Case Thrust Cutting Tips / Porta-tool

[Air Cooleds Only]

Hey Guys, looking for a little advise. I just picked up a portatool line bore setup. I like the finish of the thrust surface after I'm done cutting, but the thrust surface in not parallel with the opposite thrust surface, it's about .005-.006 out in spots , I believe factory spec is w/in .002 // .
When I received the tool, it only had two pages of info, not to much information, wonder if anyone has a more detailed instruction manual?

To mix is up a bit, I have another style of thrust cutter. Not sure on the manufacture on this. The hub locates on the inner thrust surface, and has a spring plate (kind of similar to a pressure plate) that expands to locate the inner #1 main bearing bore to hold the tool in place. Then you use a drill to turn the cutter.
I like this setup as far a ease of setup. It usually cuts w/in .003ish, but chatters like a son of a bitch. Which could be giving me the deviation.

So to my forefathers and fellow machinist. If you care to share some tips, I'm all ears.


Thanks a Bunch!
Chris

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Air Cooleds Only

[vugbug68]

I have a porta tool line bore/ thrust cutter and I usually don't cut the thrust unless I need too to fit the bearing or if the thrust surface is damaged.
Are you saying that the thrust surfaces on each half of the case dont line up? You can do a small cut to make them even but then you have to make sure the bearing fits snug in the saddle otherwise you'll need a different bearing and cut the thrust even more.
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71 Super - Backroad Thrasher
66 Corvair - Weekend Cruiser
90 4 Runner - Muddin

[mark tucker]

cut the min it taks to clean it up.

[nsracing]

The TruLine thrust-cutter (lowe pic) will give much better accuracy than the PortaTool. The TruLine homes in on the back of the thrust and locked in place...hence the only deviation you will get is if the bushing is worn.

The above tool will NOT give you an accurate thrust cut coz the bar is held in between two bushings and the angularity might be offset in the along the length of the mains. That is why you are getting the 0.005 difference in thickness. No way to correct that w/ the PortaTool. It is just NOT that great of a cutting tool.

Use the TruLIne thrust cutter instead. As far as the chatter, use slower speeds and take only a little at a time until you get the proper thrust. Make you some "dummy thrusts" made on a lathe so you can set the toolbit to proper height. Mark the depth and cut oversize to about 0.002" or so and then take the final finishing cut slow by reading on the dial.

Don't cut your fingers. Enjoy.

[mark tucker]

I would rather have one that alines from 1 end of the case to the other off the main bores.

[vugbug68]

[modok]

there's really only two explanations for that.

When cutting thrust faces with a line bore bar...any flex in the feed mechanism can really screw with you. You can put an indicator on the end of the bar and see if it is doing that. If it is not then it is cutting square with the axis it is on, and I would have to ask how it is so far off? is it the case? what is going on there?

once again you can for instance put a ball end thingy in place of your cutting tool and have an indicator on the end of the bar and move it by hand and see if it is square with the thrust face or not. This is how I check that. Not usre how else it could be done

[Air Cooleds Only]

[vugbug68]

It sounds like you have it right for the porta tool, When doing the cut put the lever to closed so it moves inward at an even pace while cutting. I've thrust cut and line bored a few cases with mine and I think its pretty easy to use. Not the best tool for sure but I haven't had any problems with bearings not fitting right. The .040" cutters are the ones I use the most
_________________
71 Super - Backroad Thrasher
66 Corvair - Weekend Cruiser
90 4 Runner - Muddin

[Air Cooleds Only]

[vugbug68]

[Air Cooleds Only]

[vugbug68]

[vwmorten]

Hi

I just bought a Porta tool line bore bar like the one in this thread, but we have found that the bar is bent 0,04mm, and needs to be straightened.

We can straighten it, but to do so we need to get the feeder mecanism off the bar. do anyone know how to disassemble it?
I think it needs to be pressed off in a hydraulic press, but i might as well ask here before we try.

anyone?
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54 judson oval
58 Porsche speedster replica
60 single cab
65 westy
67 samba
71 earlybay

[samhayne]

I too have purchased a Porta Tool and am working on getting it tuned up so it can be used. I'd like to remove the bar and rebuild as it has a little run-out. If anyone has a damaged or trashed one, I'd be interested to purchase for purpose of disassembly and analysis. I'm monitoring most threads in the forums as well.

[mark tucker]

I realy dont know if runn out will affect it as long as the size is set to the bore.as in if the bar is .010 out the cutter will have to be .020 in or sometin like that...Ive been out in the sun all day changing a effing honda starter. but yes it does depend on the bend of the bar. the bar can be crankshaft shaped as long as the cutters are making the right size hole. now if it's wobbeling in the bushings that has to be corrected. as for thrust cut being done on the case and pourposely not done to the crank bearing center line like vugbug was tring to do or thinking it needed to be diferent...well....you cant fix stupid. if the crank bearing bores are off this way or that way the thrust also needs to be off the same as the bores.or...you will have a small thrust contact that trys to cock the bearing&crank when thrusted upon.

[samhayne]

I understand what you are saying. The thing is, if you set up the cutters on a jig and the bar is out of round, then you really don't know what your final size will be. The only way I think it could work would be to setup the bar on V blocks on a surface plate and check the size in multiple places on the rotation. Way too sketchy.

I'm going to get this bar true one way or another. I'm hoping someone knows how to get it apart without damaging it. If not, I'll eventually risk it as I'm semi confident I can re-create what I damage getting it apart.

[rugblaster]

I have nothing really to add, as far as straightening the bar?? or any of that shit, I'd just say we used one for years with no problems. I know the PortaTool gets reamed (pun) but I think they do a good job for what they are.

VWoA never sanctioned the use of them anyway. The cases were a wear item to be replaced.

Does it cut the thrust perfectly, I have no idea. But the one's I did worked. Everyone of them. Most of the time we would just find a better case back when they were laying around, literally, everywhere.

I always made sure everything was super clean. I torqued ALL the case half fasteners, used WD-40 spray as the machine ran and ran the bar through the case twice.....if you do this you'll notice just a wisp of material being removed from the case on the second pass. For something being run by a drill motor, they do an awesome job.
_________________
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'09 MB E350 '18 MB E400, '65 Plymouth Valiant convertible and a '19 Ford F250 King Ranch (nicer, but dirty, farm truck)

VWoA factory trained line tech 75 till 90 or so
ASE Master Certification
VWoA Assoc. of Quality Technicians inductee (One of 25 in the five state southwest region)
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TCU ......GO FROGS!!!!!!

[nsracing]

WE can practice boring w/ a bowed shaft.

The bits can still cut a fairly straight hole despite having the cutters not lined up in the bar axis line. But I would think you have to know where in the bar it is bowed -so have the bit stick-out on the lowest point of bend. When you set the toolbit - it will be less in height from the others.

You wont know anything until you do a trial cut in the case. I usually set the bits to oversize by0.010" oversize and inch my way so to speak to final bore specs. Then don't touch the bar again or reset any bits.

No secret I am not a fan of the Porta-Tool. But you can get it to work if that is all available. It is like an orphan child nobody wants to me...

NOTE: I have taken apart a PortaTool before (coz I was curious) - there is nothing there...just a large brass screw-type ACME threading to move the fluid from one side to the other. You will need a press to get the brass off. I would not recommend beating on it.

It is made of case iron so as the 'bushing area' wears so does all the fluids. Be good if you can install-machine a small seal.

[modok]