ShopMaster Tri-Power Locked Up in Y-Axis

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toddalin
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ShopMaster Tri-Power Locked Up in Y-Axis

Post by toddalin »

The other day I was just getting the CNC to operate and was using the Y-axis power feed (without the CNC) to free up the mechanism and the table jambed about 0.6 inch before the end of its travel (toward the back) and I instantly stopped the feed.

While the slotted shaft and gear arrangement is cool, it does/did seem to have lots of backlash. Now I can't get anything to move in the Y-direction because I can't turn the crank and the power feed won't back it out.

I've tried to disassemble the front around the screwshaft to try to pull the gears apart, but find that I'll have to get a slide vise grips to get the locating pins out... if I'm even going about this the right way at all. Being located with the back of the machine near the wall is no help either.

Does anyone have any experience in this area to free the axis and/or have an exploded view of the table assembly? It sure would be nice to get this thing running. :cry:
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ctwo
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Re: ShopMaster Tri-Power Locked Up in Y-Axis

Post by ctwo »

can you loosen the gib, help the table by pulling or using a scissor jack or wedge?
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toddalin
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Re: ShopMaster Tri-Power Locked Up in Y-Axis

Post by toddalin »

I don't think so and access is very limited. :(
Torch
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Re: ShopMaster Tri-Power Locked Up in Y-Axis

Post by Torch »

Detailed photos might help others see possible solutions.
toddalin
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Re: ShopMaster Tri-Power Locked Up in Y-Axis

Post by toddalin »

I was able to remove the table and fix the problem with the Y-axis. The table had come to the end and then started to pull the thread forward locking it forward inplace. When I removed the table and released the gearing, it freed up.

The problem is that the manufacturer has a scale on the table that goes 5" in either direction from the Zero point. But they mounted the scale 1/2" off, so it only goes to 4.5" in one direction, but goes off-scale to 5.5" in the other direction. So, when the power feed hit 4.5" it locked up when I thought it still had 1/2" to go. :evil:

That then tore up the "dogs" in the transmission and I hope I can get a replacment.

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TomB
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Re: ShopMaster Tri-Power Locked Up in Y-Axis

Post by TomB »

JT at Shopmaster will sell you the hubs for what seems like too much, but they are sintered and probably expensive to make. I have the same machine and have bought several of the hubs and and had my machine apart numerous times. The plus and minus 5" gauge is probably correct but the table was not put on the lead screw correctly. When you screw the two round anti-backlash nuts onto the lead screw keep them as close to the back end of the acme as you dare. Then push the table and clamp block onto the anti-backlash nuts, and note where the indicator is with respect to the gauge. It will probably be off by 1/4 to 1/2 and inch so turn the two anti-backlash nuts in or out that amount. Put the table back on and check its travel. The travel will probably be centered on the scale.

I'm more confused by what you think pulled out to lock your table. The lead screw is locked in place by a pair of thrust bearing and if everything is there it can't move. However, the lead screws caries the bevel gear that links it to the matching bevel gear on the slotted shaft. If the lead screw did move in and out that pair of gears would probably jam as you describe. I am not at my shop and I don't have a picture that shows how it should go together but I've attached one with it disassembled. You can see the end of the table lead screw, one of the two thrust bearings (two races and a ball bearing cage) and the bevel gear on the lead screw. (The picture was taken because I was trying to show a looseness related to the bevel gear on the grooved shaft, so it conveniently comes with a feeler gauge pointed at it.) When the shaft is installed correctly the thrust bearing shown pushes up against the inside of the dirty yellow boss. A second trust bearing then slips over the end of the lead screw and it is then locked in place with a nut and washer that goes on the front end of the lead screw. If you don't have all those parts I can't see how the machine would begin to work correctly.

Tom
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toddalin
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Re: ShopMaster Tri-Power Locked Up in Y-Axis

Post by toddalin »

JT has not responded to my emails. I guess I'll have to try calling him.

The coller for the lead screw was perfectly centered on the table tensioning clamp with maybe 1/16" of the collar to either side of the clamp. To get almost 3/4" difference would require that a portion of the collar would be beyond the clamp. The collar would then bottom out to one side and the table to the other I guess.

What locked up was that when the table "bottomed" at the back this pulled the lead screw forward. What was actually binding was the cog gear for the Y-axis against the back of the table mount. I undid the bolt in front and this didn't free up anything. After I pulled the table, I undid the bolt on the cog gear, and this freed up the table coller that was bound against the inside back of the table. I probably didn't need to pull the table and between loosening the front bolt and cog gear would probably have done the trick.

I couldn't back it out by hand because it was jambed to tightly, and because the hub to the gear had snapped, I couldn't use the power feed to back it out.

At this point, I removed the pointer arrow, cut it down (because it is right next to the tensioning bolt) and used so CA to glue it so the scale centers. :roll:
TomB wrote:JT at Shopmaster will sell you the hubs for what seems like too much, but they are sintered and probably expensive to make. I have the same machine and have bought several of the hubs and and had my machine apart numerous times. The plus and minus 5" gauge is probably correct but the table was not put on the lead screw correctly. When you screw the two round anti-backlash nuts onto the lead screw keep them as close to the back end of the acme as you dare. Then push the table and clamp block onto the anti-backlash nuts, and note where the indicator is with respect to the gauge. It will probably be off by 1/4 to 1/2 and inch so turn the two anti-backlash nuts in or out that amount. Put the table back on and check its travel. The travel will probably be centered on the scale.

I'm more confused by what you think pulled out to lock your table. The lead screw is locked in place by a pair of thrust bearing and if everything is there it can't move. However, the lead screws caries the bevel gear that links it to the matching bevel gear on the slotted shaft. If the lead screw did move in and out that pair of gears would probably jam as you describe. I am not at my shop and I don't have a picture that shows how it should go together but I've attached one with it disassembled. You can see the end of the table lead screw, one of the two thrust bearings (two races and a ball bearing cage) and the bevel gear on the lead screw. (The picture was taken because I was trying to show a looseness related to the bevel gear on the grooved shaft, so it conveniently comes with a feeler gauge pointed at it.) When the shaft is installed correctly the thrust bearing shown pushes up against the inside of the dirty yellow boss. A second trust bearing then slips over the end of the lead screw and it is then locked in place with a nut and washer that goes on the front end of the lead screw. If you don't have all those parts I can't see how the machine would begin to work correctly.

Tom
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