Here is a list of all the postings PANAGIOTIS EVRIPIOTIS has made in our forums. Click on a thread name to jump to the thread.
|Thread: Fly cutting flat and parallel|
After reading everything and considering all of the things everyone posted here I guess the way to go is the following along with the material specs:
I usually work with grade 5 titanium or stainless tools steel. A mag chuck will hold the steel which is actually magnetic because hardenable tool steel with more than 14% (if I remember correctly) are considered stainless.
Ideally if I find someone to surface grind them at reasonable price then I will do just that else I will fly cut and then lap. The thickness that needs to be removed is not eveytime the same, some times it is just 0.2mm and some times it could be up to 1mm.
The problems are introduced when there is a bow in the part since twists are very rare.
Yesterday I wanted to flaten a piece of grade 5 titanium that had a bow in the middle. So I took it to the belt grinder and used the flat part or platten as it is called which is surface ground to take out the bow by grinding. After some hand lapping I got a surface with 0.01mm difference from one end to the other. After that I took it to the fly cutter on the vise after giving it a few light taps and milled the surface, then some more hand lapping on that side and I was good to go.
Of course all that is possible as long as you have enough thickness to sacrifice.
Thanks everyone for your answers I got some very useful info and understanding of the situation. Nice tip on the side clamps by the way.
@ Howard Lewis It doesn't sound that much to me for such a small piece but on the other hand I am an amateur so I could be completely mistaken. Surface grinding is the ideal way to go but the problem of a bowed or twisted piece remains even for surface grinding.
@Tony So you are suggesting to just lay the workpiece on the parallels and properly tighten the vise? I guess for the first pass the bow should be facing upwards in order for the workpiece to sit straighter on the parallels and avoid making it worse. The steel is magnetic but I have no practical or theoretical knowledge on how to remove bows and twists on a magnetic chuck and it sounds interesting to me. If you have any resources regarding the subject please let me know.
@Andrew I get what you mean and I can imagine that it would work with the assumptions made. I have no experience with the side clamps, do they apply downward pressure at all? If not then I guess that in this situation the bow should be facing up else the workpiece will rock here and there during milling.
@Wally that is what I always do when clamping something into a vise but that does not counter the problem of a twisted or bowed workpiece of course.
Another thing is to give it to someone to grind it with a surface grinder but if the part is twisted or bowed I don't know how it will react. I cannot buy it ground because it is a very specific tool steel which cannot be found in a ground state, only by the company that produces it and it is about triple the price. If I can't find a way to do it myself then I will resort to that solution but due to the cost of that I need to be sure that I cannot do it in a time effective way.
@ChrisB Thats an idea but unfortunately not possible because it would double the price of the steel that is already extremely expensive
@ Dave this is seems like a practical solution that could theoretically lead to the desired results.In order to do that I just need to get bigger pieces of that steel to clamp them on the table.
The bows are very subtle and you can notice them only by placing a parallel on it or checking on a surface plate, so I would guess that a mag chuck as Tony said would take such a warp out but I am just making guesses now.
@ Andrew I have a manual mill and I fly cut on parallels. I am trying to achieve a uniform flatness with an accuracy of +- 0.02mm maximum across the whole piece. I can take that of with some sanding on a surface plate or something later. Regarding flatness and parallelism I want to achieve the best results I can with the setup I explained in the first post.
@ Martin I thought about the belt sander too and it could work to get the warp out by using very light pressure on the sander and then move to the milling machine. I might give it a try.
I try to make it as tight as needed on the vise. I could theoretically measure if there is any distortion easily firstly on a surface plate and then after I clamp it to check if there are any differences. Regarding the flycutter point that you made, I understand that and I am pretty sure that my head is properly trammed although I will check again before the I do it again. Usually the parts that I am trying to flatten have a bow in the middle and so far I have done only a few and haven't noticed if the bow was there in the beginning or it was introduced during milling. I would like to know if it is actually possible due to the heat generated from a depth of cut of 0.05mm cut for example to distort the piece but that is probably a matter for another post. Right now I am trying to make sure that I have a bulletproof set up and troubleshoot after that if the problem persists.
Also I would like to avoid using small endmills and clamps that I will have to move around to save some time from the operation if possible.
@ Bazyle I checked those side clamps and I don't see how I could use them in this situation due to the thickness of my workpiece as well as the fact that I want to face the whole piece and not just part of it. Also I don't know how they will react when force is applied from a cutter to a high spot from the warp.
