Giant Lapping Plate

[turboprop]

After years or toiling away on old FXRs, I have come to the realization that nobody that has ever owned an FXR has also owned a torque wrench. I have never seen a an FXR specific trans case or inner primary that did not have at least one stripped out threaded hole, had holes that were not somewhat pulled or did not have warped or otherwise distorted mating surfaces.

Currently blueprinting and building a transmission and primary out of a friends '00 FXR. Even the latest FXR is nineteen years old and has had plenty of hacks in it.

I am currently planning to build a lapping plate large enough to lap the outer flange of the inner primary case. Thinking of ordering a piece of float glass, 36" x 36" x 1" and making a wooded box to float it in. Maybe on top of 1/8" of epoxy or something similar. Probably cover it with 1200 grit wet sandpaper.

I am sure plenty of members here have cast iron lapping plates or granite surface plates, and that s fine, but not what I am interested in.  Would really like to hear from people that have used or made a lapping plate from thick glass as I have described.

[Norton Commando]

I made a small version of what you are describing. Mine is only 10" X 6" X 0.375" thick and I use it to lap oil pump gears, oil pump bodies and other small parts. 

What you are describing should work, but the glass will be expensive. I would also build a sturdy shallow box and fill it with an inch or so of sand.  Put your plate lap in the sand and you'll have a stable and flat lapping surface.

Jason

[Geezer_Glider]

Maybe float it on some cut pile carpet? Would give enough to let the plate be what takes the load. A lot less mess, you won't be putting that much force on it. Granite plates can be had really cheap, you don't need  Starrett pink block for what you are doing. They are a bit heavy though.
R Meyer

[turboprop]

I have priced both float glass and machinist type granite. Float glass is less expensive. Have not considered counter top grade grant. I do not have any idea how flat the kitchen stuff is.

[ecir50]

outer flange on the inner? may be over thinking this one get a cometic gasket. I can see where the mating surfaces of the inner of the inner may help.

[turboprop]

outer flange on the inner? may be over thinking this one get a cometic gasket. I can see where the mating surfaces of the inner of the inner may help.

Not asking for advice about parts but would like to hear about your experiences with making a lapping plate from float glass. Do you have any experience with float glass lapping plates?

[turboprop]

Update

I just ordered a piece of float glass from a local mom and pop glass company. $142.00 for a piece of clear 36" x 24" x ½" with polished edges and chamfered corners. Will be here next week.

Local wood place is going to build a case with a removable lid. This is sized so that it will fit in a drawer in my Lista cabinet and should be plenty big enough to lap an inner primary case or anything else on a bike.

[JW113]

What are you planning to use for lapping compound?

-JW

[turboprop]

800-1200 grit wet/dry sandpaper and some type of spray adhesive to hold it to the glass.

[FXDBI]

800-1200 grit wet/dry sandpaper and some type of spray adhesive to hold it to the glass.

2 sided tape around the outside edge works very well holding the paper down. Don't know about finding the paper in 36in width. Glueing sheets down until its covered results in the corners of the sheets giving u problems. It takes less time on the lapping if you use a stone on the faces first to get rid of the high spots. Still takes a touch to lap large items and keep it flat and even. Normally you lap in a figure 8 to get flatness.   Bob

[turboprop]

800-1200 grit wet/dry sandpaper and some type of spray adhesive to hold it to the glass.

2 sided tape around the outside edge works very well holding the paper down. Don't know about finding the paper in 36in width. Glueing sheets down until its covered results in the corners of the sheets giving u problems. It takes less time on the lapping if you use a stone on the faces first to get rid of the high spots. Still takes a touch to lap large items and keep it flat and even. Normally you lap in a figure 8 to get flatness.   Bob

Thanks, much appreciated.

I have used smaller plates and compound, but nothing this large. Sort of curious to see how this works out. I think I have a source for 24" wide belts that once cut will be about 40" long. Should have less than $250 in this once its all done.

[FSG]

we used glass plates around 18" square in the oil patch

used them for lapping shuttles that sealed 5000psi with a control pressure between 450 to 900 psi

we used WD40 on the wet-n-dry paper as a lube but spraying it on the back of the paper also held it to the glass

figure 8's the only way to go   

[Hossamania]

Figure 8 is how we polish fiber optic glass ends. Those have to be done perfectly to pass test.

[FSG]

Figure 8 is how we polish fiber optic glass ends. Those have to be done perfectly to pass test.

  them 62.5 micron fibres need the ceramics around them to get it done, used them in the patch as well

[ecir50]

found this YouTube video I watched a few years back that may give you some ideas. He is using 80/100/120 grit.

https://www.youtube.com/watch?v=HyKN52HD6RU

[koko3052]

I just use cooking oil to "glue" my sheets to the granite I have & used for the "lube" also. I can see that you may have issues with the sheet corners curling up...in that case I think you are right in using some spray adhesive...but it will have to be an even coat or you will have high spots on the sand paper.

[turboprop]

Thats what I was thinking about the spray adhesive. Haven't really nailed down a source for it yet. I am sort of excited to try this lapping plate. I have a small pile of junk to practice with before doing a somewhat rare FXR specific part.

