This also moves the apron in the opposite direction. you can cut any standard metric pitch on your small Logan, Southbend or other quality lathe. It's so incredibly valuable I can't believe
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$C-. This assumes your tailstock is at about the right height. Let's say you're threading towards the headstock, up to a shoulder. This is performed by taking successive cuts with a threading toolbit the same shape as the thread form required. key is pointing the handle towards your belly button, then going 29 CCW. you're not cutting metric threads now, you will be sooner or later. negative rake situation, so the tool should be as sharp as possible, allowing it to shave that side slightly as the compound
The end relief angle varies with the hardness and type of material and type of cut being taken. If you were making lead
The ratio is 1.26984, an excellent match, but the gears are still quite large
shown. List the number of teeth on any non-standard
the rear position pointing backwards. 1.27027027 That's an error of 0.021%, which is only 0.0026" per foot. spindle stopped on the previous cut. reduction there, it has to be figured in. 0000000896 00000 n
The thread dial would have to rotate many turns to reach the correct starting point, and you have no
This angle may be from 5 to 30 degrees depending on the type of cut and finish desired. for specific dimensions. In the absence of an index chart showing gear combinations for various threads, it is necessary to calculate the proper gears to use for cutting threads. All that's necessary is a small squirt of way
The coast-down time of the lathe is
It may not display this or other websites correctly. 1. Use plenty cutting fluid for reaming. If I multiplied by 4 instead of dividing it would be in tpi, but since I multiplied by it is in pitch. The gear ratio has nothing to do with pitch or tpi until it is multiplied by one or the other. In this way you
If it started out at 0 it will now read 29. 5. The hole to be reamed with a machine reamer must be drilled or bored to within 0.010 inch of the finished size so that the machine reamer will only have to remove the cutter bit marks. Width of Flat = P / 8 = (1 / 8) x (1/10) = .0125 in. The thread dial will go a bit beyond the chosen number as the lathe coasts to a stop. Sawyer Tool Mfg. flat at the tip is rarely known to sufficient accuracy, at least by the hobbyist. and away on the tool holder, reducing or eliminating chatter since it's no longer pulled into the work by cutting pressure. If you lose the position of the half nuts on the
JavaScript is disabled. it isn't more widely described. I also have the gear quadrant (swing arm). Describe how to set the correct tool bit. Copyright 2007-2022 LittleMachineShop.com, 7x10/12/14 Mini Lathe (C2/C3) Accessories, HiTorque Large Bench Mill (SX3.5) Accessories, HiTorque Lathes, Bench 8.5x16/8.5x20 (SC4), Coolant Systems and Lubricants: Mist Systems, Videos, Books and Seminars: Machinist Books, Coolant Systems and Lubricants: Cutting Compounds, Mill: HiTorque Bench Mill (SX2.7) Accessories, Mill: HiTorque Mini Mill (SX2) Accessories, Coolant Systems and Lubricants: Lubricants, Lathe: 7x10/12/14 Mini Lathe (C2/C3) Accessories. most common Logan and Southbend lathes are 1:1. 12. Use plenty cutting fluid for reaming. Using the Center gage to position the tool for machining Threads. The forces on the gear train increase tremendously and broken gears
wear. Scribe it out, cut it out, file off the burrs and you'll have a
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Engage the half nuts to begin your first threading pass just as you always do. The usual tool post (and the
In simple gearing, an idler gear is used to transmit motion from the stud gear to the lead screw gear (Figure 8-8). When you adjust your gearing, there should be a slight
Clack! I have attached some photos of what I have to work with. Now I now the stand for inches pitch, Mmm is millimeters pitch, D.P. My guess is that they'd even stand up to moderate production
It only has the and it has pictures instead of numbers. Here's the 2 mm pitch thread cut on a short stub to prove out the gearing above. Watch for crud in the teeth and use a small stiff brush to clean out any chips or hardened lube. really practical for the hobbyist. You've installed the metric transposing gears and now think in terms of
Run the gears all the way around by hand to be sure there aren't any tight
The idler gear does not change the gear ratio. With just a few extra gears
trailer
to convert. They should be capable of standing up to high temperatures developed during the cutting operation. On the back of the gage
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gears. train. Contrary to everything I've said above, my tool will be almost
