Jump to content
Sign in to follow this  
Marian65

Recentering Issue, Trimming Problem

Recommended Posts

For a few months now I've had an issue about centering when trimming.  I use a Giffin Grip and love it, but something has started going wrong somewhere and I can't figure out what it is.  My items come off the wheel (I use bats) centered and level.  When they're ready to trim, I put them on the GG and they're NEVER centered!  I've used a small level to test the level of the GG surface, so I don't think that's the problem.  I always use a needle tool to lightly mark the bottoms so I'll have a visual of how far in to make the trim.  When I put the needle tool on now, the bottom is up to half an inch off center!  It's as though they lean while drying, but I don't know why they would do that.  This problem is driving me crazy because I feel as though I'm losing almost all my work or just following it through and trying to compensate for the 'off-ness' in other ways, such as putting a mug handle on the leaning side in order to visually balance it.  I'd rather identify the problem and fix it, but no matter how many sleepless hours I log, I can't seem to come up with what's causing it.  When it first started, I thought the GG was not level on the wheel. 

 

I have not tried recentering for trimming by using clay lugs like I used to.  I was never much good at that, thus the reason for getting a GG.  That worked wonderfully for three years and now ... not.

 

I can't make large items, so most of my ware is shorter than seven inches.  Maybe some of my problem comes from unsteady hands, but I can't figure why the pieces seem nice and well-made enough until I get them to the trimming stage.  I've got too much invested in time and dollars just to quit, but I get so upset I don't throw for weeks at a time.  I realize that behavior just feeds the other issues, so whatever suggestions you have will be appreciated.

 

Thanks,

Marian

 

 

Share this post


Link to post
Share on other sites

this sounds so similar to the problem i had with my giffin grip.  i found that somehow i had changed the bolts on the bottom so that one of the three slides was set at 33 and the others at 32.  these are the tiny slots that are almost invisible and are how the thing is set up to fit over your particular wheelhead.  why they could not be a little more user-friendly is beyond me.

Share this post


Link to post
Share on other sites

do you wire under the pots to remove them from the wheel?  is the cut level?   i know how stupid this sounds and i am sure you have considered this as a possible answer but someone will ask it, so i did.

 

and one more, are you certain that the opening was made in the center and not slightly off center?

Share this post


Link to post
Share on other sites

As Babs asked, how are you removing the pots from the bat. I place a bat over my bowls and casserole type pots, flip the whole thing over and then gently remove the bat that was on the bottom. Vases and such, unless larger heavier pieces I do not use a bat. Larger jars and vases 20+" I will leave on the bat until leather hard, then flip by hand. Canisters I use the first technique.

Share this post


Link to post
Share on other sites

I wire off my pots as soon as I'm finished with them and leave them on the bat until time to trim.  They usually detach easily.  Sometimes I rewire them, but there's nothing out of the ordinary that I'm doing now that I haven't done for many years.  For Pres, as you notice in my original post, I can't throw tall or big.  I'm not able to center more than about four pounds of clay and I can't pull taller than seven inches tall.  When all of you mention "smalls," I guess everything I make is what some would call small if I make it on the wheel.  There's nothing that should distort.  Oh, yeah, about the flipping ... The pieces are already stiff enough to handle when I take them off the bats, so turning them over is no big deal. 

 

I thought for sure that I'd find one of the Giffin Grip's sliders off a little, but they're exactly the same as they have been since I put it together.  I've just got m'self a mystery.  I've decided that after I throw more pieces, I'll place paper on the top and if the diameter is small enough, I'll put the little level on it and see if maybe it shows anything.  They all feel level and in-center when I'm done and they're visually centered.  I've really messed up a whole evening's throwing this week due to the trimming being so much off center, but the stage is too dry to fold back into wet clay, so it's just more to put aside with the intention of reworking some day or adding it to the fill for a larger studio driveway.  :-)

 

Thanks for everyone's input.  Guess we can put the subject to rest and if I ever learn what the heck's goin' on, I'll post it.

Share this post


Link to post
Share on other sites

I never was comfortable using the gripper. My first teacher felt it was a crutch. He claimed it better to actually center work upside down on a bat and secure it with lumps of clay. For lots of reasons, from skill in throwing to drying unenevenly might cause pots to go off center. Regardless, I just make sure the part I am trimming is centered and go from there. It's how I was taught so it has become habit.

Share this post


Link to post
Share on other sites

Take a top/lid from  a jar and place it in the GG to check for centering. Sometime one leg can have something between the clip and the wheel keeping the GG og\ff center, the lid will show up any off center. Maybe one of the sliders skipped a track

Wyndham

Share this post


Link to post
Share on other sites

Yes this-needs to be looked at with a close eye.forget the level at this point.

