Tapered Gibb making

[Larry$]

I'm in the process of restoring an old Italian made cold saw. I'm at the point where I feel the need to make a new gibb. Someone has made one out of a scrap of plastic. No matter how I try to adjust it it has a lot of drag. I'd like to make a new metal one. All the ones I've seen have been steel of some sort. I have no faith that the plastic one is the proper taper. The gibb is enclosed except for one end. The dovetail column is vertical with the gear box and motor hanging on one side. Heavy! I'm going to try measuring the taper by first removing the plastic one then sliding various thicknesses of aluminum in. Measuring when they wedge and what thickness they are. By measuring several different thicknesses and the depth that they wedge I should be able to find a taper. Is there any sort of standard used?

Making one. I don't have access to a surface grinder. The plan is to screw a piece of steel to a heavy back up. Shim it on the mill table to match the measured, guessed at, taper and just cut the taper with a shell mill. The machining marks will hold oil. By bluing the gibb and trial fitting I might get in the ball park. Hand scrape the high spots. The motor & gear case with the mating dovetail is very heavy and tricky to a align. Any suggestions would be appreciated. Does it matter what kind of steel I make the gibb from? 12L14?? There is a pump on the machine for oiling.

 

[benmychree]

Cast iron would be the preferred material.

 

[Richard King 2]

Another way to do it is to get 2 sets of feeler gage sets, the king tou buy at an auto store to measure sparkplug gaps. There are multiple sizes shim stocks aprox. 1/2" x 3" long from .0015" to .030" thicknesses, each one is .001" bigger, so there are normally 32 shims in a fold up cover.. . Then slide one in on the big end and the other on the other end. Many times I draw it out on some graph paper. If you measure the length of the opening you should be able to get close. Many taper gibs are made .008" per inch. If you have a milling machine you can mill cast iron straight on one side and then swivel the cast iron plate over to mill the taper.

 

[Larry$]

then swivel the cast iron plate over to mill the taper.

"Swivel"? I was thinking attaching it to a steel plate then shimming to the correct angle. Is that the same thing?
I got some feeler gages this morning. I tried to get the gibb loose but no go. I had a jack supporting the load of the motor and gear case. The gibb has a notch in the part that sticks out. The machine has a stud with two larger diameter "nuts" that fit in the notch and top of the gibb to make adjustments. The plastic just gives. I'll take another pass at it tomorrow. Unless I can get the gibb to slide up there is no way to measure the space @ the bottom. The problem with the plastic is "stick/slip" motion. There is no play that I can detect.

I have a gibb out of an old machine, not cast iron, seems to be steel. Won't fit my cold saw but is the reason I was going to use steel. Another reason is the notch that adjusts the gibb on the saw looks like it would break off if it was cast. Would brass be better than steel? If cast is the only good solution I'll order some. I'll post photos when I get home.

 

[Richard King 2]

You can do it anyway you want to do it. Ive done it both ways. both work.

You know communication on the internet is hard for you to understand what I am saying and what your telling me. The plastic may be Turcite. Photo's. will help a lot

 

[Larry$]

Best I could do to show the gibb. You can see the adjusting notch.

The plastic may be Turcite. Photo's. will help a lot

The gibb is black plastic that had been "recycled" from something else, there are odd screw holes in it. In the bottom of the gear case photo you can see a screw holding a wiper on and just behind that the bottom of the gibb. The dovetail gibb photo shows it's notch and the top adjusting "nut" with the other "nut" in the notch back side. 3rd photo shows the tight space under the gear case.