Flank: The surface of the tool which is adjacent to and below the cutting edge. metal gage with some 60 notches. Using only the compound micrometer, feed in .001 to .002 inch. more gear issues trying to understand the math, Thread cutting question. Is there any place that sells cheap blanks? lead screw. Compound gearing actually consists of two ratios whose product is equivalent to the total ratio as follows: When compound gearing is used, the ratio of the compound gears is usually 2 to 1, so that the threads are twice the number per inch as when simple gearing is used. The better gages were hardened and had precision lapped edges. If angle is over 30 degrees, the tool will tend to chatter. If the cutting action tends
This angle may be from 6 to 10 degrees. The same technique is useful for angle templates to grind tools where you want to
should have an adjustable stop screw. The half nuts pop open and you have semi-automatic threading on your simple manual machine. This angle must be measured when the tool bit is held in the tool holder. The angle formed by the end cutting edge and a line at right angle to the centerline of the tool bit. This is expressed as the following formula: For example, to determine the size of the stud gear and the lead screw gear required to cut 12 threads per inch in a lathe having a lead screw with 8 threads per inch, use the following formula: To cut 12 threads per inch, the spindle (or stud gear on an even-geared lathe) must make 12 revolutions to 8 revolutions of the lead screw. screws (known as "inch" or "imperial"). Another technique is the use of a spring tool. Choose 7x Mini Lathe for most 7x10, 7x12, 7x14, and
All Rights reserved. Using a layout solution, coat the area to be threaded. The traditional 127 and 100 tooth transposing gears are big and expensive. cutting very coarse threads, the forces on the gear train are low. 0000003484 00000 n
16. Set the depth for the next cut, just as you always do, and repeat the process until the thread is complete. Another possible pair is 80 and 63 teeth. Some switch all ranges within the gearbox and others shift both internal and external gears to change ranges. 6. Sherline uses this to good advantage. retailers and representatives some years ago, alas in days long gone. 391 0 obj
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use with little trouble. external gears and the ratios available within the gear box. When cutting inch threads with an inch lead screw you keep track of synchronization with the lead screw using a thread dial. You want just a bit less then half the thread angle, never more. As the wrench is revolved by hand, the hand reamer is fed into the hole simultaneously by turning the tailstock handwheel. flat the tip of your tool with a fine oil stone or similar. Chamfer the end of the thread to protect it from damage. Back rake permits the chips to flow away from the point of the cutting tool. 2021 Copyright Practicalmachinist.com. With that info, working out the metric pitches is reasonably easy. Continue this process until the tool is within .010 inch of the finish depth. reference for each pass. Back the tool out of the thread just as you always do, preferably while the spindle is still turning. diameter. It is necessary only to arrange the levers on the gearbox for the various threads per inch, as indicated on the index plate. Spring tools have also been popular for use with cutoff tools, since they also tend to chatter more often than
Figure 9. pitches you'll need compound gearing- another pair of gears to increase the division ratio. The following diagrams and formulas will be helpful when calculating thread dimensions. 4. might be a simple yoke, so the unit could be easily attached and removed when not in use. Measure this with wires or a pitch mic. On
7. Set the quick change gearbox for the required pitch in threads. few metric pitches that can be cut using simple ratios. spreadsheet described below should prove helpful, especially if your QC gearbox is the same or similar to the Logan arrangement. Lathe tool bits should possess the following properties. on the left side of the tool (as we look into the back side of the tool) will have to be greater than the angle of the thread. 19. To what angle must the compound be turned for Unified Thread? Various solutions have been applied over the years,
Changing these gears varies the speed that the lead screw turns in
If you have to thread to within 0.002" of a shoulder with a coarse thread,
Power is also limited to a safe amount- you're more apt to back off the cutting depth if you can't
Think about how annoying it is to have
Enter the desired pitch in TPI (Threads Per Inch)
Grind the end cutting angle so that it form an angle a little less than 90 degrees with the side cutting edge. before the dial goes all the way around and you risk losing track of the starting point. 10. Mini lathes sold in the US have 16 TPI lead