@Robert sorry mate I didn't quite catch what you mean. Are you suggesting that I should do what I have been doing with the difference of breaking the procedure into 2 flips instead of 1 and to a stress relieve in between?
I have been trying to find something like theoretical information and not specific approaches in the beginning of how machinists deal with slightly twisted or bend parts that have to be square parallel and flat. All with a 2k manual milling machine.
Keep em coming guys just to clarify the steel is a stainless hardenable tool steel and it comes already annealed and stress relieved.
I will read your comments more carefully a bit later to make sure I understood the ideas.
Also let me know your thoughts on getting flat and parallel both sides. In theory would it be enough to mill one side flat and then just flip it to do the other side? (Assuming there are no warps)
Edited By PANAGIOTIS EVRIPIOTIS on 30/01/2020 13:08:41
I want to ask a question (or a few) about milling something flat and parallel under certain conditions to find ways to overcome some problems.
So I got a manual milling machine trammed and ready to go. I want to fly cut pieces of steel of dimensions of 130mm x 50mm x 5mm so as you can see it is a pretty thing part. I want to reduce the thickness with the fly cutter and as stated above make the two big sides flat and parallel.
I usually clamped the piece on two parallels, milled one side and the flipped it around to mill the other. If I am not mistaken that should theoretically give me what I need but that is not the case.
First question would be this: Is this approach of fly cutting one side and then the opposite correct for making two sides flat and parallel or should I use the theory of squaring up stock and go from side to side to make everything square and parallel. I am not sure as to the importance of squaring up the small sides (perimeter of the stock)
Second question: The stock since it is that thin most of the times come with some warp into it. The problem with that is that when I tighten the piece on the vise and give it a few taps the warp goes away, then I mill and when I unclamp of course the warp comes back. I thought of outsourcing those parts to a machinist with a surface grinder but theoretically the problem should persist since the macgnetic chuck power of such a machine should take out the warp and when removed from it, introduce it back up.
So I would appreciate any info, videos, books, resource or whatever regarding the subject (especially the 2nd one) because I am having a bit of trouble overcoming those problems.
Thanks in advance everyone!
|Thread: Reamer size questions|
Ok everyone thanks a lot for your input. I think all this has given me a better understanding on the matter!
I on't have a lathe to do that, so I will need to find precision ground hardenable steel rods to do that. Also with my experience and the machines that I have I am not sure I can make as accurate tools as I need
You certainly helped a lot, thank you for that info.
Could you make a suggestion regarding size please so I can make my conversions and order metric reamers.
Say that I have, as I mentioned before, a shaft of 1/4inch +-0.0002" and I want to achieve a tight fit, meaning that I will need for example a set of pliers and some force to remove or a mallet.
Now I can easily find for example H7 reamers who according to standards have a tolerance of +0.00059" in the range of 6mm to 10mm(if I am reading correctly).
In order to achieve such a fit with the above circumstances what should the reamer size be in inch or metric?
P.S. I know I am probably not using the term "tolerance" correctly but you get what I mean.
Firstly, I would really like to use just metric but in order to do that I need to understand the theory. How lower should I go to get a tight fit in the scenario mentioned above if my reamer is exact and has no tolerances. If I get a number for that then I can make my own calculations, account for tolerances etc. and see what I am going to buy to achieve that.
By the way give me please the names of these two shops.
P.S. I can download the resource from your 2nd link but it seems broken. It fails to extract
That's the answer I am looking for to get an understanding
Ok I will rephrase my question. Let's consider the following scenario.
I have a very accurate shaft as I mentioned above (+-0.0002 tolerance) of 1/4 inch.
I need to find the appropriate H7 reamer to get a tight fit therefore it has to be a bit undersized. The tolerances of H7 reamers are available online and I know for a fact that this scenario can be achieved.
So the questions is what should be the size of that H7 reamer to get that fit. As I said I will go undersized, my problem is how much I should buy.
I see your point. When I said that I want the user to be able to disassemble it, I meant if he has too and to my mistake I didn't mention frequency. This disassembly will happen very rarely if ever therefore I will avoid what you said. Also I don't go for a press fit because I want the user to have the option of removing the staff.
Hello again everyone, I am having some second thoughts regarding reamer sizes for different kind of fits.