( Sometime one leg can have something between the clip and the wheel keeping the GG og\ff center, the lid will show up any off center. Maybe one of the sliders skipped a track

Wyndham)

Share this post


Link to post
Share on other sites

Yeah, both the clips that grip the wheel head, and the bottom of the grip, have those little teeth.  If the teeth are on top of each other, as opposed to offset, like they are supposed to be, that may be able to cause an issue.

Share this post


Link to post
Share on other sites

surely a level on the gg head will make that obvious. I think the pots need to be flipped before trimming hardness arrives. Rim will be drying way faster  htan the foot which if recaught on bat will lead to warping.

 

Being level - and being centered are two different things.  It's possible for the GG to be perfectly level, and still not be centered on the wheel-head. 

 

Try using a pencil or piece of chalk (instead of a needle-tool) to check both the wheel-head and the GG to make sure they are centered and round.  (This will leave a mark on the 'high' spots if there are any, and make it easier for you to see where it's off.)

Share this post


Link to post
Share on other sites

The other issue with the GG is that if you're using the sliders that hold the pot at the lip, then the lip is being centered, not the foot. The foot is where you're trimming, so that's where it needs to be centered. No matter how perfectly centered it is when you throw it, differences in drying will cause it to become slightly off by the time you trim. Ditch the Giffin Grip and learn to tap center. It's faster, and you can get the foot centered.

Share this post


Link to post
Share on other sites

Marian,

There are many here that are not fans of the GG, and many that are. If you have been most comfortable with it for whatever reason we need to figure it out. I center my pieces for trimming in a variety of ways, being comfortable with all, and often use the GG when others do not work for what I am doing. I do not like thrown chucks that are either damp or bisquefired as I have found they distort my pieces with either ridges, or clay nerds sticking where the chuck holds the pot. The GG and a little creativity get around this.

 

A few thoughts and questions.

  • If you are only throwing as you call it smalls, shrinkage on drying to leather hard should be negligible, so I really don't think you would see 1/2 an inch difference.
  • When throwing, do you follow up with a chamois to compress the rim of your pieces? Is everything level at the rim when you start this? Reason I ask is I have seen some students throw slightly off center, and have one side higher than another and then pressure the chamois to even up the rim. This causes objects like bowls to actually warp/collapse on the high side.
  • Many of the objects I throw are off of the hump, and my cutting process can be a little. . . crooked. I have taken to leveling the bottom of pieces by using a hack saw blade held all the way across the base of the piece directly over the center. With the wheel going at my  preferred trimming speed I will press lightly on the hack saw blade until the piece is level, then complete the trim in a normal manner.

The GG probably is not the culprit unless

  • The hold tabs underneath have moved, become slightly bent, or even chewed in some way. If this is the case, repair of replace them.
  • The rubber band and washers underneath are not there, or there is clay under them. If not there, replace, if there clean up.
  • If you are using the holders with rods and pillows, make certain that all holes are cleaned out. If there is a bit of clay in the bottom of a hole, the rod does not fit all the way in and can change the centering minutely. Also make certain the rods are not bent, it is hard to bend them, but have seen one longer rod get bent. You can check the entire assembly for level by placing a bat over top of the positioned rods and pillows and placing your level on that. If there is a discrepancy between that and the level of the GG table then you know where the problem lies-in the pillows and rod assembly.
  • Finally if you are using a pad only type holder, try using the other set that came with your GG. There could be a worn pad on one of the holders that you don't notice.

Hope this helps you out,

best,

Preston

Share this post


Link to post
Share on other sites

1. I never was comfortable using the gripper. >>> me neither<<<

2. My first teacher felt it was a crutch. >>>if it is not now, it will be<<

3. He claimed it better to actually center work upside down on a bat and secure it with lumps of clay.>>>True<<<

4. For lots of reasons, from skill in throwing to drying unenevenly might cause pots to go off center.  >>>true<<<

5. Regardless, I just make sure the part I am trimming is centered and go from there. It's how I was taught so it has become habit. >>> Same here<<<

1. The Jr. College ceramic dept had an old GG when I started there...  I learned not to like it.  It only centered the base and

quite often on one side or the other of the vessel is trimmed thru or severely thinned.  When the vessel was flipped over

to trim the foot, often the foot ring was off centered also.  By the time shims were placed here and there you could have used clay

tabs and been on the 2nd or 3rd vessel.  The 3 stress cracks on the rim only showed up in either the bisque or glaze fire.

