How To Hold This Part In Lathe?

WesPete66

WesPete66

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I have an Atlas TH54/QC54 lathe, with basic tooling. (3 & 4 jaw chucks, face plate, steady rest, milling fixture etc) I have a part that I would like to face flat, but am not sure if I can do it with what I have available. The part is a cylinder head for an antique engine, about 6.5" dia, irregular shaped, with four thru-holes. I'd like to clean up the mounting/gasket surface as it was badly rusted. There is no way I can hold the part in a chuck, so my thought was to use a face plate, placing spacers to support the part on four bolts. The problem is that the bolt heads would be sitting right where I want to face the part. So is there another method to hold this? Something other than a bolt to hold the part?
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i know it may be a risky proposition,
but you could possibly make a support fixture that used the valve guide holes with brass studs (or other soft studs) and a holding plate, to tighten the head up to it's spaced out position on a faceplate.
you could utilize some studs that don't protrude all the way through the head as an extra measure of security, when machining the head flat.

the only other choice i can think of is a very large swing'd lathe that you could put the whole head in the chuck's center bore and hold it with a 4 jaw around the diameter. :fat:

you could always scrape it flat too...:grin:
i'd be happy to do it (scrape it) for you.
 
I like Mike's idea of bolting it to the face plate through the valve guides, steel bolts shouldn't hurt as there'd be no movement. Then use 4 bolts with nuts acting as jack screws into the head bolt holes. With them you can level it up.
No spark plug hole, is it off a diesel?

Greg
 
You could MAYBE try a belt sander of adequate size and with a good flat platen. I can’t stress the maybe part enough. Finesse would be paramount in this operation. One bad move or selection in any part of this idea and it could be all over.
 
You could put it in your milling fixture and use an end mill. Of course that would be a pain because the fixture probably doesn't have sufficient travel. You would have to re-position it during the operation. Still it could work if done with care and judicious use of a dial indicator.
 
Is it cast iron?
If so, she might be scraped in.
I've heard of high compression automotive race engine heads being scraped in so precisely that the need for head gaskets is avoided, and thus no gasket failure.

Steel can also be scraped, but it's difficult due to hardness.

Daryl
MN
 
Thanks for the good suggestions! This is from a hit & miss gas engine using an igniter (battery & coil ignition). and it is cast iron.
Would concrete anchors be acceptable? I would put the anchor end into the head's thru-hole, and bolt it to the face plate?
Thanks again & keep em coming!
 
Per Ulma Doctor,

So something like: Starting out with an aluminum round or square plate (something like 1/2" by 7 - 8") to use as a mount in the lathe chuck, mill or saw out the section on the mount for the head mounting bracket on the head. Turn 4 posts that will snugly into the head mounting holes so they have a shoulder on both sides (this will provide better stability and set a fixed distance between the head and plate) and fasten the other ends into the aluminum plate (thread the standoff or bolt through). The length of the four posts between the shoulders need to be slightly higher than the valve guides and allow enough space behind the mounting plate for the head mounting bracket, so about 2.5" between the mounting plate and head bolt holes. Drill two holes in the mounting plate to align with the valve guide holes, use washers with bolts extending through the valve guide and into the aluminum plate. These will tension the head to pull it down against the 4 posts. The 4 posts just act to stabilize the head. I would make sure on the bolts there is no thread up against the valve guide, you do not want the thread to damage the guide if there is any movement.

It looks like the two valve guides and 4 head mounting holes are all symmetrical around the center of the head, so you could just pull off the measurements and build a jig to hold the head. You may want to use a 4J independent chuck if you need to center the milling area. If using a square plate in a 4J, may want to use some spacers between the chuck and the mounting plate so it stays parallel when turning. Low speed, sharp cutter, multiple light passes. Sometimes I mock things up with wood to check clearances.

Other option would be to use a mount in a rotary table on a mill.
 
Interesting part especially since the combustion chamber is proud of the gasket surface. You won't be able to use a belt sander and a milling machine will be tricky as you will have to creep up on the ridge and not cut into the chamber.

I would be inclined to bolt a round piece of aluminum to the combustion chamber side with two bolts through the valve guides. Then you can chuck the aluminum block and indicate the surface as well as the combustion chamber diameter. As long as the lathe is large enough, you can then come around from the chuck side to resurface it. I hope this makes sense.
 
Techie1961 said:
Interesting part especially since the combustion chamber is proud of the gasket surface. You won't be able to use a belt sander and a milling machine will be tricky as you will have to creep up on the ridge and not cut into the chamber.

I would be inclined to bolt a round piece of aluminum to the combustion chamber side with two bolts through the valve guides. Then you can chuck the aluminum block and indicate the surface as well as the combustion chamber diameter. As long as the lathe is large enough, you can then come around from the chuck side to resurface it. I hope this makes sense.
Click to expand...

Would't surfacing the rusted part then change the combustion chamber? Is it a diesel? What about Valve to piston interference? Seems to me that what ever was removed from gasket surface would then need to be made up with gasket thickness or equal amount be removed from combustion area.

Now for you original question, how to hold? I think a lathe would be the best. I agree with a fixture, or a large enough lathe to use a 4 jaw chuck. You may still have to make a fixture or fixture pieces to hold in chuck. I find when puzzled by a set up that sleeping on it usually provides the answer.

I just read techie1961's post again. That is a great idea, if your machine is big enough or make a mandrel and a fixture and hold it at the tailstock end and surface away.

Tim
 
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