Lathe Tool Rests ... What is This?

[Cheechako]

I have a Mark V 510 from about 1990's. I started bowl turning, so I purchased the upgraded tool rest package for about $100 and a set of lever knobs to make quick tool rest adjustments and exchanges.

The new tool rests that arrived are machined differently from the original that came with the machine. These new parts have an expanded nubbin at the bottom of the shaft (marked in red) which is not there on the original tool rest (on the left in photo).

Or maybe a better description is that the middle of the shaft has been recessed.

Either way, this new shape for the tool rest shaft creates a big problem for me. Now, I have to unwind the lever knob multiple turns in order for the nubbin to escape the set screw. Lever knobs are not designed for rotating, say, 3 full turns. In order to swap out the tool rest, I must manually untwist the set screw using a star driver in one hand while pulling back on the lever knob with my other hand. What a pain to do, and defeats the purpose of the quick adjust lever knob entirely.

Anyone else notice the same thing?

What is the purpose of this recess in the tool rest shaft?

The SS is a great turning machine, but the tool rest system is no where near as versatile and easy to adjust as a conventional banjo. I was hoping to overcome some of those deficiencies by switching to the lever knobs, but the new tool rest shafts have frustrated my intensions.

What can I do? Should I take the new tools rest parts to my grinder and remove the metal labeled in red below? (another painful step)


Thanks

[BuckeyeDennis]

Set screws are notorious for making burrs on shafts. Which can then cause the shaft to bind in a mating bore. The purpose of the recess is to prevent any such shaft burr from binding on the inside diameter of the mating bore.

Hardened screws that bear on a softer shaft without such a recess are a recipe for jammed assemblies. When I see such an arrangement, I generally grind a smooth flat on the end of the hardened screw.

[Cheechako]

Great explanation !! Thanks. Now I understand the purpose of this recess.

I can easily grind the set screw flat to reduce burring. But how can I facilitate quick swap out of the tool rests without being forced to use the star drive to unwind the set screw?

When watching turning videos using conventional banjo's, the turner can quickly adjust the tool rest with a quarter turn of the lever knob. I upgraded to get that functionality, and now have a new problem....

[RFGuy]

Said a different way, you are using the standard tool rest arm and it doesn't really work well with quick release knobs because you don't have the clearance. IF you had the UTR (Universal Tool Rest) from Shopsmith, using quick release knobs would be no problem, i.e. you wouldn't need another tool to more quickly turn that quick release screw. See pic below for the difference in the tool rest arm on the UTR and how you have effortless 360° rotation possible on the quick release handle for the tool rest arm. I have the UTR and it is well worth it if you do A LOT of woodturning on a Mark V. Of course, the price has ballooned to $400 today, so more difficult to justify. I bought it for around $250 just a few years ago.

P.S. Don't forget to apply paste wax to all of the tool rest or it will rust as shown.

UTR_2.jpg (116.79 KiB) Viewed 473 times

[chapmanruss]

Cheechako,

Lastly you asked,

What can I do? Should I take the new tools rest parts to my grinder and remove the metal labeled in red below? (another painful step)

The answer is no. Grinding off the bottom of the post would leave it poorly fitting in the Lathe Tool Rest Arm.

Due to the design of the Standard Lathe Tool Rest Arm having the Set Screw for the Tool Rest in line with the arm does make using the Lever type Lock more of a hassle with only a half turn at a time. As RFGuy suggested changing to the Universal Tool Rest with its design makes turning the Lever type Lock much nicer to use for changing the Tool Rests themselves. It does limit the post lock to rotate the Arm to a half turn which is not as much as a problem. I have a Universal Tool Rest and I prefer it to the standard Lathe Tool Rest Assembly.

BuckeyeDennis answered the reason for the change to the posts of the Lathe Tool Rests themselves being made. It's no fun having any part bind because of burrs on any shaft.

[JPG]

Rube Goldberg 'solution'.

Cut strips of aluminum pop can to fill in the recessed portion of the shaft.

[Cheechako]

I have a Universal Tool Rest and I prefer it to the standard Lathe Tool Rest Assembly.

I have been eyeing the Universal Tool Rest as a solution. I can only find limited information on how it is mounted onto the SS carriage. It appears to be bolted down with some kind of a U-bolt system.

Do I need to remove the UTR to switch back to the table saw mode?

One of the features I really like on the SS is the drill press, with its large table, included fence system, etc.

If I bolt down the UTR, am I going to add so much weight that its now a problem to lift up into to the drill press?

[chapmanruss]

The Universal Lathe Tool Rest is attached to the Carriage with the Mounting Plate Bar (1) under the Carraige and two long bolts (4) to hold the Mounting Plate (3) in position. Below is a picture of the parts list and drawing.

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UTR_diagram_small.jpg (154 KiB) Viewed 287 times

.
It is better to remove the entire UTR for other functions. Installing and removing it is very easy and does not require any special alignment. Just attach the Mounting Plate (3) on the center of the Carriage.

Leaving the Mounting Plate (3) in position on the Carriage limits the Table Adjustment some and the weight of the Plate adds more effort needed to raise up to Drill Press position. In Drill Press position the extra weight of the Mounting Plate puts extra force against the Carriage Lock. Leaving the Mounting Plate attached to the Carriage has the Carriage Bolt (2) used for locking the Support Base (6) in position still coming up through the Plate.

One of the pluses of having the UTR for turning is the weight it adds to the Shopsmith with those heavy cast iron parts.

[RFGuy]

As Russ showed, just two bolts (4) have to be removed and the entire UTR can be removed. Those two bolts clamp the UTR to the carriage with the mounting plate bar (1). It really is easy to take off and remove. It is heavy though and it does take some time to remove, a relatively short time, but then again changeovers take time on a Mark V anyway. If you decide to get one, I don't think you will be disappointed. I much prefer woodturning on my Mark V with the UTR. I just wish they weren't so expensive from the mothership now.

[Cheechako]

Thanks to everyone for their advice. The UTR may be in my future, as I get more turning experience.

I remain concerned about the added weight, esp in the drill press position. I can imagine a scenario where the carriage brake starts to slip and the table drops while applying downward pressure on the quill when drilling. The added weight on the carriage brake, for me, is a downside. Plus, I know I will use the drill press less often if the added weight discourages me from lifting the SS into the drill press mode, or I have to unbolt the UTR each time. I would also need a place in my shop to store the UTR between uses, etc. And of course the additional cost....

I came up with a compromise that suites me for now. I may have gone full renegade on this one, but here are the photos of my solution.

I just moved the position of the retaining bolt on the tool rest !!

RelocatedBolt1.jpg (224.16 KiB) Viewed 214 times

RelocatedBolt5.jpg (224.91 KiB) Viewed 214 times

RelocatedBolt6.jpg (256.33 KiB) Viewed 214 times

Now I can twist the retaining bolt in either direction without interference using only one hand. All the tool rest attachments pop right out, no issues. Easy exchanges. In my limited testing, the holding power is great. When the bolt is tightened, the attachments do not twist, turn, or come loose.

It is too early to tell if this is a final solution, or I will need another. It is possible that in some positions the knob will be inhibited by the tailstock, but I will need to test more setups to see if this is a problem.

Cost me about $2 and about 60 minutes to figure out how to do it. It works equally well with lever knobs or star knobs.

If anyone is interested, I have photos of how I drilled, tapped, and supported the new bolt position.

Just let me know and I can post the photos.

Thanks.