bunch of holes 6.99mm apart:
IMG_2537.jpg (https://metalworkforums.com/attachment.php?attachmentid=397093&d=1645184438)IMG_2538.jpg (https://metalworkforums.com/attachment.php?attachmentid=397094&d=1645184442)
My plan is to drill thru, and then hammer/press/grind the centre slug out.
I have a bunch of old 1/8" drills, so try to get most of the way through with them, then enlarge to 1/4".
A few go well, but then one of the little ones breaks. IMG_2539.jpg (https://metalworkforums.com/attachment.php?attachmentid=397095&d=1645184645)
And its getting late, so I go home to deal with that the next day.
Next morning, I ignore the broken one, and drill a few more to 1/4", but the wear rate on my drills is higher than expected. So I look at alternatives.
•Don't have an Annular cutter. Particularly not one at 65mm or 70mm diameter.
•Don't have a Trepanning cutter (like a parting blade, but curved).
•Do have a little high speed spindle. Lets see how that goes on the lathe:
Half an hour. Only 4mm deep: IMG_2540.jpg (https://metalworkforums.com/attachment.php?attachmentid=397096&d=1645185102)
Two hours. About 8mm deep. Another second-hand carbide insert (which had broken face) is destroying itself...
IMG_2541.jpg (https://metalworkforums.com/attachment.php?attachmentid=397097&d=1645185250)
but I'm nearly through the broken drill?
Keep going???
It gets to lunchtime. My groove is about 16mm deep, in a 38mm deep slab of steel. The day is getting hot (about 31° inside), I realise that I didn't have enough sleep, and could have drilled all the way through by now - even if I had to hand-sharpen two drills every three holes!
So, instead of waste the whole day, I admit defeat, throw the chunk of steel in the big lathe, and drill about 30mm deep, then bore the usual cavity out. At least I will keep the 16mm deep disc, right?
WRONG!!!!! I somehow mis-calculate the depth of my bored cavity, and end up saving a whole 11mm thick disc of 55mm diameter steel.
Sigh.
Maybe next time I'll borrow a rotary table, and mill the disc. That's sure to let me save the material from the centre. Right?
Attached Images
https://metalworkforums.com/images/attach/jpg.gif IMG_2541.jpg (https://metalworkforums.com/attachment.php?attachmentid=397097&d=1645185250) (143.5 KB)
https://metalworkforums.com/images/attach/jpg.gif IMG_2540.jpg (https://metalworkforums.com/attachment.php?attachmentid=397096&d=1645185102) (145.1 KB)
https://metalworkforums.com/images/attach/jpg.gif IMG_2539.jpg (https://metalworkforums.com/attachment.php?attachmentid=397095&d=1645184645) (217.3 KB)
https://metalworkforums.com/images/attach/jpg.gif IMG_2538.jpg (https://metalworkforums.com/attachment.php?attachmentid=397094&d=1645184442) (188.4 KB)
https://metalworkforums.com/images/attach/jpg.gif IMG_2537.jpg (https://metalworkforums.com/attachment.php?attachmentid=397093&d=1645184438) (224.5 KB)
https://metalworkforums.com/images/attach/jpg.gif IMG_2524.jpg (https://metalworkforums.com/attachment.php?attachmentid=397088&d=1645184099) (257.3 KB)
https://metalworkforums.com/images/attach/jpg.gif IMG_2533.jpg (https://metalworkforums.com/attachment.php?attachmentid=397089&d=1645184104) (159.5 KB)
https://metalworkforums.com/images/attach/jpg.gif IMG_2534.jpg (https://metalworkforums.com/attachment.php?attachmentid=397090&d=1645184234) (184.0 KB)
https://metalworkforums.com/images/attach/jpg.gif IMG_2535.jpg (https://metalworkforums.com/attachment.php?attachmentid=397091&d=1645184238) (169.9 KB)
https://metalworkforums.com/images/attach/jpg.gif IMG_2536.jpg (https://metalworkforums.com/attachment.php?attachmentid=397092&d=1645184242) (172.4 KB)
https://metalworkforums.com/images/attach/jpg.gif IMG_2523.jpg (https://metalworkforums.com/attachment.php?attachmentid=397087&d=1645184093) (257.9 KB)
Read the full thread at metalworkforums.com... (https://metalworkforums.com/showthread.php?t=207787&goto=newpost)