 

[Richard King 2]

I just spent 2 hours researching IPB Corporation of Wabasha MN - Cold Saw info. Much more then I ever wanted to know. Seeing it is a holiday weekend I can't call anyone. I know the Owner of Gladwin Machinery in Minneapolis, MN who buy and sell metal fabrication machines. I'll call or drive over to see them on Tuesday and see if they have a manual of the machine. From the photo's it looks like there is a cover plate missing that the gib screw gib screw attaches thru . The round nut is for adjustment and the hex nut is a jam nut. If I were you I would take apart the saw slide and clean it. The machine is not a precision machine, but from the little I can see of the slide it looks like it needs a good cleaning and stoning. It appears the gib is out of adjustment and a shim behind the gib would be all you need to recondition the slide gib. It is common in the machine rebuilding trade to epoxy a phenolic fiber shim or a brass shim behind the gib and no need to make a new gib. It appears from my research IBP is no longer in business, but the owners are still living in Wabasha. It also looks like the company may have been sold to an Italian company who makes metal Fab machines. It looks like the design is sound and has oil lubrication tubes. More info later. Rich

 

[Larry$]

Thank you, When I had the machine apart I cleaned the dovetails with mineral spirits then coated with oil way oil before reassembly. I didn't stone them. A case of not knowing that I should have. There were no obvious nicks/burs. On the photo posted: https://www.hobby-machinist.com/threads/cold-saw-rehap.93741/#post-866880 you can see a blue arrow I drew on it pointing to the notch that the lower "nut" engages to raise the gib. But the plastic just wants to crush instead of moving. Too bad I didn't photo the gib while I had it apart. It appears someone machined it with a chainsaw. There are a lot of tapped holes in the top of the castings but nothing was there when I got the machine. The machine cuts very nicely. Faster and far smoother than a bandsaw.

The company I got it from TMCO closed a division that had gotten the assets of National Mfg Co. Lincoln, NE. National's name is on on the blade guard. National was in business when I was in grade school, I'm 79!

 

[Richard King 2]

It would help if I had a blue print. I am trying to help you, Not knowing is difficult. I am familiar with all sorts of tapered gibs though and assembling them when rebuilding machines. Before I made a new gib I would first try to figure out if applying a shim to either side would help. A quick method to figure out how much you need is to do what I wrote about before. Set the gib where it would be when new and slide in feeler gage on both ends so they are snug. Depending on the thickness would help in making the decision. I have glued Linen Grade Phenolic on the backs of gibs. It sounds as if the plastic shim the former owner used some sort of make shift shim and didn't glue it on and it moves. In other applications is to use a Teflon product called Turcite / Rulon or Garlock/ Garlock is black or a deep brown color. the others are usually aqua color. They are glued on with Epoxy Glue. And the part it is glued to is roughed up surface that could resemble a chainsaw as you spoke of.

You can make a new gib, but on 95% of all machines I rebuild I do not make a new gib if I can apply a shim on one side or the other. On the wear side we call it a "wear-strip" Many machines are made new with wear strips. Also that machine makes a lot of small chips and the mfg. would not leave the top exposed so those chips could fall down there to wear the ways. There must be some sort of cover that bolts on there. If you want me to help you further I will. If you have a plan and don't need anymore help I will stop.

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[Larry$]

Richard, Thanks for the help. The plastic gib is one piece, has never been laminated. It hasn't worn down in thickness, there is no room to add on . When I reassembled the machine I had moved the gib up slightly to make it not quite so tight. It is still tighter than I'd prefer. I put way oil on during assembly and when I was testing the oil pump. There is a wiper on the bottom and you are correct that there should be some cover on the top. A parts diagram would be nice but I will cobble together something of a tall 2 piece sliding cover. Maybe I'll cast one in aluminum. I think I'll try to get good measurements and make a gib out of the recommended material, cast iron.

Since I'm a long way from being a machinist I thought about how to get a fit by trail & error. Trap, screw the extra long cast iron blank on a sturdy steel support that is well supported & clamped from the side. Progressively shim one end and shell mill until when test fitting, it will drop down into the space with no clearance top or bottom. Support the gear case on blocks. Do plenty of wiggling and tapping with a mallet. Mark for the adjusting slot while gib is in place. A real machinist would just measure the space and mill to that size.

I'll photo my setup for your critique. Would you tell me how to improve my result? This is a prime example of "should have done it correctly in the first place!"