[FXDBI]

Thats what I was thinking about the spray adhesive. Haven't really nailed down a source for it yet. I am sort of excited to try this lapping plate. I have a small pile of junk to practice with before doing a somewhat rare FXR specific part.

Just remember that spray adhesive needs to be cleaned off changing papers, 2 sided tape is much easier( been there done that). The parts your doing do not need to be optically flat.
The thing is to get the feel for being flat on the paper and getting the feel of even pressure on the object being lapped.  Clean up the parts for sharp edges and high spots before u lay it on the lap. Large flat smooth file and a good stone are your friend. Even pressure and that figure 8 gets the surface like new. In the millwright industry its called DETAILING the parts on them big turbines its about 80% of the work detailing. Stuff sure goes together nice if its all detailed and dry fit before any assembly takes place.  That's how the pro's do it, no getting in a rush or panic. Have fun with it!   Bob

[turboprop]

Thats what I was thinking about the spray adhesive. Haven't really nailed down a source for it yet. I am sort of excited to try this lapping plate. I have a small pile of junk to practice with before doing a somewhat rare FXR specific part.

Just remember that spray adhesive needs to be cleaned off changing papers, 2 sided tape is much easier( been there done that). The parts your doing do not need to be optically flat.
The thing is to get the feel for being flat on the paper and getting the feel of even pressure on the object being lapped.  Clean up the parts for sharp edges and high spots before u lay it on the lap. Large flat smooth file and a good stone are your friend. Even pressure and that figure 8 gets the surface like new. In the millwright industry its called DETAILING the parts on them big turbines its about 80% of the work detailing. Stuff sure goes together nice if its all detailed and dry fit before any assembly takes place.  That's how the pro's do it, no getting in a rush or panic. Have fun with it!   Bob

This is good stuff, exactly the type of information I was after. I am really curious to see how flat some of the stuff in my junk pile is.

To say that I am a fanatic would be an understatement. The TC style engines and drive trains have come a long way  towards being oil tight. Older Evo and Shovel drive trains not so much, especially after thirty years of hacks touching them. This lapping plate if it works as planned will provide a significant improvement in my ability to seal these things up. Glass will arrive next week when I am out of the country. Such is life.

[FXDBI]

Thats what I was thinking about the spray adhesive. Haven't really nailed down a source for it yet. I am sort of excited to try this lapping plate. I have a small pile of junk to practice with before doing a somewhat rare FXR specific part.

Just remember that spray adhesive needs to be cleaned off changing papers, 2 sided tape is much easier( been there done that). The parts your doing do not need to be optically flat.
The thing is to get the feel for being flat on the paper and getting the feel of even pressure on the object being lapped.  Clean up the parts for sharp edges and high spots before u lay it on the lap. Large flat smooth file and a good stone are your friend. Even pressure and that figure 8 gets the surface like new. In the millwright industry its called DETAILING the parts on them big turbines its about 80% of the work detailing. Stuff sure goes together nice if its all detailed and dry fit before any assembly takes place.  That's how the pro's do it, no getting in a rush or panic. Have fun with it!   Bob

This is good stuff, exactly the type of information I was after. I am really curious to see how flat some of the stuff in my junk pile is.

To say that I am a fanatic would be an understatement. The TC style engines and drive trains have come a long way  towards being oil tight. Older Evo and Shovel drive trains not so much, especially after thirty years of hacks touching them. This lapping plate if it works as planned will provide a significant improvement in my ability to seal these things up. Glass will arrive next week when I am out of the country. Such is life.

Flat piece of glass be awesome to put a light spread of Prussian blue and slide the gasket face around on the plate you will see the high spots real good. Also good for laying parts on and using a feeler gauge to check the flatness. Many uses for a flat surface. Being anal with the details feels even better when it starts first hit and its perfect better than new! Only way for those results to be obtainable is being anal.   Bob

[koko3052]

"Just remember that spray adhesive needs to be cleaned off changing papers, 2 sided tape is much easier( been there done that)."


I can't see 2 sided tape working unless you had a sandpaper sheet that is large enough that you can work in of the confines of the tape...but then you could use oil to "stick the paper down"....otherwise you are going to have raised sections where the tape is. Maybe I'm missing something in your reply? 

[turboprop]

I plan to use spray adhesive. Seems like a no brainer.

If this works out as expected, I will probably start lapping every flanged surface. Machinist dye and this plate will reveal all.

FWIW - I have to give credit for this idea to rbabos. He had a thread a while back about his neighbors shovel that leaked and talked about chamfering threaded holes that had been slightly pulled and lapping surfaces flat to give the gaskets the best chance of sealing.

[FXDBI]

https://www.aervoe.com/product/prussian-blue-high-spot-indicator/

https://www.permatex.com/products/specialized-maintenance-repair/rebuilders-aids/permatex-prussian-blue/

[turboprop]

That Prussian Blue is dangerous stuff in the wrong hands. If I had some it would have to be kept inside the office safe. If any of my buddies found this stuff in my garage, well, it would not be good for anyone.

[PoorUB]

That Prussian Blue is dangerous stuff in the wrong hands. If I had some it would have to be kept inside the office safe. If any of my buddies found this stuff in my garage, well, it would not be good for anyone.

Why is that? I looked it up and don't understand why there would be any issues.