• This site uses cookies. By continuing to use this site, you are agreeing to our use of cookies. Learn more.
  • Untitled 1

    As promised, a formal announcement has been made regarding recent changes in the administrative staff here at H-M.

    Please take a few moments to go to our home page and review that announcement.

[4]

Cutting a shallow taper

[10] Like what you see?
Click here to donate to this forum and upgrade your account!

JimSchroeder

Active User
Active Member
Joined
Aug 14, 2011
Messages
99
Likes
20
#1
Most of the lathes that we have access to do not have taper attachments and without such fixtures cutting tapers that are accurate can be a challenge. I have on numerous occasions had to cut tapers for collet adapters and for these to function properly they must be accurate. Fortunately the length of the taper is short and thus the compound slide can be used to provide the correct tool angle. The trick is to get the slide adjusted at or very close to the desire angle. One of the more common collets is the R8 which requires a taper of 8.425 degrees over a distance of 0.872”. An earlier post showed how to use a miter square in conjunction with 1-2-3 blocks to align the compound slide at the desired angle. I use a different method and I present that as an alternative, take your pick.

Measuring taper.jpg

















































Photo 1 – An ER-40 collet adapter aligned for turning. Note the dial indicator used to measure the slope of the compound slide.

With some simple trig tables it is very easy to compute the slope measured in decimal fractions per inch of carriage travel. Table 1 below shows the slope measured to ten thousands per angles between zero and twenty degrees and the tenths in between. To use this information place a dial indicator on “Y” axis and either using your DRO or another dial indicator move the carriage one inch and measure the slope of the compound slide. The slope of the ER-40 collet is 8.0 degrees for a depth of 1.377” From Table 1 this shows a slope of 0.1405 inches per inch of carriage travel. Dial indicators with 1 or 2 inches of travel will not measure in tenths but you should be able to extrapolate fairly closely.


