LATHE GAP BED REMOVE/REPLACE

[george wilson]

The gap fitting back into place has nothing to do with how many tools you have on hand. As I mentioned,the gap block on the 16"lathe we had at work sprung UPWARDS a bit when removed,and simply would not quite blend back into the ways when replaced.

I have been using lathes since 1959,and I can tell you it is just a GAMBLE on Asian made lathes as to if the gap piece WILL go back perfectly after removed. The cast iron may not be perfectly seasoned. Or it may have developed stress when machined,INDUCTION HARDENED and ground in situ. They don't check those things in Asian lathes at the factory. The lathe at work had about a .015" misalignment when replaced. The front way on the gap block was about .015" TOO HIGH . I'd say the gap block cupped a bit INWARDS when removed,causing the front way to be too high. So,not caused by loose debris under the gap at the factory. It would have been MUCH easier to deal with had the gap gone back in a bit LOW! Possibly,I could have solved the problem by drilling and tapping extra bolts in the gap block,close to the edges,to draw it back down to level.

The same model,I have at home,fortunately went back perfectly. I won't say I was afraid when I removed it,after having the problem with the identical lathe at work. I WAS concerned,though. I knew it was a gamble. I had had the lathe since 1986 without a job coming along that required removal of the gap block. This was about in 2014.

Fortunately,we got a new,larger lathe at work before I got to dealing with the gap piece. No budget at home for a new lathe,though!

If there is stress in the gap block,it will not quite fit back when replaced. It can be a real PAIN to try re machining it,too. I can handle it,but many may not be able to. It can be a complicated item to deal with.

 

[dlane]

Now what happened

 

[Tozguy]

The gap in my lathe has never been removed but I fail to see why it couldn't go back properly in its place until I try it. Fear of it not going back in would not prevent me from pulling the gap out to do a job. I believe and respect other person's experience but in this case it is not an operation that is guaranteed to fail. Where would I be today if I had not taken some calculated risks in the past?

Why shouldn't we encourage someone to remove the gap piece if they want to and then support them if they hit a snag getting it back in place?

 

[Superburban]

Removing the gap was one of the first things I did with my Shopfox. I figured if it would not go back perfectly, then I would try out their warranty. I did measurements from as many directions, and ways I could think of, then after replacing the gap, checked them. Had to loosen it once, and give it a few taps with a lead hammer, then every test was spot on.

 

[george wilson]

It really is a gamble with Asian lathes,Tozguy. If you fail to see why it wouldn't go back perfectly,re read some of the posts,including my actual experience in post #4. We can certainly support others who have problems with their gap pieces not fitting back perfectly. But,we aren't there to refit them if they get sprung. Depending upon HOW the gap pieces get sprung,it can be a big problem trying to get them refitted perfectly. Might just be about impossible in some cases.

I am sure the problem stems from the gap pieces being screwed down in the unfinished lathe bed,then machined with the rest of the bed,and induction hardened IN PLACE with the rest of the bed. This can easily cause internal stresses to build up,which are released when the gap piece is unbolted. The Asian castings may not have been seasoned carefully enough?

Superburban,you got lucky! Trying out their warranty could have involved you packing the lathe up and paying to send it back to them! I know a professional machinist at NASA who had to do just that for a Jet lathe he bought for his home shop.

 

[Tozguy]

George,

I have already read the posts above and don't need to do it again. I understood the first time you explained your experience. I am fully aware of the shortcomings of my budget lathe and the potential problem of refitting a gap piece. If I ever do have a problem with it I am confident that there are solutions that don't involve shipping the lathe back. As you mentioned above

The same model,I have at home,fortunately went back perfectly.

I don't think that Suburban got lucky so much as you got unlucky with the lathe at work. But then luck is just a matter of perception.

I am not about to avoid using a feature on my lathe based on what I have read here so far.

 

[Superburban]

So what would be the difference in the production of a good gap bed lathe, and a bad gap bed? I can't imagine even American companies making the gaps separately, and to exacting specs. Maybe hardening the ways separately, then inserting the gap, and grinding the ways? That's not overly time consuming, that would preclude an Asian company from doing the same.

 

[Superburban]

Superburban,you got lucky! Trying out their warranty could have involved you packing the lathe up and paying to send it back to them! I know a professional machinist at NASA who had to do just that for a Jet lathe he bought for his home shop.

That's true, but I originally bought the lathe for the ability to turn larger flat stuff, especially flywheels. But later picked up a shoptask drill/mill/lathe combo, which has a 17" lathe capacity, and enough quality for flywheels.

 

[george wilson]

Tozguy,I DID use the gap feature on both of my 16" Grizzly TAIWAN made lathes. I had gone to Williamsport in 1986,to Grizzly and hand picked 2 identical 16 x 42" lathes.

So,I had a 50% success rate in not having my gap pieces fail to fit back even on TAIWAN made lathes. I am lucky they weren't Chinese,though I hear the Chinese send castings to Taiwan. I don't know if they did that back in 1986. We got a Romanian made ProMaster from MSC to replace the Grizzly. Its gap did fit back properly. Unusual,because there were so many OTHER faults with that lathe!!

I have to say,your saying " As crazy as it may sound to you" sounds a bit contentious,since I had already stated clearly that I DID remove the gap pieces in both the Grizzly lathes. The one at work came out to handle a 20" bandsaw wheel that was warped in welding(by someone else). The one at home had to turn a 4" thick piece of maple 24" across its diagonal. Barely made it!

I don't see how luck is perhaps just a matter of perception. Either the gap piece goes back perfectly or it doesn't! And,I am exceedingly careful about getting surfaces CLEAN when fitting things in a vise,or a gap,etc..

I think the quality of Taiwan made machines in 1986 was good,since I still have my 1986 Taiwan made Bridgeport clone. Still in perfect condition,with no repairs ever made necessary. I had also bought the same machine for the toolmaker's shop,and it is still in great shape,and has been used a lot more than my mill at home.

That was quite a trip,when I bought 2 lathes and 2 mills.

 

[george wilson]

Superburban,Better quality machines might have their castings seasoned more carefully than in Asian machines. That is about all I can think of in regard to stabilizing gap piece castings. I had no trouble replacing the gap piece in a Promaster lathe we got to replace the Grizzly. It cost about 4x the price of the Grizzly. Unfortunately,for many of us,if we fail to get a perfect OLD USA or European made vintage lathe,the best we can do budget wise is get an Asian made machine.

My Grizzly is a very accurate lathe,but I am fortunate that my gap piece did fit back O.K.. Also,the motor on the one at work shorted out across the bearings. The electricians said it was a poorly made motor. I know they don't dip their armatures. Mine still works.

Perhaps Tony has a better idea about how gap pieces could be made more reliable?