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Mistake

Some MT's don't have the extra flat to allow removal with a key in the slot, some even have a threaded hole to allow a draw bar. Those tend to be for lathe spindles where you have access from the back.

For those applications a simple 1/2 steel rod about a 1ft longer that the spindle is required. Side in touch off pull back about 3-6" and slide in with speed, one such tap releases the MT with no damage, did this for about 30 years on my Logan Lathe. My bar I put a brass handle on it as I was using a lot years ago, still have the same bar and use it for my CX707 the larger MT5 from the lathe spindle just as easily.
 
PeterT said:
There is probably a recommended torque rating out there but I try not to over tighten.
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I don't know what it is for MT3, but prolly less than R8.

I found lots of very credible references based on actual testing that suggest a proper torque for R8 is 20 ft lbs for small tools, 30 on average, and 40 for large ones. 30 ft lbs on the drawbar will hold 2000 on the taper.

I have a peak recording torque gauge. It seems I average around 25 ft-lbs even with my size. I can do 30 no trouble but it seems I usually don't. 50 with a 12in wrench is doable but more than I am comfortable doing. The other day a 5 and a half foot neighbour dropped by and I asked him to tighten it to his ability. He only hit 16 ft-lbs (half the recommended 30). I would easily imagine that torque is highly sensitive to how far above your head the drawbar is.

I do not have MT3 torque recommendations, but the MT3 taper is much longer and also less aggressive so I would speculate that it is much less than R8. I'd offer a SWAG guess that 1/4 is prolly more than adequate. Say 5, 7, and 10 for small medium, and large tools.
 
mbond said:
I have only manual feed, so I felt it work well for the first 1/8th or so, and then grind to a halt
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mbond said:
It started life as a fitness weight. I assume it is mild, but I don't know for sure
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+1 on fitness weights containing all kinds of booby traps.
I've drilled about 200 holes with my HSS annular cutter, in 3/16 and 1/4 material, with mill scale and tubing welds, and the first cutter is still going strong. In part I attribute longevity to 2 things: soluble coolant, mixed 10:1 (instead of 40:1) in a spray bottle, and not 'pecking'. Unless the hole is very deep, the cutters are designed to take it in a single cut. On a 1/2" hole I take it in 2 steps. Between them I completely clear out of the hole.

If you peck, the chips get jammed in the clearance between the cutter and the wall of the hole on either side of the hole- this can lead to burning, chipping or breaking off of the teeth entirely.
 
I got a lead billet from a guy who said it is used for swaged cables in the oil field. It is harder than normal lead and makes great hammer heads. Brass and copper hammers will work harden to the point that they can easily damage a machined surface. Lead does not work harden.
You can use wheel weight lead from clip on weights as it is a 10 -12 Brinell. Stick on wheel weights are soft almost pure lead, pretty soft for a hammer.
A rotabroach drill can be resharpened for $20
 
I have only had these tools for about 6 months and am still trying to build my inventory - and more importantly improve my skills.

In that time, I have only every tightened my MT3 to 'hand tight'. Often when I want to take it out, the draw bar is completely loose - all the load is taken by the taper.

I don't have any boring bars etc. if those are the best tools for this job, then I guess that's what I should buy next ;)
 
A decent source for harder lead is used roof flashings. I picked up about 100# of them for 10 bucks at a roofing recycle centre.
 
mbond said:
I don't have any boring bars etc. if those are the best tools for this job, then I guess that's what I should buy next
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What I've read is that cast iron parts, like your weights, can have 2 major problems. Casting sand embedded or hard spots (due to too-rapid cooling).

If you've hit casting sand, I think you ought to be able to feel that with your finger. But I don't think that sand would cause the level of damage that is shown in your first picture.

AIUI, hard spots in cast iron can be exceptionally hard. And the abrupt transition from good material to the hard spot can even wreck carbide tooling. Some people report that you can eliminate hard spots by heating the part and then letting it _slowly_ cool. Apparently this can be achieved with a bonfire or maybe even in a wood stove. Put the part into a roaring fire. I don't know just how hot it has to get. Surely if it is glowing red, that's good. Then heap the part in coals and ashes and let the fire go out by itself. Drag it out the next day and supposedly it should now machine like butter.

As you can guess, I have no personal experience. Would love to hear detailed report on this process.

The following page talks about hard spots due to chilling in connection with welding cast iron:

CAST IRON, Hard Spots | Weldcor

weldcor.ca weldcor.ca

HTH,

Craig
 
I recently had to pull the temper on a Cat40 tool holder to modify it. After heating it red I put it into a bucket of floor dry. I could not believe it when I burrowed into the bucket after 6 hours the piece was still too hot to touch. Excellent for slow cooling.
 