are few and far between. Turn on the lathe and engage the half nut. The cost to get one gear made is around $500!! You can also bore it
If
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Manual
Becksmachine can you explain more on the difference from LEAD to Pitch. It is, in fact, a
After completing this unit, you should be able to: Explain how to calculate the pitch, depth, and minor diameter, width of flat. Doubling these figures results in 16 teeth for the stud gear and 80 teeth for the lead screw gear, respectively. thread cleanly to a shoulder. The ratio depends on the pitch of the lead screw and the number of teeth to be cut. If you can support the tool with a springy loop, at a point above the tool,
In return for this small compromise you get a pair
The normal set of
appropriate moment. The first example worked using LEAD calculations but for the second calculation did not work for metric. Be sure to click the correct
2. Mine is 4 tpi wich does make sense with the 127 tooth gear. Because of this, I make my transposing gears,
This calculator will work for most lathes
2. This angle may be 14 degrees for general purpose tool bits. With transposing gears in the gear train this simple relationship is lost. Nose radius: The radius to which the nose is ground. Because a 16-tooth gear is usually the lowest number of teeth furnished in the set, multiply by 2 as follows: Because a 160-tooth gear is entirely out of range of most equipment, and the required diameter would probably be too large to mesh with the stud gear, compound gearing is necessary so that smaller gears can be used. to derive the standard metric pitches. For a better experience, please enable JavaScript in your browser before proceeding. the lead screw is overdriven by the spindle, one suggested method is to fabricate a crank for the lead screw and drive
tempered and lapped. involves a lot of repetitive back and forth motion, keeping things clean and oiled will reduce wear and tear on the lathe. the maintenance interval is irregular. Though you can calculate the helix angle of the thread and work out the necessary tool angles, an eyeball estimate is
This "compound gear assembly" is necessary when a large ratio between the stud gear and lead screw gear is required to cut extra-fine threads. most would like. For finer threads and for in-between
similar to a carriage stop, but mounts on the ways of the cross slide so you can simply run up to a fixed position. It's not terribly difficult if you keep your wits about you; here it is in list form: It's easy to make mistakes even with standard inch threading, and you now have a couple more things to remember. It's far better to simply check the thread
make your own. If you see any evidence of poor finish and suspect the tool is rubbing, increase the clearance angle. to get a clean round ID and use it to practice inside threads. It contains preworked tables for 8 TPI, along with worksheets for thread data and custom
In some cases, the combination of gears given will produce an approximation
Grip the tool bit firmly while supporting the hand on the grinder tool set. Side Relief (clearance) angle: The angle ground on the flank of the tool below the cutting edge. When it reaches the number where you were threading, re-engage the half nuts. back gear and go slower. Change gears are either simple or compound in form. Never wait until the spindle is stopped before withdrawing
exactly to the original setting. If you know the geometry of your threading tool, you can calculate the plunge depth at 30, but the exact width of the
to the mark. Round or
ratios, so you should be able to generate complete gearing tables for any lathe and any lead screw, with or without a QC gearbox. is usually inaccessable) the cross slide can simply be brought to the cutting position by running to the stop. This is not covered in the readingthink it out? When the tool is back to the start of the thread, shut off the lathe. 0000005725 00000 n
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Either way it still does not add up for the metric pitch. change gears includes the following gears: 20, 20, 35, 40, 40, 45, 50,
At the end, back the crossfeed out by 1 turn so the
to pull the tool deeper into the cut, an oscillation can be created that you detect as chatter. On the subject of lube,
spots. Compound Figure 8. So I am heading down the path of cutting my own. It also can be thrown from forward to reverse while running. 0000003753 00000 n
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This is probably a good time to mention that not all lathes have a 1:1 tumbler/reverse gear setup. The Starretts were running about $7.50 in 1989 and
The lathe speed for machine reaming should be approximately 1/2 that used for drilling. these gear trains with little trouble. If there's an additional
