- Joined
- May 29, 2014
- Messages
- 188
I have a couple of problems, and I now submit them to the group. I shall attempt to thoroughly explain the problem and my methodology. Please be patient.
First, the obligatory disclosure: I have not contacted Matt, or QMT. I am not upset. I am not PO'd. I just want to get it fixed.
There, I feel better already.
Next, a bit about me. I am not a complete machining rookie, nor an expert. I consider myself to be somewhat of an advanced amateur. I used a Grizz 9x20 for 10+ years, and this PM 12x36 for just over a year. I also have a PM 932 mill.
OK, on to the problems.
I have never been totally satisfied with the surface finish obtained with this 12x36. I have used CRS, HRS, 6061, Brass, Bronze, 1144, & 12L14. What is wrong with the finish?--It generally looks as though the material has been very very lightly hammered with a tiny ball-pien hammer.
I have used Carbide inserts, Brazed Carbide, & HSS tooling.
I have several TCGT inserts which (with the 9x20) provided nearly mirror finish on Aluminum and also the 12L14. The finish retains the hammered appearance on Aluminum on my 12x36. HSS tooling is not wonderful, either. I will freely admit that my tool grinding skills are not the best--although, good enough (in most instances) to get by with.
So, I started investigating. The first thing I did was to observe the belts with the guard removed--please do not tell the safety Nazis. The 2 belts were not tensioned evenly. I checked the alignment of the motor pulley to the input pulley and made small a adjustment. No improvement. I removed both belts (one was way too loose) and obtained 2 new Gates belts--No change. One of the new belts is also a bit too loose. I removed the loosest belt and rechecked the alignment--hammered appearance was better, but not yet right. Next, I obtained some of the Link Belting and created one to fit. Better again, but still not good enough.
I'm beginning to get a bit frustrated.
I put the DTI (B&S--0.0005) on the spindle taper & hand rotated the spindle--No perceptible movement. This should eliminate a spindle bearing issue.
Next, I put the DTI on the machined surface of the motor pulley--Very little (almost none) movement. This should eliminate a motor issue.
Next, I put the DTI on the machined surface of the input pulley---Whoa--High to Low = 0.006. Further, I can easily deflect that pulley further with gentle hand pressure. I know someone will ask, so here is how I set up the indicator.
As you face the lathe on the gear train end (looking toward the tailstock), the DTI pointer is in the machined (belt) groove at the 9 o'clock position--with the pointer oriented parallel to the indicator (vertical). If I grasp the pulley at the 9 & 3 position and push-pull (not in & out) the indicator will change about an additional 0.003. In-out movement is non-existant. Up-down movement is non-existant (I repositioned the indicator).
Oh yes, I did remove the pulley to check the input shaft for variations or bending, & found none. All of the rotating was done via the motor pulley (by hand) with the belt still in place. I now suspect that the input pulley is not correctly machined. The machined surfaces where the belt runs are very rough (like sandpaper), too. All 4 grooves in the input pulley exhibit nearly the same amount of wobble.
So, what say you? Do you think that the 0.006 of wobble on the input pulley could cause the hammered appearance that I have described?
Since I cannot re-machine the pulley on this lathe (my only one), I will need to either contact Matt for a replacement or proceed to the next step, below.
Before I get too terribly involved in a repair, I am considering a toothed belt and pulley system to replace the current system. Is this a good or bad idea? If a good idea where would be a good source for the replacements?
I realize that this has been exceedingly long. I thank you for your patience.
Jerry in Delaware
First, the obligatory disclosure: I have not contacted Matt, or QMT. I am not upset. I am not PO'd. I just want to get it fixed.
There, I feel better already.
Next, a bit about me. I am not a complete machining rookie, nor an expert. I consider myself to be somewhat of an advanced amateur. I used a Grizz 9x20 for 10+ years, and this PM 12x36 for just over a year. I also have a PM 932 mill.
OK, on to the problems.
I have never been totally satisfied with the surface finish obtained with this 12x36. I have used CRS, HRS, 6061, Brass, Bronze, 1144, & 12L14. What is wrong with the finish?--It generally looks as though the material has been very very lightly hammered with a tiny ball-pien hammer.
I have used Carbide inserts, Brazed Carbide, & HSS tooling.
I have several TCGT inserts which (with the 9x20) provided nearly mirror finish on Aluminum and also the 12L14. The finish retains the hammered appearance on Aluminum on my 12x36. HSS tooling is not wonderful, either. I will freely admit that my tool grinding skills are not the best--although, good enough (in most instances) to get by with.
So, I started investigating. The first thing I did was to observe the belts with the guard removed--please do not tell the safety Nazis. The 2 belts were not tensioned evenly. I checked the alignment of the motor pulley to the input pulley and made small a adjustment. No improvement. I removed both belts (one was way too loose) and obtained 2 new Gates belts--No change. One of the new belts is also a bit too loose. I removed the loosest belt and rechecked the alignment--hammered appearance was better, but not yet right. Next, I obtained some of the Link Belting and created one to fit. Better again, but still not good enough.
I'm beginning to get a bit frustrated.
I put the DTI (B&S--0.0005) on the spindle taper & hand rotated the spindle--No perceptible movement. This should eliminate a spindle bearing issue.
Next, I put the DTI on the machined surface of the motor pulley--Very little (almost none) movement. This should eliminate a motor issue.
Next, I put the DTI on the machined surface of the input pulley---Whoa--High to Low = 0.006. Further, I can easily deflect that pulley further with gentle hand pressure. I know someone will ask, so here is how I set up the indicator.
As you face the lathe on the gear train end (looking toward the tailstock), the DTI pointer is in the machined (belt) groove at the 9 o'clock position--with the pointer oriented parallel to the indicator (vertical). If I grasp the pulley at the 9 & 3 position and push-pull (not in & out) the indicator will change about an additional 0.003. In-out movement is non-existant. Up-down movement is non-existant (I repositioned the indicator).
Oh yes, I did remove the pulley to check the input shaft for variations or bending, & found none. All of the rotating was done via the motor pulley (by hand) with the belt still in place. I now suspect that the input pulley is not correctly machined. The machined surfaces where the belt runs are very rough (like sandpaper), too. All 4 grooves in the input pulley exhibit nearly the same amount of wobble.
So, what say you? Do you think that the 0.006 of wobble on the input pulley could cause the hammered appearance that I have described?
Since I cannot re-machine the pulley on this lathe (my only one), I will need to either contact Matt for a replacement or proceed to the next step, below.
Before I get too terribly involved in a repair, I am considering a toothed belt and pulley system to replace the current system. Is this a good or bad idea? If a good idea where would be a good source for the replacements?
I realize that this has been exceedingly long. I thank you for your patience.
Jerry in Delaware