Just to get a good grasp could someone explain in the case of a shaft that is .250 with a tolerance of +- 0.0002, what the size of an H7 reamer would have to be to achieve a tight fit? (to be able to disassemble with a punch and mallet
One last question would be if anyone know of any vendors that sell hardened stainless steel dowel pins, maybe from 416 or 440c steel. So far in Europe I see that the standards are either soft stainless steels or non stainless hardened steels.
Thanks for your help everyone
@mark costello 1
Nope it wouldn't because I need to be easily disassembled with a mallet and punch otherwise I would opt for a press fit and avoid locktite.
I do not own a lathe otherwise I could theoretically make my own toolmaker's reamer although I do not have the knowledge to do that yet and also not the time to experiment on it.
I have bought from Rotagrip before through ebay. I checked your link already but the problem is that I do not have a good grasp of tolerances yet so I can't really judge how smaller does the reamer have to be in order to get a tight fit for a 0.250 hole. Maybe you or any of the others can advice as to how lower I should go to get that tight fit.
Also for anyone who might be interested I contacted drill service as mentioned above and they can make a 0.249 and 0.1560 reamer but they sell at 45 and 40 pounds respectively and that is for HSS reamers. It is quite a high price I think
As I said it the shaft that goes in the hole is of fixed size so I can't go with Tim's method for now.
Regarding the adjustable reamer, if I need it only for this hole and set it up by trial and error as you said then theoretically I can leave it like this and use it only for reaming that hole for a tight fit right?
That was my solution in the beginning and I contacted mcmaster carr in the US and they told me that they will not accept my orders due to US export regulations which is very strange.
I will be more descriptive. So I am mainly drilling and rimming 6al4v titanium and stainless tool steel. both of them have a 1/4 hole and another 5/32 hole. Each hole is for a different part. The thickness I am drilling is 1.5mm to 5mm max.
Right now I am using a carbide reamer and I am guessing that your ideas refer to an HSS reamer. Can you give me some info or resource regarding stoning a reamer and about the jig that you are referring to?
The design with my current set up is not possible to be changed to metric unfortunately because I am buying some parts from the US which I can't make yet. I will check out the dowel pins. I was also considering of going to a machining shop in my area and ask that they make me one but I am not that sure of the accuracy that they can achieve.
I didn't know anything about toolmaker's reamers, theoretically they would work but I am guessing I will need to find someone to make them.
To sum up, to achieve the tight fit I need on the aforementioned materials I can only mess with the hole and not the shafts. I cannot buy undersized reamers from the US because of some stupid reason about regulations so my only option is to get something from the UK if I can find.
If I can't find that then other ways are to get an adjustable reamer and by trial and error set it up ones and keep it that way. Or I can buy HSS reamer stone it or run it through cast iron. Lastly I will contact the shop mentioned about sizes.
Thank you all for your answers!
Tapered won't cut it in my case I think. I also considered the adjustable but in my knowledge there are no adjustable machine reamers, only hand ones. Theoretically I could buy and adjustable and do my job since I don't need to make a lot of these parts but I would like to search all the alternatives and as a last option resort to the adjustable hand reamer.
I will definetely check it out, I don't really care if it is in London if I can just order from them and they ship it to me.
I read about this somewhere else too but I don't how if I can get consistent results with that method. I will try it probably tomorrow and give an update.
I didn't mention this in the beginning because it is not an option. The shaft that goes into the hole is precision ground hardened stainless tool steel and I buy it already made since I don't have a lathe.
H7 is plenty enough, I will check out the document and ask.
If anybody else has and idea or a shop in mind please let me know. Although not that important I am also looking for 1/4 inch diameter precision ground hardened tool steel rod minimum 10cm in length.
Thanks again everyone for all your help
New member here and I got some questions regarding reamers where you might be able to help me.
I am making some parts with imperial size reamers. The part has a hole of a 1/4 inch and 5/32. I want to achieve a tight fit for the parts that will fit into the hole and somebody suggested me to use undersized reamers by 0.001 inch.
Since it is quite hard for me to find in Greece undersized reamers, especially in inches I wanted to ask if anyone know any online shop or physical shops in London where I will be coming for a few days where I could buy undersized 1/4 and 5/32 inch reamers. I am only interested in chucking reamers preferably HSS (H7,H8 tolerances).
Thanks in advance for your help,
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