[TABLE="width: 583"]
[TR]
[TD="colspan: 3"]Slope per inch of travel[/TD]
[TD][/TD]
[TD][/TD]
[TD][/TD]
[TD][/TD]
[TD][/TD]
[TD][/TD]
[TD][/TD]
[TD][/TD]
[/TR]
[TR]
[TD][/TD]
[TD="colspan: 3"]Tenths of degree[/TD]
[TD][/TD]
[TD][/TD]
[TD][/TD]
[TD][/TD]
[TD][/TD]
[TD][/TD]
[TD][/TD]
[/TR]
[TR]
[TD]Degrees[/TD]
[TD]0[/TD]
[TD]0.1[/TD]
[TD]0.2[/TD]
[TD]0.3[/TD]
[TD]0.4[/TD]
[TD]0.5[/TD]
[TD]0.6[/TD]
[TD]0.7[/TD]
[TD]0.8[/TD]
[TD]0.9[/TD]
[/TR]
[TR]
[TD]1[/TD]
[TD]0.0175[/TD]
[TD]0.0192[/TD]
[TD]0.0209[/TD]
[TD]0.0227[/TD]
[TD]0.0244[/TD]
[TD]0.0262[/TD]
[TD]0.0279[/TD]
[TD]0.0297[/TD]
[TD]0.0314[/TD]
[TD]0.0332[/TD]
[/TR]
[TR]
[TD]2[/TD]
[TD]0.0349[/TD]
[TD]0.0367[/TD]
[TD]0.0384[/TD]
[TD]0.0402[/TD]
[TD]0.0419[/TD]
[TD]0.0437[/TD]
[TD]0.0454[/TD]
[TD]0.0472[/TD]
[TD]0.0489[/TD]
[TD]0.0507[/TD]
[/TR]
[TR]
[TD]3[/TD]
[TD]0.0524[/TD]
[TD]0.0542[/TD]
[TD]0.0559[/TD]
[TD]0.0577[/TD]
[TD]0.0594[/TD]
[TD]0.0612[/TD]
[TD]0.0629[/TD]
[TD]0.0647[/TD]
[TD]0.0664[/TD]
[TD]0.0682[/TD]
[/TR]
[TR]
[TD]4[/TD]
[TD]0.0699[/TD]
[TD]0.0717[/TD]
[TD]0.0734[/TD]
[TD]0.0752[/TD]
[TD]0.0769[/TD]
[TD]0.0787[/TD]
[TD]0.0805[/TD]
[TD]0.0822[/TD]
[TD]0.0840[/TD]
[TD]0.0857[/TD]
[/TR]
[TR]
[TD]5[/TD]
[TD]0.0875[/TD]
[TD]0.0892[/TD]
[TD]0.0910[/TD]
[TD]0.0928[/TD]
[TD]0.0945[/TD]
[TD]0.0963[/TD]
[TD]0.0981[/TD]
[TD]0.0998[/TD]
[TD]0.1016[/TD]
[TD]0.1033[/TD]
[/TR]
[TR]
[TD]6[/TD]
[TD]0.1051[/TD]
[TD]0.1069[/TD]
[TD]0.1086[/TD]
[TD]0.1104[/TD]
[TD]0.1122[/TD]
[TD]0.1139[/TD]
[TD]0.1157[/TD]
[TD]0.1175[/TD]
[TD]0.1192[/TD]
[TD]0.1210[/TD]
[/TR]
[TR]
[TD]7[/TD]
[TD]0.1228[/TD]
[TD]0.1246[/TD]
[TD]0.1263[/TD]
[TD]0.1281[/TD]
[TD]0.1299[/TD]
[TD]0.1317[/TD]
[TD]0.1334[/TD]
[TD]0.1352[/TD]
[TD]0.1370[/TD]
[TD]0.1388[/TD]
[/TR]
[TR]
[TD]8[/TD]
[TD]0.1405[/TD]
[TD]0.1423[/TD]
[TD]0.1441[/TD]
[TD]0.1459[/TD]
[TD]0.1477[/TD]
[TD]0.1495[/TD]
[TD]0.1512[/TD]
[TD]0.1530[/TD]
[TD]0.1548[/TD]
[TD]0.1566[/TD]
[/TR]
[TR]
[TD]9[/TD]
[TD]0.1584[/TD]
[TD]0.1602[/TD]
[TD]0.1620[/TD]
[TD]0.1638[/TD]
[TD]0.1655[/TD]
[TD]0.1673[/TD]
[TD]0.1691[/TD]
[TD]0.1709[/TD]
[TD]0.1727[/TD]
[TD]0.1745[/TD]
[/TR]
[TR]
[TD]10[/TD]
[TD]0.1763[/TD]
[TD]0.1781[/TD]
[TD]0.1799[/TD]
[TD]0.1817[/TD]
[TD]0.1835[/TD]
[TD]0.1853[/TD]
[TD]0.1871[/TD]
[TD]0.1890[/TD]
[TD]0.1908[/TD]
[TD]0.1926[/TD]
[/TR]
[TR]
[TD]11[/TD]
[TD]0.1944[/TD]
[TD]0.1962[/TD]
[TD]0.1980[/TD]
[TD]0.1998[/TD]
[TD]0.2016[/TD]
[TD]0.2035[/TD]
[TD]0.2053[/TD]
[TD]0.2071[/TD]
[TD]0.2089[/TD]
[TD]0.2107[/TD]
[/TR]
[TR]
[TD]12[/TD]
[TD]0.2126[/TD]
[TD]0.2144[/TD]
[TD]0.2162[/TD]
[TD]0.2180[/TD]
[TD]0.2199[/TD]
[TD]0.2217[/TD]
[TD]0.2235[/TD]
[TD]0.2254[/TD]
[TD]0.2272[/TD]
[TD]0.2290[/TD]
[/TR]
[TR]
[TD]13[/TD]
[TD]0.2309[/TD]
[TD]0.2327[/TD]
[TD]0.2345[/TD]
[TD]0.2364[/TD]
[TD]0.2382[/TD]
[TD]0.2401[/TD]
[TD]0.2419[/TD]
[TD]0.2438[/TD]
[TD]0.2456[/TD]
[TD]0.2475[/TD]
[/TR]
[TR]
[TD]14[/TD]
[TD]0.2493[/TD]
[TD]0.2512[/TD]
[TD]0.2530[/TD]
[TD]0.2549[/TD]
[TD]0.2568[/TD]
[TD]0.2586[/TD]
[TD]0.2605[/TD]
[TD]0.2623[/TD]
[TD]0.2642[/TD]
[TD]0.2661[/TD]
[/TR]
[TR]
[TD]15[/TD]
[TD]0.2679[/TD]
[TD]0.2698[/TD]
[TD]0.2717[/TD]
[TD]0.2736[/TD]
[TD]0.2754[/TD]
[TD]0.2773[/TD]
[TD]0.2792[/TD]
[TD]0.2811[/TD]
[TD]0.2830[/TD]
[TD]0.2849[/TD]
[/TR]
[TR]
[TD]16[/TD]
[TD]0.2867[/TD]
[TD]0.2886[/TD]
[TD]0.2905[/TD]
[TD]0.2924[/TD]
[TD]0.2943[/TD]
[TD]0.2962[/TD]
[TD]0.2981[/TD]
[TD]0.3000[/TD]
[TD]0.3019[/TD]
[TD]0.3038[/TD]
[/TR]
[TR]
[TD]17[/TD]
[TD]0.3057[/TD]
[TD]0.3076[/TD]
[TD]0.3096[/TD]
[TD]0.3115[/TD]
[TD]0.3134[/TD]
[TD]0.3153[/TD]
[TD]0.3172[/TD]
[TD]0.3191[/TD]
[TD]0.3211[/TD]
[TD]0.3230[/TD]
[/TR]
[TR]
[TD]18[/TD]
[TD]0.3249[/TD]
[TD]0.3269[/TD]
[TD]0.3288[/TD]
[TD]0.3307[/TD]
[TD]0.3327[/TD]
[TD]0.3346[/TD]
[TD]0.3365[/TD]
[TD]0.3385[/TD]
[TD]0.3404[/TD]
[TD]0.3424[/TD]
[/TR]
[TR]
[TD]19[/TD]
[TD]0.3443[/TD]
[TD]0.3463[/TD]
[TD]0.3482[/TD]
[TD]0.3502[/TD]
[TD]0.3522[/TD]
[TD]0.3541[/TD]
[TD]0.3561[/TD]
[TD]0.3581[/TD]
[TD]0.3600[/TD]
[TD]0.3620[/TD]
[/TR]
[TR]
[TD]20[/TD]
[TD]0.3640[/TD]
[TD]0.3659[/TD]
[TD]0.3679[/TD]
[TD]0.3699[/TD]
[TD]0.3719[/TD]
[TD]0.3739[/TD]
[TD]0.3759[/TD]
[TD]0.3779[/TD]
[TD]0.3799[/TD]
[TD]0.3819[/TD]
[/TR]
[/TABLE]

