Slotting Saw Arbor for Unimat

I had been using a commercially available slotting saw arbor (Enco part 370-9050) held in a 3-jaw chuck for cutting slots with my Unimat milling head (see Homemade Lathe Modifications ). I made a new slotting saw arbor that threads directly onto the spindle.

The arbor uses 12L14 steel hex bar that is 1.25” across the flats. One end has an internal thread of M12X1 to fit the Unimat spindle and the other end has a ½-20 internal thread for a flat head hex screw. The hex shape plus two holes for 4mm tommy bars allow easy setup and removal. I use mainly 1/32" and 1/16" thick HSS slotting saw blades with 0.875” hole and keyway slot. The nose of the arbor has a 0.8745” diameter step and a matching end cap that retains the slotting saw blade. I used part of a 0.070” dia. hardened pin from an old minicomputer paper tape punch for the blade retaining pin. Also removed 0.050” from the top of the flat head hex screw to allow it to seat below the end cap.

By the way, for the Unimat purists, the arbor and end cap could have been made completely on the Unimat like I did for the milling cutter holders (see Homemade Milling Cutter Holders ). However, this time I used my 12” swing geared-head lathe to machine the countersink on the end cap but the rest of the arbor was machined on the Unimat.

Thanks Paul Jones! We've added your Slotting Saw Arbor to our Milling category, as well as to your builder page: Paul Jones' Homemade Tools. Your receipt:

<div id="blocks"> <div class="block b1 pngfix"> <div class="bimg"> <div> <a href="http://www.homemadetools.net/slotting-saw-arbor"><img src="http://www.homemadetools.net/uploads/133050/slotting-saw-arbor.jpeg" /></a></div> </div> <div class="head pngfix"></div> <div class="left pngfix"></div> <div class="right pngfix"></div> <div class="blockover b1 pngfix"> <div class="title"> <a href="http://www.homemadetools.net/slotting-saw-arbor">Slotting Saw Arbor</a> <span> by <a href="/builder/Paul+Jones">Paul Jones</a></span> </div> <div class="tags">tags: <a href="http://www.homemadetools.net/tag/mill">mill</a>, <a href="http://www.homemadetools.net/tag/arbor">arbor</a></div> </div> </div> </div>

Nicely done Paul.

very clean, nicely done

Beautiful work and finishes, Paul. All that dampening work you did really paid off even on Leadloy! The internal M12 & 1/4-28 threads are gorgeous. Did you do those with a tap or SP them? Also admired trimming the head of the FHCS for the recess and re-purposing the pin! Great build, well thought out and execution! Thanks! ~PJ

PJs,

Thank you for the compliments. Yes, all the anti-vibration work on the 12" swing gear-head lathe has proven successful. Turning 1018 CRS would have looked just as nice as the 12L14. I used a single point tool for the 1/2-20 threads and a tap for the M12X1. My lathe quick change gear box can select metric threads but I am still missing a 30 tooth conversion gear and will have to modify it similar to the my 40 tooth replacement gears ( Homemade Change Gears ).

Thanks for reminding me about the FHCS. This was another part not totally machined on the Unimat. My 7" swing mini lathe is now dedicated with an ER32 collet holder and is used primarily for collet work like trimming the head of the FHCS.

Thank you,
Paul Jones

My bad on the 1/2-20...trifocals (knew it was fine pitch from the pic..wrong ball park), but great threads in both cases. I've wanted an MT3 ER set for mine for quite a while now for more precision. Been curious about the LMS set...good price. Nice to know you still have a purpose for the peanut.

Thanks for the link...Really nice gears you put together...sorry I missed it before for some reason. That is quite a range of threads! ~PJ

PJs,

I just reviewed my old article about modifying the 40T gears and looked again at the photo of the lathe quick change gear box diagram. I wish I had looked a little closer at the left-hand side diagram because the I could have cut a 1mm pitch thread with the existing 40T gears but have to reverse the lower 40T gear to get the 127/120 ratio.

The 30T gear just provides more typical metric thread pitches. The only challenge with cutting metric threads on this lathe is that the split nut has to stay engaged and the motor reversed for each threading pass.

Paul

Went back and looked also...basically it looks to me if you had a 30 and 32 you would be set to do any metrics. Personally I haven't used but about 5-6 on that list but the comfort of being able to maximize the machines capability is comforting...to me anyway. That is a challenge with the split nut/reverse under power but I have been considering after my latest foray into SPT to finally build a crank for mine and do them by hand...obviously long threads would be a challenge but most of my stuff is an inch or under. Your big lathe may be more problematic to reach though. Thanks again for sharing! ~PJ

PJs
The new slotting saw arbor is the better and safer way to do this work on my small Unimat. Previously, I had used a commercially available slotting/slitting saw arbor held in my Unimat 3-jaw chuck but there was no way to prevent it from coming loose. I do not recommend doing the cutting this way as shown in the photo. The new arbor will make this work safer to do.
Paul

Definitely safer...a lot of spun mass there...wouldn't be pretty if something went hinky. Your new arbor is a beaut, and will be much closer coupled than the old way! Thanks for the comparison. ~PJ

Quote:

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Originally Posted by Paul Jones

PJs,
The only challenge with cutting metric threads on this lathe is that the split nut has to stay engaged and the motor reversed for each threading pass.

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Well, although it's the inherited wisdom, it's not exactly true, at least in some cases. Consider the following truism...

If we disengage the half-nuts and move the carriage a distance to the right that is an integer multiple of the thread pitch AND also an integral multiple of the leadscrew pitch, we can reengage the half-nuts without losing registration on the thread we're cutting.

Such a movement, once calculated can be accomplished accurately in a variety of ways including a DI and a "stick" cut to the correct length working against a stop fixed to the lathe ways.

If you're interested in trying this, there's a program (STICK) on my site that will calculate the required displacement.

Sometimes the required length is too long to be practical and one will have to resort to the "keep the half-nuts engaged" method but when it does work it's a real time saver.

Here's an example output from STICK...

THREAD CHASING OFFSETS

Type of leadscrew thread (M)etric or [I]mperial? I
Leadscrew pitch [8 tpi] ? 8
Type of thread [M]etric or (I)mperial? M
Pitch of thread being cut [1 mm] ? 0.5

Move carriage 2.500 in = 63.5 mm to right to recapture thread