Having a terrible time getting the foam cores to line up w/the back side of reel seat. When I shape the grip it will not fit nice and flush w/the backside of the reel seat when I
put the foam core and reel seat on the rod blank. Any suggestions? Thanks, Chuck Gray

You should take a parting tool and cut straight in on the ends of the core. This gives you a perfectly flush end.

If the core and the seat aren't fitting flush, then there is something wrong with your assembly, most likely the centering of the bore in the grip or the arbors inside the seat. Do they fit flush off the rod blank? If so, the problem is with your mounting of them. Something isn't centered.

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Hi tom, totally new to rod building so this is my first time making foam cores, i'm using your method w/the pvc pipe. The end caps where the mandrel fits through is as close to center as i could get it. Before fitting the handle and foam on the blank the two fit fine, when i put the two on the blank that's when the two won't match together. The other thing i noticed is when i shape the grip, it is not equal distance around the ends, one side will have more material than the other, I'm guessing that's a lathe centering issue with the foam core? Thanks for your help. Chuck

How are you shaping them? You have to cut, not sand the basic shape in order to have the core concentric. Otherwise the sandpaper just floats on whatever you've got there, which may not be perfectly concentric to start with.

If the two fit flush off the rod, but not on the rod, then there is a problem with one or both bores being off at some angle.

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I'm using the lathe to take off the material, I'll have to try again w/a new piece of foam and as i procede w/each step, I'll measure and see where I'm making the mistake. Thanks for your help. Chuck

But what are you using to cut/turn the foam with? You have to use a gouge or a scraper or it's not going to turn concentrically.

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It's a tool attached to the lathe, turn on lathe, switch a handle and it automatically cuts the foam as it turns.

If it's not cutting concentric, something is wrong. Make sure the tool doesn't "float" with the stock.

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To those that use a drill powered lathe like mine and you haven't got a tool rest to hold a cutting tool then try a coarse wood rasp. Works for me but you still have to be careful that it doesn't "float" with the core as Tom has indicated. The one I use is flat on one side and curved on the other and does a decent job for me.

ESFNEM Col
Port Kembla, NSW
Australia

I turn my foam cores on a metal lathe. First I put the core on the mandrell, then put it in the lathe - I do a first pass to get my core perfectly round before I begin shaping any shape to the grips.

all shaping is done on the mandrel - 1 end in the chuck, the other end in a free spinning tailstock.

Once the carbon skin is on, I size the inside of the core foe the blank and dry fit the rear grip, reel seat, and foregrip...

I have been using a mandrel along w/a metal lathe, how much pressure should be placed on the mandrel by the tailstock? I believe my problem lies here? Thanks again for all your help.

Col

I do all my ruff shaping on my ( poor mans lath ) with a drill Usually at hight speed

Did not know if that wood rasp would work on cores Now I know Thanks

Bill - willierods.com

Now that could be. If you apply so much pressure that the mandrel is bending you'll definitely have an out of concentric piece.

All you want to do is slide the tailstock up into the mandrel bore and advance the tailstock wheel just a tad. You don't need much pressure, just enough to ensure the mandrel isn't going to come out of the tailstock live center. It doesn't take that much.

Do make sure the mandrel in the chuck end can't slide back into the chuck. You may want to put a tape ridge there so it can't slide back.

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Also if your core and mandrel are flexing while the cutter is moving, you are trying to remove too much material in one pass. Take smallet cuts - that will reduce the deflection and give you a more accurate cylinder.

The bore of the cores, whether you make them yourself or buy them, will not be perfectly concentric with the outer diameter of the core. That is the nature of the beast-there is no way to make them perfectly concentric. But, if you do your machining on a mandrel then you will cut the excess off resulting in a perfectly concentric bore. If you clamp the outer diameter of the core and machine with that setup you will be unable to get a concentric bore.

Another operation that can introduce eccentricity is the reaming of the core bore to get it to fit onto the blank. This stuff cuts so fast that you must be very careful with the boring operation to keep the reamed bore concentric. It only takes a few thousanths of an inch to be noticeable.

You can use sandpaper to machine the material; I've done it for years successfully, but you should use coarse sandpaper and mount it onto a sanding block, then progress very slowly and carefully, with little presssure, to prevent the sandpaper from following the surface of the eccentric core. Using lathe cutting tools is the best way, but I do not have a lathe. I turn mine on a mandrel mounted on my drill press with a stabilizing bearing at the lower end. You must machine it on a mandrel!

I have had handles on my drill lath come out like that
But since I use a very high speed they come out well

maybe you are going too slow and like said the mandrill is flexing

Bill - willierods.com

The foam core material, like the reel seat shims I've used for years, machines so fast that I just can't believe anyone can put enough pressure on it to bend a mandrel without having the material basically machine away almost instantly. I think he's either spinning on the OD or allowing the tool/sandpaper to follow the eccentric OD when spinning on a mandrel. That would be easier to do if spinning slowly. I spin mine pretty fast, but don't know the exact rpm. But even at high rpm I have to be careful to not let the sandpaper follow the OD. Once the eccentricity is machined off the spin and the reaction of the sandpaper on the surface become very smooth and stable.

I have eccentric cores - even turned on the lathe. This happens when the core slips on the mandrel. As Tom mentioned, a bit of tape wrapped on the mandrel will allow you to snug the core to the mandrel and the results will be much better.