Ironman said:
I recently had to pull the temper on a Cat40 tool holder to modify it. After heating it red I put it into a bucket of floor dry. I could not believe it when I burrowed into the bucket after 6 hours the piece was still too hot to touch. Excellent for slow cooling.
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That's a great tip, thanks!
 
Here are my two mallets. I
vastly prefer the first one for breaking a taper. One light rap and its loose. The bigger rubber one works too, but not as well. Both are highly superior to brass or lead.

20231130_155410.jpg


20231130_155433.jpg
 
Until the next bonfire then

I'll try drilling + boring? Unless there is some other way of getting lead, plastic, copper, or some other talisman
 
mbond said:
Until the next bonfire then

I'll try drilling + boring?
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When I was cutting off dumbbell ends for later machining, I noticed that the shaft/handle was steel and the end iron weights were cast around the shaft. So there was a (harder) mystery steel rod part way through the end weight. YMMV - the dumbell I was using was older, origin unknown. A few voids but not a lot of non-iron inclusions.
BTW, if you just want something to use to 'hit stuff', you could just saw off one end of a dumbbell; use the shaft for a handle. Wrap the handle with duct tape for a professional look.. (or use a light dumbbell 'end on'....).
Lead- depending on where you live (and your level of 'thriftiness' :) ) you could just buy a lead downrigger ball from the local fishing supply. 30 yrs ago there were junkyards that sold lead scrap; but I think that may be a thing of the past? Somebody told me that tire wheel weights aren't lead any more; I don't know if that's true. If it isn't it probably will be, soon enough. Too many people eating tire weights, I suppose.
 
Looks like you burnt it up from to little pressure (or to much speed, mag drills run around 400-500rpm) there is probabaly junk in the cast iron as well, so I'm sure that didn't help

It is still in one piece, so your not doing to bad!

Annular cutters require a good bit of pressure to work properly, to little pressure will burn them up, it looks like that may have been a factor

the sweet spot is much easier to find with an actual mag drill rather than a mill as you can hear the motor loading down, as it gets the proper chip load, unfortunately with a mill you need to get a feel for the pressure, and a sharp eye for the chips

As for the cutter, those accusize hss cutters are decent, I normally get a few hundred holes out of one with coolant use, and I don't think I've gotten a bad/dull one from new yet


As for tapping the spindle out, on my r8 i loosen the draw bar maybe 1/8 and give the draw bar a wack with a small brass hammer, the same one I tap parts in the vise with, doesn't take much of a tap for the taper to let go
 
At least half of the reason for making this project is to get better at making 'stuff'. I found a nice piece of hard wood from a tree in my yard, and I found this chunk of metal and thought great! And if it makes a useful tool than even better!

At the beginning of the cut, I certainly did use too little pressure. Having no idea how much to use, I started with light pressure. It did not really cut, but skated over the surface of the work. I applied some more pressure and some good looking chips started coming up. Going cautiously, that worked for several cycles and I thought I was in business. Then all of a sudden I wasn't.

I think heating the work and letting it cool slowly has the best chance, but since I live in the city, I have to plan how to do that carefully

As an aside, I didn't even think that this could be hard metal. I used a carbide cutter to make a flat face and it cut like butter. I guess others would have been warned by the nature of these chips - as always, more to lean!

1701481827468.webp
 
mbond said:
As an aside, I didn't even think that this could be hard metal. I used a carbide cutter to make a flat face and it cut like butter. I guess others would have been warned by the nature of these chips - as always, more to lean!
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One of the things you need to get used to is the fact that chips can carry away the heat of the cut. This can greatly improve the life of the cutter.

As an engineer, you can appreciate that deformation takes a lot more energy than a fracture. Carbide cutters are usually designed to deform the metal they remove which then results in hot chips but a cooler tool. There is a lot more to it than that, but it helps explain why a bigger cut can be better than a shallow one.

There are many charts and formulas that help define the optimum process for different cutters and/or inserts. You can play with these to a great extent but in general regular carbide inserts like the ones in your photo like more aggressive cuts. If you need to go slower you can use a HSS tool or an insert designed for aluminium.
 
I think I'm continuing to demonstrate that I'm a novice in the practical parts of this craft and have a lot to learn
 
mbond said:
I think I'm continuing to demonstrate that I'm a novice in the practical parts of this craft and have a lot to learn
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Get yourself some lathe/mill intro books. Harold Hall and Stan Bray are two authors I have found to be use full.
 
mbond said:
I think I'm continuing to demonstrate that I'm a novice in the practical parts of this craft and have a lot to learn
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We are all novices in one way or another. There is more to learn about machining than anyone can learn in a lifetime. The more you know, the more you know you don't know.
 
Dabbler said:
Also try Southbend "How to run a Lathe" - it's the first book I started with...
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My first lathe was an old girl built in the 1880s. It was given to me by an old fellow I knew. He died many years ago. I had used a lathe a little before that but this is the first book I read about lathes too. It's a great start.
 
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