2. No one who used the GG realized it as a crutch when the room was empty, but when lines formed just to use the GG and

the annoying student often asked "Do you have many to trim?"  which is art-speak for "Hurry up, I've got pottery to trim and

a life" you realized it was a crutch for some people.

3.  Using clay tabs to fasten pottery to the bats is an advantage several ways.  a. any wheel head can be used.  b. Any vessel

that is trimmed and too fragile to move can be picked up by the bat, moved to the drying shelf and another bat put down.

4. & 5 Just about every cylinder I throw is off center.  So its best for me to center the neck, trim, center the body, trim,

center the lower half of vessel and trim.  Then trim the foot last.  I let the tackiness of the clay and the weight of the vessel

to hold itself in place.  Sometimes I have to use clay tabs, but not often. 

     I cannot "tap center"...  I've read about it, and seen it on "you tube".  To me its like watching a magician at work.

I'm amazed watching someone tap centering and see it as cheap entertainment.. 

To center and re-center I use the finger nail scratch method.

     In theory the GG works just fine.  I liked the idea about calibrating the center with a cap, since you already have one.

 

All best,

Alabama

Share this post


Link to post
Share on other sites

I tap and use the GG depending on the piece. Like any tool , you use it as it benefits you.

I learned many times, it's not the machine/tool it's the operator!

I don't ever use pressure on the rim of the pot on the GG to centre the pot. Flattish peices I tap and hold with clay tabs.

Share this post


Link to post
Share on other sites

For anyone still following this thread, I've determined that my Giffin Grip is in good working order and that my trimming problem is almost certainly my doing.  Can't fault any of the machinery.  I've been giving some thought to crutches.  I guess I've learned not to use that term except for its literal definition.  The use that has been adopted for our society seems to be "to use a thing as a way to avoid."  I would add "to use a thing as a way to compensate."  When one has handicaps, crutches are wonderful and allow us to continue to do the things we love when we don't have the ability to do them the "right" way.  Clay is such a wonderful medium for all the people who choose it. 

 

I've been making pottery for many years and was never any good at tapping something into center.  One instructor enlightened me that it depends on the position one's fingers take when tapping and I had more success after doing it his way, but tapping doesn't always work for the piece.  When I first learned pottery back in the early '80s, I was taught to use my needle tool (or fingernail) and lugs and that worked well over the years until I got my GG.  I adore it because it saves me so much time and aggravation.  I'm more toward the end of my creative life now, I'm still a hobbiest vs professional, and whatever makes my throwing days easier for me, I'll happily use as crutches and keep on enjoying having my hands in the mud.  I love sculpting and hand building, as well, so I shouldn't have to quit working yet! 

 

Thanks, Pres, for reminding me about the rims.  I think that may be my total problem, but I can't put it to the test until I start throwing some more this week.  If a jar is not level at the rim, that leans the bottom when it's turned over and thus a simple solution to my issue.  No matter where the lugs are placed or the posts of the GG, the thing would still be leaning a little, wouldn't it?  At least enough to make a difference in the trimming, but perhaps not quite enough to be obvious when I'm looking down on it and depending on the tapping, scratching, or the GG to get it right.  Being more alert and more open to all the angles should do it.  I appreciate everyone's input and I appreciate the differences in methods.

Share this post


Link to post
Share on other sites

Marian65, if you are still reading the forum, I feel your "pain".  I have many years left in my creative life (I'm 54 and only started with Ceramics in 2012), but with arthritis in my thumbs and carpal tunnel syndrome, I have limitations, too.  

 

One thought occurred to me when reading your post of Oct 19, 2014 is perhaps you can hire or trade for someone to trim your feet.  This may not solve the off-center throwing problem, but someone who is expert at trimming with tap centering or the thumbnail method might be able to do the job for you "just right".

 

A thought as I look at how I must adapt to my limitations.  I have a broken wrist and won't be throwing for long time, until the bone has completely remodeled and is no longer a fragile point.  In the meantime, I have been teaching a coil and a slab workshop for beginners, even with the cast still on.

 

Many people in the recreational studio where I live don't trim feet AT ALL, so I am planning to do a foot trimming workshop.  Those that do trim, don't get how the foot is supposed to look in profile to the rest of the pot, so there is definitely room for any level of explanation that can improve the pot-growing-out-of-the-table-top approach.

 

Good luck with everything, and happy potting!

Share this post


Link to post
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

Sign in to follow this  

×
×
  • Create New...

Important Information

By using this site, you agree to our Terms of Use.