Table 1 – To determine the slope per inch of carriage travel select the degrees and tenths of a degree the value is in the intersecting box. Example, 8.0 degrees is 0.1405” per inch of travel. I keep a copy of this on the wall over my lathe.

After you have removed enough material from the sloped surface so that the width of the cut is half way or more to the final dimension use some high spot blue to confirm you taper adjustment. In this business you need to make some assumptions from time to time and in this case I assume that the collet is of the correct size and has the correct taper. If some adjustment is needed reattach the dial indicator to help guide your adjustment. Photo 2 shows this on an ER-32 collet and adapter.

Hi spot blue.jpg


















































Photo 2 – High spot blue used to confirm the angle of the collet adapter, this is a ER-32 collet.

Being able to construct collet adapters for your equipment is a handy skill. I find more and more uses for collets as venture into new areas. I am particularly happy with the double-cut ER style of collets. As show I have an ER-40 adapter on my 10x22 lathe and use it extensively. Photo 3 shows a R8 adapter that is part of the tool head for a cutter grinder I built.

Tool head mounted on table.jpg


















































Photo 3 – Tool head for a cutter grinder that uses R8 collets.

These collets holders are not ground or hardened but for the average hobbyist they should give many years of service. My oldest and most used is the R8 holder on a cutter grinder that has been service for three years. As always if you have any questions or comments feel free to contact me either on this post of via private message.

Jim

Measuring taper.jpg Hi spot blue.jpg Tool head mounted on table.jpg
 

grumpygator

Gatekeeper
Staff member
Administrator
Joined
Sep 18, 2012
Messages
1,211
Likes
958
#3
:man: Bookmarked this one.
*********Thanks**************Gator******
 

Rbeckett

Platinum
Rest In Peace
Joined
Sep 24, 2010
Messages
2,606
Likes
35
#4
Thanks for the well thought ans well put tutorial Jim. That is a great article and since I am considering doing some collet type of work I will definately be refering to it often. Being a nobb machinist is tough, but I have learned some really creative ways to make parts and tools from projects just like yours. Again thanks for the info.

