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9" SM Utilathe Restoration
- Thread starter YYCHM
- Start date
Brent H
Ultra Member
Hey Craig,
That style blade is designed to fit into a parting tool holder that is also tapered or dovetailed to that profile. That can be an issue for you if your holder is designed to hold just a flat blade. I ordered a blade and it came like that and I ground off the angles to make it flat and fit my blade holder more properly. Ticked me off as the taper/angle was not mentioned. Lots of things like that to watch out for.
That style blade is designed to fit into a parting tool holder that is also tapered or dovetailed to that profile. That can be an issue for you if your holder is designed to hold just a flat blade. I ordered a blade and it came like that and I ground off the angles to make it flat and fit my blade holder more properly. Ticked me off as the taper/angle was not mentioned. Lots of things like that to watch out for.
The blade came with the holder as a set and the holder has some peculiar angles to it. I can only assume it's all correct. It worked pretty well on my mini.
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That's the classic style that has relief on one side only & supposedly finishes the part on the zero clearance side. The top slop & point is intended to break through slightly ahead so the part comes off with little to no burr. But unless you have a rigid setup, they also can gave a tendency to drift & usually always that's bad news. I don't find that HSS finishes the face all that well unless all the planets align. I usually part with the expectation that I'm going to finish that face. The T style has side relief on both sides, the top edge of the T does all the cutting. I typically grind them square looking down at the top (neutral) so the chip curls straight back & it has the least propensity to wander left or right into the cut. The rake angle is a function of material, similar to regular cutting geometry.
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That tip back rake is going lower the tip some. I may have to modify my tool post to allow for adjustment.
That's where the adjustable dovetail toolposts are worth it. You preserve the rigidity of your blade clamping but just need to tweak the height up or down with the adjusting wheel. Adding shims takes fiddling & rarely ends up being as rigid. Don't assume the nominal blade height will work out the same as your previous setup, repeat the setup procedure. Remember its the point of the tool should be on center of the stock, the 9-o'clock position or using the vertical ruler method. Every time you regrind / extend / retract... the blade you need to reconfirm horizontal position & squareness. At least start there, you may find very slight variations improve the cut as Dabbler says.
That's where the adjustable dovetail toolposts are worth it. You preserve the rigidity of your blade clamping but just need to tweak the height up or down with the adjusting wheel. Adding shims takes fiddling & rarely ends up being as rigid. Don't assume the nominal blade height will work out the same as your previous setup, repeat the setup procedure. Remember its the point of the tool should be on center of the stock, the 9-o'clock position or using the vertical ruler method. Every time you regrind / extend / retract... the blade you need to reconfirm horizontal position & squareness. At least start there, you may find very slight variations improve the cut as Dabbler says.
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Finished up my Tool Post yesterday.
I was originally thinking 2 tool, but the milling was going so smoothly I went 4 tool. I'm loving 2 flute end mills. They seem to give me less grief that 4 flute for some reason. Ya, in hind sight now, I should have position the screws differently.
With the tool post finished I tried some threading. 1/2" 13TPI. I ran the machine at 180 RPM not wanting to crash the saddle, and that was more than quick enough for me. Can't picture running at recommended cutting speed, it would have traversed in the blink of an eye LOL. For depth, I took her down 0.01 per pass until the nut just started to fit and then 0.005 until she threaded on. This was my second attempt at threading ever. It went well, I re-entered the thread bang on every pass. Not having to fool with change gears is going to make threading a much more appealing proposition.
I was originally thinking 2 tool, but the milling was going so smoothly I went 4 tool. I'm loving 2 flute end mills. They seem to give me less grief that 4 flute for some reason. Ya, in hind sight now, I should have position the screws differently.
With the tool post finished I tried some threading. 1/2" 13TPI. I ran the machine at 180 RPM not wanting to crash the saddle, and that was more than quick enough for me. Can't picture running at recommended cutting speed, it would have traversed in the blink of an eye LOL. For depth, I took her down 0.01 per pass until the nut just started to fit and then 0.005 until she threaded on. This was my second attempt at threading ever. It went well, I re-entered the thread bang on every pass. Not having to fool with change gears is going to make threading a much more appealing proposition.
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So with all the grief I was having parting off, I decided to make a monolithic tool post replacement for the compound rest.
At 3" in dia I may have to thin it down some should I find space is tight. Should be rigid enough I would think.
In order to build the replacement post I had to replicate the mounting boss that is on the compound rest.
I managed to nail the replication pretty darn close. She fits nice and tight.
I'm wondering if this recess on the compound mounting surface is significant. Thoughts?
At 3" in dia I may have to thin it down some should I find space is tight. Should be rigid enough I would think.
In order to build the replacement post I had to replicate the mounting boss that is on the compound rest.
I managed to nail the replication pretty darn close. She fits nice and tight.
I'm wondering if this recess on the compound mounting surface is significant. Thoughts?
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DPittman
Ultra Member
To hold grease/oil??
I believe the recess is to improve the stability of your compound and move the load of the cutting forces out from the center to reduce the “rocking” tendency.
Above is a sketch of your assembly (I am doing this from memory). You have two brass wedges that come in from the side that engage on the tapered boss. They pull it into the bore and “lock” the compound at the set angle to the cross slide.
schematic A) shows the forces without the recess (the bending is greatly exaggerated). Note where the opposing resulting force acts: very close to the applied force and the moment arm is very short.
schematic B) shows the forces with the recess: the moment arm is much longer.
Imagine your tool sitting on top of the compound at some distance from the center. You can appreciate that arrangement A) is way less stable than arrangement B)
In the picture above, bottom right, you can see a grinding wheel hub nut. It has a very wide recess to move the clamping force 1 3/8” out from the center to support an 8” grinding wheel. It also uses a washer (shown to the left of it) to further distribute the force and help stabilize the wheel.
Same principle in your compound case.
I would machine the recess in your solid block. It would make things even better for not much more work on an already very good improvement.
Above is a sketch of your assembly (I am doing this from memory). You have two brass wedges that come in from the side that engage on the tapered boss. They pull it into the bore and “lock” the compound at the set angle to the cross slide.
schematic A) shows the forces without the recess (the bending is greatly exaggerated). Note where the opposing resulting force acts: very close to the applied force and the moment arm is very short.
schematic B) shows the forces with the recess: the moment arm is much longer.
Imagine your tool sitting on top of the compound at some distance from the center. You can appreciate that arrangement A) is way less stable than arrangement B)
In the picture above, bottom right, you can see a grinding wheel hub nut. It has a very wide recess to move the clamping force 1 3/8” out from the center to support an 8” grinding wheel. It also uses a washer (shown to the left of it) to further distribute the force and help stabilize the wheel.
Same principle in your compound case.
I would machine the recess in your solid block. It would make things even better for not much more work on an already very good improvement.
Does this sound right to you? I've always considered "forward" meaning towards the spindle. Do you agree?
On my Utilathe with the lead screw reverse lever set in one position, the power carriage and cross feed move in opposing directions? ie engaging the carriage power feed moves the saddle towards the spindle yet engaging the cross feed moves the tool post away from the spindle. Changing the lead screw reversing lever position just swaps the behavior.
Is this behavior correct? Is something installed backwards?
On my Utilathe with the lead screw reverse lever set in one position, the power carriage and cross feed move in opposing directions? ie engaging the carriage power feed moves the saddle towards the spindle yet engaging the cross feed moves the tool post away from the spindle. Changing the lead screw reversing lever position just swaps the behavior.
Is this behavior correct? Is something installed backwards?
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