Ideally your lathe manufacturer has supplied recommended gearing configurations for various metric pitches. My lathe a TOS S 28 has change gears and a gear box. Describe how to set both compound and crossfeed on both dials to zero. on the near side, the stop insures that you will clear the thread when the tool is backed out, then you would always move
The reason for all the math is because the change gears I do have, none of them make up any of the sets in the table. Move cross feed to the back tool off the work, move carriage to the end of the part and reset the cross feed to zero. On lathes equipped with tumbler reverse gears, it must first be determined whether the lathe is even-geared or odd-geared. The point is, you have quite a bit of time
For any normal length thread you'd be hard
At the end of each threading pass you need to withdraw the tool, then return it to the original position plus the cutting
It would be neat to have some kind of sliding tool holder that could hit a stop at
practice the above technique using an imaginary shoulder- just thread to a certain point and stop. 0000003087 00000 n
food for thought. If mounted
very critical and sometimes quite difficult. I also have one more that shows a picture of a tool cutting from right to left. gear train is less. The rest of the gear train simply multiplies or divides that new pitch value to get to the desired pitch. 3. Check the size using a screw thread micrometer, thread gage, or using the three wire system. That's 3.175 mm, not a terribly convenient number from which
The 127 and 100 tooth gears are the smallest gears that offer an exact metric conversion. Possibly a rod could contact the headstock to
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General Home Preparedness for You and Your Family, Manifestation Guide: How To Manifest Anything You Want, Electromagnetic Radiation and Human Health. actuate it. I don't have very specific ideas on how to do them, but maybe they'll be
Consider the above gearing where (24/60)*(32/64)*2.5 = 0.5 will also give the correct
My lathe does use metric module pitch 1.5 and 2. I also added a picture of them installed. 14. is usually a chart of threading depths for inch threads, not terribly useful for this discussion. Because this is a 10 to 1 ratio, the stud gear must make 10 revolutions to 1 revolution of the lead screw. 0000002222 00000 n
You can head off trouble by making a stop for the cross slide. This is the reason that most lathes have a limit on how coarse a thread should be cut, and experience
cutting angles on both sides. spindle at my lowest normal speed without the back gear. I tried to use the gearing setup of the easily read gears to do the math. Rotate the compound counterclockwise (CCW) exactly 29 and lock it down. I find a relatively sharp pointed tool, say suitable for a #2-56 or an M2-.5 metric will work fine
A common metric transposing pair is 47 and 37 teeth. Note that in most cases these variations are very small and the
including duplicates and the gears that are mounted on the lathe for
Doug does your gear set similar to mine? backwards, including the thread dial. It
by adding another pair of gears to create a compound ratio. It is impossible to use gears with 8 and 80 teeth to cut the required thread. {TmPH:
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This calculator determines the correct change gears for any thread pitch. If you look at a ground thread on a spindle, you'll see the grinding wheel was automatically lifted from the cut at the
Side cutting edge angle: The angle which the cutting edge forms with the side of the tool shank. Blackalloy 525 tool. The connection to the lever
The gears are
those two gears, 1.27, gives us 2.5 mm, a much easier number to further divide or multiply into standard metric pitches. Depth = .7500 x Pitch = .7500 x .100 = .0750 in. Describe how to set the correct quick change gearbox. You want a perfect facet. If you have gears that are constantly engaged, a very light grease may be appropriate, especially if
Any opinions on equipment, price, ease of use, and web sites/ books on how to cut gears? gears you have (if any), separated by commas (,). I believe center gages with company names engraved were sometimes free promotional give-aways by tool
used like this, though a variety of other orientations are possible: Almost all the precision tool makers made center gages. Dividing head calculations and some quick spur gear design utilities are also included should you desire to make your own change
Ok I figured out the math problem for the metric it still has to be multiplied by and multiplied by 25.4 and I match the chart. about $20 today. Still, the basic mechanism is simple. 13. If
than a specific how-to. On an even-geared lathe, the stud gear revolves at the same speed as the spindle gear (that is, the two gears are equal in size). The Gears I do have that are original have a Module pitch of 1.5.
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