Bob
 

stevecmo

Active User
Active Member
Joined
Dec 22, 2011
Messages
717
Likes
5
#5
Jim,

Excellent work as usual and a great documentation. Thank you!

Steve
 

Tony Wells

Former Vice President
Staff member
Administrator
Joined
Jan 22, 2011
Messages
6,883
Likes
1,919
#6
Very accurate method. I would only add that if you're tracing an existing taper to copy your contact tip on your indicator must be on center. If not, it will introduce error in the travel you read. One trick to get it there, if you are using a dti mounted on a QCTP is to eyeball it 0.050 below center and take a reading, then insert a 0.100 gage block under the stop nut and read again from the same start position. If the sweep readings don't agree, then adjust the nut. When you get them to agree, substitute a 0.050 block and you will be very, very close to center. It will practically eliminate error from being off centerline.

Also, the method described assumes that the side of the compound is actually parallel to the ways of it, and although usually they are close, no guarantees. But you can use the same basic method to check your taper after you cut it, and adjust as needed.
 

JimSchroeder

Active User
Active Member
Joined
Aug 14, 2011
Messages
99
Likes
20
#7
All good points Tony. The number of variables that can affect a setup such as this is long and sometimes almost impossible to take them all into account. That is the purpose of using the collet as the "master" and high point blue as the witness.

Jim
 

Tony Wells

Former Vice President
Staff member
Administrator
Joined
Jan 22, 2011
Messages
6,883
Likes
1,919
#8
Totally agree, Jim. The final say is how the intended mating part fits. I've worked with seal tapers that required a blue wipe from a master certified plug, and it wasn't always easy to hit it first time no matter what was done.
 

martik777

Active User
Active Member
Joined
Apr 19, 2011
Messages
339
Likes
31
#9
Great idea! Have you ever tried making the ER collet nuts? I'd like to make an ER chuck but all the collet nuts are in metric threads.
 

tigtorch

Active User
Active Member
Joined
Dec 25, 2012
Messages
118
Likes
2
#10
Very nice suggestion, JimShroeder!

One question though, these numbers are obviously obtained from the sine of the angle. Every number in your table is slightly bigger than the sine of the angle. Example: sin(6.5 degrees)= 0.1132032 your table=0.1139 Why is this?
 

British Steel

Active User
Active Member
Joined
May 12, 2011
Messages
700
Likes
535
#11
I think I see where the discrepancy in the tables comes from, the values given appear to be tangents not sines. For very small angles the difference is negligible, but they diverge significantly once you get over a degree or so, wildly once you approach 90* - at 90* sine is 1.000, tangent is infinite! Jim's method appears to use the tangent, as he's measuring the slope relative to carriage movement (adjacent of the angle) rather than topslide (compound) movement, the hypotenuse, which would give a.sine ratio?

I'm not clear how Jim gets from measuring the (known) angle to a topslide setting for the taper, as most will be locking the carriage in place and using the topslide to cut the taper?

My preferred method (without a taper attachment or for steeper tapers) is to set up a dti on the toolpost and rotate the topslide to an approximate angle, then adjust for no dti deflection against a 'master' taper (if copying) or a ground bar plus gauge block over a fixed distance, 5" if I have enough topslide travel (if cutting a taper from scratch).

If I want 90* included angle, I just engage both feeds... ;)

I did see a nice setup on another forum's shop made tools thread with a table and fence that popped in the chuck/collet to set a sine bar 'on its side' for setting the compound, looked very handy and once I have some spare tuits....

Dave H. (the other one)

Edit: one more thing, when bluing the taper with a collet, put an accurately sized ground bar in the collet to be sure the collet's taper is correct!
 
Last edited:

tigtorch

Active User
Active Member
Joined
Dec 25, 2012
Messages
118
Likes
2
#12
Clearly you are right about it being the tangent and not the sine, British Steel, thank you.
 

