I Cut in to the Compound on my Lathe

It's one of those mistakes you learn from. Back several years ago I was making a back plate for a new chuck. At the time my only lathe had change gears. I read the chart, selected the gears, and set everything up for cutting 1 7/16-12 threads. Everything went according to plan, and after several cuts I made a final finish pass. The threads looked like they were straight out of the factory. I was so proud of my self my right arm grew 6 inches just from patting myself on the back. I took the back plate out of the chuck, removed the chuck and attempted to screw on the new back plate. As hard as I tried I couldn't make it fit.

I measured the thread angle and depth until I was blue in the face, but still couldn't find the problem. As a last resort I got out the thread gauges and stuck the 12 tpi one into the threads. Close but no cigar. I measured in several different places with the same results. I went through a number of pitches and finally found the one that fit. It was 11 1/2 tpi. I had inadvertently grabbed a wrong gear and spent an afternoon making a worthless part. To this day I keep the part in prominent view so I can remind myself to double check everything before making a cut.

At the time I had never heard of an 11 1/2 tpi thread and had no idea what it would fit. Just last year I needed to make an adaptor from a garden hose to pipe thread. Guess what, a garden hose fitting is 11 1/2 tpi. You live and learn. Fortunately you made a mistake that only caused a cosmetic blemish. It may have been the first, and hopefully it will be the last.
 
Forget the ding! What are those ghastly scratches I see next to the tool post? :oops: With a distraction like that staring you in the face, it’s no wonder that you inadvertently ran the compound into the workpiece.
<sarcasm off> ;)

As for the ding itself, smooth it out as best you can and if anyone asks, tell them it was needed for extra clearance on a special one-off project. Now get back to making chips. :encourage:

Tom
 
All good replies, except the welding one. I hate to say it, but it will get more dings with time. Just the nature of tools. Powerfeeds have a way of doing such things. Keep a hand on the control and feed the last little way by hand. Use the $ you considered spending on a shinny new part for more tooling.
 
I was so upset when I gouged my mill table I bought a brand new table for 600.00. It has been leaning on the wall for 5 years, I never put it on. ZH!t's gonna happen.
 
Sorry to hear about this, Erik.

You went into debt to buy your dream machines and now you've gone and damaged it, all because of your own stupidity, right? It's like parking your brand new car in the farthest corner of the lot to make sure some bozo doesn't park next to you and ding your door, only to open your door into a steel post you didn't notice. Been there, done that.

I get it, trust me, I get it. As you can see, most of us get it. I'm sure you've heard of the Arc of Shame and this is exactly what that is, or at least part of an Arc. In this hobby, there are those who have an Arc and those who will have an Arc; that's just how it is. I have an Arc on the face of the cross slide of my Sherline lathe. I got too close while trying to face off that last thou, even knowing the chuck was close to the cross slide. I got that last thou but after over 25 years on that lathe, I also got an Arc. You go through that period of self-flagellation but you eventually get over it and learn to be more careful in the future.

My suggestion is to let it go for now. Don't go ordering parts. Instead, go make more stuff on your still beautiful lathe and give this some time. Eventually, the lathe will have scratches and dings here and there and that little ding won't seem like such a big deal anymore. The lesson will stay with you for the rest of your life and that will make you a better machinist.
 
erikmannie said:
I bought this PM-1660TL new 4 months ago.

This was obviously 100% my fault. I had the compound set at 37 1/2°. My plan was to turn, groove & then cut the taper.

The workpiece was 4” pipe. As I was turning (on power feed), the pipe rotating at 180 RPM collided with the compound.

Precision Matthews has replacement parts for all their machines. This damage is only cosmetic, so there is no emergency. The gibs are probably hand fit, so I will have to consider that.

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Ooops, sh*t happens.

Good thing lathe still works fine, better that you aren't injured either.

I'd TIG in a bit of bronze and file flush if you're really worried about the cosmetics.
 
I agree, just deburr it, and don't fret over it; nearly every other lathe that you will ever see will have the same battle scars. Any person that will say that they never had such a thing happen to them Are very likely not being completely honest. If you want to go the JB weld route, I'd suggest drilling and tapping a hole in it and inserting a small screw to anchor the JB. I definitely would not weld/braze on it.
 
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