JimSchroeder

Active User
Active Member
Joined
Aug 14, 2011
Messages
99
Likes
20
#13
You folks are killing me with the math questions, but let me take a try at it. Tigtorch, the sine of 6.5 degrees is 0.1132 but the number we are looking for is the length of the opposite side. You are assuming that the hypotenuse is 1.000", actually the adjacent side is 1.000" and the hypotenuse is 1.0065" in your example. I used the tangent function to calculate the length of the opposite side and as British steel points out there are some differences depending upon the number of decimal points that you use and how close to zero you are. The objective of the post was to show that for many tasks using inexpensive equipment, in this case imported lathes, reasonable accuracy level could be achieved using this method to set the compound slide angle versus the built in protractor. British Steel is correct on using blue with the collet compress to the native size however in the small home shop that is frequently a challenge. For ER collets, since they are double cut you will be very close with or without compressing them in my humble opinion. R8 collets less so.

If you would like to check my math I suggest this as a good trig calculator to use:

http://www.carbidedepot.com/formulas-trigright.asp

I have not tried to make a ER collet nut, these need to be hardened and cutting the retainer piece is beyond my skill level and the limited equipment that I have. For a few bucks you can buy a good nut and save the aggravation.

British Steel is working at an accuracy level that is beyond my skill level and the capabilities of my equipment. Thanks for the very good feedback.

Jim
 

stevecmo

Active User
Active Member
Joined
Dec 22, 2011
Messages
717
Likes
5
#14
I have not tried to make a ER collet nut, these need to be hardened and cutting the retainer piece is beyond my skill level and the limited equipment that I have.
Jim
Jim,

From what I've seen of your work, I think you're selling yourself a little short. Believe me, if I can make one there's no doubt in my mind that you can make one.

http://www.hobby-machinist.com/attachment.php?attachmentid=38905&d=1360464663&thumb=1

http://www.hobby-machinist.com/attachment.php?attachmentid=38906&d=1360464663&thumb=1

Steve
 

stevecmo

Active User
Active Member
Joined
Dec 22, 2011
Messages
717
Likes
5
#16
SteveCMO, you do nice work. How did you cut the retainer lip? Very nicely done.

Jim
Jim,

Thanks for the kind words.

It seems like it would be harder than it actually is. I basically turned the locking ring, or lip, concentric with the rest of the nut. Then using the four jaw, offset the nut .070" and used the boring bar to remove one side of the ring. This basically created an eccentric ring. The collet can "spring" and lock into the shorter side of the ring. It was a little hard to snap the collets in and out at first but after smoothing the rough edges with a little emory cloth it works great.

Hope that helps. Give it a try!

Steve
 

tigtorch

Active User
Active Member
Joined
Dec 25, 2012
Messages
118
Likes
2
#17
Align tool post EXACTLY first?

I know this thread is a few weeks old but I want to confirm an observation I made while successfully using this method. Since we are measuring the angle from a tool placed in the tool post (reference the photo in the first post of this thread) doesn't the tool post need to be aligned EXACTLY to the compound travel first? Once the angle is set, the tool post angle is not so critical since it travels in the compound direction regardless, but since the angle it presents to the dial indicator is used to set the compound it seems to me that MUCH care should first be used to set the tool post parallel to the compound travel.

Is this correct or am I missing something? BTW, I carefully used this method to make my ER40 chuck and it worked beautifully, my TIR including the collet was less than 0.0005.
 

stevecmo

Active User
Active Member
Joined
Dec 22, 2011
Messages
717
Likes
5
#18
Hi tigtorch,

I'm probably not understanding correctly, but......

In the first photo Jim has his indicator touching the compound and is using that for his measurements, not the tool or tool post. As long as the compound is set to the correct angle, and you only use the compound to cut the taper, the angle of the tool doesn't matter - it always moves at the same angle as the compound.

Does that answer your question or did I not understand it?

Steve
 

tigtorch

Active User
Active Member
Joined
Dec 25, 2012
Messages
118
Likes
2
#19
Steve,

I see that now, thanks! My compound doesn't lend itself to this as easily. I guess my old eyes failed me.
 

stevecmo

Active User
Active Member
Joined
Dec 22, 2011
Messages
717
Likes
5
#20
Steve,

I see that now, thanks! My compound doesn't lend itself to this as easily. I guess my old eyes failed me.
Yeah, sometimes I wish my old lathe had more of the "billet" type compound and cross slide. It would sure make it easier to mount mag bases and indicate off.
 
[6]
[5] [7]